Showing papers in "Journal of environmental chemical engineering in 2021"
TL;DR: In this paper, a review of different textile industry processes, wastewater generation, its nature and chemical composition, environmental impacts and health hazards and treatment approaches available for TIWW treatment is presented.
Abstract: Textile industry wastewater (TIWW) is considered as one of the worst polluters of our precious water and soil ecologies. It causes carcinogenic, mutagenic, genotoxic, cytotoxic and allergenic threats to living organisms. TIWW contains a variety of persistent coloring pollutants (dyes), formaldehyde, phthalates, phenols, surfactants, perfluorooctanoic acid (PFOA), pentachlorophenol and different heavy metals like lead (Pb), cadmium (Cd), arsenic (As), chromium (Cr), zinc (Zn) and nickel (Ni) etc. TIWW is characterized by high dye content, high pH, chemical oxygen demand (COD), biochemical oxygen demand (BOD), total dissolved solids (TDS), total suspended solids (TSS), total organic carbon (TOC), chlorides and sulphates. Thus, requires adequate treatment before its final discharge into the water bodies to protect public health and environment. The treatment of TIWW is a major challenge as there is no particular economically feasible treatment method capable to adequately treat TIWW. Therefore, there is a need to develop a novel, cost-effective and eco-friendly technology for the effective treatment of TIWW. This review paper emphasizes on the different textile industry processes, wastewater generation, its nature and chemical composition, environmental impacts and health hazards and treatment approaches available for TIWW treatment. It also presents various analytical techniques used to detect and characterize TIWW pollutants and their metabolites, challenges, key issues and future prospectives.
312 citations
TL;DR: In this paper, the authors have reviewed efforts and technological advances achieved so far in the pursuit of more efficient removal and recovery of heavy metals from industrial wastewaters and have evaluated their efficiency dependence on various parameters such as pH, temperature & initial dosing.
Abstract: Rapid industrialization, with economic prosperity set as the prime goal, has always created some secondary intolerable problems such as heavy metal contamination, wastewater that need remediation. Industrial wastewater is the major contributors to contamination of aquatic and terrestrial ecosystems with toxic heavy metals like arsenic, copper, chromium, cadmium, nickel, zinc, lead, and mercury whose hazardous bio-accumulative nature in biotic systems is attributed to their high solubility in the aquatic environments. There has, therefore, always been a need for the removal and/or recovery of these toxic, non-biodegradable, and persistent heavy metals from the industrial wastewater. For several decades, extensive investigations have been performed for easy, efficient, and economic removal of heavy metals with a varying degree of success. Chemical precipitation, adsorption, ion floatation, ion-exchange, coagulation/flocculation and electrochemical methods have been the most readily available conventional methods for the removal of these heavy metals. These methods however have posed some serious shortcomings such as high sludge production needing further treatment, low removal efficiency and high energy requirements. In the present years, newer more efficient, more economic and innovative technologies are being investigated. Recently photocatalysis, electrodialysis, hydrogels, membrane separation technique and introducing newer adsorbents have been developed for better adsorption. Hence in this paper, we have reviewed efforts and technological advances achieved so far in the pursuit of more efficient removal and recovery of heavy metals from industrial wastewaters and have evaluated their efficiency dependence on various parameters such as pH, temperature & initial dosing.
173 citations
TL;DR: In this paper, the metal binding potentials of bacterial biomass towards different metal ions, cell wall constituent, biofilm, extracellular polymeric substances (EPS) in metal binding, and the effect of various environmental parameters influencing the metal removal were summarized.
Abstract: Heavy metal pollution caused due to the industrialization has been considered as a significant public health hazard, and these heavy metals exhibit various types of toxicological manifestations. Conventional remediation methods are expensive and also yield toxic by-products, which negatively affect the environment. Hence, a green technology employing various biological agents, predominantly bacteria, algae, yeasts, and fungi, has received more attention for heavy metal removal and recovery because of their high removal efficiency, low cost, and availability. However, bacterial biosorption is the safest treatment method for the toxic pollutants that are not readily biodegradable such as heavy metals. Metal biosorption by bacteria has received significant attention due to a safe, productive, and feasible technology for the heavy metal-containing wastewater treatment. These metal tolerating bacteria can bind the cationic toxic heavy metals with the negatively charged bacterial structures and live or dead biomass components. Due to the large surface area to volume ratio, these bacterial biomasses efficiently act as the biosorbent for metal bioremediation under multimetal conditions. This review summarizes the biosorption potentials of bacterial biomass towards different metal ions, cell wall constituent, biofilm, extracellular polymeric substances (EPS) in metal binding, and the effect of various environmental parameters influencing the metal removal. Suitable mathematical models of biosorption and their application have been discussed to understand and interpret the adsorption process. Furthermore, different desorbing agents and their utilization in heavy metals recovery and regeneration of biosorbent have been summarized.
148 citations
TL;DR: Herin et al. as mentioned in this paper used jasmine flower extract as capping as well as stabilizing agent to synthesize metal and metal oxide nanoparticles, which achieved a maximum degradation efficiency of 78% at the end of 120min.
Abstract: Herin, we prepared silver NPs using jasmine flower extract. The green synthesis process reports a eco-friendly, nontoxic, cost-effective and simple approach to the synthesis of metal and metal oxide nanoparticles. Extract of jasmine flower acts as capping as well as stabilizing agent. The average crystalline size of the XRD pattern is estimated to be 40 nm. FT-IR (Fourier Transform Infrared) spectra confirm the existence of Ag NPs. The UV-Visible spectrum exhibits an absorption peak of between 380 and 440 nm. Structural analysis for silver nanofibers reveals with SEM and TEM technique. The antimicrobial activity of silver NPs was tested for both grams positive and negative bacteria by Agar well diffusion method. Methylene blue is used as a pollutant dye. Silver nanoparticles result in a maximum degradation efficiency of 78% at the end of 120 min.
