Experimental and computational study of removal of methyl green and eosin yellow from aqueous solutions using novel sulfamic and sulfanilic acid grafted chitosan-epichlorohydrin -Fe2O3 nanocomposites

Two novel chitosan-based adsorbents, sulfamic acid-chitosan-epichlorohydrin-Fe2O3 (HK-1) and sulfanilic acid-chitosan-epichlorohydrin-Fe2O3 (HK-2), were successfully synthesized and characterized by XRD, TGA, DSC, BET, and SEM techniques. The ability of the synthesized adsorbents for removing cationic Methyl Green (MG) and anionic Eosin Yellow (EY) from aqueous solutions was investigated at different solution pHs, adsorbent dosages, and contact times. The results showed a removal efficiency of 93.5 % and 96.8 % for adsorbing cationic MG respectively by HK-1 and HK-2 at pH = 8. The removal efficiency for adsorbing anionic EY by HK-1 and HK-2 was respectively 90.8 % and 94.6 % at pH = 3. The results also showed that >50 % of MG was adsorbed within the first 30 min of contact with HK-1 and HK-2, but it took about 75 and 45 min to adsorb 50 % of EY respectively by HK-1 and HK-2. DFT calculations confirmed the spontaneous adsorption of EY and MG on the surface of HK-1 and HK-2. These promising results suggest that HK-1 and HK-2 can be used to remove other cationic and anionic dyes from aqueous solutions.