Influence of the coexisting Pb2+ on the phenanthrene adsorption behavior in the soil

• 1、School of Environmental Science and Engineering, Sun Yat-sen University

Abstract：The potential influences of coexisting heavy metal solutions on the phenanthrene adsorption capacity were studied by series of batch experiments, where a natural clayish soil and bentonite were tested. The adsorption kinetic experiments show that the solution pH increases during the phenanthrene adsorption. As a result, a low initial pH in the solution facilitates the phenanthrene adsorption. Therefore, to eliminate the influence of the pH decrease resulting from the added heavy metal solution, the initial pH of the adsorption experiments was all adjusted at 5.8±0.1. Under this pH condition, we found that the phenanthrene adsorption isotherm is all linear in the studied concentration range. The presence of Pb2+ all increases the adsorption capacity of phenanthrene to some extent. In the natural clayish soil, such an enhancement could be partly attributed to the decreased organic matter in solution and increased SOM. However, when part of SOM in the clayish soil was destroyed by heating over 550 oC, phenanthrene adsorption enhanced by Pb was more significant, indicating that the enhancement may be partly independent of SOM. That speculation is corroborated by the similar enhancement phenomenon observed on bentonite, which may be the results of the formation of cation-π bond between the adsorbed soft metal cations and aromatic ring of the phenanthrene in solution.

Keywords： Soil adsorption heavy metals poly aromatic compounds