Adsorption of chromium(Ⅵ) in the sewage with attapulgite-chitosan adsorbent
LI Zeng-xin,WANG Guo-ming,WANG Tong,MENG Yun(Department of Chemistry,Teachers College,Qingdao University,Qingdao 266071,Shandong,China)
This paper is inclined to provide an innovated approach to controlling and remedying chromium(VI) contaminated sewage by attapulgite,especially,for the chromium(VI) contaminated sewage. So far as we know,although non-metallic mines are widely used as water amender,there are still a few reports on taking attapulgite,especially,chromium(VI) contaminated waste as remedy for heavy metal contaminated sewage. It is just for the purpose of providing a new way to control and remedy for such sewage,we have conducted the equilibrium adsorption isotherm experiments to investigate the effects of the adsorption behaviors toward chromium(VI) in the solution on the compound sorbent. In our experiments,the compound adsorbent was prepared through combination of chitosan and attapulgite,which are characteristic of natural attapulgite ions,with chitosan being positive in charge in the acid solution for its interchangeability. Based on the two properties mentioned above,attapulgite is added to the chitosan slurry of 90% of deacetylation when the adsorbent is prepared with mass ratio being 1∶20 (chitosan∶attapulgite). Besides,experiments also prove that chitosan loading rate on attapulgite is 32.6% at 700 ℃. Its adsorption to Cr(VI) has also been found. And finally,the experimental results also indicate that the dosage of the adsorbent is 12 g/L,with the mass concentration of Cr(VI) in the sewage below 40 mg/L. While the pH=46,the adsorption equilibrium time is expected to last about 35 min with Cr(VI) removal efficiency reaching 90%. Thus,it can be inferred that the adsorption isotherm proves to follow Langmuir isotherm equation.The results show attapulgite-chitosan can used for remedying chromium(VI) contaminated waste water effectively.