Use of algae for removing heavy metal ions from wastewater: progress and prospects.
ABSTRACT Many algae have immense capability to sorb metals, and there is considerable potential for using them to treat wastewaters. Metal sorption involves binding on the cell surface and to intracellular ligands. The adsorbed metal is several times greater than intracellular metal. Carboxyl group is most important for metal binding. Concentration of metal and biomass in solution, pH, temperature, cations, anions and metabolic stage of the organism affect metal sorption. Algae can effectively remove metals from multi-metal solutions. Dead cells sorb more metal than live cells. Various pretreatments enhance metal sorption capacity of algae. CaCl2 pretreatment is the most suitable and economic method for activation of algal biomass. Algal periphyton has great potential for removing metals from wastewaters. An immobilized or granulated biomass-filled column can be used for several sorption/desorption cycles with unaltered or slightly decreased metal removal. Langmuir and Freundlich models, commonly used for fitting sorption data, cannot precisely describe metal sorption since they ignore the effect of pH, biomass concentration, etc. For commercial application of algal technology for metal removal from wastewaters, emphasis should be given to: (i) selection of strains with high metal sorption capacity, (ii) adequate understanding of sorption mechanisms, (iii) development of low-cost methods for cell immobilization, (iv) development of better models for predicting metal sorption, (v) genetic manipulation of algae for increased number of surface groups or over expression of metal binding proteins, and (vi) economic feasibility.
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ABSTRACT: The aim of this study was to determine the growth and the bioremoval capacity of the green microalga, Botryococcus sp. grown in industrial wastewater contaminated with heavy metals. The freshwater green microalga, Botryococcus sp. was cultured in different concentrations of wastewater (25%, 50% and 100%) with an initial cell concentration of 1000 cells/ml for a period of 12 days. Bold basal medium and sterile distilled water were used as positive and negative control, respectively. The Botryococcus sp. grown in Bold's basal medium showed the highest (P<0.05) average growth rate (7.8 × 106 cells/ml) after a period of 12 days, whereas, the lowest (P<0.05) growth was observed in 50% concentration of wastewater (4.8 × 104 cells/ml). Similar results were obtained for the specific growth rate (µ/day) with an average of 1.93µ/day and 1.22µ/day for the positive control and the 50% concentration respectively. Highest reduction of heavy metals was achieved for chromium which is equivalent to 94%, followed by copper (45%), arsenic (9%) and cadmium (2%). The results of this study suggest the potential of Botryococcus sp. as bioremediator of wastewater contaminated with heavy metals.Journal of Science and Technology 12/2014; 6(2):29-40.
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ABSTRACT: A bead-shaped biosorbent for removal of Cr(VI) from industrial waste waters/aqueous media was fabricated using water soluble Spirulina platensis extract (SPE). The addition of LiCl to DMSO affected the solubility of SPE, and 1 M LiCl/DMSO was the optimal solvent system for the preparation of SPE beads. The shape of the SPE bead was determined by the concentration of SPE, and the type of coagulant affected the mechanical properties of the bead. The optimum pH for the Cr(VI) adsorption was 2.0. The maximum adsorption capacity of the SPE beads was 41.12 mg/g at pH 2.0, and the adsorption behavior of Cr(VI) on the SPE beads followed the Brunauer–Emmett–Teller (BET) isotherm. The results indicated that 0.1 M NaOH was the most effective desorption agent. The successive recycling of the adsorption–desorption process was stable for more than five cycles, and the recycling efficiency was 70%.Algal Research 01/2015; 7. · 4.10 Impact Factor
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ABSTRACT: Biosorption of Pb and Cd by using free living, immobilized living and non—viable forms of Nostocmuscorum was studied as a function of pH (3—8), contact time (5—240 min) and metal concentration (10—100 &mgr;g ml—1), to find out the most efficient physiological formfor metal removal. Results revealed that optimum conditions for biosorption of both the metals by different states of biosorbentwere almost same (contact time— 30 min, metal concentration— 100 &mgr;g ml—1 and pH— 5.1 and 6, for Pb and Cd, respectively) however, the immobilized biomass of N. muscorum was found to be more suitable for the development of an efficient biosorbent as evident from theqmax(1000 mg g—1protein) and Kf (0.08 mg g—1protein) values obtained from the Langmuir and Freundlich isotherms. A pseudo second order kinetics was found more suitable for describing the nature of biosorption of both the metals by all the three forms of N. muscorum. An analysis of correlation revealed that as the metal concentration increases, the removal of Pb and Cd by N. muscorum also increases significantly. The regression analysis showed that the rate of removal of Pb by free living and dead biomass was 1.89 and 1.58 times higher than the rate of removal of Cd by respective biomass. In contrast, the rate of removal of Cd by immobilized biomass was 1.46 times higher than that of Pb.Cellular and molecular biology (Noisy-le-Grand, France) 01/2014; 60(5):110-8. · 1.46 Impact Factor