The performance of the perovskite CaNixCu1-xO3-δ in the degradation of cefixime and humic acid from aqueous solutions under dark conditions

• CaNi₀.₂₅Cu₀.₇₅O₃−δ showed high dark catalytic activity for CFX and HA removal. • Over 95 % pollutant degradation achieved without light or added chemicals. • •OH and ¹O₂ radicals were the main reactive species in pollutant breakdown. • Catalyst retained high efficiency over multiple reuse cycles. • Offers a sustainable route for pollutant removal under light-free conditions. Contamination of water by pollutants such as cefixime (CFX) and humic acid (HA) poses a growing environmental and public health challenge. In this study, CaNi x Cu 1−x O 3−δ composites with various x values were synthesized via the sol–gel method and evaluated as novel dark catalysts for the degradation of CFX and HA in aqueous solution. Structural and surface properties of the catalysts were characterized using diagnostic analyses. SEM and TEM showed variable particle sizes, and BET analysis revealed a surface area of 6.82 m²/g, pore volume of 1.44 cm³/g, and pore size of 17.81 nm. Among the synthesized catalysts, CaNi 0.25 Cu 0.75 O 3−δ demonstrated the highest removal efficiency, achieving 95 % for CFX and 99 % for HA under optimal conditions, including acidic pH, elevated temperature, and appropriate catalyst dosage. The presence of interfering anions negatively affected the process, reducing pollutant removal by over 10 %. The catalyst maintained over 90 % efficiency across three reuse cycles, with some performance decline at six cycles due to active site loss and competitive adsorption. Scavenging experiments confirmed that adsorption, electron transfer, hydroxyl radicals (•OH), and singlet oxygen (¹O₂) were key contributors to degradation. Based on its high stability, reusability, and light-independent performance, CaNi 0.25 Cu 0.75 O 3−δ is a promising catalyst for efficient CFX and HA removal in dark conditions.