128 citations
TL;DR: In this article, a new ensemble machine learning model called Extra Tree Regression (ETR) was introduced for predicting monthly WQI values at the Lam Tsuen River in Hong Kong.
Abstract: The Water Quality Index (WQI) is the most common indicator to characterize surface water quality. This study introduces a new ensemble machine learning model called Extra Tree Regression (ETR) for predicting monthly WQI values at the Lam Tsuen River in Hong Kong. The ETR model performance is compared with that of the classic standalone models, Support Vector Regression (SVR) and Decision Tree Regression (DTR). The monthly input water quality data including Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Dissolved Oxygen (DO), Electrical Conductivity (EC), Nitrate-Nitrogen ( NO 3 -N), Nitrite-Nitrogen ( NO 2 -N), Phosphate ( P O 4 3 - ), potential for Hydrogen (pH), Temperature (T) and Turbidity (TUR) are used for building the prediction models. Various input data combinations are investigated and assessed in terms of prediction performance, using numerical indices and graphical comparisons. The analysis shows that the ETR model generally produces more accurate WQI predictions for both training and testing phases. Although including all the ten input variables achieves the highest prediction performance ( R 2 t e s t = 0.98 , R M S E t e s t = 2.99 ), a combination of input parameters including only BOD, Turbidity and Phosphate concentration provides the second highest prediction accuracy ( R 2 t e s t = 0.97 , R M S E t e s t = 3.74 ). The uncertainty analysis relative to model structure and input parameters highlights a higher sensitivity of the prediction results to the former. In general, the ETR model represents an improvement on previous approaches for WQI prediction, in terms of prediction performance and reduction in the number of input parameters.
127 citations
TL;DR: In this article, the data of 52 articles (containing 225 experiments of adsorption kinetics) were collected, and the kinetic data were treated using the linear and nonlinear PFO and PSO models.
Abstract: In the literature, the linear form of the pseudo-first-order (PFO) and pseudo-second-order (PSO) models are often applied for fitting the data of adsorption kinetics. Many authors have applied the linear form of the PSO model and concluded that such a kinetics is better fitted, based on the values of adsorption capacity at the equilibrium (qe) and the high value (which should be close to 1.0) of the coefficient of determination (R2). The linearized PFO model is usually ruled-out because the values of qe and R2 are worse than those obtained by the linearized PSO. On the other hand, the nonlinear fitting of data is highly recommended for the use of equations that are not typically linear such as kinetics data. In this communication, the data of 52 articles (containing 225 experiments of adsorption kinetics) were collected, and the kinetic data were treated using the linear and nonlinear PFO and PSO models. Results indicated that the values of k2 (the rate constant of the PSO model) calculated from the nonlinear fitting method were quite different from those acquired from the linear one. However, the values of qe2 (adsorption capacity at the equilibrium of the PSO model) are in complete agreement, which induces users to an erroneous decision. Using a linearized kinetic model, all the 225 values of R2 of the PSO model were closer to 1.0 than PFO. However, when nonlinearized fitting of the data was used, 122 out of 225 cases (54.22%) showed that the nonlinear PFO is better fitted than the PSO kinetic model.
127 citations
TL;DR: The role of noble metals-based catalysts (such as Rh and Ru) and the transition metals containing Ni-species supported on zeolites in CO2 conversion to (HC) fuels is discussed in this paper.
Abstract: Meeting the ever-increasing global energy demands is one of the serious challenges of the 21st century. It is estimated that about 80% of the global energy demand is supplied by the fossil fuels which in turn promote global warming upon their consumption and cause harmful effects on the environment. One of the major causes of global warming is the excessive accumulation of CO2 into the atmosphere. An important way for mitigating the excessive amount of CO2 is to transform it into the hydrocarbons (HC) fuels. In this article, we have addressed various issues aroused by CO2 emission and their possible solutions. Various routes for CO2 upgrading into HC fuels are comprehensively elaborated. Furthermore, we have focused on the heterogeneous catalysis for CO2 conversion to value-added HC fuels by utilizing zeolite and non-zeolite based catalysts. The role of noble metals-based catalysts (such as Rh and Ru) and the transition metals containing Ni-species supported on zeolites in CO2 conversion to (HC) fuels is discussed. In addition, the role of Fe- and MOFs based non-zeolite based catalysts for the generation of HC fuels via the CO2 hydrogenation is also discussed. Finally, this review article highlights the prospective areas for research and technology advances. In brief, this review is focused on zeolite and non-zeolite based catalytic route for CO2 to HC fuel and reflects its importance for both the industries and academia.
126 citations
TL;DR: In this article, a new magnetic Schiff's base-chitosan-Benzil/zinc oxide/Fe3O4 nanocomposite was developed to be a promising and recoverable adsorbent for Remazol Brilliant Blue R dye (RBBR) removal from the aquatic environment.
