A novel strategy for Cr(VI) removal from aqueous solution via CYPH@IL101/chitosan capsule

A novel adsorbent, chitosan capsule with filler of CYPH@IL101 (CYPH@IL101/chitosan capsule), was prepared using a summary process for the adsorption of Cr(VI) from aqueous solution. The effects of CYPH@IL101 content, pH, contact time, rotational speed and Cr(VI) concentration on the adsorption were studied. The results showed that the adsorption capacity of the chitosan capsule was benefit from the increase of CYPH@IL101 content. Besides, solution pH also played an important role in the adsorption process and the maximum adsorption capacity was achieved at pH 3. Kinetic studies suggested that the adsorption rate was controlled by the diffusion step at low rotational speed (50 r/min), but was controlled by chemical reaction at high rotational speed (150 and 250 r/min). Furthermore, the adsorption isotherms were studied by using Langmuir, Freundlich, BET, and Temkin models. The results demonstrated that the adsorption process fit Langmuir and TemKin models better, which indicated that the adsorption of Cr(VI) onto CYPH@IL101/chitosan capsule mainly depended on chemisorption and the active sites were uniformly distributed on the adsorbent surface. While, the maximum adsorption capacity obtained from Langmuir model was 104.38 mg/g. Finally, XPS and FTIR analyses revealed that Cr(VI) was adsorbed and then reduced to Cr(III) by CYPH@IL101/chitosan capsule.