A new magnetically separable zwitterionic copolymer hydrogel: Synthesis, characterization, and adsorption studies

•New magnetic organic-inorganic zwitterionic copolymer hydrogel composite was successfully prepared.•The new composite was based on zwitterionic copolymer hydrogel and bimetallic FeCo nanoparticles.•The new composite was porous, ferromagnetic, and the bimetallic FeCo nanoparticles was partially oxidized to CoFe2O4.•The composite with higher ratio of the hydrogel was the most efficient adsorbent for RY160 dye and Ni2+.•The new composite showed a qL for Ni2+ (99.07mg/g) higher than several reported adsorbents. In this study, a new magnetic organic–inorganic hydrogel composite was prepared and applied as an adsorbent for the removal of contaminants from aqueous media. The composite was prepared by loading FeCo nanoparticles on a zwitterionic copolymer hydrogel (poly(4-vinylbenzenesulfonate-co-[3-(methacryloylamino) propyl] trimethylammonium chloride), poly(MPTC-co-VBS)). Three composites with different FeCo contents were prepared to find the poly(MPTC-co-SVBS): FeCo ratio that achieves the highest adsorption of reactive yellow 160 (RY160) and Ni2+ ions. The prepared materials were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffractometer (XRD), and vibrating-sample magnetometer (VSM). The characterization results revealed that the FeCo nanoparticles, poly(MPTC-co-SVBS) zwitterionic copolymer hydrogel, and FeCo-zwitterionic copolymer hydrogel composites were successfully prepared. The VSM and SEM analysis showed the ferromagnetic nature and porous structure of the FeCo-zwitterionic copolymer hydrogel composite. According to the XRD and FTIR, the FeCo was partially oxidized to CoFe2O4 during the preparation of the FeCo-zwitterionic copolymer hydrogel composite. The composite with the ratio of 2 wt% of poly(MPTC-co-SVBS) to 1 wt% of FeCo (2ZCPH-1FeCo) achieved the highest removal of both RY160 and Ni2+. The optimum removal of RY160 (92 %) was attained using 0.5 g/L of 2ZCPH-1FeCo at pH 7 after 60 min., while the optimum removal of Ni2+ (92 %) was attained using 1.0 g/L at pH 6.5 after 60 min. The PFO and PSO kinetic models described accurately the adsorption of RY160 and Ni2+, respectively. While the isotherm data of RY160 dye and Ni2+ was best described by Freundlich and Temkin models, respectively. Overall, the new FeCo-zwitterionic copolymer hydrogel composite demonstrated remarkable adsorption efficiency and simple magnetic separation post-treatment which makes it