Abstract: In this research work, a new magnetic Schiff's base-chitosan-Benzil/zinc oxide/Fe3O4 nanocomposite (Cs-Bz/ZnO/Fe3O4) was developed to be a promising and recoverable adsorbent for Remazol Brilliant Blue R dye (RBBR) removal from the aquatic environment. Parametric optimization by Box–Behnken design was made to optimize the synthesis condition (loading ZnO nanoparticles into polymeric matrix of Cs) in addition to adsorption operation parameters (adsorbent dose, solution pH, temperature, and contact time). The obtained results show that the fast RBBR removal (98.8%) can be achieved by loading 25% ZnO nanoparticles into polymeric matrix of Cs (Cs-Bz/ZnO-25/Fe3O4), and at optimum adsorption operation parameters (adsorbent dosage of 0.04 g, solution of pH 4, temperature of 60 °C, and contact time of 10 min). At these optimum conditions, the maximum adsorption capacity was found to be 620.5 mg/g. The best isotherm and kinetic models were Freundlich model and pseudo-second-order kinetic model, respectively. The probable RBBR dye adsorption mechanism can be assigned to various types of physicochemical interactions (i.e; electrostatic, n-π, π-π interactions) in addition to hydrogen bonding and Yoshida H-bonding. The output of this research confirms that Cs-Bz/ZnO-25/Fe3O4 is a superior, recoverable, and environment friendly biohybrid nanocomposite adsorbent. The remarkable output of this research can open a window for other possible significant applications such as tenement of real waste water, removal of heavy metal ions, and reduction of chemical oxygen demand.
121 citations
TL;DR: The current review provides a countrywide waste generation amount, estimated using the infected number of cases for some selected countries, and some suggested approaches towards a better waste management service and future implications of waste management are discussed with viable consideration for the waste workers.
Abstract: The COVID-19 pandemic and lockdown situation have shown both positive and negative effects on the environmental aspects. With an unprecedented rate the different types of waste volume have up surged along with the COVID-19 contamination rate. As the situation has mandated people as well as the most infected persons to stay at home, the amount of generated hazardous waste is 3.40 kg that can be expected daily from each infected person. China and other countries have seen a massive increment in the hazardous waste generation (about 600 % increase in Hubei province) amount. While dealing with this sudden increase in waste amount, the conventional incineration facilities have been outstripped and waste management industry is facing an immense pressure over handling hazardous waste generated from COVID-19 infected patients. Alongside with the hazardous waste volume, single-use plastic items and personal protective equipment (PPEs) have induced a new type of "PPE pollution" in the land and aquatic environment. The current review provides a countrywide waste generation amount, estimated using the infected number of cases for some selected countries. In contrast with the poor waste management noticed during this pandemic, some suggested approaches towards a better waste management service and future implications of waste management are discussed with viable consideration for the waste workers.
116 citations
TL;DR: In this paper, the structural and optical properties of Au-ZnO hetero-nanostructures were studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Energy-dispersive Xray spectrography (EDX), High-resolution transmission electron microscope (HRTEM) and UV-vis spectrophotometer (UV-vis).
Abstract: Pure Zinc Oxide (ZnO) nanoparticles (NPs) and gold (Au) decorated (Au-ZnO) hetero-nanostructures were synthesized using green-synthesis method employing pecan nuts (Carya illinoinensis) leaves extract as reducing agent. The structural and optical properties studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), High-resolution transmission electron microscopy (HRTEM) and UV–vis spectrophotometer (UV–vis). Structural modification with the introduction of Au in ZnO have been confirmed by the XRD and TEM results. UV data confirmed the decrease in Au-ZnO energy band-gap Eg value, which validates the formation of hetero-structure. The modulation of energy band-gap causes visible light absorption and hence enhances the photodegradation activity of Au-ZnO. Photocatalytic activity was carried-out by degradation of RhB dye under UV light irradiation in aqueous solution. The maximum degradation of 95 % was obtained during the time of 180 min for the basic pH of the dye. The Enhanced degradation in Au-ZnO as compared with bare ZnO NPs, was attributed to Au, which controls the amount of electron and suppress electron-hole ratio at ZnO surface. In the recycling study of the Au-ZnO Photocatalyst, the hetero-structure showed good stability up to five cycles.
112 citations
TL;DR: In this article, a photo-assisted peroxymonosulfate (PMS) activation process was used to degrade Azorubine (AZB) under UVA-LED irradiation.
Abstract: Food dyes are a large group of dyes which have been widely used in the food industry. The presence of them in aquatic media results in water pollution. In this work, a heterogeneous photo-assisted peroxymonosulfate (PMS) activation process was used to degrade Azorubine (AZB). Fe2O3 loaded on multi-wall carbon nanotube (Fe@MWCNT) was synthesized and applied to activate PMS under UVA-LED irradiation. Fe@MWCNT catalyst was characterized by XRD, FTIR, EDX-map, BET, FESEM, and TEM analyses. UVA-LED/Fe@MWCNT/PMS process removed around 95% of AZB from aqueous solution under pH= 5, PMS= 1.8 mM, and 130 mg/L Fe@MWCNT. Sulfate radicals showed a higher contribution for AZB degradation compared to hydroxyl radicals and singlet oxygen. Pseudo-first-order model was fitted on AZB degradation with a rate constant of 0.095 min−1. Bicarbonate ions and humic acid had an ultra-inhibitory effect on the oxidative process. Carboxylic acids were monitored during AZB degradation, with the results indicating that aromatic rings of AZB were opened by the attack of sulfate and hydroxyl radicals. Six cycles of the catalyst reuse demonstrated no significant change in the performance of the UVA-LED/Fe@MWCNT/PMS process. The implementation of the UVA-LED/Fe@MWCNT/PMS process was also successfully studied on other food dyes and real wastewater. UVA-LED/Fe@MWCNT/PMS process was an efficient approach for the degradation of organic contaminants in water with high stability.
TL;DR: In this paper, a critical analysis of the present phase of knowledge concerning the exposure and effects of nanomaterials has been discussed in-depth, including the potential benefits and unknown dangers.
