Recent advances in heavy metal removal by chitosan based adsorbents.

Exopolysaccharides from probiotic bacteria and their health potential.

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.

Technological trends in heavy metals removal from industrial wastewater: A review

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.

Biosorption and removal of toxic heavy metals by metal tolerating bacteria for bioremediation of metal contamination: A comprehensive review

Current advancement and future prospect of biosorbents for bioremediation

Fresh water accounts for 3% of water resources on the Earth. Human and industrial activities produce and discharge wastes containing heavy metals into the water resources making them unavailable and threatening human health and the ecosystem. Conventional methods for the removal of metal ions such as chemical precipitation and membrane filtration are extremely expensive when treating large amounts of water, inefficient at low concentrations of metal (incomplete metal removal) and generate large quantities of sludge and other toxic products that require careful disposal. Biosorption and bioaccumulation are ecofriendly alternatives. These alternative methods have advantages over conventional methods. Abundant natural materials like microbial biomass, agro-wastes, and industrial byproducts have been suggested as potential biosorbents for heavy metal removal due to the presence of metal-binding functional groups. Biosorption is influenced by various process parameters such as pH, temperature, initial concentration of the metal ions, biosorbent dose, and speed of agitation. Also, the biomass can be modified by physical and chemical treatment before use. The process can be made economical by regenerating and reusing the biosorbent after removing the heavy metals. Various bioreactors can be used in biosorption for the removal of metal ions from large volumes of water or effluents. The recent developments and the future scope for biosorption as a wastewater treatment option are discussed.

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Application of Biosorption for Removal of Heavy Metals from Wastewater

An exopolysaccharide (EPS) producing strain CC30 was isolated from raw milk and identified as Streptococcus thermophilus with morphological and 16S sequencing analysis. The strain was shown to produce 1.95 g/L of EPS when grown in skim milk lactose medium at 30°C by increasing the viscosity of the medium. The EPS was isolated and purified, and it was shown to consist of glucose and galactose in 1 : 1 ratio, with molecular weights ranging from 58 to 180 kDa. FTIR spectroscopy indicated the EPS to have amide, hydroxyl, and carboxyl groups. Under Atomic Force Microscopy, EPS showed spike-like lumps of EPS. Scanning Electron Microscopy (SEM) studies showed that it had irregular lumps with a coarse surface. The EPS displayed pseudoplastic nature. Thermogravimetric analysis (TGA) reported a degradation temperature of 110.84°C. The purified EPS exhibited reducing activity, hydrogen peroxide radical scavenging activity, and emulsification activity. The results of the present study indicated that EPS producing Streptococcus thermophilus could serve as a promising candidate for further exploitation in food industry.

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Characterization of Exopolysaccharide Produced by Streptococcus thermophilus CC30.

Various microbial biomasses have been employed as biosorbents. Bacterial biomass has added advantages because of easy in production at a low cost. The study investigated the biosorption of iron from aqueous solutions by Bacillus subtilis. An optimum biosorption capacity of 7.25 mg of the metal per gram of the biosorbent was obtained by the Inductive Coupled Plasma Optical Emission Spectroscopy (ICP-OES) under the experimental conditions of initial metal concentration of 100 mg/l, pH 4.5, and biomass dose of 1 g/l at 30°C for 24 hrs. The data showed the best fit with the Freundlich isotherm model while following pseudo-first-order kinetics. Scanning Electron Microscope (SEM) and Energy Dispersive X-ray (EDX) analysis confirmed iron biosorption as precipitates on the bacterial surface, and as a peak in the EDX spectrum. The functional hydroxyl, carboxyl, and amino groups that are involved in biosorption were revealed by the Fourier Transform Infrared spectroscopy (FTIR). The amorphous nature of the biosorbent for biosorption was indicated by the X-ray Diffraction (XRD) analysis. The biomass of B. subtilis exhibited a point zero charge (pHpzc) at 2.0. Various microbial biomasses have been employed as biosorbents. Bacterial biomass has added advantages because of easy in production at a low cost. The study investigated the biosorption of iron from aqueous solutions by Bacillus subtilis. An optimum biosorption capacity of 7.25 mg of the metal per gram of the biosorbent was obtained by the Inductive Coupled Plasma Optical Emission Spectroscopy (ICP-OES) under the experimental conditions of initial metal concentration of 100 mg/l, pH 4.5, and biomass dose of 1 g/l at 30°C for 24 hrs. The data showed the best fit with the Freundlich isotherm model while following pseudo-first-order kinetics. Scanning Electron Microscope (SEM) and Energy Dispersive X-ray (EDX) analysis confirmed iron biosorption as precipitates on the bacterial surface, and as a peak in the EDX spectrum. The functional hydroxyl, carboxyl, and amino groups that are involved in biosorption were revealed by the Fourier Transform Infrared spectroscopy (FTIR). The amorphous nature of the biosorbent for biosorption was indicated by the X-ray Diffraction (XRD) analysis. The biomass of B. subtilis exhibited a point zero charge (pHpzc) at 2.0.

