Fast and environmental-friendly approach towards uniform hydrogel particles with ultrahigh and selective removal of anionic dyes

Based on the strategy of copolymerization, methacrylatoethyl trimethyl ammonium chloride (DMC) and acrylamide (AM) copolymer hydrogel particles (PCM HPs) were prepared by precipitated droplets in-situ cross-linking polymerization, to overcome the easily fragile property of pure PDMC HPs and the low adsorption capacity of pure PAM HPs. Corn oil and deionized water were used for the reaction, which would not cause any pollutions; and the preparation process only took 40 s. Through the studies on various feeding ratios of DMC to AM, the hydrogel particles (PCM 5-1 HPs) with the mass ratio of 5:1, showed the best mechanical strength and adsorption capacity. The compression strength of the PCM 5-1 HPs was 207.7 K Pa, and no obvious mechanical loss occurred during five compression-rebound cycles. In addition, the removal ratios of anionic dyes such as amaranth red, orange G, and methyl orange were all higher than 94% (the initial dye concentration was 100 μmol/L and the adsorbent mass was 4 mg); and the adsorption capacity of orange G could reach as high as 992.63 mg/g. Meanwhile, the PCM 5-1 HPs exhibited excellent selective adsorption of anionic dyes in mixed dye solutions. Therefore, the hydrogel particles prepared by the fast and environmental-friendly method had both mechanical strength and ultrahigh adsorption capacity, which verified their practicality in the removal of anionic dyes in sewage.