Release Behavior of Se from Coal into Aqueous Solution

The release of harmful trace elements from solid such as coal into the water is closely related to human health. The aim of this paper is to study the release procedure of selenium (Se) from coal in aqueous solution. Effects of contact time, pH, and temperature were investigated via a set of batch release tests. Experimental results were also analyzed from the aspects of dynamics and thermodynamics. Batch release tests showed that the release capacity of Se increasees with the increase of contact time and temperature, and it is higher in strong acid or alkaline conditions than in neutral conditions. Dynamic fitting analyses indicated that the release model of Se from coal into water is different with different pH values, and the applicability of different models suggested that the release mechanism of Se is multiple. The first-order kinetics fitting demonstrated that the release procedures of Se from coal into the water with the initial solution pH of 3 and 11 are two-stage release processes. And the best fitting of a pseudo-second-order model manifested the process is mainly controlled by chemical reaction. Thermodynamics analyses indicated that the release of Se from coal into water is an endothermic reaction, and the release enthalpy of Se is 18.314 and 3.533 kJ/mol at the solution pH 7 and 11, respectively.