壳聚糖对Cd2+和Pb2+的吸附作用

为开发新型吸附剂,降低重金属对水体的污染,研究了壳聚糖对Cd²⁺和Pb²⁺的吸附条件,探讨了pH、温度、反应时间、壳聚糖添加量和金属离子初始浓度等因素对壳聚糖吸附性能的影响。结果表明,pH 7~8和pH 5~6条件下壳聚糖对Cd²⁺和Pb²⁺的吸附能力最强;低温有利于壳聚糖的吸附;在8 h时壳聚糖对Cd²⁺的吸附容量达到最大,而对Pb²⁺的吸附在实验时间内是随着吸附时间的延长而增大;随着壳聚糖添加量的增加,其对Cd²⁺和Pb²⁺的吸附能力也增强;初始金属离子浓度的变化对Cd²⁺的影响不大,而在高的金属浓度下对Pb²⁺的吸附率显著降低。壳聚糖对Cd²⁺、Pb²⁺的吸附动力学和热力学分别符合Lagergren方程二级吸附模型和Langmuir吸附方程。研究表明,壳聚糖对不同金属离子的吸附能力不同,在单一金属溶液中,壳聚糖对Cd²⁺的吸附能力要强于对Pb²⁺的吸附能力。系统地研究了壳聚糖对Cd²⁺和Pb²⁺的吸附条件及性能,为壳聚糖作为重金属吸附剂的应用提供理论依据。

Adsorption of Cd2+ and Pb2+ by chitosan

At present,with the development of industry and agriculture,heavy metal contamination of environment is intensifying,and the toxic effects on the human beings have attracted extensive attention.For the development of new adsorbent,reducing the pollution of heavy metals in water body,the chitosans were used to investigate the adsorptions of two metals of Cd2+ and Pb2+ in an aqueous solution.The absorption properties of chitosan were evaluated by the effects of pH,temperature,reaction time,adsorbent dose and initial metal ion concentration.The results showed that at pH 7-8 and pH 5-6,the chitosan had the best absorption of Cd2+ and Pb2+,respectively; low temperature was beneficial to absorption; the maximum absorption of Cd2+ was at 8 h,but of Pb2+ it always increased in the experimental period; the absorption of Cd2+ and Pb2+ was enhanced with the increase of chitosan amount; initial metal ion concentration had little effect to Cd2+,but at high metal concentration,the absorption of Pb2+ was significantly reduced.At the same time,the dynamical and the equilibrium isotherm adsorption studies of Cd2+ and Pb2+ followed the Lagergren second-order kinetic equation and the Langmuir isotherm equation in the concentration range studied,respectively.Conclusion:the adsorption capacity of chitosan is different with the changes of metal ions,in single metal solution,the adsorption capacity of chitosan for Cd2+ is stronger than Pb2+.Finally,this work systematically studies the adsorption conditions and performance of chitosan for Cd2+ and Pb2+ which may provide theory basis for chitson as heavy metals adsorbent.