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Structural Changes of Bacillus subtilis Biomass on Biosorption of Iron (II) from Aqueous Solutions: Isotherm and Kinetic Studies

The biomass of Lactobacillus fermentum was used as biosorbent for the biosorption of iron (II) ions from aqueous solutions. Batch biosorption experiments were carried out with varying initial concentrations of Fe(II) ions, biosorbent dose, pH and time intervals. From the inductive coupled plasma optical emission spectroscopy (ICP-OES) result, the maximum biosorption capacity per gram of the biosorbent was found to be 7.25 mg for Fe(II) ions at a biomass concentration of 1 g/L at pH 4.5, contact time of 24 hrs, and an initial Fe(II) ion concentration of 100 mg/L. The equilibrium data was found to fit better with the Freundlich isotherm and pseudo second order kinetic model. The surface morphology and elemental composition of the biomass was characterized by using a scanning electron microscope (SEM) equipped with EDX, which confirmed that the iron was biosorbed, evident as bulky particles on the surface of the biomass, and as a peak for Fe in the EDX spectrum. Fourier transform infrared spectroscopy (FTIR) indicated that hydroxyl, amino and carboxyl functional groups are mainly involved in the biosorption of iron ions. Point zero charge of the biosorbent was found to be 3.0. X-ray diffraction (XRD) analysis revealed the amorphous nature of the biomass. The biomass of Lb. fermentum can be used as an efficacious and inexpensive biosorbent for the removal of Fe (II) ions from contaminated

http://www.pjoes.com/pdf-103443-47156?filename=Biosorption of Iron _II_.pdf

Biosorption of Iron (II) by Lactobacillus fermentum from Aqueous Solutions

The current research is the first to focus on the study of biosorption potential of a novel bacterium Chelatococcus sp. to biosorb metal ions from aqueous samples. An isolated bacterial strain Pb1S1 was characterized for biosorption efficiency for Pb (II) ions. Based on microscopic and phylogenetic analysis, the isolated strain was identified as belonging to the genus Chelatococcus. At optimized experimental conditions, the maximum biosorption efficiency for Pb (II) ion was 86.44% at metal concentration of 100 µg/mL, pH 6.5, biomass dose of 60 mg/L, temperature of 35 °C and incubation of 18 h at 60 rpm. Analysis of biomass by scanning electron microscope and energy-dispersive X-ray shows the morphological changes and alteration in elemental composition attained due to biosorption. Functional groups of biomass involved in biosorption were identified by Fourier transform infrared spectroscopy. The experimental data were fitted well with Langmuir isotherm, while kinetic data showed the best fit with pseudo-first-order kinetic model. At optimized biosorption conditions, Chelatococcus biomass showed good capability for biosorption of Pb (II) from contaminated water sources. Hence, the study interprets that Chelatococcus biomass can be considered as robust, inexpensive and efficient novel biosorbent for the removal of metals.

Isolation, identification, biosorption optimization, characterization, isotherm, kinetic and application of novel bacterium Chelatococcus sp. biomass for removal of Pb (II) ions from aqueous solutions

Sudhamani Muddada

Papers

Application of Biosorption for Removal of Heavy Metals from Wastewater

Characterization of Exopolysaccharide Produced by Streptococcus thermophilus CC30.

Structural Changes of Bacillus subtilis Biomass on Biosorption of Iron (II) from Aqueous Solutions: Isotherm and Kinetic Studies

Biosorption of Iron (II) by Lactobacillus fermentum from Aqueous Solutions

Isolation, identification, biosorption optimization, characterization, isotherm, kinetic and application of novel bacterium Chelatococcus sp. biomass for removal of Pb (II) ions from aqueous solutions