Abstract: Arsenic is listed as one of the most important poisons in the environment. The influence of organic matter on the environmental geochemical behavior of arsenic has attracted more and more attention. Aiming to understand the influence of different active functional groups of organic matter on arsenic adsorption, a batch experimental method was used to explore the adsorption isotherm and adsorption kinetics of arsenic on goethite with the coexistence of different organic matters. The influence of different organic matters on arsenic adsorption was explored by Zeta potential and infrared spectrum. The results showed that the addition of carboxymethyl cellulose, tannic acid, p-benzoquinone and dodecylbenzene sulfonic acid inhibited the adsorption of arsenic on goethite, and the adsorption of which was fit well with the Freundlich adsorption isotherm model. When the four kinds of organic matter were added respectively, the adsorption of arsenic on the surface of goethite was well described by pseudosecondorder kinetic model. Moreover, with the changes of pH, organic matter with different functional groups had different effects on the adsorption rate of arsenic. The arsenic adsorption rate constants of tannic acid, dodecyl benzenesulfonic acid, carboxymethyl cellulose and pbenzoquinone were 0.37, 0.03, 0.02, and 0.01 mg·g-1·h-1, respectively. Ta〖HJ*4〗nnic acid can significantly increase the adsorption rate of arsenic, while p-benzoquinone can effectively reduce the adsorption rate of arsenic, probably due to the different modes of interaction between their functional groups and arsenic. The results of Zeta potential measurement showed that the ternary complexes were formed among arsenic, tannic acid, and goethite. The results of infrared spectrum also evidenced the formation of ternary complexes.

Key words: arsenic, organic matter, goethite.