Enhanced removal of P(V), Mo(VI) and W(VI) generated oxyanions using Fe-MOF as adsorbent from hydrometallurgical waste liquid: Exploring the influence of ionic polymerization.

Environmentally hazardous P(V), Mo(VI) and W(VI) generated oxyanions exist widely in the waste liquid of nonferrous hydrometallurgy. In this work, Fe-MOF material was simply prepared via solvothermal synthesis and then used as an adsorbent to remove P(V), Mo(VI) and W(VI) oxyanions from hydrometallurgical waste liquid. Several important parameters, including solution pH, oxyanion concentration, contact time, adsorbent amount, temperature and coexistent heavy metal ions, were systematically investigated. The results demonstrate that adsorption process was almost pH-independent over a broad range of pH 3.0-10.0. The adsorption efficiency was strongly associated with the chemical species of oxyanions. The higher polymerisation degree of oxyanions was more favourable for removal efficiency. Additionally, the maximum removal efficiencies for P(V), Mo(VI) and W(VI) oxyanions under optimum conditions were approximately 100%. Furthermore, the adsorption kinetics and isotherms of oxyanions on the adsorbent separately belonged to the pseudo-second-order and Langmuir isotherm models. XPS analysis revealed that inner-sphere complexation played a dominant role in the adsorption removal process. Fe-MOFs with pH-independent properties, abundant binding sites and high stability are prospective adsorbents for treating waste liquids in the hydrometallurgical industry.