Preparation and adsorption properties of citrate-crosslinked chitosan salt microspheres by microwave assisted method

Citrate-crosslinked chitosan salt (CSC) microspheres were prepared using chitosan as raw material and citric acid as salifying agent by microwave assisted heating method. The product was characterized by XRD, SEM, NMR, TG, FT-IR, GPC and BET. The citric acid solution concentration, microwave reaction temperature and microwave reaction time showed influence on the morphology and size of chitosan citrate salt microspheres. The prepared chitosan citrate salt microsphere showed a high-efficiency adsorption ability to remove Cr(VI) in water. The best adsorbent CSC-2-1H had an ability to absorb Cr(VI) of 172 mg⋅g^-1 and reached adsorption equilibrium at 30 min. The adsorption equilibrium data of CSC-2-1H were analyzed with Langmuir and Freundlich adsorption models. The adsorption kinetics and adsorption thermodynamics of Cr (VI) on CSC-2-1H was also analyzed using the pseudo-first-order model, pseudo-second-order model, van't Hoff equation and Arrhenius equation, respectively.