Showing papers in "Journal of water process engineering in 2015"
TL;DR: In this article, a review of magnetic adsorbents and their adsorption behavior under diverse conditions is presented. But, the practical utility of such adorbents needs to be explored before they can be commercially applied.
Abstract: In recent years, adsorption has displayed promising and effective results as a treatment technology for water and wastewater by industries. In the process, a number of adsorbents have been synthesized and applied for the treatment of pollutants such as metals, dyes, pharmaceutical products in solutions. However, for adsorption to be unconditionally adopted by industries, a few obstacles such as high capital cost, difficult segregation of adsorbent from solution, and complex synthesis processes need to be addressed. The removal of suspend adsorbents in wastewater from a continuous flow system is a challenge which if addressed properly would enable us to recover the spent adsorbent efficiently. The spent adsorbents can then be regenerated and used again by the industries thereby leading to reduced capital investment. Therefore, studies have been carried out aiming at the incorporation of magnetism in such adsorbents to aid their removal from wastewater. This review aims to comprehensively list and discuss adsorbents which exhibit magnetic properties and their adsorption behaviour under diverse conditions. The literature survey presented in this paper renders evidence to the good potential of magnetic adsorbents to remove various pollutants from wastewater. However, the practical utility of such adsorbents needs to be explored before they can be commercially applied.
312 citations
TL;DR: In this paper, the authors presented a review of green and biobased coagulants for water and wastewater treatment operations, and the factors militating against the transition of the applications of these non-conventional coagULs from bench-scale to real-life applications were discussed.
Abstract: Metal and polymer based materials are the conventional coagulants used in water and wastewater treatment operations. Despite the wide applicability of these genera of coagulants, the challenges associated with the usage have engendered research efforts towards the development of green biobased coagulants, whose applications are capable of obviating the challenges synonymous with the usage of these conventional coagulants. Taking into cognizance the goals that informed the development of green technology, perspectives on the promising non-conventional coagulants that are green and biobased are presented in this treatise. The perspectives on these green biobased coagulants were anchored on the background information of the material, the economic importance, mode of application of the extract as coagulant, underlying coagulating mechanism and the shortcomings of the usage in water and wastewater treatment operations. On the basis of the information provided by different researchers, on the appraisals of these green biobased coagulants for water and wastewater treatment operations, the factors militating against the transition of the applications of these non-conventional coagulants from bench-scale to real life applications were discussed.
179 citations
TL;DR: In this paper, the effect of initial pH, chemical dosing, and irradiation time on the removal efficiency of pesticides and chemical oxygen demand (COD) were assessed, the maximum removal of COD by photo-Fenton process was 90.7%, while by TiO 2 photocatalysis was 79.6%.
Abstract: Solar photo-Fenton and solar TiO 2 photocatalysis processes were investigated for degradation of pesticides from real industrial wastewater. Chlorpyrifos, lambda-cyhalothrin, and diazinon were the major contaminants found in the wastewater. The effect of initial pH, chemical dosing, and irradiation time on the removal efficiency of pesticides and chemical oxygen demand (COD) were assessed. The maximum removal of COD by photo-Fenton process was 90.7%, while by TiO 2 photocatalysis was 79.6%. Moreover, the photo-Fenton process was more efficient for degradation of pesticides fractions. Employing of H 2 O 2 in photocatalysis process (UV/H 2 O 2 /TiO 2 ) improved the removal of COD (84%) and the degradation of pesticides. The kinetic study showed that the degradation of pesticides fractions follows pseudo-first-order pattern. Amortization and operating costs of full scale solar oxidation plant were estimated. The estimated costs for photocatalysis and photo-Fenton processes were 8.69 and 5.2 €/m 3 , respectively.
168 citations
TL;DR: In this paper, the effects of pH value, initial concentration of MB, catalyst dosage, and hydrogen peroxide (H 2 O 2 ) concentration on the degradation of MB were systematically investigated.
Abstract: Highly effective nanoscale zero valent iron (nZVI) immobilized on magnetic Fe 3 O 4 -reduced graphene oxide (Fe 0 –Fe 3 O 4 –RGO) was successfully fabricated and firstly proposed as a heterogeneous Fenton catalyst for the removal of Methylene Blue (MB). The characterization of the hybrids revealed that Fe 3 O 4 were distributed on RGO nanosheets evenly, the nZVI were wrapped by Fe 3 O 4 assembled on the RGO nanosheets. The effects of pH value, initial concentration of MB, catalyst dosage, and hydrogen peroxide (H 2 O 2 ) concentration on the degradation of MB were systematically investigated. Typically, 98.0% removal of 50 mg/L MB could be achieved within 60 min with the initial pH value of 3.00, H 2 O 2 concentration 0.8 mmol/L, catalyst dose 0.10 g/L. The analysis of kinetics showed that the removal of MB followed the pseudo-second-order kinetics better than the pseudo-first-order kinetics. In addition to its high catalytic activity, the reusability and superparamagnetism make it a promising candidate as heterogeneous Fenton catalyst to remove organic contaminants in water.
