Multifunctional Ca2+/Mg2+ codoped ZnO nano-semiconductors with enhanced photocatalytic performance and photo-modulated antibacterial action for the remediation of methyl orange dye and chlorpyrifos pesticide in binary systems

The development of multifunctional nanomaterials for the remediation of complex wastewater is increasingly urgent. Based on this, the current study focused on optimizing decontamination and disinfection of a simulated wastewater via heterogeneous photocatalysis using Ca 2+ /Mg 2+ codoped ZnO nano-semiconductors (ZnO-CaMg x%, with x = 0; 1.0; 3.0; 5.0; 7.0 mol%), synthesized by a modified sol-gel method. These nano-semiconductors exhibited improved properties over undoped ZnO, including smaller crystallite size, higher specific area and increased structural defects with the insertion of Ca 2+ /Mg 2+ codopants. Notably, ZnO-CaMg 3.0 % showed the best performance, degrading ∼90 % of methyl orange (MO) dye and 99 % of chlorpyrifos (CPF) pesticide, in single systems under UV–vis irradiation (240 min, pH 9.0), while undoped ZnO (ZnO-CaMg 0 %) degraded only 56 % and 73 %, respectively. In MO/CPF binary system, ZnO-CaMg 3.0 % photodegraded ∼99 % of both pollutants (λ = 229 nm) after 600 min of UV–vis irradiation. The main reactive species involved in the photocatalytic process were identified, and quality parameters evidenced the efficient mineralization of the pollutants. ZnO-CaMg 3.0 % also exhibited excellent recyclability , degrading 80 % of MO and 99 % of CPF after five photocatalytic cycles in single or binary system. Additionally, these nano-semiconductors exhibited efficient bacteriostatic activity against the harmful pathogens Staphylococcus aureus ( S. aureus ) and Escherichia coli ( E. coli ). Against S. aureus, MIC values for ZnO-CaMg 0 % and 3.0 % reduced from 1.0 mg mL −1 to 0.12 mg mL −1 after 1 h of visible irradiation. For E. coli , ZnO-CaMg 3.0 % was more effective in the absence of light, but only ZnO-CaMg 0 % showed photo-modulated antibacterial action, reducing MIC from 1.0 mg mL −1 to 0.5 mg mL −1 after 1 h under light incidence. These findings highlight ZnO-CaMg 3.0 % as a promising environmental agent for simultaneous decontamination and disinfection of real wastewater , reducing costs and treatment steps.