近海沉积物对粪固醇的等温吸附和热力学研究

采用大连湾近海表层沉积物为吸附剂,粪固醇为吸附质,通过批量平衡法,研究了近海沉积物对12种粪固醇的吸附行为.结果表明,12种粪固醇在24 h吸附达到平衡后,5种粪固醇的指纹值变化趋于稳定;用Henry、Freundlich、Langumir、Dubinin-Radushkevich(D-R模型)、Temkin这5种等温吸附模型来拟合,其中Langumir模型不适合拟合沉积物对粪固醇的吸附数据,其他4种模型均能较好地拟合.D-R模型拟合效果表明,12种粪固醇的吸附平均自由能在7 071.1～9 128.7 J.mol-1之间,12种粪固醇的吸附过程主要是物理吸附的作用.Temkin模型拟合效果表明,加氢胆固酮(Kf=8.89×106)的Kf值最大,说明沉积物吸附加氢胆固酮之间的作用最大,加氢胆固酮更容易被吸附.热力学参数吸附焓ΔH0<0,熵变ΔS0<0,ΔG0<0呈现出放热反应,自发过程的特征.

Sorption Isotherms and Sorption Thermodynamics of Faecal Sterols on Offshore Sediment

Experiments of faecal sterols adsorption from aqueous solutions onto Dalian offshore sediment were done by a batch equilibrium method,and the sorption of 12 kinds of faecal sterols in sediment were investigated in this paper. It was shown that the adsorption equilibrium time was 24 h, and after 24 h the variation tendency of 5 kinds of fingerprint values was stable. It indicated that adsorption isothermal data was interpreted by the Henry, Freundlich, Langmuir,Duhinin-Radushkevich(D-R) and Temkin equations, and demonstrated that the other 4 isotherms provided stronger data fitting than the Langumir isotherm. It inferred that from D-R model the mean free energy of adsorption process of 12 kinds of faecal sterols was from 7071.1 J·mol^-1 to 9128.7 J·mol^-1, and concluded that it was mainly physical adsorption of the sorptive process of 12 kinds of faecal sterols in sediment. It discovered that from the Temkin model the value of Kfof cholestanone was the maximum,and extrapolated that cholestanone was adsorbed most easily on sediment. It stated that the enthalpy and entropy change of the adsorption were both less than zero,and inferred that the adsorption process was exothermic and spontaneous.