Oxidation kinetics of pentachlorophenol by manganese dioxide

Abstract

This study examined the abiotic transformation kinetics of pentachlorophenol (PCP) by manganese dioxide (MnO2) at different solution chemistry and initial concentrations of PCP and MnO2. The measured PCP transformation rates were found to be on the order of 1.07 with respect to [PCP] and 0.91 and 0.87 with respect to [MnO2] and [H+], respectively. Dissolved Mn2+ and Ca2+ as background electrolytes considerably decreased the reaction rate because of their adsorption and hence blocking of active sites on MnO2 surfaces. The dechlorination number, 0.59 chloride ions per transformed PCP after a 1-h reaction, suggests that a fraction of the transformed PCP was not dechlorinated and may be coupled directly to dimeric products. Gas chromatography/ mass spectrometry and liquid chromatography/mass spectrometry/mass spectrometry techniques were used to identify two isomeric nonachlorohydroxybiphenylethers as major products and 2,3,5,6-tetrachloro-1,4-hydroquinone and tetrachlorocatechol as minor products. Product identification suggested that the reaction may include two parallel reactions to form either dimers or 2,3,5,6-tetrachloro-1,4-hydroquinone and tetrachlorocatechol via simultaneous dehydrochlorination and hydroxylation.

Transformation of Bisphenol A in the Presence of Manganese Dioxide

“…The observation that the rate of disappearance of BPA rapidly decreased as the reaction proceeded is consistent with previous studies (Zhao et al, 2006(Zhao et al, , 2009Stone, 1987;Laha and Luthy, 1990;Rubert and Pedersen, 2006;Klausen et al, 1997;Ukrainczyk and McBride, 1993;Lin et al, 2009;Ulrich and Stone, 1989;Stone and Morgan, 1984). The lowered rates at later stages of the reaction probably resulted from the decreased availability of active Mn sites on MnO 2 surfaces caused by adsorption of oxidative products of BPA and the reduced Mn 2+ on the surfaces.…”

“…Manganese dioxide was obtained from Acros Organics (Fair Lawn, NJ) and was characterized following a procedure described elsewhere (Zhao et al, 2006). Crystallographic d spacings determined by X-ray diffraction were 2.42 (100%), 2.12 (90%), 1.64 (100%), 1.43 (20%) Å , which match those reported for C-MnO 2 (Ulrich and Stone, 1989).…”

“…1B, the amount of the adsorbed BPA was approximately 2% to 3% of the total BPA mass within the system at a given reaction time. This is much lower than the 10% pentachlorophenol sorbed by the same MnO 2 solid (Zhao et al, 2006). Such sorption difference may result from the differences of hydrophobicity between the two organic solutes because the log K OW values of BPA and pentachlorophenol are 3.18 and 5.1, respectively.…”

“…Manganese dioxide (MnO 2 ) is commonly found in soils and sediments and is a highly oxidative mineral constituent in the environment (McKenzie, 1989). Previous studies have shown that MnO 2 facilitates hydrolysis, oxidation, or reduction of a wide range of organic pollutants including fluoroquinolone antibacterial agents, substituted anilines, substituted phenols, pentachlorophenol, triclosan and chlorophene, oxytetracycline and atrazine in the environment (Zhang and Huang, 2003, 2005a, 2005bZhang et al, 2008;Zhao et al, 2006Zhao et al, , 2009Stone, 1987;Laha and Luthy, 1990;Rubert and Pedersen 2006;Klausen et al, 1997;Ukrainczyk and McBride, 1993). Lin et al (2009) reported the oxidative transformation of BPA initiated by an MnO 2 reaction system, and their results showed that BPA (999%) was eliminated in 6 min at a solution pH 4.5 in a batch system that initially contained a single concentration of 800 Kmol/L MnO 2 and a fixed concentration of 4.4 Kmol/L BPA.…”

Detoxification of phenol through bound residue formation by birnessite in soil: Transformation kinetics and toxicity

“…A similar relationship between rate constant and reactant's concentration was also reported when pentachlorophenol was oxidized with manganese dioxide. [26] Interestingly, phenol was more rapidly removed when soil was present.…”