From waste to waste treatment: Mesoporous magnetic NiFe2O4/ZnCuCr-layered double hydroxide composite for wastewater treatment

Mesoporous magnetic NiFe2O4/ZnCuCr-LDH composite is synthesized by an environmental-friendly hydrothermal process from saccharin wastewater to achieve the goal of "treating the wastes with wastes". During this process, all waste iron-catalyst and 82% of chemical oxygen demand (CODcr) are removed from the wastewater. The composite is characterized by FT-IR, XRD, SEM, EDS, TEM, XPS, BET, and VSM analyses and its potential for wastewater treatment is evaluated by Congo Red (CR) adsorption. An over 97% removal efficiency is achieved with an initial CR concentration ranging from 100-450 mg/L. The adsorption kinetic is investigated and it is found that the experimental data agrees well with the pseudo-second-order kinetic model, intra-particle diffusion and Langmuir adsorption isotherm model. Adsorption isotherm indicates a spontaneous and endothermic adsorption type. The adsorption mechanism is also explored and the important roles of electrostatic attraction and anion exchange are demonstrated. (C) 2019 Elsevier B.V. All rights reserved.