Adsorption behavior and mechanism of p-arsanilic acid on a Fe-based framework

Hypothesis: Organic arsenic pollutant p-arsanilic acid (p-ASA) in wastewater can be converted into highly toxic inorganic arsenic under natural conditions, causing serious harm to the environment and human health. In this study, an Fe-based metal-organic framework (MOF) material, activated MIL-88A, was synthesized as an adsorbent to remove p-ASA in water. Experiments: Various influencing factors in the material synthesis process, including temperature, time, solution, and annealing process, were investigated to obtain the optimal reaction conditions. The synthesized activated MIL-88A had great porosity and excellent adsorption capacity for p-ASA in a wide pH range (3 similar to 10). When the pH of the solution was 6, the activated MIL-88A achieved a great adsorption capacity of 813 mg?g(-1) for the p-ASA solution with an initial concentration of 0.334 mmol?L-1. In addition, it still had excellent adsorption capacity after 4 times of repeated usage and washing. Findings: The adsorption kinetics of p-ASA on the activated MIL-88A followed the pseudo-second-order models, and the adsorption isotherms can be fitted by the Langmuir models well. The adsorption behavior was spontaneous and endothermic, and was dominated by Fe-O-As coordination and hydrogen bonding. (C) 2022 Elsevier Inc. All rights reserved.