Gelatin-Grafted Granular Composite Hydrogel for Selective Removal of Malachite Green

Featured with biodegradability and biocompatibility properties, gelatin (GE) was selected as the backbone to graft poly(acrylic acid) (PAA) to fabricate a granular hydrogel at room temperature in air. Using attapulgite (APT) as an inorganic component, the resulting GE-g-PAA/APT hydrogel was characterized by means of Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and zeta potential analysis and then used as the adsorbent to be applied in a mixed dye solution containing malachite green and orange G. The addition of APT can significantly reduce the swelling degree during the adsorption process, though its influences on the adsorption capacity are not so expectable. The as-prepared hydrogel shows a wide pH-independent adsorption from 3.0 to 10.0, with the maximum adsorption capacity of 1370 mg/g for GE-g-PAA and 1190 mg/g for GE-g-PAA/APT (5 wt%). More importantly, the as-prepared hydrogel shows high adsorption selectivity for cationic dyes and the dyeloaded hydrogel can be easily regenerated and recovered for successive adsorption cycles.