Improvement of Reduction Method and Activated Carbon Adsorption Method for Removal of Cr(VI) in Water

Key words: 
• Reduction-modified activated carbon adsorption method /
• water body /
• Cr（VI） /
• removal rate /
• flame atomic absorption spectrometry

Abstract: Experimental conditions for reduction method and activated carbon adsorption method were optimized to remove Cr（VI） in water,and both methods were combined to observe their effect on removal of Cr（VI）.The orthogonal experiments and double-check test were used to optimize the reduction method for removal of Cr（VI）,resulting in optimum conditions for the reduction method with sodium metabisulfite,sodium bisulfite,sodium sulfite,sodium hydrosulfite and sodium thiosulfate as reducing agents.Under these optimal conditions,the reducing agents had a Cr（VI） removal rate of 96.59 %-99.48% in the water body.Activated carbon modified with manganese nitrate at different concentrations produced different effects on Cr（VI） removal and had the highest removal rate when modified with manganese nitrate at the concentration of 0.03 mol/L.The modified activated carbon had better removal effect than the unmodified one.The removal rate was affected by pH,initial concentration of Cr（VI） and treatment time.When the pH was 3,the removal rate was the highest（94.6%）.The modified activated carbon had better removal effect when the contaminated water contained lower initial concentration of Cr（VI）,and the Cr（VI） removal rates increased fast at the early and middle stage of absorption.The combined reduction and modified activated carbon absorption method had better effect on removal of Cr（VI）than the reduction method or the modified activated carbon absorption method alone.The simulated water samples collected from Haidian Stream,Haikou,Hainan,China were treated by using the combined reduction and modified activated carbon adsorption method,and the results showed a satisfactory treatment of the actual sample matrix by using the combined method.