Abstract: Currently, nanotechnology is referred to be one of the attractive research sectors in several countries because of its vast potential and commercial impact. Nanotechnology includes the investigation, development, fabrication, and processing of structures and materials on a nanoscale in various fields of science, health care, agriculture, technology, and industries. As such, it has provided a steady restructuring of related technologies. However, the irregularities and uncertainties in dimensions and chemical compositions, makes the viability of such materials questionable. Concerns have been inclined about the transport, destiny, and transformation of nanomaterials discharged into the environment. A critical analysis of the present phase of knowledge concerning the exposure and effects of nanomaterials has been discussed in-depth. In this review, different nanomaterials along with their applications have also been reviewed, that include graphene-based nanomaterials, carbon nanotubes, and their composites, nanoclay composites, nanostructured thin films, metal-organic frameworks, conducting polymers and their composites, MXenes, chalcogenide nanocrystals, and quantum dots. Besides, a few of the groundbreaking applications of nanomaterials for different sectors like human health, processes, photochemical process, energy conversion and energy storage, separation and purification processes, optoelectronics, etc. are discussed in detail with their chemsitry. Moreover, the unique characteristics and applications of nanomaterials, they inherently introduce challenges for their applications and large-scale production. Acknowledgment of the potential benefits and unknown dangers of nanomaterials is critically is critically analyzed and discussed in the manuscript.
TL;DR: In this article, the efficacy of agro-biomass/byproducts (belonging to plants, microbes and animals) either as biosorbents (raw biomass) or adsorbents(modified biomass) for direct removal of dyes and their role as co-substrate to stimulate the biodegradation/decolourization of the dyes by bacteria and fungi.
Abstract: The dyeing wastewaters are composed of complex chemical compositions, which are toxic and cause biotic risks. For eco-friendly remediation of such toxicants, agro-based materials are used as biosorbent/adsorbent and co-substrate in both physiochemical and biological treatment processes. The present study comprehensively reviews the efficacy of agro-biomass/byproducts (belonging to plants, microbes and animals) either as biosorbents (raw biomass) or adsorbents (modified biomass) for direct removal of dyes and their role as co-substrate to stimulate the biodegradation/decolourization of dyes by bacteria and fungi. In physiochemical process, agro-based biosorbents/adsorbents with porous structures and cellulosic content (≥ 40%) could exhibit excellent potential for removal of both ionic and non-ionic dyes from aqueous medium. Advancement of chemically modified agro-wastes in the form of bio-composites, or doped with nano-materials are used to enhance the sorption of dyes from wastewater in column-flow mode. In biological processes, co-substrate such as jack-fruit-seed-powder, sago-waste, and molasses can act as ē-donor, nutritional supplement, and solid-phase substratum for bacteria in dye decolourization medium, which reduces the color and organic loading in bio-treated water. Such low-cost agro-based co-substrates could be used in bioreactors for biodegradation of dyes and coupled bio-energy production at industrial scale. However, it is required to investigate the potential of biosorbent for real-dyeing-wastewater treatment, comprehensive economic analysis of the agro-based bio-treatment process, a suitable solid-phase co-substrate for immobilization of microorganism to reduce sludge, and reusability of agro-wastes for effective treatment of wastewater.
TL;DR: In this paper, the authors used biomass of grass waste (GW) as sustainable precursor to produce highly porous activated carbon (GWAC) with mesoporosity using a K2CO3-assisted pyrolysis approach and tested for its methylene blue (MB) dye adsorption.
Abstract: In this study, biomass of grass waste (GW) was utilized as sustainable precursor to produce highly porous activated carbon (GWAC) with mesoporosity using a K2CO3-assisted pyrolysis approach and tested for its methylene blue (MB) dye adsorption properties. The prepared GWAC was characterized using the various techniques of specific surface area (SSA), Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX), X-ray diffractometer (XRD), thermogravimetric analysis (TGA), and Fourier Transform Infrared (FT-IR) spectrophotometer. The characterization results indicate the successful conversion of GW into mesoporous GWAC with high and desirable surface area of 1245.6 m2/g. The adsorptive performance of GWAC towards MB uptake was evaluated. To attain higher performance of the activated carbon for MB adsorption, the adsorption key parameters such as GWAC dosage (A: 0.04–0.06 g/L), pH (B: 4–10), temperature (C: 30–60 °C), and time (D: 5–15 min) were optimized using the Box–Behnken design (BBD) method. The adsorption equilibrium data were accurately described by the Langmuir model, where the adsorption capacity (qm; 364.2 mg/g) was recorded at the optimized process temperature of 45 °C. The present research also examined the mechanisms associated with the removal of MB using GWAC and observed the contribution of various MB-GWAC surface interactions (e.g., electrostatic, π-π, and H-bonding interactions). The present investigation shows the utility and effectiveness of GW biomass based activated carbon due to its favorable mesoporosity and cationic dye uptake in aqueous media.
TL;DR: In this paper, an eco-friendly and cost-effective approach was established to cope with real textile and tannery effluents via the biosynthesis of highly adsorbent magnesium oxide nanoparticles (MgO-NPs).
