title: Coagulation of methylated arsenic from drinking water: Influence of methyl substitution.
abstract: Methylated arsenic can be found in virtually all earth surface environments. So far, however, little information has been collected regarding their removal by coagulation. In this study, the removal of monomethylarsenate (MMA) and dimethylarsenate (DMA) from drinking water by coagulation was investigated from the viewpoint of methyl substitution. Results indicated that FeCl3 was more efficient than AlCl3 and polyaluminum chloride (PACl) in methylated As removal. For the initial arsenic concentration of 200 μg/L, an FeCl3 dosage of 0.2 mmol Fe/L was sufficient to attain about 95% removal of MMA, while a dosage of 0.6 mmol Fe/L achieved about 57% removal of DMA. Arsenic removal efficiency was negatively correlated with the degree of methyl substitution. With the increase in methyl group number, the quantity of negatively charged arsenic species decreased and molecular size increased, leading to the decrease of methylated As removal by coagulation. Adsorption on preformed hydroxide flocs was the major mechanism during coagulation. Both FTIR and XPS results indicated that the As−O group of As might substitute the O−H group of Fe/Al hydroxide to form a Fe/Al−O−As complex. Furthermore, the use of traditional oxidants and coagulation aids exhibited limited help for improving coagulation removal of DMA.
authors: Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China. Electronic address: czhu@rcees.ac.cn.
authors: Chengzhi
authors: C
authors: Hu
authors: Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
authors: Qingxin
authors: Q
authors: Chen
authors: Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
authors: Huijuan
authors: H
authors: Liu
authors: Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
authors: Jiuhui
authors: J
authors: Qu
mesh_terms: D000327:Adsorption; D000536:Aluminum Hydroxide / Q000737:chemistry; D001149:Arsenates / Q000737:chemistry; D001151:Arsenic / Q000737:chemistry*; D002712:Chlorides / Q000737:chemistry; D060766:Drinking Water / Q000737:chemistry; D005290:Ferric Compounds / Q000737:chemistry; D008745:Methylation; D016877:Oxidants / Q000737:chemistry; D011196:Potassium Permanganate / Q000737:chemistry; D012973:Sodium Hypochlorite / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods
chemical_list: D001149:Arsenates; D002712:Chlorides; D060766:Drinking Water; D005290:Ferric Compounds; D016877:Oxidants; D014874:Water Pollutants, Chemical; D011196:Potassium Permanganate; C016213:aluminum oxychloride; D000536:Aluminum Hydroxide; D012973:Sodium Hypochlorite; D001151:Arsenic; C024555:ferric chloride
keywords: Aluminum; Coagulation; Floc; Iron; Organic arsenic