Comparison of arsenite removal processes by ferric salts and ferrous salts
ZHANG Ming-yue1, ZENG Hui-ping1, LV Yu-feng1, ZHU Jin-feng1, YANG Hang2, LI Dong1, ZHANG Jie1,2
1. Key Laboratory of Beijing for Water Quality Science and Water Environment Recovery Engineering, Beijing University of Technology, Beijing 100124, China;
2. State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, China
The present study was directed towards the feasibility of purification of water with low concentration of As (III), using coagulant of ferrous salts and ferric salts without pre-oxidation technique, as well as the differences. Experiments about dosage, the best pH, adsorption capacity and oxidation capability of As (III) with ferric salts were conducted. The results showed that ferrous salts was more effective in removal of As (III), just half of the dosage was needed compared with ferric salts. Both pH of the treated water fluctuated narrowly. Adsorption was proved the main mechanism for As (III) removal in the coagulation processes, and the adsorption made the greater contribution with the increasing dosage, while the ferrous salts had the better absorption efficiency than the ferric salts all the time. The adsorption of As (III) by coagulation particles cost nearly 6hours to reach equilibrium and the maximum adsorption capacity were 42.445μg/mg for ferric salts, 50.865μg/mg for ferrous salts respectively. Due to a poor adsorption efficiency, ferric salts did worse in As (III) removal, even though 40% of As (III) was catalytically oxided in the process.
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