Abstract: Industrial wastewater treatment is one of the greatest challenges of humanity that require an increased awareness to address water scarcity worldwide. Herein, an eco-friendly and cost-effective approach was established to cope with real textile and tannery effluents via the biosynthesis of highly adsorbent magnesium oxide nanoparticles (MgO-NPs). Physicochemical characterization of as-formed MgO-NPs confirms the successful fabrication of MgO nano-rods (30–85 nm) and nano-rectangular (18.6–27.6 nm) by harnessing metabolites secreted by Aspergillus niger strain F1. Moreover, the energy dispersive spectroscopy (EDX) confirms that Mg and O are the main components in the sample with weight percentages of 41.1% and 33.6%, respectively. X-ray photoelectron spectroscopy (XPS) confirms the successful formation of MgO at different bending energies. The catalytic degradation and decolorization analyses were conducted under sunlight and dark conditions. These analyses demonstrated that the highest decolorization of real textile and tannery effluents (92.8% ± 0.06% and 97.5% ± 0.7%, respectively) was accomplished after 180 min by treatment with 1.0 mg mL−1 of MgO-NPs in the presence of sunlight. At optimum experimental conditions, the quality of treated effluents was monitored by the reduction of total suspended solid (TSS), total dissolved solid (TDS), and chemical oxygen demand (COD) levels at the percentages of 86.9% ± 0.8%, 77.0% ± 0.8%, and 89.3% ± 0.9%, respectively, for textile effluent and the percentages of 94.3% ± 1.6%, 80.7% ± 1.6%, and 97.4% ± 0.9% respectively, for tannery effluent. The reusability of MgO-NPs showed its activity for textile effluents treatment for four cycles. Biosynthesized MgO-NPs showed a high adsorption capacity for predominant tannery heavy metals, namely, Cr, Co, Pb, Cd, and Ni having removal percentages of 94.2% ± 1.2%, 63.4% ± 1.7%, 72.7% ± 1.3%, 74.1% ± 1.8%, and 70.8% ± 1.5%, respectively. The toxicity of treated effluents was assessed by the germination of corn and broad bean seeds, which exhibited a decreased toxicity as compared with untreated effluents. Interestingly, the biosynthesized MgO-NPs exhibit antimicrobial activity against different pathogenic microbes and their activities were dose-dependent.
TL;DR: This article circumscribes the various emerging technologies, which have been used to treat PhACs and pathogens, and emphasized the global concern of the presence of SARS-CoV-2 RNA in hospital wastewater and its removal by the existing treatment facilities.
Abstract: The hospital wastewater imposes a potent threat to the security of human health concerning its high vulnerability towards the outbreak of several diseases. Furthermore, the outbreak of COVID-19 pandemic demanded a global attention towards monitoring viruses and other infectious pathogens in hospital wastewater and their removal. Apart from that, the presence of various recalcitrant organics, pharmaceutically active compounds (PhACs), etc. imparts a complex pollution load to water resources and ecosystem. In this review, an insight into the occurrence, persistence and removal of drug-resistant microorganisms and infectious viruses as well as other micro-pollutants have been documented. The performance of various pilot/full-scale studies have been evaluated in terms of removal of biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), PhACs, pathogens, etc. It was found that many biological processes, such as membrane bioreactor, activated sludge process, constructed wetlands, etc. provided more than 80% removal of BOD, COD, TSS, etc. However, the removal of several recalcitrant organic pollutants are less responsive to those processes and demands the application of tertiary treatments, such as adsorption, ozone treatment, UV treatment, etc. Antibiotic-resistant microorganisms, viruses were found to be persistent even after the treatment of hospital wastewater, and high dose of chlorination or UV treatment was required to inactivate them. This article circumscribes the various emerging technologies, which have been used to treat PhACs and pathogens. The present review also emphasized the global concern of the presence of SARS-CoV-2 RNA in hospital wastewater and its removal by the existing treatment facilities.
TL;DR: In this paper, the authors focused on adsorption of dimethoate by using highly adsorptive porous membrane based on metal organic framework@cellulose acetate (Cu-BTC@CA).
Abstract: The current study focused on adsorption of dimethoate by using highly adsorptive porous membrane based on metal organic framework@cellulose acetate (Cu-BTC@CA). The porous Cu-BTC@CA membrane was prepared in two steps; formation of porous CA membrane and secondly, Cu-BTC was in-situ synthesized within the porous CA membrane. The preparation was performed to incorporate different ratios of Cu-BTC (20–60%) within the CA membrane to study their efficiency in the adsorption of dimethoate. Micro-crystals Cu-BTC was successfully immobilized in the macroporous CA membrane with pore diameter of 112.6–496.0 nm. The BET surface area was significantly increased from 78.4 m2/g for CA membrane to 965.8 m2/g for 40% Cu-BTC@CA membrane. Adsorption of dimethoate upon the synthesized membrane was fitted well to Langmuir isotherm and pseudo-second order model. The adsorption capacity was observably enhanced from 207.8 mg/g for CA membrane to 282.3–321.9 mg/g for Cu-BTC@CA membrane. Incorporation of 40% Cu-BTC resulted in acceleration of the dimethoate adsorption by factor of 2.1. The applied membrane showed quite good recyclability and the adsorption efficiency was reduced by 22.5% after 5 recycles. The synthesized Cu-BTC@CA membrane could be promisingly applied in the effective removal of pesticides with sufficient recoverability, and in general environmental purposes.
TL;DR: In this paper, a comprehensive review of municipal solid waste generation and its characteristics is presented, providing a bird's-eye view of the suitability of various technologies for energy production, providing up-to-date information about it.
Abstract: Solid waste treatment and disposal is a global challenge for the development of a sustainable society. The problem has been exacerbated by a rise in waste products as a result of population growth and urbanization. Ever-increasing municipal solid waste, together with its high proportion of organic waste and its unscientific disposal, contributes to Greenhouse gas emissions and other air pollutants. Municipal solid waste (MSW) mismanagement not only has harmful environmental consequences but also poses public health risks and raises other socioeconomic concerns. The mitigation approach requires an environmentally sustainable interpretation of the waste for its management and treatment. The waste-to-energy conversion provides a solution to environmental issues such as Greenhouse gas emission and waste management, thereby helping to achieve a green environment with a simultaneously prospering economy. This paper provides a comprehensive review of municipal solid waste generation and its characteristics. It provides a bird's-eye view of the suitability of various technologies for energy production, providing up-to-date information about it. It also covers challenges and perspectives in this field of research.
TL;DR: In this paper, two-dimensional metal-organic frameworks (MOFs), called copper-terephthalate, and CuO@C were investigated as catalysts for the reduction of 4-nitrophenol (4-NP) via hydrogenation using sodium borohydride (NaBH4) as a reducing agent.
