Adsorption kinetics of azo dyes on an organic-inorganic zincophosphate hybrid

Abstract

Effective methods are essential to addressing water pollution caused by the industrial use of azo dyes. Adsorption is a promising approach for water pollution treatment. Organic-inorganic hybrid crystals, composed of various ligands and metal centers, can serve as selective adsorbents for specific pollutants. In this study, a hybrid zinc phosphate with a two-dimensional layered structure, Zn3(C22H22N8)0.5(C22H24N8)0.5(HPO4)3(H2PO4)1 (herein referred to as KR5), was synthesized using zinc metal as coordination centers, phosphorous acid as the inorganic ligand, and 1,2,4,5-tetrakis(imidazole-1-ylmethyl)benzene (TIMB) as the organic linker under solvothermal conditions. Notably, the structural features of KR5 contribute to its excellent adsorption and removal capabilities for azo dye molecules. Furthermore, the adsorption kinetics of KR5 were investigated for four model dyes, enabling an assessment of its adsorption capacity for different ionic dyes. The change in adsorption amount was analyzed, and a kinetic model was fitted to evaluate the adsorption mechanism of KR5 for each dye molecule. This analysis aids in the effective design, optimization, and discovery of subsequent experimental processes, offering deeper insight into the adsorption characteristics of the material and providing valuable guidance for future research and applications.