脱硫石膏对重金属污染沉积物中Cd的稳定固定化作用

研究了掺杂不同比例脱硫石膏的沉积物中Cd的吸附热力学特征及其稳定固定化效果。实验将脱硫石膏掺杂比例不同的沉积物与不同初始质量浓度的Cd溶液混合、振荡、离心后测定上清液中Cd的质量浓度,结果表明,脱硫石膏掺杂量不同的沉积物吸附Cd的热力学过程均符合Langmuir吸附等温线;脱硫石膏掺杂比例的提高增强了沉积物对溶液中Cd的吸持能力,二者显著正相关;脱硫石膏的掺杂还削弱了溶液中Cd初始质量浓度对其固定率的影响,使研究中8个初始质量浓度下沉积物对Cd的固定率均维持在较高水平。通过16个时间点对连续搅拌下的沉积物样品溶液中Cd质量浓度的测定,研究了模拟重金属污染沉积物和自然沉积物掺杂脱硫石膏前后对照了其中Cd的稳定性,结果表明,脱硫石膏的掺杂降低了沉积物中Cd的释放量,并将实验条件下两种沉积物中Cd的固定率均保持在99.2%以上且保持相对平稳状态。同时,脱硫石膏的掺杂可导致吸附体系pH的升高,促进了Cd与固相介质之间由吸附向沉淀作用的转化,从而提高了沉积物中Cd的稳定性,有利于重金属污染沉积物中Cd的稳定固定化。

Effect of desulfurization gypsum on Cd immobilization in heavy metal polluted sediments

Adsorption thermodynamics of Cd and its immobilization in sediments with various doping rates of desulfurization gyp-sum were investigated. In the experiment, sediments with different rates of desulfurization gypsum and Cd solutions with various initial concentrations were mingled, oscillated and decentralized, and then the mass concentration of the supernatant is detected. The results illustrated that the adsorption processes of sediments with different proportions of desulfurization gypsum to Cd were consis-tent with Langmuir adsorption isotherm curves; a higher proportion of desulfurization gypsum increased the sorption capacity of sediment towards Cd in solution, with a positive correlation; desulfurization gypsum also reduced the impact of initial Cd concentra-tion on fixation rates, which were kept on a relatively high level with 8 Cd initial concentrations in this research. The immobilization of Cd in simulated heavy metal-polluted and natural sediments before and after desulfurization gypsum doping were researched, according to the Cd mass concentrations during 16 time points while constantly stirred. The results showed that doping of desulfuri-zation gypsum also reduced the release of Cd, keeping the fixation rates of Cd in sediments above 99.2% and on a relatively stable state. Meanwhile, doping of desulfurization gypsum resulted in pH increase in the adsorption system, and promoted the translation of process between Cd and the solid phases from adsorption to precipitation, and thus improved the stability of Cd in sediments, which is favorable to the immobilization of Cd in heavy metal polluted sediments.