Abstract: Two-dimensional (2D) metal-organic frameworks (MOFs), called copper-terephthalate, and CuO@C were investigated as catalysts for the reduction of 4-nitrophenol (4-NP) via hydrogenation using sodium borohydride (NaBH4) as a reducing agent. Copper-terephthalate frameworks were synthesized using the solvothermal method. While, CuO@C was synthesized using carbonization of copper-terephthalate at temperature of 400 °C, 500 °C, 600 °C, and 700 °C. Both materials displayed a complete reduction of 4-NP to 4-aminophenol (4-AP) in a short time (3 min) with a rate of 15.1× 10−3 min−1, and 6.0× 10−3 min-1 at room temperature for CuBDC, and CuO@C, respectively. The materials could be used for more than five times without obvious fading in their catalytic activities. The mechanism of the reduction was also discussed. The materials are promising for catalytic applications such as organic synthesis via the reduction of the nitro groups.
TL;DR: In this article, a review comprises several synthesis ways which are low-cost and environmentally friendly and detail analysis of the relationship between morphology control and photocatalytic performance of Tungsten oxide (WO3).
Abstract: Environmental pollution and global energy demand require advanced photocatalytic materials such as visible-light-driven semiconductor photocatalysts. In particular, Tungsten oxide (WO3) appears promising candidate because of high absorption of visible light (up to 480 nm), its tunable bandgap, and outstanding optical properties. Fascinatingly, WO3 also hold advantages like nontoxic nature, economic cost, and stability in oxidative and acidic conditions. It is well-known that various synthetic procedures can be utilized for fabrication of a photocatalyst with different morphologies, sizes and structures which are dynamic on its catalytic performance to distinctive degrees. This review comprises several synthesis ways which are low-cost and environmentally friendly and detail analysis of the relationship between morphology control and photocatalytic performance of WO3. Additionally, some top strategies for enhancing the photocatalytic performance of semiconductor WO3, like as elemental doping, hybridization with co-catalyst, heterojunction formation etc. are also summarized. Moreover, photocatalytic enhancement aspects and photocatalytic mechanisms of WO3/semiconductor photocatalyst were elaborated. Lastly, the conclusion and main future prospects of WO3-based semiconductor photocatalysts were deliberated.
TL;DR: In this article, a detailed assessment of literature review depicting the classical processes and technological innovations in the latest few decades for the degradation and abatement of dyes and other pollutants from textile waste-effluents with a proposal of a novel economic and eco-friendly cutting-edge technology.
Abstract: Amidst the exponentially growing world economy, textile industries are referred to as one of the largest contributors to the economic growth and also the biggest pollution causing production sector. The conventional methodologies for waste effluent treatment involves huge energy, time, infrastructure, material, land, manpower, and capital consumption. The presented report consists of a detailed assessment of literature review depicting the classical processes and technological innovations in the latest few decades for the degradation and abatement of dyes and other pollutants from textile waste-effluents with a proposal of a novel economic and eco-friendly cutting-edge technology. Extensive literature review on photocatalytic degradation reveals that homogeneous and heterogeneous photocatalysis could be developed as a true sustainable technology where the later one is complemented as more accomplishing in fruitful degradation of organic pollutants. But long degradation time and low degree of removal efficiencies are still major challenges to the scientific community for providing a viable treatment process. In this circumstance, hybrid process development employing pre-clarifying stage of flocculation; degradation of waste effluent employing integrated adsorbent supported photocatalyst with a membrane integrated catalyst recovery, could be the best possible solution for sustainable treatment of liquid industrial waste effluent. Final stage membrane filtration can separate out the spent catalyst along with the discharge of reusable clean water. Such a comprehensive review is expected to initiate influential policies among the research community to combat the widespread risk of reluctant treatment practices of toxic organic pollutants generated from textile industrial houses.
TL;DR: In this article, reduced graphene oxide based iron oxide modified titania (rGO-Fe3O4/TiO2) was developed as a low-cost, stable, and reproducible photocatalyst, synthesized by conventional hydrothermal route.
Abstract: Reduced graphene oxide based iron oxide modified titania (rGO-Fe3O4/TiO2) was developed as a low-cost, stable, and reproducible photocatalyst, synthesized by conventional hydrothermal route. Structural and morphological features were investigated by X-Ray diffraction (XRD), Thermogravimetric analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS). The incorporation of rGO-Fe3O4 to TiO2 shifted the light absorption of TiO2 from ultraviolet (UV) to visible region. The band gap energy of the synthesized photocatalyst rGO-Fe3O4/TiO2 reduced to 2.6 eV as compared to TiO2 (3.2 eV) which shifted the light absorption into visible region in order to utilize the solar energy effectually. The as-proposed rGO-Fe3O4/TiO2 and TiO2 photocatalysts were used for the photo-degradation of malachite green (MG) and methylene blue (MB) degradation. The as-prepared photocatalyst rGO-Fe3O4/TiO2 exhibited commendable photocatalytic efficiency (99%) comparative to pure TiO2 (67%) under visible light in 55 min for MG degradation. The active species were also identified using various scavengers by trapping holes and radicals generated during the photocatalytic degradation process. Subsequently, such photo-degradation output inferred that this ternary nanocomposite partakes a great potential for visible light driven MG and MB photocatalytic degradation.
TL;DR: GumT-cl-HEMA/TiO2 hydrogel composite was used to perform adsorption to separate the molecules of malachite green (MG) from water.
