菲在沉积物上的吸附-解吸研究

Sorption and Desorption of Phenanthrene on Sediments

采用批量实验的方法,研究了盐度对菲在沉积物上的吸附的影响以及菲的初始浓度、沉积物结构性质改变、盐度对菲解吸的影响,并深入讨论了不可逆吸附的机制.结果表明,提高盐度促进菲的吸附,促进程度与沉积物所含有机质(SOM)有关.由菲吸附增加计算得到的盐常数0.299 L.mol-1高于由菲溶解度降低计算得到的盐常数0.125 L.mol-1.菲的解吸具有不同程度的迟滞性,实验数据用Freundlich方程拟合,解吸迟滞性用热力学指数TII表征.随着菲初始加入浓度增加,TII值先降低后又增加,以淡水中菲的解吸为例,随着菲初始浓度由0.5 mg.L-1增加到2.5 mg.L-1,TII值先由0.80降到0.38又增加到0.55,表明解吸迟滞性呈先下降后增加的趋势.氢氧化钠处理后的沉积物与原沉积物相比解吸迟滞性减弱,TII值由0.55降到0.33,说明对菲的锁定能力变弱.首次报道了盐度对菲解吸的迟滞性影响,结果表明,菲的解吸迟滞性指数TII值由淡水中的0.55减少到盐水中的0.42,说明盐水中菲解吸迟滞性比淡水中弱,解吸迟滞性的变化可以用菲分布到的吸附点位能量高低不同以及菲分子是否能够锁定在吸附剂内部微孔来解释.

Batch experiments were employed to investigate the influences of salinity on the sorption of phenanthrene. Influences of initial phenanthrene concentration, sediment properties and salinity on desorption of phenanthrene were also studied and the mechanism for desorption hysteresis was deeply discussed. Salinity enhanced the sorption of phenanthrene on sediments, and the enhancement extent was related to sediment organic matter （SOM）. A salting constant of 0. 125 L·mol^-1 was derived from the PHE solubility in fresh water and salt water, and in the presence of sediment, salting constant was enhanced to 0. 299 L· mol^-1 . Desorption of phenanthrene all exhibited hysteresis to some extents and desorption hysteresis were described by a thermodynamic index TII. With the initial phenanthrene concentration increasing from 0.5 mg· L^-1 to 2.5 mg· L^-1, the value of TII first decreased from 0.80 to 0.38 and then increased to 0.55, suggesting the desorption hysteresis of phenanthrene first decreased and then increased. Sediment treated by NaOH showed a reduced sequestration ability on phenanthrene than the original sediment did, with the value of TII decreased from 0.55 to 0.33. Desorption of phenanthrene in fresh water was found for the first time to have a greater hysteresis than in salt water, indicated by the greater TII value of 0.55 in fresh water than that of 0.42 in salt water. Desorption hysteresis could be explained by the sorption of phenanthrene to sorption sites of different energies and sequestration inside the mieropores of the sediments.