163 citations
TL;DR: In this paper, the separation efficiency of a nanofiltration membrane was investigated and the relationship between the rejection rates of magnesium and lithium was established, and the extractions of lithium from salt lake brines were also evaluated.
Abstract: Owing to the high ratio of Mg 2+ to Li + in most of the salt lake brines in China, it is difficult to extract lithium. Therefore, the separation efficiency of a nanofiltration membrane was investigated in this study. Operating conditions such as operating pressure, inflow water temperature, pH, and Mg 2+ /Li + ratio were investigated. Relationship between the rejection rates of magnesium and lithium was established. Moreover, the extractions of lithium from salt lake brines were also evaluated. The results indicate that the separation of magnesium and lithium was highly dependent on the Mg 2+ /Li + ratio, operating pressure, and pH. When the Mg 2+ /Li + ratio was 2+ /Li + ratio. The permeate flux of membrane for the East Taijiner brine was higher than that for the West Taijiner brine.
152 citations
TL;DR: In this paper, a compact AOP reactor that generates ozone by UV irradiation was developed, and the ozone was generated using the Chapman method, i.e., by irradiating oxygen with UV light; the use of this method saves energy.
Abstract: The treatment of persistent organic pollutants in wastewater from chemical factories by decomposition using advanced oxidation processes (AOPs) has recently been studied. However, the AOPs studied to date suffer from problems such as high running costs for ozone generation and difficulties with operational parameters in the addition of hydrogen peroxide. In this study, a compact AOP reactor that generates ozone by UV irradiation was developed. Ozone was generated using the Chapman method, i.e., by irradiating oxygen with UV light; the use of this method saves energy. The decomposition activity of the designed reactor and the effects of a combination of ozone, UV, and TiO 2 were examined. The results showed that 100% decomposition of 50 mg/dm 3 phenol was reached within 120 min using an O 3 –UV–TiO 2 process, and COD removal reached 100% within 240 min. COD analysis confirmed that a synergistic effect was obtained using ozone, UV, and TiO 2 simultaneously.
134 citations
TL;DR: In this paper, a halloysite-magnetite-based composite was used for the removal of methyl violet 2Bcationic dye, and the adsorption capacity of the composite was evaluated in a temperature-controlled batch system.
Abstract: Despite the important role of the textile industry in the global economy, its effluents generate deepconcern with regard to treatment and disposal. Adsorption is a promising technique for the removal oftextile color effluent at relatively low cost and with satisfactory efficiency. This study aimed to evaluatethe adsorption capacity of a halloysite-magnetite-based composite in the removal of methyl violet 2Bcationic dye. After preparation, the obtained composite was characterized by applying several instrumen-tal techniques, including X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopyand determination of pH at the point of zero charge. The influences of stirring rate, adsorbent mass, pH,initial concentration of dye and contact time on the adsorption process were also studied. The adsorptioncapacity of the composite was then investigated in a temperature-controlled batch system. The experi-mental results showed that the adsorption kinetics were better described using a pseudo-second-ordermodel. Regarding the adsorption equilibrium, the experimental results suggest that both the Langmuirand Freundlich models were applicable. The thermodynamic data showed that dye adsorption onto thecomposite was spontaneous and endothermic and occurred by physisorption. The employed compositecould also be regenerated at least four times using a 1.0 mol L−1solution of NaOH as an eluent and wasshown to be a promising adsorbent for the removal of cationic dyes.
124 citations
TL;DR: In this article, a novel graphene based adsorbent was synthesized from sugar and sand using green chemistry approach and adsorption of Cr (VI) ions from aqueous solution was studied by batch adaption technique under varying experimental conditions.
Abstract: Cr (VI) is one of the most toxic contaminants recognized as a carcinogenic and mutagenic agent and needs complete removal from wastewater before disposal. In the present study, a novel graphene based adsorbent was synthesized from sugar and sand using green chemistry approach and adsorption of Cr (VI) ions from aqueous solution was studied by batch adsorption technique under varying experimental conditions like contact time, pH, adsorbent dose, initial Cr (VI) concentration and temperature. The characterization of the prepared graphene sand composite (GSC) was accomplished by Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction(XRD) analysis, Raman spectroscopy, electron diffraction measurements, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy (EDX) and surface area measurements. The specific surface area of the GSC before and after activation was determined to be 100 m 2 /g and 157 m 2 /g, respectively. The optimum adsorption of Cr (VI) by the new adsorbent, coined as GSC, was observed at pH 1.5 The maximum adsorption capacity of GSC for Cr (VI) was found to be 2859.38 mg/g at room temperature which is claimed to be one of the exceptionally high values reported so far in the literature. The equilibrium sorption data were fitted satisfactorily to the Langmuir adsorption model with R 2 value of 0.99108. The progress of the adsorption process was found to follow the second order kinetics. The results obtained in this study illustrated that the prepared graphenic material could be an effective and economically viable adsorbent for removal of Cr (VI) ions.
103 citations
TL;DR: In this article, wheat straw pulp fine cellulosics were used as a biosorbent for the removal of Pb(II) in aqueous solutions after nanofibrillation and sulfonation pretreatments.