Abstract: In this work, 2-hydroxyethyl methacrylate cross-linked gum tragacanth hydrogel (GumT-cl-HEMA) was systematically synthesized to attain maximum swelling (396.9 %) by simple microwave-assisted green polymerization technique. The prepared GumT-cl-HEMA hydrogel was further modified by using TiO2 nanoparticles to generate TiO2 loaded 2-hydroxyethyl methacrylate cross-linked gum tragacanth (GumT-cl-HEMA/TiO2) hydrogel composite. The GumT-cl-HEMA hydrogel and GumT-cl-HEMA/TiO2 hydrogel composite were characterized through XPS, BET, XRD, FTIR, TGA and SEM. The GumT-cl-HEMA hydrogel and GumT-cl-HEMA/TiO2 hydrogel composite were used to perform adsorption to separate the molecules of malachite green (MG) from water. Batch adsorption parameters were examined to analyze the pH effect, time effect and adsorbent dose for the adsorption of malachite green dye from aqueous solution. The inclusion of TiO2 particles inside the GumT-cl-HEMA hydrogel led to increased adsorption rates and stability. The adsorption was accurately followed the pseudo second order model and Langmuir isotherm model. The reported GumT-cl-HEMA/TiO2 hydrogel composite removal efficiency was 99.3 % adsorbent dose = 90 mg, MG = 50 ppm, pH = 7, volume = 50 mL and time = 80 min). The synthesized samples were regenerated and then reused for five repeated adsorption-desorption cycles. The construction of GumT-cl-HEMA hydrogel and GumT-cl-HEMA/TiO2 hydrogel composite gives a facile scheme for efficient adsorbents.
TL;DR: In this article, a review of biochar-based advanced oxidation processes (AOPs) is presented, including biochar modifications, characterizations, radical determinations, and catalytic mechanism.
Abstract: In recent years, refractory organic pollutants (ROPs) have been progressively detected in wastewater. Persulfates (peroxymonosulfate and peroxydisulfate)-based advanced oxidation processes (PS-AOPs) are efficient for ROPs degradation. Biochar and its composites, which have the dual advantages of adsorption and catalysis, have been widely used in PS-AOPs. Research advances on PS activation by biochar-based materials are systematically summarized, including biochar modifications, characterizations, radical determinations, and catalytic mechanism. Biochar modifications applied to PS-AOPs are introduced involving morphology regulation, heteroatomic doping, and metals loading. Characterization techniques are described to reveal the physicochemical properties of biochar-based catalysts. Various methods for radical determinations are discussed. The catalytic mechanism in the PS-AOPs is depicted from the point of radical pathway and non-radical pathway. Based on current knowledge, the perspectives and challenges that may be encountered in basic research and practical applications are put forward. This review offers novel insights into catalyst design and better understanding of PS-AOPs.
TL;DR: In this article, the adsorptive performance of hydroxyapatite (HAp) was improved by using Fe3O4 magnetic nanoparticles and polydopamine (PDA) and was applied to eliminate Hg(II), Co(II, and Ni(II).
Abstract: In the current investigation, the adsorptive performance of hydroxyapatite (HAp) was improved by using Fe3O4 magnetic nanoparticles and polydopamine (PDA) and was applied to eliminate Hg(II), Co(II), and Ni(II). The tests of XPS, XRD, EDX, FTIR, TGA, and VSM were applied to identify the HAp/Fe3O4/PDA structure and adsorption mechanisms. Based on the finding, pH was of the most effective variables in the elimination process and the highest yield was determined at pH 6 for all studied metals. The equilibrium data followed the Langmuir and Freundlich models (R2 > 0.9). According to isotherm modeling, Hg(II), Co(II), and Ni(II) removal using HAp/Fe3O4/PDA has a physical mechanism. The highest elimination capacity (qm) for Hg(II), Co(II), and Ni(II) was set at 51.73 mg/g, 49.32 mg/g, and 48.09 mg/g, respectively. The effect of contact time had a good consistency with the findings of the Weber and Morris kinetic, as the process was done in two steps. The Gibbs free energy parameter revealed that the abatement process is spontaneous and its spontaneity degree decreases with elevating temperature. Various analyzes were used to explore the characteristics of the HAp/Fe3O4/PDA composite. In summary, HAp/Fe3O4/PDA had an effective capability to remove toxic metals from distilled water and landfill leachate.
TL;DR: In this paper, the Box-Behnken design in the response surface methodology (RSM) was used to investigate the modelization and optimization of Methyl Orange (MO) mineralization parameters.
Abstract: In the present study, the Box-Behnken design in the response surface methodology (RSM) was availed to investigate the modelization and optimization of Methyl Orange (MO) mineralization parameters. The process was carried out in the presence of lanthanum (La) doped mesoporous titanium dioxide (TiO2) by a simple impregnation method using various La doping amounts (0.5, 1.5 and 3 wt%). The physico-chemical characteristics of each catalysts are studied under several approaches. The effects of the wavelength of irradiation light, catalysts weight and MO concentration on the yield of MO mineralization were investigated. Based on ANOVA analysis, the results show that the response of MO mineralization (R) in photocatalytic process was significantly affected by a positive individual effect of wavelength and catalyst weight. However, the individual effect of MO concentration has an antagonist impact through the whole process. The optimum conditions were achieved for the light irradiation wavelength of 310 nm, catalyst weight of 80 mg, and MO concentration of 20 ppm, which allowed reaching 99.89 % of mineralization. Overall, the adjusted coefficient of determination (R2) value of 0.9956 indicated that the used model was quite suitable and the selected RSM was successful in optimizing the mineralization conditions of MO.
TL;DR: In this article, a comprehensive assessment of occurrence, ecotoxicological effects, and treatment methods of emerging contaminants (ECs) is provided, and a comprehensive risk assessment analysis of the EC has been performed, and it was found that caffeine, bisphenol-A, diazinon and malathion had high risk quotients.
