Efficient enzyme-mediated degradation of various emerging pollutants, including 2-mercaptobenzothiazole, paracetamol, and sulfamethoxazole, using HRP@UiO-66-NH2.

Abstract

The increasing contamination of water sources due to industrialization and population growth poses significant environmental and health risks, even at trace pollutant concentrations. Enzymatic bioremediation, particularly using horseradish peroxidase (HRP), has shown great potential in pollutant degradation due to its high selectivity and catalytic efficiency. However, limitations such as poor operational stability and reusability hinder its large-scale application. The degradation of structurally diverse emerging pollutants by UiO-66-NH2-immobilized HRP, including the influence of redox mediation, remains insufficiently investigated. This study addresses this gap by immobilizing HRP onto UiO-66-NH2, a metal-organic framework (MOF) with high stability and surface area. HRP@UiO-66-NH2 was characterized using SEM-EDX, PXRD, FTIR, TGA, and BET analyses, while pollutant degradation was quantified by LC-MS/MS. HRP loading concentrations ranging from 0.5 to 4 mg/mL were evaluated, and 1 mg/mL was selected for subsequent experiments. The immobilized HRP exhibited an optimum H2O2 concentration of 1.08 mM within the tested range of 0-2.43 mM. Both free and immobilized HRP showed maximum activity at pH 4, while the optimum temperature shifted from 30°C for free HRP to 40°C following immobilization. The immobilized enzyme also retained approximately 95% of its initial activity after four reuse cycles. HRP@UiO-66-NH2 was evaluated for the degradation of nine emerging pollutants, including 2-mercaptobenzothiazole, paracetamol, sulfamethoxazole, methylparaben, salicylic acid, lincomycin hydrochloride, atenolol, thiabendazole, and DEET. It degraded 99.7% of 2-mercaptobenzothiazole and 97.4% of paracetamol within 30 min. The addition of 1-hydroxybenzotriazole (HOBT) increased the degradation of sulfamethoxazole, methylparaben, and salicylic acid from 23.3%, 14.5%, and 12.4% to 53.1%, 57.6%, and 54.3%, respectively. The greater thermal and H2O2 tolerance of immobilized HRP suggests a protective effect of the UiO-66-NH2 framework, while the variable response to HOBT indicates pollutant-dependent redox mediation. These findings highlight HRP@UiO-66-NH2 as a promising biocatalyst for sustainable water remediation, warranting further studies to elucidate the underlying degradation mechanisms and optimize real-world applications.