Efficient capture of arsenate from alkaline smelting wastewater by acetate modulated yttrium based metal-organic frameworks

Arsenic is worldwide recognized the first-class carcinogen. How to efficiently treat arsenic in alkaline mining smelting wastewater is an urgent technical problem. Here in, acetate modulated yttrium-based metal-organic frameworks MOF-76(Y) (MOF-76(Y)-Ac) has been exploited for investing the adsorption behavior and mechanism of arsenate in alkaline conditions. MOF-76(Y)-Ac presented smaller particle size, higher porosity and larger number of coordinatively unsaturated sites, and consequently exhibited significantly enhanced adsorption affinity and capacity toward arsenate compared with that of pristine MOF-76(Y). In the optimized operating condition (pH 9–11), the maximum Langmuir adsorption capacity of arsenate by MOF-76(Y)-Ac can be 201.46 mg g⁻¹ within 30 min. The arsenate adsorption capacity of MOF-76(Y)-Ac remained stable with the presence of coexisting anions and natural organic matters, even in practical simulated gold smelting alkaline wastewater. The formation of Y-O-As coordination connected with Y nodes in MOF-76(Y)-Ac originating from ligand exchange between arsenate and the BTC linkers is the main adsorption mechanism, besides, the ligand change mechanism with Y-OH sites and chemical precipitation mechanism by forming YAsO₄ cannot be neglected. The used MOF-76(Y)-Ac can be recycled with HCl without changing its constant crystalline phase and adsorption performance. The results show that MOF-76(Y)-Ac can be a promising dearsenification reagent for high arsenic alkaline wastewater.