剩余活性污泥胞外聚合物对水中Cd2+和Zn2+的吸附效能

以占剩余活性污泥质量80%的胞外聚合物(extracelluar polymeric substances,EPS)作为新型吸附剂,考察了pH、EPS投加量和吸附时间对其在水中吸附Cd2 与Zn2 的性能的影响,以达到剩余活性污泥的资源化利用.结果表明:Cd2 和Zn2 的最佳吸附条件为:pH=6,EPS的最佳投加量分别为375mg/L和250 mg/L,Cd2 和Zn2 的吸附率分别达到36%和51%.EPS对Cd2 和Zn2 的吸附过程均可分为两个阶段,分别在90 min和60 min时达到吸附平衡.离子共存实验发现,EPS对Cd2 的选择吸附性强于Zn2 ;Freundlich和Langmuir方程均可描述EPS在常温下吸附Cd2 的热力学过程;而Zn2 的吸附等温线与Langmuir方程拟合更好.拟合系数显示,EPS对Zn2 的吸附稳定性、吸附能力和亲和力均比对Cd2 的吸附强.表明剩余活性污泥EPS作为吸附剂前景广阔,具有更深的研究价值.

Adsorption of Cd2+ and Zn2+ in Water by Extracelluar Polymeric Substances from Waste Activated Sludge

Extracelluar polymeric substances(EPS),accounting for 80% of the mass of waste activated sludge,were used as a new adsorbent.Adsorption ability of EPS for Cd~(2 )and Zn~(2 ) removal under different experimental conditions was studied in order to ensure that the waste activated sludge utilization.This paper focused on the influences of pH value,dosage of extracelluar polymeric substances and adsorption time on adsorption rate.The results showed that 6 is the optimal pH value of Cd~(2 ) and Zn~(2 ) for adsorption.The optimal dosage of EPS is 375 mg/L and 250 mg/L for Cd~(2 ) and Zn~(2 ),respectively.At optimal condition,the absorption efficiency reaches about 36% and 51% for Cd~(2 ) and Zn~(2 ),respectively.The adsorption process of Cd~(2 ) and Zn~(2 ) by EPS have two steps,and the adsorption reached equilibrium at 90 and 60 minutes for Cd~(2 ) and Zn~(2 ),respectively.The results of co-existed adsorption indicated that the selective adsorbility of EPS for Cd~(2 ) is stronger than that for Zn~(2 ).At the room temperature,both Freundlich and Langmuir isotherm equations could describe the thermodynamic adsorption processes of Cd~(2 ).However,the adsorption isotherm of Zn~(2 ) fits the Langmuir equation well.The fit coefficient shows,the adsorption stabilization,the adsorption ability and appetency of Zn~(2 ) are better than those of Cd~(2 ).This study indicated that use of EPS from waste activated sludge as adsorbent is promising and further research is desirable.