Microwave-Assisted Synthesis of Functionalized Chitosan Adsorbents for Cerium Adsorption from Aqueous Solutions

The microwave method was introduced as an alternative energy source (other than thermal or photochemical methods) in the synthesis of functionalized chitosan adsorbents for cerium adsorption from aqueous solutions. Chitosan was extracted from shrimp waste, purified, and crosslinked with epichlorohydrin at pH 10 to enhance its chemical stability. The crosslinked chitosan-epichlorohydrin adsorbent was modified with epichlorohydrin to introduce a terminal exchangeable chloride ion into the chitosan-epichlorohydrin structure. The chitosan product obtained was further modified with tetraamine ligand, which was followed by the reaction with chloroacetic acid/isopropyl alcohol solution to produce multidentate amine chitosan and multidentate oxygen/nitrogen adsorbents. All the synthesis steps were done in a microwave oven. Shrimp waste and all the other synthesized adsorbents were characterized using appropriate analytical methods. The multidentate amine chitosan and multidentate oxygen/nitrogen adsorbents were tested for cerium ion adsorption from an aqueous solution using the batch technique. The adsorbents show high adsorption capacities for cerium ions. At 298 K, the maximum capacities of cerium adsorption onto the multidentate amine and multidentate oxygen/nitrogen adsorbents are 61.8 and 84.4 mg/g, respectively, with the monolayer saturation capacities of 70.42 and 99.01 mg/g, respectively.