Abstract
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•Amphoteric carboxymethyl chitosan/gelatin microspheres (CCGMs) with hierarchical porous structure were synthesized.•Ultra-high adsorption properties (383.142 mg g−1 for MO and 584.795 mg g−1 for MB) were demonstrated.•pH induced selective removal of cationic and anionic dyes from the binary mixed solution was achieved.•Selectivity mechanism was illustrated as the synergy of electrostatic interaction and π-π stacking.•Superior and stable re-adsorption efficiency, higher than 80% after 5 cycles, was realized.
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.