Decontamination of Cr(VI) and tetracycline hydrochloride by Bi@NH2-MIL-88B-enhanced photocatalytic electron-rich microenvironment and its internal mechanism.

Non-precious metals that demonstrate surface plasmon resonance (SPR) effects have attracted considerable attention due to their ability to enhance the photocatalytic degradation of unexpected pollutants in water. Here, the interfacial charge transfer and improvement of the Bi-metal center are accomplished through in-situ synthesis, along with a comprehensive analysis of the catalytic activity and mechanism of the Bi-metal center. On this basis, the response surface method (RSM) and statistical analysis are used to evaluate the performance of Cr(VI). The adequacy results of the models showed that all models could predict the photoreduction efficiency of Cr(VI) by Bi@NM-88. The results of process optimization showed that pH = 5, Cr(VI) concentration = 80 μmol L-1, photocatalyst dosage (100 mg L-1), and ammonium oxalate concentration (0.21 mmol L-1) are the optimal levels of the study parameters. Additionally, the Bi@NM-88 is capable of efficiently eliminating Cr(VI) from wastewater generated by industrial electroplating. The removal rate of Cr(VI) surpasses 80 % after 240 min of exposure to light, indicating its promising potential for real-world wastewater treatment applications. In addition, the toxic effects of the solution after photocatalytic reduction of Cr(VI) on plant growth are further studied through experiments on photosystem II (PSII) of wheat seedlings and ecotoxicity experiments on the roots and stems of rice seedlings. Moreover, the Fukui index and quantitative structure-activity relationship (QSAR) are used to determine the reaction sites and toxicity of reaction intermediates of TC-HCl molecules. It should be emphasized that the junction of Bi with the amino functional group of Bi@NM-88 is the most significant place for charge transfer under UV-Vis light, indicating that this is the center of its catalytic activity. This study inspires the design of high-performance core-shell structured photocatalysts and expands their practical applications in environmental remediation.