Ultra-high efficient pH induced selective removal of cationic and anionic dyes from complex coexisted solution by novel amphoteric biocomposite microspheres

The substandard discharge of highly toxic dyestuff wastewater will pose a serious threat to the environment and human beings, even causing unimaginable irreversible damages. In the current study, novel amphoteric carboxymethyl chitosan/gelatin microspheres (CCGMs), synthesized by a facile inverse suspension route with two-step successive crosslinking process, were evaluated as a potential adsorbent for high efficient pH induced selective removal of azo-dyes. The as-prepared CCGMs were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry analysis (TGA) and X-ray photoelectron spectroscopy (XPS). Various influential factors such as solution pH, temperature, and contact time were employed to ascertain the optimal condition for representative azo-dyes adsorption, including methyl orange (MO) and methylene blue (MB). The maximal adsorption of MO and MB on the CCGMs at pH values of 3 and 11 were 383.142 mg g(-1) and 584.795 mg g(-1), respectively. The adsorption mechanism were demonstrated as the synergistic effect of electrostatic interaction and pi-pi stacking between dyes and CCGMs. Besides, the outstanding and stable regeneration of as-prepared CCGMs were also verified with five consecutive recycling. Thus, the newly developed CCGMs could be a highly promising candidate for dyestuff wastewater treatment.