TY - JOUR
T1 - Effects of anion species and concentration on the removal of Cr(VI) by a microalgal isolate, Chlorella miniata
AU - Han, Xu
AU - Wong, Yuk Shan
AU - Wong, Ming Hung
AU - Tam, Nora Fung Yee
N1 - Funding Information:
The research work was supported by the Areas of Excellence Scheme established under the University Grants Committee of the HKSAR (Project No. AoE/P-04/2004). The funding support of the Research Centre for Coastal Pollution and Conservation, City University of Hong Kong, was also acknowledged.
PY - 2008/10/30
Y1 - 2008/10/30
N2 - The presence of nitrate, chloride and sulfate anions on the removal of Cr(VI) by Chlorella miniata was investigated. Results of kinetic studies indicated that the equilibrium time in each anion system increased with increases of the initial salt concentration, and the inhibitory order was NO3- > Cl- > SO42- for Cr(VI) removal and was SO42- > Cl- ≈ NO3- for the biosorption of the bioreduced Cr(III). The inhibitory effect caused by different anions was attributed to biosorption mechanism and metal speciation. Since both biosorption and bioreduction were involved in Cr(VI) removal, the presence of anions could compete with Cr(VI) for the adsorption sites, and the affinity of anions to the algal biomass followed the order of NO3- > Cl- > SO42-, which was consistent with their inhibitory order on Cr(VI) removal. Speciation results also indicated that the formation of CrO3SO42- in the sulfate system made it easier to be adsorbed on the biomass than HCrO4-. The biosorption-bioreduction model further suggested that the bioreduction rate constant k decreased with increases of anion concentrations ranging from 0 to 0.5 M, and followed the order of SO42- > Cl- > NO3-. The biosorption constant b also decreased with anion concentrations in the range of 0-0.2 M, suggesting that this parameter was more sensitive to anion effects than the k values. The higher b values in the sulfate than in the nitrate and chloride systems indicated that Cr(VI) in the sulfate system was more easily adsorbed on the algal biomass. These findings demonstrated that the presence of anions significantly affected the removal of Cr(VI) by C. miniata. Since chloride, nitrate and sulfate ions are commonly found in industrial wastewater, it may be necessary to eliminate these ions prior to chromium removal.
AB - The presence of nitrate, chloride and sulfate anions on the removal of Cr(VI) by Chlorella miniata was investigated. Results of kinetic studies indicated that the equilibrium time in each anion system increased with increases of the initial salt concentration, and the inhibitory order was NO3- > Cl- > SO42- for Cr(VI) removal and was SO42- > Cl- ≈ NO3- for the biosorption of the bioreduced Cr(III). The inhibitory effect caused by different anions was attributed to biosorption mechanism and metal speciation. Since both biosorption and bioreduction were involved in Cr(VI) removal, the presence of anions could compete with Cr(VI) for the adsorption sites, and the affinity of anions to the algal biomass followed the order of NO3- > Cl- > SO42-, which was consistent with their inhibitory order on Cr(VI) removal. Speciation results also indicated that the formation of CrO3SO42- in the sulfate system made it easier to be adsorbed on the biomass than HCrO4-. The biosorption-bioreduction model further suggested that the bioreduction rate constant k decreased with increases of anion concentrations ranging from 0 to 0.5 M, and followed the order of SO42- > Cl- > NO3-. The biosorption constant b also decreased with anion concentrations in the range of 0-0.2 M, suggesting that this parameter was more sensitive to anion effects than the k values. The higher b values in the sulfate than in the nitrate and chloride systems indicated that Cr(VI) in the sulfate system was more easily adsorbed on the algal biomass. These findings demonstrated that the presence of anions significantly affected the removal of Cr(VI) by C. miniata. Since chloride, nitrate and sulfate ions are commonly found in industrial wastewater, it may be necessary to eliminate these ions prior to chromium removal.
KW - Algae
KW - Anion
KW - Bioreduction
KW - Biosorption
KW - Chromium
UR - http://www.scopus.com/inward/record.url?scp=50549087577&partnerID=8YFLogxK
U2 - 10.1016/j.jhazmat.2008.02.024
DO - 10.1016/j.jhazmat.2008.02.024
M3 - Article
C2 - 18367329
AN - SCOPUS:50549087577
SN - 0304-3894
VL - 158
SP - 615
EP - 620
JO - Journal of Hazardous Materials
JF - Journal of Hazardous Materials
IS - 2-3
ER -