Synthesis of chitosan zero-valent iron nanoparticles-supported for cadmium removal: characterization, optimization and modeling approach

Herein, chitosan (CS) impregnated with nanoparticles of zero-valent iron (NZVI) was fabricated onto a magnetic composite of CS@NZVI as an adsorbent for cadmium (Cd2+) removal from aqueous solution. The characteristics of CS@NZVI were analyzed by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, CHONS and Brunauer, Emmett and Teller techniques. The average diameter of NZVI was found to be 50 nm, and it was successfully coated onto the CS. The influential experimental variables such as contact time, solution pH, adsorbent dosage and initial Cd2+ concentration were investigated to determine optimum conditions. Results revealed that with an optimum dosage rate of 0.6 g/L, Cd2+ concentration was reduced from 10 to 0.016 mg/L within 90 min reaction time at pH of 7 +/- 0.2. Experimental data were fitted to the Freundlich and pseudo-secondorder models. Maximum adsorption capacity was obtained from the Langmuir monolayer 142.8 mg/g. Desorption experiments showed that the CS@NZVI had good potential with regard to regeneration and reusability, and its adsorption activity was preserved effectively even after three successive cycles owing to its good stability. As a conclusion, CS@NZVI can be considered as an effective adsorbent for heavy metals removal from water and wastewaters, because it can be separated both quickly and easily, it has high efficiency, and it does not lead to secondary pollution.