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A novel superparamagnetic micro-nano-bio-adsorbent PDA/Fe3O4/BC for removal of hexavalent chromium ions from simulated and electroplating wastewater

Li, Lincheng, Zhong, Dengjie, Xu, Yunlan, Zhong, Nianbing
Environmental science and pollution research international 2019 v.26 no.23 pp. 23981-23993
Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, activation energy, adsorbents, adsorption, biochar, chromium, endothermy, ions, iron oxides, kinetics, moieties, pollutants, scanning electron microscopes, scanning electron microscopy, surface area, wastewater
In order to improve the adsorption efficiency of the adsorbent and solve the problem of separation difficulty, a novel superparamagnetic micro-nano-bio-adsorbent (PDA/Fe₃O₄/BC) was prepared by in situ self-assembly of polydopamine (PDA). The results of scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR), X-ray photoelectron spectrometer (XPS), and vibrating sample magnetometer (VSM) characterization showed that the size of bio-adsorbent was about 200 nm. PDA and Fe₃O₄ modifications increased the specific surface area of adsorbent, changed the surface functional group of biochar (BC), and made the adsorbent have super-high magnetization (294.76 emu g⁻¹). PDA/Fe₃O₄/BC was applied to treat Cr wastewater. The results show that the adsorption of Cr by PDA/Fe₃O₄/BC includes single-layer and multilayer adsorption. The adsorption follows the pseudo-second-order kinetic model. The adsorption is spontaneous and endothermic, and its maximum adsorption capacity and activation energy are 25.25 mg g⁻¹ at 318 K and 23.108 kJ mol⁻¹, respectively. After adsorption treatment, PDA/Fe₃O₄/BC still possesses high magnetization (233.04 emu g⁻¹). PDA/Fe₃O₄/BC can treat actual electroplating wastewater with Cr(VI) concentration from 20 mg L⁻¹ to less than 0.2 mg L⁻¹, which met the PRC discharge standard (GB/21900-2008) of electroplating pollutants. Graphical abstract