Adsorption of Arsenite by Six Submerged Plants from Nansi Lake, China

Abstract

Nansi Lake is the largest and the most important freshwater lake in north China for the South-North Water Transfer Project. Due to long-time and large-scale fish farming of history, the excess fish food and excretion usually release pentavalent arsenic, which is converted into trivalent arsenic (As (III)) in the lake sediment and released into lake water. Adsorption of arsenite using six submerged plants (Mimulicalyx rosulatus,Potamogeton maackianus,Hydrilla,Watermifoil,Pteris vittata, andPotamogeton crispus) as adsorbing materials was investigated. The experimental data obtained have been analyzed using Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models and the pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetics models. According to the results, the As (III) equilibrium data agreed well with the Freundlich isotherm model. The adsorption capacity of the plants was in the following order:Potamogeton crispus>Pteris vittata>Potamogeton maackianus>Mimulicalyx rosulatus>Hydrilla>Watermifoil. The sorption system with the six submerged plants was better described by pseudo-second-order than by first-order kinetics. Moreover, the adsorption withPotamogeton crispuscould follow intraparticle diffusion (IPD) model. The initial adsorption and rate of IPD usingPotamogeton crispusandPteris vittatawere higher than those using other plants studied.