The usage of zerovalent iron (ZVI) activated persulfate to induce sulfate radical (SO(4)(-)·) oxidation of both aqueous and solid phase naphthalene (Nap) was investigated. It was determined that the removal of Nap particles occurred through an indirect route. Specifically, Nap released through dissolution from the pure Nap particles was subsequently oxidized in the aqueous phase by SO(4)(-)·. Rapid destruction of dissolved Nap created a greater concentration gradient between the solid and aqueous phases. This caused more Nap particles to be dissolved which were then available for the subsequent oxidative destruction of dissolved Nap. The rate constant (k(obs,Nap)) of ZVI activated persulfate degradation of dissolved Nap was determined to be 3.74 min(-1). The overall dissolution mass transfer coefficients (k(L)a) for the Nap particles were determined, 3.0 × 10(-2) min(-1) with initial 10 mg Nap in 40 mL water, and found to be proportional to the quantities of the Nap particles present. The results indicate that the k(obs,Nap) is much greater than the k(L)a. The net result of the dissolution of Nap particles and the destruction of dissolved Nap by oxidation was the removal of Nap particles. Sequential additions of ZVI at a lower concentration to slow down the formation of SO(4)(-)· can prevent the scavenging of SO(4)(-)· by ZVI and enhance the removal of Nap particles. The results of the mass balance analysis during the oxidized, aqueous and solid phases of Nap were consistent with experimental observations.

This bench-scale study investigated the feasibility of activated persulfate (S(2)O(8)(2-)) oxidation of methyl tertbutyl ether (MTBE), using pyrite (FeS(2)) as the source of ferrous ion activators. Under the FeS(2)-activated S(2)O(8)(2-) condition, the sulfate free radical (SO(4)) is the predominant reactive species generated. The oxidation reactions were able to completely degrade MTBE when given sufficient doses of FeS(2) and S(2)O(8)(2-) and sufficient reaction time (e.g., 3 g FeS(2)/L and 5 g Na(2)S(2)O(8)/L within 4 h) and exhibited generation and subsequent degradation of the primary MTBE degradation intermediate products including tert-butyl formate, tert-butyl alcohol, methyl acetate, and acetone. The detailed reaction mechanism proposed for a SO(4)(-)driven oxidation process in this paper indicates that the destruction of MTBE most likely happens through alpha-hydrogen abstraction via attack of the SO(4)(-) at the intermediate methoxy group

No abstract

This paper reports an investigation of different persulfate (PS) activations, including PS at 20°C (PS), thermally activated PS at 70°C (T-PS), ferrous-ion activated PS at 20°C [Fe(II)-PS)], hydrogen peroxide activated PS at 20°C, and sodium hydroxide activated PS at 20°C, for degradation of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) in aqueous phase. Several findings were made in this study including the followings: the 2,4-D degradation rates in T-PS and Fe(II)-PS systems were higher than other systems. However, complete degradation of 2,4-D and associated derivatives can be reached in all oxidation systems, with various reaction times. When considering the results of PS consumption during the 48 h reaction time to reach complete 2,4-D degradation, the T-PS system consumed all of the PS while only 10 % of the PS was consumed in the Fe(II)-PS system.

No abstract