Degradation of sulfamethoxazole by a new modified Fenton-like process using Cu(II)-nitrilotriacetic acid complex as catalyst at neutral pH in aqueous medium

Fenton process is among the most effective advanced oxidation process in wastewater treatment , but the necessity to work at acidic pH, in order to avoid metal precipitation, limits its large-scale application. In this work, a new Fenton-like process using copper(II)-nitrilotriacetic acid (Cu II -NTA) complex as catalyst, was used for the activation of hydrogen peroxide (H 2 O 2 ) to degrade sulfamethoxazole (SMX) in aqueous medium under neutral pH conditions. The results showed that the Cu II -NTA/H 2 O 2 process was not efficient in the degradation of SMX. The reason being that the generation of HO radicals is still limited by the extremely slow Cu II -NTA/Cu I -NTA redox cycle. Therefore, the combination of hydroxylamine (HA) accelerate the Cu I recovery to induce the continuous production of HO radicals by the decomposition of H 2 O 2 . It was evident that the steady-state Cu I concentration in Cu II -NTA/HA/H 2 O 2 process was much elevated than the Cu II -NTA/H 2 O 2 process due to the quick regeneration of Cu I -NTA complex by HA. Kinetic profiles were evaluated under a wide range of experimental conditions in order to assess the effects of the initial concentrations, working pH, Cu(II):NTA molar ratio and reaction temperature. The results showed that the degradation rates were enhanced with the increase of H 2 O 2 and Cu II -NTA concentration during SMX oxidation. SMX was fully (83.64 %) degraded for an initial SMX concentration of 0.01 mM and an optimal Cu(II):NTA molar ratio of 1:1. Solution pH influenced SMX degradation and the highest degradation rate constant was achieved at pH 7.2. The radical scavenging experiments indicates that hydroxyl radical (HO ) has major role for SMX degradation. The presence of metal ions such as Mg II , Ca II and Mn II had no impacts or little inhibitory effect on the Cu II -NTA complex catalyzed Fenton-like reaction, however, a complete degradation of SMX was achieved in the presence of Fe III ions. Also, the effects of various inorganic anions such as Cl − , SO 4 2− , NO 3 − and HCO 3 − on the oxidation efficiency of SMX were studied. The efficiency of mineralization of aqueous solution of SMX was evaluated by measuring total organic carbon (TOC). These results demonstrate that Cu II -NTA catalyzed Fenton-like oxidation may be an efficient approach for remediation of wastewater containing antibiotics.