부산대학교 도서관

An intelligent adsorbent for Cr6+was prepared with microwave irradiation, using carboxymethyl cellulose (CMC) and acrylamide (AM) as grafted skeleton and monomer. Preparation conditions including microwave power, time, crosslinker, initiator and molar ratio of CMC to AM were all optimized, and characterizations of CMC-AM were performed with XRD, SEM, FTIR, XPS, TG, etc. Adsorption tests such as static and dynamic breakthrough curve were both carried out. 99% Cr6+ions were removed by CMC-AM when Cr6+concentration was 1.5 mg·L-1, pH value was 5 and CMC-AM dosage of was 1.0 g·L-1. The adsorption kinetics fitted well with pseudo-second order reaction and adsorption equilibrium accorded well with Langmuir isothermal model. It was observed that adsorption of Cr6+was a spontaneous endothermic reaction based on values of ∆G, ∆S and ∆H. According to XPS analysis, it was found that Cr3+appeared on the surface of CMC-AM, suggesting that Cr6+was adsorbed on the surface of CMC-AM and then reduced in situ to Cr3+. Hence four dominant steps were involved in the removal of Cr6+: amino protonation (-NH3+) → adsorption of HCrO4-→ reduction of HCrO4-by -OH group and production of Cr3+→ desorption of Cr3+. Differing with other common disposable adsorbents, CMC-AM resin could self-regenerate active adsorption sites spontaneously via coulomb repulsion between -NH3+and Cr3+, displaying an intelligent self-generation function. Furthermore, the cyclic test of CMC-AM showed that 86% of Cr6+ions were still removed after 6 cycles without any additional chemical treatment, indicating that CMC-AM has a satisfying self-regeneration capability.