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

Abstract 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 π-π 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.