Oxidation of Carbamazepine by Mn(VII) and Fe(VI): Reaction Kinetics and Mechanism

Abstract

Experimental studies were conducted to examine the oxidation of carbamazepine, an anticonvulsant drug widely detected in surface waters and sewage treatment effluent, by potassium salts of permanganate (Mn(VII); KMnO4) and ferrate (Fe(VI); K2FeO4). Results show that both Mn(VII) and Fe(VI) rapidly oxidize carbamazepine by electrophilic attack at an olefinic group in the central heterocyclic ring, leading to ring-opening and a series of organic oxidation products. Reaction kinetics follow a generalized second-order rate law, with apparent rate constants at pH 7.0 and 25 degrees C of 3.0 (+/-0.3) x 10(2) M(-1) s(-1) for Mn(VII) and 70(+/-3) M(-1) s(-1) for Fe(VI). Mn(VII) reaction rates exhibit no pH dependence, whereas Fe(VI) reaction rates increase dramatically with decreasing pH, due to changing acid-base speciation of Fe(VI). Further studies with Mn(VII) show that most common nontarget water constituents, including natural organic matter, have no significant effect on rates of carbamazepine oxidation; reduced metals and (bi)sulfide exert a stoichiometric Mn(VII) demand that can be incorporated into the kinetic model. The removal of carbamazepine in two utility source waters treated with KMnO4 agrees closely with predictions from the kinetic model that was parametrized using experiments conducted in deionized water at much higher reagent concentrations.

Oxidation of triclosan by ferrate: Reaction kinetics, products identification and toxicity evaluation

“…2. The rate constants of the reaction decreased with increasing pH values as observed in previous studies [29,38,39]. These pH-dependent variations in k app could be attributed to the speciations of both ferrate and triclosan.…”

“…Because the contribution of FeO 4 2− to the overall reactions of Fe(VI) is negligible, therefore the last two terms in Eq. (7) can be neglected [29,38,40,41]. As a result, Eq.…”

Pharmaceuticals and personal care products in effluent matrices: A survey of transformation and removal during wastewater treatment and implications for wastewater management

“…However, it has been shown that they are capable of efficiently degrading endocrine disruptors and antimicrobials, 161,162 as well as carbamazepine. 163 Furthermore, their disinfection byproducts are considered benign 164 and the products of their reduction (i.e., MnO 2 (s) and Fe(OH) 3 (s)) can be exploited as coagulants to further contribute to the removal of PPCPs and EfOM (see Hu et al 163 and references therein).…”

Permanganate oxidation of diclofenac: The pH-dependent reaction kinetics and a ring-opening mechanism

“…Recently, a study demonstrated that Mn(VII) can effectively degrade carbamazepine (CBZ), with an electrophilic attack at the olefinic group in the central heterocyclic ring of CBZ, leading to the formation of a series of ring-opening oxidation products (Hu et al, 2008). In addition to CBZ, the degradation kinetics and mechanisms between Mn(VII) and three other widely used antibiotics were investigated, where the apparent second-order rate constants were reported to be 0.61 ± 0.02 M À1 s À1 (ciprofloxacin), 1.6 ± 0.1 M À1 s À1 (trimethoprim) and 3.6 ± 0.1 M À1 s À1 (lincomycin) at pH 7 and 25°C (Hu et al, 2010(Hu et al, , 2011.…”