Bifunctional Bi12O17Cl2/MIL-100(Fe) composites toward photocatalytic Cr(VI) sequestration and activation of persulfate for bisphenol A degradation

Highlights: • Bi₁₂O₁₇Cl₂/MIL-100(Fe) (BMx) was constructed by facile ball-milling method. • BM200 composite was an efficient photocatalyst for Cr(VI) and BPA cleanup. • BM200/light/PS system exhibited synergistic effect in BPA degradation. • BM200 showed good reusability and high stability. • DFT calculation with high Fukui index interpreted the easy-attacking sites on BPA. Bifunctional Bi₁₂O₁₇Cl₂/MIL-100(Fe) composite (BMx) was firstly constructed via facile ball-milling method. The optimal BM200 was highly efficient for Cr(VI) sequestration and activation of persulfate (PS) for bisphenol A (BPA) decomposition under white light illumination, which was much more remarkable than the pristine MIL-100(Fe) and Bi₁₂O₁₇Cl₂, respectively. Furthermore, the photocatalytic reduction efficiency can be significantly improved via the addition of some green small organic acids (SOAs). As well, the BPA degradation can be achieved over an extensive initial pH range of 3.0–11.0. When the PS concentration increased to more than 2.0 mM, the BPA degradation efficiency decreased due to the SO₄⁻• self-scavenging effect. It was also found that the co-existence of inorganic anions like H₂PO₄⁻, HCO₃⁻, SO₄²⁻, Cl⁻ and NO₃⁻ could decelerate the BPA degradation. The excellent photocatalytic Cr(VI) reduction and persulfate activation performances originated from both MIL-100(Fe) with excellent PS activation ability and Bi₁₂O₁₇Cl₂ with a favorable band position, which not only enabled the efficient separation of charges but also accelerated the formation of SO₄⁻• radicals. The BM200 displayed prominent stability and recyclability. More importantly, the credible degradation pathway was proposed based on UHPLC-MS analysis and DFT calculation. This research revealed that the Fe-based MOFs/bismuth-rich bismuth oxyhalides (Bi_xO_yX_z, X = Cl, Br and I) composites possessed great potential in wastewater remediation.