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Behaviors of Biosorption and Desorption of Anatimony by Naturally Occuring Cyanobactrria Microcystis

Author: WuShan
Tutor: WuFengChang
School: Chinese Academy of Environmental Science
Course: Environmental Science
Keywords: Antimony Cyanobacteria Biosorption Oxidation Complexation
CLC: X173
Type: Master's thesis
Year: 2012
Downloads: 94
Quote: 0
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Abstract


Antimony (Sb) which belongs to the group VA in the periodic table is a naturally-occurring metalloid element. Antimony is ubiquitously present in the environment and has been considered as a global contaminant. Antimony is of significant environmental concern with increasing knowledge on its high toxicity and the contamination in waters and soils. At present, the studies regarding the interaction mechanism of metal and algae are still in the initial stage. Morover, there is less information available on metalloid (such as antimony) biosorption by non-living freshwater algae.In this study, biosorption characteristics of Sb(Ⅴ) and Sb(Ⅲ) by naturally occurring cyanobacteria Microcystis were investigated using a batch equilibration method under various environmental parameters to evaluate the potential of Microcystis to remove Sb from wastewater. This study can provide theoretical basis for the removal of Sb in waste water pollution by Microcystis and for the protection of the water resources to realize the resource utilization of the eutrophication algae.The results indicated that the biosorption efficiency of Sb (Ⅴ) by the biomass was enhanced greatly under the treatment of0.1M HC1. The biosorption capacity of Sb(Ⅴ) on the original and the HCl-treated biomass achieved equilibrium within1h. The biosorption of Sb(Ⅴ) by the original and the HCl-treated biomass decreased with increasing pH. The biosorption processes of Sb(Ⅴ) on the original and the HCl-treated biomass obeyed the Freundlich isotherm model. The occurrence of Cl-, NO3-, SO42-and PO43-significantly inhibited the biosorption of Sb(Ⅴ) by HCl-treated biomass.The results of zeta potential and ATR-IR suggest that the binding of Sb(OH)6-on the biomass occurred through electrostatic attraction and complexation. The ATR-IR spectra further confirmed the involvement of amino, carboxyl and hydroxyl groups in the removal of Sb(OH)6-. SEM-EDXA analyses indicate that the biosorption was highly heterogeneous.The biosorption process of Sb(Ⅲ) by Microcystis followed the pseudo second-order rate kinetics and equilibrium was reached in60min. The maximum biosorption capacity was determined to be4.88mg/g at pH4.0, according to the Langmuir model. There were increasingly inhibitive effects of ionic strengths of NaCl on the biosorption capacities. The ATR-IR spectra analysis suggested the involvement of carboxyl, hydroxyl and amino groups in the binding of Sb(III) through surface complexation reaction.The biosorption efficiency of Sb(V)(38%) by the biomass is significantly lower than that of Sb(III)(nearly90%). This might be attributed to the difference of solution chemistry between the anionic Sb(OH)"6and neutral Sb(OH)3. The biosorption mechanisms of Sb(V) are similar to that of Sb(Ⅲ). The carboxyl and hydroxyl groups on the surface of cell wall of cyanobacteria formed inner-shpere complexes with both Sb(OH)"6and Sb(OH)3.The reusability experiments demonstrated a desirable regeneration performance for the biomass in the repetitive biosorption-desorption cycles. The high desorption efficiency for Sb(V and III) by the original biomass was achieved using4mol/L HCl. As for the acid-treated biomass, the high desorption efficiency was obtained under the treatment of6mol/L HCl. The regeneration studies show that the biomass could be used for a minimum of five repetitive cycles for the removal of Sb(V and III).In our study, the results of speciation analysis confirmed the concurrence of oxidative reaction of Sb(III) with the biosorption process. The chemical conversion of Sb(III) into Sb(V) was pH and time dependent. The oxidative agents and mechanisms for Sb(III) during the biosorption process will be investigated and elucidated in the further studies.This study suggests that Microcystis biomass can be considered as an potential alternative biosorbent to immobilize Sb(V) and Sb(III) from wastewater, in view of the good performance in the biosorption and regeneration processes and economical advantages.

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