Adsorption and removal of direct red 31 by Cu-MOF: optimization by response surface

Abstract

Cu(PABA) is a Cu-based MOF material assembled from Cu2+ and the organic ligand p-aminobenzoic acid (PABA).Cu(PABA) was synthesized by solvothermal method, characterized and applied to the adsorption of direct red 31 dye(DR-31). The effects of pH, DR-31 concentration and temperature on the adsorption performance of Cu(PABA) were investigated. The adsorption kinetics was analyzed by pseudo-first-order, pseudo-second-order and intra-particle diffusion models, and the adsorption equilibrium data was fitted by Langmuir and Freundlich isotherm models. The pseudo-first -order kinetics and Langmuir model satisfactorily described the adsorption kinetics and adsorption equilibrium, respectively. The maximum adsorption capacity of Cu(PABA) for DR-31dye at room temperature was 1,244.8 mg/g, as calculated using the Langmuir adsorption isotherm model.By response surface methodology (RSM), the optimal adsorption was found at pH value of 10.9, DR-31 dye concentration of 216.6 mg/L, and temperature of 27 °C, and the removal rate was as high as 99.4%.Therefore, Cu(PABA) can be used as an efficient adsorbent for removing DR-31 dye from aqueous solution.