Plasma-catalytic remediation of pharmaceutical-contaminated wastewater: Catalyst design and mechanistic insights from DFT.

Contaminants of emerging concern (CECs), characterized by persistence, poor biodegradability, and high toxicity, pose significant risks to aquatic ecosystems and human health. Plasma-catalytic processes may eliminate CECs, particularly micropollutants, from wastewater. However, discharge-zone thermalization and heavy-metal leaching from metal-based catalysts pose challenges for industrial adoption of cold plasma technology. This study presents a novel coaxial plasma electrode and a heteroatom-doped carbonaceous catalyst that overcome these limitations. Catalysts with varying boron and oxygen contents are synthesized through the pyrolysis of waste wood, boric acid, and zinc borate at 1000 °C. Boron-doped graphene-like carbon with 15-wt.% boric acid and 15-wt.% zinc borate exhibits superior ozone degradation and hydrogen-peroxide formation. The plasma-catalytic system demonstrates high-efficacy micropollutant degradation, achieving complete naproxen degradation in less than 30 min with a 0.1112 degradation rate and 75.67 % mineralization. Additionally, it effectively removed naproxen, rhodamine B, and Congo red from real wastewater spiked with 10 ppm of each pollutant. Density functional theory calculations elucidate the high affinity of armchair BC2O for ozone adsorption. Moreover, the dual role of zinc borate as both an activator and dopant in the synthesis of boron-doped graphene-like carbon is revealed. As the synthesized metal-free catalyst exhibits high performance for treatment of real wastewater samples, and the plasma setup is simple and efficient, this system has scalability and practical applicability in wastewater treatment plants.