Recycling of Ujala Neel-Treated Water through Photocatalytic Approach: A Scientific Study from the Perspective of Indian Tradition

Ujala Supreme or Ujala Neel, commonly used as fabric whiteners, has become a significant yet often overlooked source of water pollution, where the key ingredient is Acid Violet 49, a synthetic triphenylmethane dye. In this study, we investigated the recovery of Neel-treated water under simulated solar light irradiation by using photocatalysts such as NiO–ZnO, NiFe2O4/rGO, and CuO–ZnO. Photocatalytic degradation performance was evaluated under varying conditions of initial Neel concentration, catalyst dosage, and different light conditions to optimize the efficiency of the degradation process. Among these photocatalysts, 25 mg of NiO–ZnO with 3 mg of oxone (oxidizing agent) exhibited 98.4% degradation of 50 mL of 1% Neel solution (i.e., 1 mL Neel solution in 100 mL distilled water) within 60 min under sunlight irradiation. The NiO–ZnO photocatalyst showed promising activity toward Neel water degradation with 85.06 % mineralization. NiO–ZnO also displayed high catalytic stability up to the 5th cycle, acting as a potential green catalyst for the degradation of Neel from domestic as well as textile industry effluents. The kinetic study showed that the reaction was of first order with a rate constant of 0.068 min–1, and the mechanistic study revealed that holes were the active species for the photodegradation process.