Abstract: Low-cost sorbents derived from abundant natural resources, industrial by-products, or waste materials are considered amongst the most viable novel materials for heavy metal removal. In this study, wheat straw pulp fine cellulosics were used as a biosorbent for the removal of Pb(II) in aqueous solutions after nanofibrillation and sulfonation pretreatments. The effect of the initial lead concentration, sorption time, and solution pH were studied, and the isothermal data were modeled with the Langmuir and Freundlich isotherm models. Pb(II) was adsorbed efficiently (1.2 mmol/g) from the model solution by sulfonated nanocelluloses which had a width between 5 and 50 nm and a sulfonic acid content of 0.45 mmol g −1 . This adsorption capacity is comparable to those of commercial adsorbents. The Pb(II) adsorption onto nanofibrillated and sulfonated cellulosics followed the Langmuir isotherm model and showed rapid initial kinetics. Thus, nanofibrillated and sulfonated cellulosics are promising green alternatives for the recovery of metals from aqueous solutions.
101 citations
TL;DR: In this paper, the effect of different concentrations of graphene oxide (GO) nanoplates on fouling mitigation of polyethersulfone (PES) membranes applied in membrane bioreactor (MBR) to treatment milk processing wastewater was investigated.
Abstract: This study was performed to investigate effect of different concentrations of graphene oxide (GO) nanoplates on fouling mitigation of polyethersulfone (PES) membranes applied in membrane bioreactor (MBR) to treatment milk processing wastewater. The GO was prepared from graphite and characterized by FTIR, SEM and XRD. The mixed matrix membranes were prepared in three concentrations of 13, 15 and 17 wt% of PES polymer. Static contact angle of the membranes were decreased significantly with addition of the GO nanosheets caused to increasing of pure water flux and MWCO. Cross sectional SEM images showed that the finger-like pores for all of the GO embedded membranes were slightly wider than that of the unfilled PES membrane. Ultrafiltration performance and fouling resistance of the membranes were tested by filtration of activated sludge. With addition of GO nanoplates, fouling resistance ratio (FRR) of the nanocomposite membranes was improved. AFM images and FRR results presented that a membrane with smoother surface has greater fouling resistance ability. Based on antifouling and water flux results, the PES/GO membrane with 15 wt% of PES and GO content of 0.5 wt%, was selected as an optimal membrane and tested in MBR system. The MBR showed an increased capacity for removal of organic matter, both in terms of COD and BOD5 of milk processing wastewater. With increasing of MLSS concentration, flux of the membrane was increased due to a decrease in soluble microbial products and extracellular polymeric substance from the bacterial cells in the lower food to microorganism ratio (F/M).
94 citations
TL;DR: In this article, an evaluation of heterogeneous Fenton behavior of nano nickel-zinc ferrite catalysts in the wet peroxide Oxidation for the degradation of 4-chlorophenol is presented.
Abstract: An evaluation of heterogeneous Fenton behavior of nano nickel-zinc ferrite catalysts in the Wet Peroxide Oxidation for the degradation of 4-chlorophenol is presented A series of spinel type Ni x Zn 1− x Fe 2 O 4 ( x = 00, 025, 05, 075, 10) catalysts were prepared by sol-gel auto combustion method and characterized by X-ray diffraction, Transmission Electron Microscopy, X-ray fluorescence and Fourier Transform Infra-Red spectroscopy Fenton's reaction was performed over different compositions of nickel zinc ferrite catalysts under neutral conditions and the catalytic activities were studied The yield of the reaction, based on Gas Chromatographic and Chemical Oxygen Demand (COD) parameters were very high and the experimental results indicated complete degradation of target pollutant with significant reduction of COD with all catalysts within 75 min Zinc substitution enhanced the catalytic activity of nickel ferrite and the un-substituted ZnFe 2 O 4 degraded the target compound completely within 45 min Catalysts were found to be reusable and the extent of iron leaching, quantified by Atomic Absorption Spectroscopic studies was negligible after five consecutive cycles indicating the mechanism to be heterogeneous Phase analysis of catalyst using XRD after the completion of each catalytic cycle confirmed the stability of the catalyst toward the Wet Peroxide Oxidation of 4-chlorophenol
TL;DR: An attempt is made to correlate membrane biofouling with QS activity, recent trends in membrane bio fouling control based on QS are presented and the mechanisms by which different agents mitigate membrane bioFouling based onQS are discussed.
Abstract: Exploring novel biological strategies to mitigate membrane biofouling is of significant value in order to allow sustainable performance of membrane systems for water and wastewater treatment. Quorum sensing (QS) is a bacterial communication process that involves small diffusible signalling molecules, which activate the expression of myriad genes that control a diverse array of phenotypes such as bioluminescence, virulence, biofilm formation and sporulation. Since QS is often associated with biofilm formation, inhibition of QS should be a promising strategy to control membrane biofouling. Recently, a revolutionary application of bacterial QS has been as a novel strategy for the mitigation of biofouling in membrane systems. In this review an attempt is made to correlate membrane biofouling with QS activity. Moreover, recent trends in membrane biofouling control based on QS are presented and the mechanisms by which different agents mitigate membrane biofouling based on QS are discussed. The potential impact of QS-based methods of biofilm control is assessed. Lastly, brief conclusions and future research challenges in membrane biofouling control based on QS are highlighted.
