Use of Algae for Removing Heavy Metal Ions From Wastewater: Progress and Prospects
Laboratory of Algal Biology, Department of Botany, Banaras Hindu University, Varanasi, India. Critical Reviews in Biotechnology
(Impact Factor: 7.18).
10/2008; 25(3):113-52. DOI: 10.1080/07388550500248571
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.
Available from: Mousumi saha podder
- "Precipitation which can either be independent or dependent onto the cellular metabolism may also simultaneously happen. After studying a huge level of various literatures, Mehta and Gaur  have decided that carboxyl groups of cell wall polysaccharides play a major character in biosorption of heavy metal by cyanobacteria and algae. Other functional groups such as amino and sulfonates also play a comparatively minor character in metal biosorption. "
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ABSTRACT: In the present study, a thorough investigation has been done on the removal efficiency of both As(III) and As (V) from synthetic wastewater by phycoremediation of Botryococcus braunii algal biomass. Artificial neural networks (ANNs) are practised for predicting % phycoremediation efficiency of both As(III) and As(V) ions. The influence of several parameters for example initial pH, inoculum size, contact time and initial arsenic concentration (either As(III) or As(V)) was examined systematically. The maximum phycoremediation of As(III) and As(V) was found to be 85.22% and 88.15% at pH9.0, equilibrium time of 144h by using algal inoculum size of 10% (v/v) and initial arsenic concentration of 50mg/L. The data acquired from laboratory scale experimental set up was utilized for training a three-layer feed-forward back propagation (BP) with Levenberg-Marquardt (LM) training algorithm having 4:5:1 architecture. A comparison between the experimental data and model outputs provided a high correlation coefficient (R(2)all_ANN equal to 0.9998) and exhibited that the model was capable for predicting the phycoremediation of both As(III) and As(V) from wastewater. The network topology was optimized by changing number of neurons in hidden layers. ANNs are efficient to model and simulate highly non-liner multivariable relationships. Absolute error and Standard deviation (SD) with respect to experimental output were calculated for ANN model outputs. The comparison of phycoremediation efficiencies of both As(III) and As(V) between experimental results and ANN model outputs exhibited that ANN model can determine the behaviour of As(III) and As(V) elimination process under various circumstances.
- "The trends in HM uptake vary greatly among different algae and generally observed in order of (green algae) Chlorophyta > Phaeophyta > (red algae) Rhodophyta (Al-Shwafi and Rushdi, 2008). The nonliving biomass of algae sorb more metals than living algae (Mehta and Gaur, 2005). Pawlik-Skowronska (2001) discovered that Stigeoclonium sp. "
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ABSTRACT: The green macroalgae present in freshwater ecosystems have attracted a great attention of the world scientists for removal of heavy metals from wastewater. In this mesocosm study, the uptake rates of heavy metals such as cadmium (Cd), nickel (Ni), chromium (Cr) and lead (Pb) by Oedogonium westi (O.westti) were measured. The equilibrium adsorption capabilities of O. westti were different for Cd, Ni, Cr and Pb (0.974, 0.418, 0.620 and 0.261 mgg(-1), respectively) at 18°C and pH 5.0. Furthermore, the removal efficiencies for Cd, Cr, Ni and Pb were observed from 55-95%, 61-93%, 59-89% and 61-96%, respectively. The highest removal efficiency was observed for Cd and Cr from aqueous solution at acidic pH and low initial metal concentrations. However, the removal efficiencies of Ni and Pb were higher at high pH and high concentrations of metals in aqueous solution. The results summarized that O. westti is a suitable candidate for removal of selected toxic heavy metals from the aqueous solutions.
Available from: Daniel J. Lane
- "The algae can be used to remediate the ADW in bioremediation ponds by sequestering TEs dissolved in the water via a two-phase process . The first phase involves passive adsorption of the TE onto cell surfaces and the second phase involves transport of the TE across the cell wall and into the cytoplasm , where it can be stored in a non-toxic form . The produced algae is harvested, dried and then used as a feedstock for thermal conversion (i.e. "
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ABSTRACT: The work presented here assesses the potential for the mobilisation of 11 trace elements (As, Be, Co, Cu, Mn, Ni, Pb, Sb, Se, V, Zn) during the thermal conversion of micro- and macroalgae that were cultivated in ash dam water. The volatility of the trace elements was quantified by mass balances based on elemental analyses of char and ash residues. The residues were prepared in a laboratory-scale fixed-bed reactor at a range of different temperatures (500 - 1100 C) and gas atmospheres (N 2 , 2% O 2 and CO 2) to simulate pyrolysis, combustion and gasification processes. The results showed high volatilities for Se (~79 - 97%) and As (~51 - 79%) below 500 C. Zn, Pb and Sb were mainly volatilised above 700 C. The different gas atmospheres had little influence on the volatility of these elements, which increased sharply to more than 90% with increasing temperature from 700 to 1100 C. Volatilities for V, Mn, Cu, Co, Ni and Be were relatively minor over the full range of investigated operating conditions. Samples of each alga and their thermal conversion residues were subject to batch leaching in water. All of the tested trace elements, except for Pb and Be, were partially leached from the algae. Vanadium was up to 4 - 5 times more leachable in the combustion residues than in the algae. The other trace elements were generally less leachable following thermal conversion. The trace elements were more stable in residues prepared under pyrolysis and gasification conditions than in residues prepared under combustion conditions at the same temperature.
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