Influence of humic acid on the removal of arsenate and arsenic by ferric chloride: effects of pH, As/Fe ratio, initial As concentration, and co-existing solutes.
The influence of humic acid (HA) on the removal of arsenic by FeCl3was systematically studied in this paper. Jar tests were performed to investigate the influence on arsenic during FeCl3coagulation of the pH adjusting method, the initial As/Fe ratio, the equilibrium As concentration, and co-occurring anions and cations. Compared with results in HA-free systems, the removal trends of arsenic in HA solutions were quite different. It was found that As(V) removal was higher at low equilibrium concentration, yet the opposite was true for As(III) removal. The presence of HA influenced the effective number of active sites for arsenic removal by FeCl3flocculation. In addition, in the presence of HA, the impacts of co-existing solutions on arsenic removal were also different from that of an HA-free system. This study examined the influence of co-occurring anions, such as phosphate, sulfate, and silicate on arsenic removal, depending on their ability to compete for sorption sites and to hinder or facilitate the aggregation of ferric hydroxide flocs. The presence of Ca2+or Cd2+significantly increased arsenic removal at higher pH. Low concentrations of dissolved HA and high concentrations of colloid affected the adsorption of arsenic onto iron oxide. The influence of HA on the adsorption of arsenic onto iron oxide primarily depended on the relative content of the dissolved and mineral combination states of HA and the interface combination forms.
State Key Laboratory of Urban Water Resources and Environment, School of Municipal & Environmental Engineering, Harbin Institute of Technology, Harbin, 150090, China.
Yanli
Y
Kong
State Key Laboratory of Urban Water Resources and Environment, School of Municipal & Environmental Engineering, Harbin Institute of Technology, Harbin, 150090, China. jingkanghit@163.com.
Jing
J
Kang
State Key Laboratory of Urban Water Resources and Environment, School of Municipal & Environmental Engineering, Harbin Institute of Technology, Harbin, 150090, China.
Jimin
J
Shen
State Key Laboratory of Urban Water Resources and Environment, School of Municipal & Environmental Engineering, Harbin Institute of Technology, Harbin, 150090, China.|HIT Yixing Academy of Environmental Protection, Yixing, 214200, China.
Zhonglin
Z
Chen
State Key Laboratory of Urban Water Resources and Environment, School of Municipal & Environmental Engineering, Harbin Institute of Technology, Harbin, 150090, China.
Leitao
L
Fan
D000327:Adsorption; D001149:Arsenates; D001151:Arsenic / Q000032:analysis; D002712:Chlorides; D005290:Ferric Compounds / Q000737:chemistry; D005427:Flocculation; D006812:Humic Substances / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D010710:Phosphates / Q000737:chemistry; D017640:Silicates / Q000737:chemistry; D013431:Sulfates; D014874:Water Pollutants, Chemical / Q000032:analysis; D018508:Water Purification / Q000379:methods*
D001149:Arsenates; D002712:Chlorides; D005290:Ferric Compounds; D006812:Humic Substances; D010710:Phosphates; D017640:Silicates; D013431:Sulfates; D014874:Water Pollutants, Chemical; C000499:ferric oxide; C021024:ferric hydroxide; D001151:Arsenic; C025657:arsenic acid; C024555:ferric chloride
Arsenic; Co-existing solution; Coagulation; Humic acid