TL;DR: In this paper, a central composite design (CCD) was used to optimize the operating parameters of the Fenton process in removing recalcitrant organics from POME by using a response surface methodology (RSM) module in the Design-Expert ® software.
Abstract: Post treatment palm oil mill effluent (POME) is typically non-biodegradable and contains high organic and inorganic matter. This study aims to optimize the operating parameters of the Fenton process in removing recalcitrant organics from POME by using a central composite design (CCD), which is a response surface methodology (RSM) module in the Design-Expert ® software. Important parameters such as reaction time, H 2 O 2 and Fe 2+ ion concentrations, and pH were empirically determined and successfully optimized via RSM. Significant statistical quadratic polynomial for color and COD removal efficiency were obtained via regression analyses R 2 , (0.81 and 0.70) for color and COD, respectively. The highest results were 97.36% removal for color and 91.11% removal for COD at pH 3.5 and 30 min of reaction time. Numerical optimization based on desirable functions was employed; 92.1% of color and 85.1% of COD were removed efficiently at pH (3.0–5.0) with a final pH of 2.85 (after reaction settlement), 4.57 g/L H 2 O 2 and 1.88 g/L Fe 2+ ions concentration, respectively, and 30 min of reaction time at 120 rpm agitation rate. The result showed that the Fenton process, at an accurate level, may be used as an effective technology for the post treatment of POME before final discharge into a nearby water body.
TL;DR: In this paper, the authors reviewed the history and current status of Freeze Crystallization (FC) technologies for the treatment of Reverse Osmosis (RO) brines and highlighted future focus areas for research and development in the field of FC that aims at making this technology part of the mainstream suite of brine treatment technologies.
Abstract: In recent years, various Freeze Crystallization (FC) processes have been investigated and shown to have potential as an environmentally friendly and sustainable water treatment technology towards achieving a near zero waste by producing potable water and salts (in some instances pure salt(s)) from hyper-saline brines. This paper reviews the history and current status of FC technologies for the treatment of Reverse Osmosis (RO) brines. A number of water treatment examples and applications of FC are discussed. The review found that, although the outcomes from the FC research are promising, the adoption of this technology in mainstream desalination brine treatment has been insignificant despite the fact that FC could have niche applications in the treatment of brines generated from membrane processes such as RO. The review also found that a hybrid technology approach, such as an integrated RO-FC process, can provide the optimum treatment solution from both an equipment capital and operating cost perspective. Lastly, the paper highlights future focus areas for research and development in the field of FC that aims at making this technology part of the mainstream suite of brine treatment technologies.
TL;DR: In this article, the electrocoagulation (EC) process employed in the removal of phosphate from synthetic wastewater (SWW, 30mg/l) was optimized, followed by successful scale-up experiments.
Abstract: The electrocoagulation (EC) process employed in the removal of phosphate from synthetic wastewater (SWW, 30 mg/l) was optimized, followed by successful scale-up experiments. The optimum process conditions (96% phosphate removal) for laboratory-scale SSW were found to be: anode/cathode = Al/Fe (although Fe/Al performed similarly), initial pH = 5, current density = 100 A/m 2 , treatment time = 15 min, supporting electrolyte = 1.0 g/l NaCl and electrode gap = 7 mm. Real industrial phosphate-containing mining wastewater (MWW) and dairy wastewater (DWW) were also treated with EC, with high pollutant removal efficiencies (optimal phosphate removal of 79% and 93% in 30 min and 60 min, respectively) achieved over the wide initial pH range studied. Electricity consumption and operating costs values in optimum conditions were low for all wastewaters: 0.75 kWh/m 3 and 0.17 €/m 3 for SSW (laboratory scale), 2.11 kWh/m 3 and 0.28 €/m 3 for MWW, and 1.46 kWh/m 3 and 0.31 €/m 3 for DWW. To summarize, the feasibility of using EC in removing phosphate from the wastewater types studied was proven. Utilization of the resulting EC sludge – a potentially valuable phosphorus source in the future (especially in granulated bio ash-based fertilizer products) – was also studied and is discussed.
TL;DR: In this paper, the photocatalytic degradation of Monocrotophos (MCP) and chlorpyrifos (CPS) was carried out using prepared TiO 2 photocatalyst irradiated with 16 W UV light source.
Abstract: Monocrotophos (MCP) and chlorpyrifos (CPS) are most popular and broadly used organophosphorous pesticides owing to its low cost and high efficiency in controlling pests in agriculture. Presence of pesticides in aquatic environments causes serious problems to human beings and other organisms. Photocatalytic degradation has been proved to be a promising method for the treatment of water. In view of this, TiO 2 photocatalyst was prepared by sol–gel method and characterized by SEM with EDAX, XRD, BET and FTIR. The photocatalytic degradation of MCP and CPS was carried out using prepared TiO 2 photocatalyst irradiated with 16 W UV light source. The effect of various parameters, i.e., photocatalyst concentration, pesticide concentration and pH of the solution on the percentage of degradation of selected pesticides had been examined. The kinetic analysis of photodegradation of MCP and CPS under different initial concentration followed the Langmuir–Hinshelwood model. TiO 2 found to be an excellent photocatalyst for the degradation of MCP and CPS under UV light irradiation.
