Porous calcium copper titanate electrodes for paracetamol degradation by electro-oxidation via CuO-induced peroxymonosulfate activation

Some drugs cannot be efficiently eliminated using routine wastewater treatments and therefore are considered persistent organic pollutants (POPs). POPs can be removed using advanced oxidation processes. Among these processes, the combination of electrocatalysis and a sulfate-based advanced oxidation process via peroxymonosulfate (PMS) activation is an attractive approach due to its high efficiency, low energy consumption and non-selective attack. It is well known that the type of anode strongly affects the electrocatalysis performance for water treatment. Here, we evaluated perovskites as electrode material due to their unique structural properties and high chemical stability. We fabricated porous anodes of calcium copper titanate (CaCu3Ti4O12; CCTO) with different percentages (20%, 30% and 40%) of polymethyl methacrylate (PMMA) by ball-milling. The samples that included PMMA displayed 50% porosity and pores were homogenously distributed. Morphological measurements show the presence of grain structures and grain boundaries containing CCTO and CuO phases, respectively. CCTO with 30 wt% PMMA (CCTO-30) exhibited the highest CuO phase amount, defect percentage and oxidation-reduction peak, and the smallest resistance. We used the obtained CCTO nanocomposites as anodes in a beaker (210 mL) with PMS (0.5 mM) to treat 10 ppm paracetamol in 50 mM sodium sulfate. After 90 minutes, paracetamol was completely decomposed using CCTO-30 due to PMS activation by a copper catalytic cycle (Cu2+/Cu1+ and Cu2+/Cu3+) to generate (SO4-)-S-center dot radicals and Cu3+ non-radicals that are selective for its removal.

Automated summary

Some drugs classified as persistent organic pollutants (POPs) cannot be efficiently removed by routine wastewater treatments. A combination of electrocatalysis and a sulfate-based advanced oxidation process via peroxymonosulfate activation has been proven to be an efficient and non-selective method for removing POPs. Perovskites, specifically calcium copper titanate (CCTO), were evaluated as electrode materials due to their unique structural properties and high chemical stability. Through fabrication of porous CCTO anodes with different percentages of polymethyl methacrylate (PMMA), it was found that the CCTO-30 anode exhibited the highest performance in terms of CuO phase amount, defect percentage, oxidation-reduction peak, and resistance. By using CCTO-30 as anodes in a beaker with PMS, paracetamol was completely decomposed due to copper catalytic cycle activation, leading to the generation of radicals and non-radicals that selectively remove paracetamol.