Effective strategy for removing Congo Red from wastewater by M_1-XFe_X(OH)₂ (M = Mg/Co/Ni/Zn, X = 0.3–0.8) via adsorption and degradation mechanism

Ferroan brucite with different Fe²⁺ doping amounts (Mg_1-XFe_X(OH)₂, x = 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8) was synthesized for the removal of Congo red (CR) from wastewater. As the Fe²⁺ content increased, the removal efficiency initially increased and then decreased, and Mg_0.6Fe_0.4(OH)₂ exhibited the maximum removal amount which was 2745.96 mg/g. The high removal ability of Mg_0.6Fe_0.4(OH)₂ was derived from the combined removal mechanism. The removal amount of CR was highly related to the amount of Fe²⁺ in MgFe(OH)₂ and its existed state. The removal behaviors of M_0.7Fe_0.3(OH)₂ (M = Zn, Ni, Co) were also conducted to verify the function and university of Fe²⁺ in the degradation process. The influence of M²⁺ in M_0.7Fe_0.3(OH)₂ (M = Zn, Ni, Co) on the removal efficiency was explored by experimental study and calculation of the system energy and bond length change based on molecular simulation. This work provided an outstanding approach for preparation of high efficiency materials to purify organic wastewater.