TL;DR: In this paper, the performance of the electrocoagulation of can manufacturing wastewater (CMW) by using aluminium plate electrodes was investigated in a batch mode operation to obtain optimum operating conditions with minimum operating cost.
Abstract: In this study, treatment of can manufacturing wastewater (CMW) by electrocoagulation (EC) process using aluminium plate electrodes was investigated in a batch mode operation to obtain optimum operating conditions with minimum operating cost. Effects of operating parameters such as current density, operating time and electrode connection modes (monopolar series (MP-S), monopolar parallel (MP-P) and bipolar series (BP-S)) on removal efficiencies of aluminium (125.1 mg/L), zirconium (81.2 mg/L), and phosphate ( PO 4 3 − − P , 32.1 mg/L), chemical oxygen demand (COD: 850 mg/L) and total organic carbon (TOC: 300 mg/L) from the CMW were evaluated. The results indicated that removal efficiencies of Al, Zr, and phosphate at the optimum conditions (20 A/m 2 , 40 min and MP-P electrode connection mode) were determined to be 99.41% for Al, 99.38% for Zr and 99.80% for phosphate, 72% for COD, and 37% for TOC in the wastewater, respectively. In addition, charge density, electrode and energy consumptions, amount of sludge and operating cost at the optimum operating conditions were calculated as 13.196 F/m 3 or 1270.59 C/L, 0.1432 kg/m 3 , 1.366 kWh/m 3 , 1.674 kg/m 3 and 0.366 €/m 3 . The results indicated that the EC process is very effective and efficient process for treatment of the CMW.
TL;DR: In this paper, a bi-functional dye containing azo chromophore has been attempted in the presence of potassium persulfate (KPS) as an initiator, and its conditions of degradation were optimized and its kinetics was studied.
Abstract: Degradation of C. I. Reactive Yellow (RY 145), a bi-functional dye containing azo chromophore has been attempted in the presence of potassium persulfate (KPS) as an initiator in the presence of microwave irradiation. The conditions of degradation were optimized and its kinetics was studied. Complete dye degradation was observed in 3600 and 280 s, respectively, using conventional and microwave heating at the original pH (5.8) of the dye solution with COD removal of 60 and 66.5%. Under optimized conditions, efficiency of H 2 O 2 was also compared for degrading the dye. Pseudo-first-order kinetics with higher kinetic rate constant (0.0165 × 10 2 s −1 ) and maximum energy efficiency (67.6%) was achieved through microwave assisted KPS system. Additional benefit of microwave approach was accrued by the extensive reduction in electrical energy consumption by 10638.32 kW h/m 3 . The effect of addition of SO 4 2− and CO 3 2− anions to the dye solution has indicated that the former enhances the degradation, whereas the latter reduces it. The temperature study using Arrhenius equation indicated decrease in the activation energy for the microwave system along with 2.6 times higher frequency factor than that for conventional heating. Thus, the microwave radiation assisted KPS system has been found to be the most cost effective and environmentally benign for the dye degradation process.
TL;DR: In this paper, the efficiency of removing pharmaceuticals (PCs) from model aqueous solutions and raw wastewater with ultrafiltration (UF), nanofiltration (NF), activated carbon adsorption (AC), biological methods (SBR), and oxidation with ClO 2 was investigated.
Abstract: Recently, there is an emergence of endocrine-disrupting compounds, pharmaceuticals, and personal care products (EDC/PPCPs) as important pollutants to remove from drinking water and reclaimed wastewater. In this work, the efficiency of removing pharmaceuticals (PCs) from model aqueous solutions and raw wastewater with ultrafiltration (UF), nanofiltration (NF), activated carbon adsorption (AC), biological methods (SBR) and oxidation with ClO 2 was investigated. Some treatments have also been used as combined processes: UF + NF, UF + AC, SBR + ClO 2 . Ibuprofen, Acetaminophen, Diclofenac, Sulfamethoxazole, Clonazepam, and Diazepam were selected as model compounds. In order to evaluate their removal, PC solutions were also considered at several operating conditions (pH, conductivity, concentration, and temperature), and optimal conditions were obtained. Experiments were performed at usual PC concentrations in wastewaters: 1000 ng/L for Ibuprofen and Acetaminophen, 300 ng/L for Diclofenac, Sulfamethoxazole, Clonazepam, and Diazepam. Separation was evaluated by liquid chromatography–mass spectroscopy. Results indicated that the removal efficiency depends on their Log K OW , which is intrinsically related to their hydrophobicity and then, to their adsorption onto the surface (UF, NF, and AC). Also, NF, AC, and combined processes (UF + NF, UF + AC) were the most suitable separation techniques to obtain high removal efficiencies for most of the PCs used, except for Acetaminophen (which showed great removal efficacy using SBR). UF presented low removal yields for all PCs tested. ClO 2 treatment was more effective at high concentration (50 mg ClO 2 /L). Furthermore, results also showed that there are significant differences on the performance of the processes applied and which treatment is the most effective for each PC analyzed.
