Efficient Adsorption of Arsenic from Smelting Wastewater by CoMn-MOF-74 Bimetallic Composites

Removing arsenic from industrial wastewater remains a crucial task. To protect public health and safety and address environmental pollution, there is an urgent need for a material that can efficiently remove arsenic from wastewater. In this study, a simple and highly efficient adsorbent, namely, a Co/Mn bimetallic-based organic framework (CoMn-MOF-74) adsorbent, was prepared by a hydrothermal synthesis method. Experimental results demonstrate that CoMn-MOF-74 exhibits excellent adsorption capacity for arsenic ions in wastewater. It was found that the optimal Co/Mn molar ratio of the adsorbent is 1:1. The CoMn-MOF-74 adsorbent compensates for the deficiencies in the adsorption performance of Co-MOF-74 and Mn-MOF-74, increasing the adsorption rate and the highest adsorption capacity. The maximum adsorption rate of CoMn-MOF-74 is 93.4%, and the highest adsorption capacity is 531 mg/g. Fitting CoMn-MOF-74 according to two categories of models, specifically, the adsorption isotherm and adsorption kinetics models, indicated that CoMn-MOF-74 adheres to the Langmuir model and pseudo-second-order kinetic model. The adsorption process is mainly chemical adsorption and monolayer adsorption. Analysis by XPS revealed that metal–oxygen groups and hydroxyl groups play important roles in the adsorption process. In conclusion, the CoMn-MOF-74 adsorbent shows excellent prospects in the field of arsenic adsorption from wastewater and is a promising arsenic-removing adsorbent.