Adsorption behavior and mechanism of p-arsanilic acid on a Fe-based metal-organic 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 ∼ 10). When the pH of the solution was 6, the activated MIL-88A achieved a great adsorption capacity of 813 mg·g for the p-ASA solution with an initial concentration of 0.334 mmol·L. 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.