TL;DR: In this paper, the preparation of zinc oxide nano particles (ZnO NPs) using a very simple, efficient precipitation method was described, and the photo-catalytic property of ZnO NP was studied using UV-vis spectroscopy for the degradation of methyl violet (MV) by exposing to sunlight.
Abstract: Synthesis of different shaped nano-particles using novel methodologies always attracts great importance in research. This report details with the preparation of zinc oxide nano particles (ZnO NPs) using a very simple, efficient precipitation method. ZnO NPs were obtained by the calcination of zinc oxalate powder precipitated from a reaction mixture containing zinc acetate and ammonium oxalate. As obtained ZnO NPs were characterized using field emission scanning electron microscopy (FESEM), X-Ray Diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), photo-luminescence spectroscopy, etc. The photo-catalytic property of ZnO NP was studied using UV–vis spectroscopy for the degradation of methyl violet (MV) by exposing to sunlight. Complete degradation of methyl violet was noticed on exposing the suspension containing sonicated ZnO NPs in an aqueous medium with MV in 60–80 min. Antibacterial studies of ZnO NPs were performed against bacterial strains such as Pseudomonas aeruginosa , Escherichia coli and Staphylococcus aureus . ZnO NPs exhibit high inhibition towards P. aeruginosa and E. coli ; however it shows minimum inhibition towards S. aureus . A difference of 0.461 a.u was observed in the mean of optical densities between P. aeruginosa and S. aureus . Statistical t -test was performed to find the significance of this difference and the results confirmed that this difference was due to the influence of the prepared ZnO NPs on the bacterial strains.
TL;DR: The feasibility of using vibratory ball milled South African bentonite clay for neutralization and attenuation of inorganic contaminants from acidic and metalliferous mine effluents has been evaluated.
Abstract: The feasibility of using vibratory ball milled South African bentonite clay for neutralization and attenuation of inorganic contaminants from acidic and metalliferous mine effluents has been evaluated. Treatment of acid mine drainage (AMD) with bentonite clay was done using batch laboratory assays. Parameters optimized included contact time, adsorbent dosage and adsorbate concentration. Ball milled bentonite clay was mixed with simulated AMD at specific solid: liquid (S/L) ratios and equilibrated on a table shaker. Contact of AMD with bentonite clay led to an increase in pH and a significant reduction in concentrations of metal species. At constant agitation time of 30 min, the pH increased with the increase in dosage of bentonite clay. Removal of Mn 2+ , Al 3+ , and Fe 3+ was greatest after 30 min of agitation. The adsorption affinity obeyed the sequence: SO 4 2− (221.8 mg g −1 ) > Mn (30.7 mg g −1 ) > Al (30.5 mg g −1 ) > Fe (30.2 mg g −1 ). The pH of reacted AMD ranged from ≈3 to 6. Bentonite clay showed high adsorption capacities for Al and Fe at concentration 50%. Adsorption kinetics revealed that the suitable kinetic model describing data was pseudo-second-order hence confirming chemisorption. Adsorption isotherms indicated that removal of metals fitted the Langmuir adsorption isotherm for Fe and sulphate and the Freundlich adsorption isotherm for Al and Mn, respectively. Ball-milled bentonite clay showed an excellent capacity in neutralizing acidity and lowering the levels of inorganic contaminants in acidic mine effluents.
TL;DR: In this article, an advanced reduction process (ARP) that combined sulfite (SO 3 2− ) as a reducing agent and UV as the activating method to remove bromate was applied.
Abstract: Bromate is a possible human carcinogen regulated in drinking water at a maximum contaminant level (MCL) of 10 μg/L. This research applied an advanced reduction process (ARP) that combined sulfite (SO 3 2− ) as a reducing agent and UV as the activating method to remove bromate. In addition to photolysis, this UV–sulfite ARP generates sulfite anion radicals (SO 3 − ) and aqueous electrons (e aq − ) that react with and reduce the target bromate. Results from batch experiments showed pseudo first-order removal of bromate with rate constants ( K obs ) varying from 0.015 to 2.11 min −1 . The effect of process variables like sulfite dose, pH and UV characteristics on the kinetics were studied. The reduction kinetics improved with increasing sulfite doses and UV intensities. Acidic pH resulted in decreased kinetics, with pH above 7, resulting in the highest observed rate constants. Two different UV wavelengths, 222 nm and 254 nm were used to activate sulfite in solution. Lower wavelength UV resulted in kinetics two orders of magnitude higher than UV at 254 nm. Quantum yields for this ARP were calculated to be in the range of 0.016–0.036 mol/Einstein. The principal reduction end products were bromide and sulfate, with recovery of bromide ranging from 80% to 90%. The overall results indicate a promising application potential for ARPs in the removal of disinfection byproducts in water.
TL;DR: In this paper, the mechanism of nitrate removal from aqueous solutions by electrochemical denitrification process (EDN) in an undivided electrolytic cell was investigated.
