Preparation of Fe-Co based MOF-74 and its effective adsorption of arsenic from aqueous solution.

To obtain a cost-effective adsorbent for the removal of arsenic in water, a novel nanostructured Fe-Co based metal organic framework (MOF-74) adsorbent was successfully prepared via a simple solvothermal method. The adsorption experiments showed that the optimal molar ratio of Fe/Co in the adsorbent was 2:1. The FeCo MOF-74 was characterized by various techniques and the results showed that the nanoparticle diameter ranged from 60 to 80 nm and the specific surface area was 147.82 m/g. The isotherm and kinetic parameters of arsenic removal on FeCo MOF-74 were well-fitted by the Langmuir and pseudo-second-order models. The maximum adsorption capacities toward As(III) and As(V) were 266.52 and 292.29 mg/g, respectively. The presence of sulfate, carbonate and humic acid had no obvious effect on arsenic adsorption. However, coexisting phosphate significantly hindered the removal of arsenic, especially at high concentrations (10 mmol/L). Electrostatic interaction and hydroxyl and metal-oxygen groups played important roles in the adsorption of arsenic. Furthermore, the prepared adsorbent had stable adsorption ability after regeneration and when used in a real-water matrix. The excellent adsorption performance of FeCo MOF-74 material makes it a potentially promising adsorbent for the removal of arsenic.