Treatment of Four Biorefractory Contaminants in Soils Using Catalyzed Hydrogen Peroxide

Abstract

The treatment of soil contaminated with pentachlorophenol, trifluralin [2,6‐dinitro‐N, N‐dipropyl‐4‐(trifluoromethyl) benzenamine], hexadecane, and dieldrin (3,4,5,6,9,9‐hexachloro‐1a,2,2a,3,6,6a,7,7a‐octahydro‐2,7:3,6‐dimethanonaphth[2,3‐b]oxirene) using catalyzed hydrogen peroxide [H202 and iron(II)] was investigated in a soil of low development with organic C ranging from 2000 mg kg–1 to 16 000 mg kg–1. Soil treatment was conducted at pH 3 with 240 and 400 mg L–1 iron additions and 120 000 mg L–1 H2O2. Pentachlorophenol and trifluralin degradation rates decreased as a function of soil organic C content. However, soil organic C had no effect on the degradation rates of dieldrin and hexadecane. In addition, the four contaminants degraded at equal rates with soil containing organic C > 10 000 mg kg–1. The ratio of first‐order rate constants for contaminant degradation to hydrogen peroxide consumption (kcontaminant/kh2O2) was used as an empirical measure of treatment efficiency. These ratios were sensitive to both the soil organic C content and to the concentration of iron added during treatment. The efficiency ratios were highest for treatment with no iron addition; these data suggest that iron minerals and H2O2 provide a system in which Fenton‐like oxidations are catalyzed. The ability of iron minerals and H2O2 to oxidize pentachlorophenol was evaluated in goethite‐, hematite‐, and magnetite‐silica sand at pH 3. Pentachlorophenol was degraded in the mineral‐silica sand systems, which was verified by the loss of organic C and the stoichiometric recovery of chloride.

Interfacial mechanisms of heterogeneous Fenton reactions catalyzed by iron-based materials: A review

“…Ever since the discovery of heterogeneous Fenton reactions in 1991, Tyre et al (1991) proposed two possible interfacial mechanisms, i.e., the homogeneous Fenton mechanism induced by surface-leached iron and heterogeneous catalysis on the mineral surface, as illustrated in Fig. 1.…”

Fundamentos e aplicações ambientais dos processos fenton e foto-fenton

“…Posteriormente, Tyre e colaboradores 85 observaram que minerais de ferro presentes no solo podem atuar como catalisadores na decomposição do peróxido de hidrogênio, dispensando a aplicação de ferro solúvel ao tratamento. Mostraram que a degradação de pentaclorofenol, hexadecano, trifluralina e dieldrin presentes em solo foi mais eficiente estequiometricamente (quantidade de H 2 O 2 consumido por mol de contaminante) sem a adição de ferro solúvel.…”

On the Fenton degradation mechanism. The role of oxalic acid

“…The Fenton reagent has been also used to degrade organic chlorides, pesticides, monocyclic aromatics as well to reduce the COD (chemical oxygen demand) of municipal waters [3][4][5][6][7][8][9] . It also has been used in the decontamination of soils 10 . It has been proposed [11][12][13][14] that the reaction mechanism involves formation of the hydroxyl radical in a rate limiting step (Eq.1) with further diffusion-controlled rate radical attack to the organic substrate.…”