Abstract: This study is focused on the mechanism of nitrate removal from aqueous solutions by electrochemical denitrification process (EDN) in an undivided electrolytic cell. The sacrificial (Fe and Al) electrodes and Inert (graphite (Gr)) electrode are employed for evaluation of operational parameters, namely current density, electrolysis time and sodium chloride concentration. The experimental results reveal that nitrate-N removal efficiency of 92% for Al–Fe (anode-cathode) and 80% for Fe–Fe are achieved at a current density of 25 mAcm −2 and 180 min electrolysis time in 100 ppm of NaCl when the initial nitrate-N concentration is 100 ppm. However, during this process approximately 20 ppm of ammonia-N is also formed. Ammonia-N generated is significantly lower compared to the amount of nitrate-N removal. It can be attributed to the fact that nitrate ion can be removed by both electrocoagulation (EC) and electrochemical reduction (ER) processes simultaneously. Experiments using Al, Fe and Gr as cathodes as well as anodes indicate that the contribution of EC increases when dissolving anodes are used. Further confirmation of nitrate-N removal by EC pathway is obtained by quantitative estimation of nitrate present in the sludge. During EDN, pH of the solution also increases with ammonia generation.
TL;DR: Alginate-based composite bead (AB) was applied for the removal of Ni(II) ions from solutions in batch and fixed-bed systems, and the reuse feasibility of the spent adsorbent was investigated for binding azo dye as discussed by the authors.
Abstract: Alginate-based composite bead (AB) was applied for the removal of Ni(II) ions from solutions in batch and fixed-bed systems. The reuse feasibility of the spent adsorbent was investigated for binding azo dye. Elovich kinetic model and mean adsorption energy ( E ) (13.2 kJ mol −1 ) indicated that Ni(II) ions removal followed ion-exchange mechanism. 98.5% removal for Ni(II) was observed at the maximum column operation (viz. 2.0 mL/min flow rate, 100.0 mg/L influent concentration and 9.0 g dose). Artificial neural network (ANN) and central composite design (CCD) models were applied to elucidate the complex adsorption process, and the finding is consistent with the experimental data. Desorption efficiency (DE) was noted to be higher when HCl (DE = 92%) was used as desorbing agent compared to NaOH (DE = 6%) in the first cycle.
TL;DR: In this paper, the effect of inorganic ions (HCO − 3, Cl −, and SO 4 −2 ) on the adsorption process of agglomerates was investigated.
Abstract: Phosphate removal from water solution by using iron (Fe +3 ) oxide/hydroxide nanoparticles-based agglomerates (AggFe) suspension was investigated for efficiency and cost- effectiveness. The influence of inorganic ions (HCO − 3 , Cl − , and SO 4 −2 ) that are usually present in municipal and industrial wastewater on the adsorption process is reported here. The adsorption properties of the adsorbent were investigated in solutions containing different inorganic ions concentrations at different pH levels. A strong concentration effect of the used AggFe, HCO 3 and pH level of the purified water solution on removal efficiency was shown. It was found that phosphate adsorption onto the AggFe suspension may be described by pseudo-second order reaction kinetics and the Langmuir isotherm model. The rate-limiting step of phosphate adsorption onto AggFe suspension may be described by intra-particle diffusion of ions onto and within the adsorbent. The unique adsorption properties of synthesized AggFe adsorbent are demonstrated. This technique achieved a residual phosphate concentration of less than 0.1 ppm as PO 4 also at high concentration (500 ppm) of the competitive HCO 3 ion, which is acceptable by water quality regulations. The phosphate adsorption capacity on the AggFe at pH level of solution at pH 7.5 and an equilibrium concentration of 0.1 ppm as P was compared with reported results and are about 1.5 times higher than these values for granulated ferric hydroxide (fraction − and SO 4 −2 ions had no significant effect on the phosphate adsorption kinetics.
TL;DR: In this article, a series of cellulose ampholytes with a degree of cationic substitution between 0.26 and 1.08 were prepared from sodium CMC, by cationization with 2,3-epoxypropyltrimethylammonium chloride.
Abstract: Cellulose ampholytes (CAms) prepared from biocompatible and biodegradable carboxymethyl cellulose (CMC) could represent an environmentally friendly alternative for the efficient removal of anionic dyes from water effluents. In order to evaluate their potential for this application, a series of CAms with a degree of cationic substitution (DS C ) between 0.26 and 1.08 were prepared from sodium CMC, by cationization with 2,3-epoxypropyltrimethylammonium chloride. The flocculation ability of the CAms against the anionic dye Acid Red 13 (AR13) was found to strongly depend on the DS C as well as on the pH of the solution. The highest flocculation ability was observed at lower pH and higher DS C : a color removal as high as 99% was achieved at pH 3 using a CAm with the highest DS C . The kinetic analysis revealed that the flocculation of AR13 can be accurately fitted by a pseudo-second order kinetic model, which thus allows to predict the flocculation behavior of CAms under these conditions. Besides AR13, the ampholytes also showed high flocculation ability against Acid Red 9 and Acid Blue 13. The flocculation behavior of these anionic dyes followed the Langmuir adsorption isotherm model, which revealed the maximum flocculation capacity of a CAm for these dyes. Moreover, the analysis of the flocculation isotherm data and the SEM observation of the formed flocs allowed to determine the flocculation mechanism.
