Adsorption of cadmium (Ⅱ) in solution by natural zeolite-chitosan adsorbent
LI Zeng-xin, WANG Guo-ming, ZHANG Dao-lai, LI Jun,LIU Hui-luan, ZHENG Qing-hua(Department of Chemistry, Teachers College, Qingdao University, Qingdao 266071, Shandong, China)
This paper is inclined to present the study on the way to improve the natural zeolite adsorbent ability for cadmium (Ⅱ) in the solution prepared with the combination of chitosan and zeolite. Since the interchangeability is characteristic of natural zeolite ions, chitosan would be positive in charge in the acid solution. Based on the two properties mentioned above, we can add 80 mesh natural zeolites to the 90% of chitosan slurry in the 0.5% of deacetylation to prepare adsorbent. The optimal conditions for absorption can be listed as follows: the mass ratio of chitosan to natural zeolite is 1∶20, while the dosage of the adsorbent is 15 g/L. If the mass concentration of Cd (Ⅱ) in the wastewater is no more than 300 mg/L, the pH value should be controlled between 6-8. And, when the adsorption equilibrium time is nearly 8 h, the Cd (Ⅱ) removal efficiency should reach 99%. The above said method and the activated carbon absorbing method may demonstrate a similar effect. However, since the former has a lower cost, that is, only 1/6 of the latter, this absorbent may have a stronger absorbability as well as a lower cost, as compared with the single natural zeolite or single chitosan. Also, the results would provide a theoretical basis for utilizing natural zeolite to extract heavy metals from the contaminated soils.