Atacamite (Cu2Cl(OH)3) as catalyst of different AOPs for water disinfection

Atacamite (Cu2Cl(OH)3) is a natural mineral normally used as a pigment, but this study explores its photocatalytic activity in order to be used for water treatment applications, specifically, the removal of Enterococcus faecalis for reclamation of wastewater. The research demonstrates that the system atacamite/solar radiation yields efficient bacterial inactivation (total inactivation in 90 min with 100 mg/L of atacamite). The addition of oxidants such as peroxymonosulfate (PMS), persulfate (PS), and hydrogen peroxide (H2O2), to the system allowed for an increase in the kinetic of the system by promoting the reaction between the oxidants and the catalyst. The optimized system requires a concentration of 0.3 mM of oxidants and 50 mg/L of atacamite under solar radiation. Notably, the system with PMS exhibits exceptional performance, reaching total inactivation of E. faecalis in 30 min. The determination of synergistic indices for the treatments revealed that the system using PMS and PS has a synergistic effect with values of 1.42 and 1.62, respectively. However, the system using H2O2 exhibited an antagonistic behavior with a value of 0.74. Moreover, from the perspective of energy consumption efficiency, the incorporation of PMS allows for a lower energy consumption per unit of Enterococcus faecalis removal, as demonstrated by the Electric Energy per Order (EEO) Figure of Merit. The qualitative study for determination of oxidizing species involved in the reactions was performed mainly using different scavengers as MeOH, TBA and EDTA, and additionally the concentration of free chlorine generated in the system was measured. The study revealed that the PMS/atacamite/solar radiation system involves a higher number of oxidizing species, consistent with the observed results related to the kinetics of removal. Further investigation and optimization of this innovative approach hold promise for future applications in the field of water purification and environmental remediation.