Enhanced degradation and mineralization of sulfamethoxazole by integrating gamma radiation with Fenton-like processes

Degradation of sulfamethoxazole (SMX) by ionizing radiation combined with goethite (alpha-FeOOH) catalyzed Fenton-like process were studied under various conditions. The results showed that SMX could be degraded completely at 2 kGy with or without the addition of goethite. This process followed pseudo first-order kinetics model. The presence of goethite promoted the mineralization of SMX, and the mineralization ratio increased with the increase of goethite dosage. The decomposition of SMX in goethite/ionizing radiation system exhibited high activity at pH ranging from about 3.0 to 11.0. Acidic condition was more preferable than alkaline condition for the degradation of SMX. The presence of humic acid inhibited SMX degradation, due to the competition of hydroxyl radical with SMX molecules. The addition of tert butyl alcohol (TBA) resulted in the decrease of SMX removal efficiency, indicating that hydroxyl radical played the main role in this system. This investigation demonstrated that goethite combined with ionizing radiation has potential for enhancing the mineralization of toxic organic pollutants in water and wastewater.