DCP Degradation Research Articles

A comparative study of the advanced oxidation of 2,4-dichlorophenol

Advanced oxidation processes (AOPs) using UV, UV/H 2O 2, Fenton and photo-Fenton treatment were investigated at laboratory scale for aqueous solutions of 2,4-dichlorophenol (DCP). The effects on degradation of different reactant concentrations, irradiation time, temperature and pH were assessed. DCP removal, TOC mineralization, dechlorination and change in oxidation state were monitored. UV photolysis was less efficient for total DCP degradation than other AOPs. In contrast, photo-Fenton reaction in acidic conditions led to a higher DCP degradation in a short time. Sixty minutes of treatment were sufficient for 100% DCP removal with 75 mg l −1 H 2O 2 and 10 mg l −1 Fe(II) initial concentrations. In these conditions, a first-order degradation constant for DCP of 0.057 min −1 was obtained.

Photo-Fenton oxidation of pesticides

The photo-Fenton process is becoming a practical treatment option for waters contaminated with pesticides and other organic compounds that are poorly biodegradable. This process can potentially be integrated into an existing water treatment process to enhance organic compound removal. It can operate at low concentrations of contaminant and can often completely mineralise the compound or convert it into a less toxic form. The process is most efficient at around pH 2.8; however, it has been found that with the addition of suitable complexing agents for Fe(III), the process can be operated at close to neutral pH. This study used citric acid as a complexing agent, 2,4-dichlorophenol (DCP) as a model contaminant and investigated the extension of the feasible pH range of the process from pH 5 to pH 8. The study involved synthetic solutions and light from a mercury arc lamp, with a bandpass filter used to isolate the emission band at around 360 nm. Low concentrations of DCP (12 μM) and Fe(II) (10 mM) were used to simulate conditions possible in the environment. In this work, no H2O2 was added, however, a relatively high concentration of citrate (100 μM) was used. Citrate is itself degraded in the process, and since it is highly biodegradable any excess could be consumed in a subsequent biological treatment process. The extent of degradation of DCP after 2 hours was found to be 91% at pH 5, 73% at pH 6, 74% at pH 7, and 59% at pH 8.

Fate and origin of 1,2-dichloropropane in an unconfined shallow aquifer.

A shallow aquifer with different redox zones overlain by intensive agricultural activity was monitored for the occurrence of 1,2-dichloropropane (DCP) to assess the fate and origin of this pollutant. DCP was detected more frequently in groundwater samples collected in aerobic and nitrate-reducing zones than those collected from iron-reducing zones. Simulated DCP concentrations for groundwater entering an iron-reducing zone were calculated from a fate and transport model that included dispersion, sorption, and hydrolysis but not degradation. Simulated concentrations were well in excess of measured values, suggesting that microbial degradation occurred in the iron-reducing zone. Microcosm experiments were conducted using aquifer samples collected from iron-reducing and aerobic zones to evaluate the potential for microbial degradation of DCP and to explain field observations. Hydrogenolysis of DCP and production of monochlorinated propanes in microcosm experiments occurred only with aquifer materials collected from the iron-reducing zone, and no dechlorination was observed in microcosms established with aquifer materials collected from the aerobic zones. Careful analyses of the DCP/1,2,2-trichloropropane ratios in groundwater indicated that older fumigant formulations were responsible for the high levels of DCP present in this aquifer.

2,4-Dichlorophenol degradation using Streptomyces viridosporus T7A lignin peroxidase.

The Streptomyces viridosporus T7A bacterium produces the extracellular lignin peroxidase ALiP-P3. The ALiP-P3-catalyzed oxidation of 2,4-dichlorophenol (DCP) was examined to understand its kinetic behavior. Initial rate data of the oxidation of DCP were obtained by a spectrophotometric peroxidase assay, and the kinetics were best modeled with a random-binding bireactant system, which differs from the ping-pong bireactant system that is typically used for horseradish peroxidase and lignin peroxidase from the fungus Phanerochaete chrysosporium, and suggests that either DCP or H2O2 may bind first to ALiP-P3. Chloride ion measurements indicate that 16% of the reacted DCP was fully dechlorinated by ALiP-P3. Chemical ionization mass spectrometry was also utilized to identify the DCP degradation product as a hydrophobic chlorinated dimer of mass 322.