Abstract: Emerging contaminants (ECs) have been a threat to the aqueous environment because of their persistent nature and ability to adversely affect the living organisms exposed to them for a prolonged duration. An increase in detection of varying ranges of ECs in different aqueous bodies has catalyzed research on their toxic effects and removal. However, a compilation of proper legislations in terms of permissible limits of the ECs in water and understanding the capability of the different treatment technologies in bringing down their concentration to non-toxic levels is an area that needs significant attention. In this context, this review provides a comprehensive assessment of occurrence, ecotoxicological effects, and treatment methods of ECs. Statutory guidelines of different environmental organizations have been compared with the calculated drinking water equivalent limit of the ECs. Furthermore, a comprehensive risk assessment analysis of the EC has been performed, and it was found that caffeine, bisphenol-A, diazinon, and malathion had high risk quotients. The performance of the different treatment technologies was assessed based on their ability to bring down the concentration of the ECs below the established statutory guidelines. Unlike most conventional treatment methods, many advanced hybrid treatment methods could reduce the concentration of the ECs below the guideline value. Technologies involving membrane bioreactor combined with reverse osmosis, ozonation, and membrane distillation proved to be very effective with more than 90% removal. The sustainability aspects of different treatment methods have also been covered in this review to help researchers identify suitable treatment methods for removing ECs.
TL;DR: In this article, a comprehensive review of the xanthan gum derived materials is presented for the needs of drug delivery, tissue engineering, oil recovery, and environmental applications, including bio-nanocomposites containing metal, and metal oxide nanoparticles, graphene and inorganic clays.
Abstract: Xanthan gum (XG), a naturally occurring microbial exopolysaccharide, is of a great commercial significance. It has demonstrated a significant potential in targeted applications such as advanced drug delivery, wastewater treatment, protein delivery, tissue engineering, and food packaging due to its outstanding physicochemical properties, biodegradability, and non-toxicity. However, certain limitations such as low surface area, poor mechanical performance, thermal stability, and bacterial growth can hinder its uses in specific applications. As a result, there have been various endeavors to modify xanthan gum by means of diverse modification approaches for enhancing its physicochemical properties, and therefore enabling its competence for the needs of drug delivery, tissue engineering, oil recovery, and environmental applications. To the best of our knowledge, this is the first review for providing a comprehensive picture of the advanced chemical treatment, grafting procedures, hydrogel synthesis, bio-nanocomposites containing metal, and metal oxide nanoparticles, graphene, and inorganic clays, along with the fabulous properties obtained for the xanthan derived materials. Furthermore, it exhibits the recent applications for these materials in industrial, biomedical engineering, wastewater treatment, and agricultural fields. In the future, the presented data will be considered a fabulous base for designing the next generation materials to be applied in further advanced uses.
TL;DR: In this article, two-dimensional (2D) metal-organic frameworks (MOFs) were synthesized using a surfactant-assisted solvothermal method and X-ray diffraction (XRD) reveals the formation of crystalline material.
Abstract: Organic pollutants such as 4-nitrophenol (4-NP) exhibited a negative impact on human health and the environment of a biological system. Thus, several catalysts have been reported to mitigate the toxicity of 4-NP via the reduction to 4-aminophenol (4-AP). Furthermore, the reduction process is important for the synthesis of amine compounds as intermediate for several industrial sectors. Herein, two-dimensional (2D) metal-organic frameworks (MOFs) were synthesized using a surfactant-assisted solvothermal method. X-ray diffraction (XRD) reveals the formation of crystalline material. The scanning electron microscope (SEM) image showed 2D MOF with a thickness of 100−150 nm. Data analysis reveals the successful formation of a high crystalline phase of MOF with the morphology of 2D nanoscale. The synthesis procedure is simple and requires no expensive reagents or special equipment. The catalytic performance of the prepared material was examined for the reduction of 4-NP to 4-AP. The material exhibited ultrafast (2 min) catalytic performance with a complete reduction (conversion 100 %) without an induction period. The simple synthesis procedure besides the high catalytic performance of the prepared material endows the potential of 2D MOF for further applications including catalysis.
TL;DR: In this article, a Fourier transform infrared (FTIR) spectral fingerprint indicates that face masks were characterised by natural and artificial fibres including polyester fibres, polypropylene, natural latex resin.
Abstract: The threat of plastic waste pollution in African countries is increasing exponentially since the World Health Organisation declared the coronavirus infection as a pandemic. Fundamental to this growing threat are multiple factors, including the increased public consumption for single-use plastics, limited or non-existence of adequate plastic waste management infrastructures, and urbanisation. Plastics-based personal protective equipment including millions of surgical masks, medical gowns, face shields, safety glasses, protective aprons, sanitiser containers, plastics shoes, and gloves have been widely used for the reduction of exposure risk to Severe Acute Respiratory Syndrome (SARS) Coronavirus 2 (SARS-CoV-2). This paper estimates and elucidates the growing plethora of plastic wastes in African countries in the context of the current SARS-CoV-2 pandemic. A Fourier transform infrared (FTIR) spectral fingerprint indicates that face masks were characterised by natural and artificial fibres including polyester fibres, polypropylene, natural latex resin. Our estimate suggests that over 12 billion medical and fabric face masks are discarded monthly, giving the likelihood that an equivalent of about 105,000 tonnes of face masks per month could be disposed into the environment by Africans. In general, 15 out of 57 African countries are significant plastic waste contributors with Nigeria (15%), Ethiopia (8.6%), Egypt (7.6%), DR Congo (6.7%), Tanzania (4.5%), and South Africa (4.4%) topping the list. Therefore, this expert insight is an attempt to draw the attention of governments, healthcare agencies, and the public to the potential risks of SARS-CoV-2-generated plastics (COVID plastic wastes), and the environmental impacts that could exacerbate the existing plastic pollution epidemic after the COVID-19 pandemic.