Environmental behavior of iodine povidone in aquaculture: stability and sediment adsorption kinetics.

The overuse of iodine-based disinfectants poses a potential threat to both biological health and the ecological environment. However, their stability and the adsorption kinetics of active iodine by pond sediment in aquaculture settings remain poorly understood, with mechanisms unclear. This study investigates the environmental factors influencing the stability and adsorption characteristics of povidone-iodine (PVP-I) in pond sediment. Results show that under low-temperature, light-avoiding, and acidic conditions, high concentrations of PVP-I exhibit slow depolymerization, with efficacy duration significantly affected by initial concentration, temperature, and pH. Adsorption kinetics conform to the Elovich equation, indicating temperature's significant impact on adsorption rate and non-homogeneous diffusion behavior. Sediment's maximum adsorption capacity for active iodine is 4.05 mg/g, consistent with the Freundlich isotherm model. Exceeding sediment adsorption capacity may lead to active iodine infiltration into groundwater. Additionally, temperature fluctuations can disrupt adsorption-desorption equilibrium, posing seasonal risks of iodine concentration fluctuations. This study suggests controlling PVP-I dosage and blocking pollution pathways via temperature regulation and sediment improvement in aquaculture, providing a scientific basis for ecological risk assessment and safe application.