Non-thermal plasma-assisted Ag-CoFe₂O₄ as an efficient visible-light photocatalyst for pollutant degradation

Non-thermal plasma (NTP) technology has gained much interest for environmental applications, especially for air and water purification. In this study, we report a room-temperature, plasma-assisted approach for the synthesis and surface modification of Ag-doped CoFe₂O₄. Using three distinct NTP assisted pathways, Ag⁺ is efficiently reduced to metallic Ag⁰ within 30 min at 16 kV, attaining uniform Ag doping without thermal treatment. Plasma engineering significantly modifies the physicochemical properties of CoFe₂O₄, leading to enhanced crystallinity, reduced particle sizes (28-34 nm), and a narrowed band gap (1.4-1.5 eV) compared with the undoped and non-plasma-treated counterparts with particle sizes of 35-50 nm and band gap of 2.1 to 1.9 eV. These surface modifications translate directly into superior catalytic performance. The plasma-derived Ag-CoFe₂O₄ catalysts indeed show outstanding visible-light-driven activity toward the degradation of representative pharmaceutical (ciprofloxacin) and dye (crystal violet) contaminants, achieving 86-89% ciprofloxacin removal within 60 min and 48-68% crystal violet degradation. This work demonstrates that non-thermal plasma (NTP) assisted synthesis is a highly efficient, multipurpose strategy for simultaneous silver (Ag) doping and material modification. Also, it enables the development of highly active catalysts with enhanced performance for photocatalytic treatment of industrial and pharmaceutical wastewater.