Study On Adsorption Behaviors And Mechanism Of Heavy Metals On Attapulgite

As the pollution of heavy metal ions is getting more severe, pursing an economical and efficient adsorbent to remove heavy metal ions has been a difficult problem. Attapulgite is the hot material in the field of removing heavy metals via adsorption method due to its excellent adsorption efficiency, low cost and convenient regeneration. In this dissertation, attapulgite was used as the adsorbent and the adsorption of cobalt ions and competitive adsorption of copper and zinc ions on attapulgite were studied.(1) The effects of initial metal concentration, adsorption temperature, adsorption time, pH and ion strength on the adsorption for cobalt onto attapulgite were studied. The results showed that the adsorption of Co2+ followed pseudo-second-order kinetics and Langmuir model. At 35℃, the maximum Co2+ adsorption capacity is 8.88 mg·g-1. Adsorption was influenced by pH and ionic strength. The adsorption mechanism primarily involved inner-sphere complexation, with minor contributions from the replacement of structural Mg2+ and ion exchange. Attapulgite could be completely regenerated by Na2CO3, and excellent adsorption efficiencies were showed by regenerated attapulgite.(2) The effects of initial metal concentration, adsorption temperature, adsorption time and adsorbent dosage on the adsorption of cobalt onto attapulgite in single and competitive systems are compared. The adsorption followed pseudo-second-order kinetics and Langmuir model. Compared with zinc ion, copper ion showed greater affinity towards attapulgite. Compared with single system, the adsorption capacity of zinc ion in competitive system was rapidly decreased, while the adsorption capacity of copper ion was increased.