Effective adsorption of antimony(III) by MIL-101(Cr)-NH2: influencing-factor and characterization analyses and response surface optimization

With the increasing threat antimony (Sb) pollution poses to the environment, its removal from water is becoming increasingly important. Accordingly, metal-organic frameworks (MOFs) are garnering increasing research attention owing to their excellent performance as adsorbents. Here, the MOF MIL-101(Cr)-NH2 was prepared directly by solvothermal synthesis. Sb(III) adsorption using MIL101(Cr)-NH2 was evaluated systematically at varying adsorbent dosages and pHs. And the adsorption kinetics, isotherms, and thermodynamics were explored by altering the contact time, initial Sb(III) concentration, and temperature, respectively. The results revealed that Sb(III) was adsorbed onto MIL-101(Cr)-NH2 very quickly, even at low antimony concentrations. The maximum Sb(III) adsorption capacity of MIL-101-NH2 is 83.61 mg g-1. In the presence of coexisting ion (NO3-), the amount of Sb(III) adsorbed was slightly increased, which may be due to the formation of an inner-sphere complex. The Box-Behnken method was used to design and optimize a response surface with reference to three main influencing factors, that is, dosage, pH, and temperature, so as to obtain a multivariate quadratic model of adsorption behavior and identify the optimal adsorption conditions. Finally, a preliminary economic analysis of the synthetic material was carried out.

Automated summary

The study found that metal-organic frameworks show excellent performance in removing antimony pollution from water, with the ability to quickly adsorb antimony even at low concentrations. The presence of coexisting ions slightly increased the adsorption of antimony, possibly due to the formation of an inner-sphere complex. By optimizing the adsorption conditions, the best removal efficiency can be achieved.