Efficient Removal of Lead from Water Using Stabilized Iron Sulfide Nanoparticles: Effectiveness and Effects of Stabilizer
Fully stabilized FeS nanoparticles were prepared with water-soluble carboxymethyl cellulose (CMC) as a stabilizer, and investigated for adsorption of lead (Pb2+) ions from simulated drinking water. The optimum particle stabilization was achieved using 0.0025 wt.% of CMC for 50 mg/L FeS (i.e., CMC-to-FeS molar ratio of 0.0005). The particle stabilization technique increased lead removal from 78.1% to 90.3%. However, further increasing the CMC-to-FeS molar ratio to 0.0025 diminished the removal. Rapid adsorption kinetics of Pb by CMC-FeS was observed with an equilibrium time of 240 min. The kinetic data was adequately fitted by a pseudo-second-order kinetic model. The adsorption isotherm showed a sigmoidal S-shape due to complexation of Pb with soluble CMC molecules, and the Sigmoidal isotherm model well fitted the adsorption isotherm data with a maximum monolayer adsorption capacity of 77.0 mg/g. FTIR and XRD analyses indicated that both surface complexation and chemical precipitation (in the form of PbS) were the dominant adsorption mechanisms. Pb uptake was enhanced with increasing CMC-FeS dosage from 10 to 125 mg/L and increasing pH from 4.5 to 8.5. The material can perform well under typical concentrations of a model humic acid (HA) and salts. Yet, unusually high concentrations of HA or hardness ions may exerted elevated inhibitive effect. The findings indicated that CMC-stabilized FeS nanoparticles are promising for effective immobilization of lead in contaminated water and soil.
KeywordsNanoparticle Iron sulfide Lead Heavy metal Metal immobilization Adsorption
The research was partially supported by the Guangdong Innovative and Entrepreneurial Research Team Program (No. 2016ZT06N569), the National Natural Science Foundation of China (Nos. 41503085 and 41230638), and the Fundamental Research Funds for the Central Universities. The authors would like to gratefully acknowledge Dr. Byron H. Farnum and Ms. Alexandria Combs in the Department of Chemistry and Biochemistry of Auburn University for their assistance with the FTIR analysis, and Mr. Steven Moore in the Material Engineering Program of Auburn University for his help with the XRD operation.
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