TL;DR: In this paper, the results from an experimental study of ultrasonically assisted ultrafiltration, varying ultrasonic frequencies, are presented, and the performances of sonochemical oxidation, membrane ultra-filtration and their combination were evaluated on wastewater samples.
Abstract: Water scarcity is an increasing world-wide concern due to the rapid growth of population along with industrialization and urbanization. Membrane ultrafiltration represents a promising and sustainable technology for handling this problem through water reuse. However, fouling is still a significant drawback that limits the expansion of membrane filtration use. Recent studies have shown that ultrasound provides an alternative technology for membrane fouling control able to enhance the effluent water quality in an environmentally benign manner. Nevertheless, the ultrasonic parameters affecting the efficiency of the US-enhanced cleaning are not completely well known. In this work results from an experimental study of ultrasonically assisted ultrafiltration, varying ultrasonic frequencies, are presented. The performances of sonochemical oxidation, membrane ultrafiltration and their combination were evaluated on wastewater samples. Results show that ultrasonic field can drastically reduce membrane fouling. It was found that lower frequency (35 kHz) slows down the fouling formation, but, on the other hand, higher frequency (130 kHz) improves the organic matter removal.
TL;DR: In this paper, the ozone assisted electrocoagulation was applied to acid brown 214, a typical triazo acid dye, in a lab-scale rectangular air-lift reactor, where ozone gas had no influence on dielectric constant.
Abstract: Decolorization of synthetic wastewater containing Acid Brown 214, a typical triazo acid dye, was carried out by ozone assisted electrocoagulation as an advanced oxidation process. Ozonation and electrocogulation were performed simultaneously in the riser and downcomer sections of a lab-scale rectangular airlift reactor, respectively, where ozonated gas had no influence on dielectric constant. A good mixing was achieved with the liquid circulation induced by gaseous ozone, without the need of mechanical mixing. Taguchi experimental design method with orthogonal arrays L27 and the “larger is better response” category were applied to determine optimum conditions for dye removal. The operating variables considered were the initial pH, initial dye concentration, salt concentration, current density, superficial gas velocity and decolorization period with three levels. Under optimum conditions, the synergistic effect of the combined process reaching complete decolorization in 30 min with energy consumption 7.4 kWh/kg dye removed. Results indicated that combination process in innovative configuration of single airlift reactor is cost effective as compared with that obtained individually in separate conventional reactors.
TL;DR: The results showed that chitosan was generally better than the other investigated polymers in affecting the removal of Cd (29%), Ni (27%), Mn (31%), and Pb (29%).
Abstract: Dissolved air flotation (DAF) process has been widely used for many applications including waste water treatment. For the purpose of heavy-metal removal, this study will implement several commercial polymers as collectors in DAF process. The investigated polymers are polyvinyl alcohol, polyethylene glycol, and chitosan which will be used as separation-enhancing agents in the air flotation process. On the other hand, the studied heavy metals are zinc chloride, lead(II) nitrate, manganese(II) chloride, nickel chloride, and cadmium chloride. Different parameters have been studied in this work such as the concentration and types of collectors, modification of polyvinyl alcohol, and the type and concentration of the heavy metals. The results showed that chitosan was generally better than the other investigated polymers in affecting the removal of Cd (29%), Ni (27%), Mn (31%), and Pb (29%). The removal of Zn was not consistently high for any type of polymers, although it was less with chitosan. Polyvinyl alcohol was modified by carboxylation and the modified polymers were found to be more effective at removing the smaller metals such as Ni (30%), and Zn (28%), and less effective at removing the larger metals Cd (24%) and Pb (29%) at heavy concentration of 250 ppm.
TL;DR: In this paper, the authors have shown that cavitation in the presence of additives can be effectively used for complete removal of dichlorvos pesticide at pilot scale operation at a very high level of detail.
Abstract: Degradation of dichlorvos pesticide has been investigated in an ultrasonic bath having operating power of 150 W and operating frequency of 36 kHz with a capacity of 7 L. All the experiments have been performed using 20 mg/L solution of commercially available dichlorvos at an operating pH of 3 under ambient conditions. Different combined treatment processes such as ultrasound (US)/TiO 2 , solar/TiO 2 , US/solar/TiO 2 , US/H 2 O 2 , US/Fenton and US/ozone have been applied with an objective of achieving effective and complete degradation of dichlorvos. The removal of dichlorvos was found to be significant in the case of TiO 2 /solar (78.42%) and US/Fenton (81.19%) in 2 h treatment as compared to only ultrasound (6.4%) or only TiO 2 (3%) which is a clear indication of the efficacy of combined treatment processes. Complete degradation of dichlorvos was obtained by using combination of ozone and ultrasound. TOC analysis at optimum conditions was also performed to quantify the extent of mineralization and it has been observed that a maximum of 93% TOC reduction is obtained in the case of combination of ozone and ultrasound. Integral method of analysis was followed and it has been observed that pseudo-first order kinetics explains the degradation reaction very well. The present work has conclusively established that cavitation in the presence of additives can be effectively used for complete removal of dichlorvos pesticide at pilot scale operation.