Destruction of Pentachlorophenol Using Glow Discharge Plasma Process

Abstract

Pentachlorophenol (PCP), found in wood preservatives and pesticides, is an acutely toxic recalcitrant organochlorine carcinogenic compound. A point-to-plane glow discharge plasma (GDP) process was used to study the destruction of 30-50 ppm (120-188 µM) sodium salt of pentachlorophenol (PCP) in an aqueous solution. PCP was converted to less than 10% of its initial concentration in 1-3 h, at room temperature and low pressure (50 Torr). Effects of varying the headspace gas chemistry, stirring rate, pH, and current upon rate of PCP conversion were investigated. Organic acids, including formate, acetate, butyrate, and oxalate, were formed as byproducts after 1-3 h of GDP treatment of PCP. The chloride recovery suggests 50-70% dechlorination. The PCP removal rate exhibited mixed order kinetics. A reaction model developed to verify mixed order kinetics compares well with the experimental data. The increase in order may be due to the production and subsequent destruction of several reaction products throughout the process. An increase in current and stirring rate increased the rate of PCP removal in the GDP reactor. However, the rate of PCP removal decreased when the initial pH of the solution is raised to 11.4. Rapid removal of PCP was observed when the headspace gas was argon, air, or oxygen. Bench scale data was used to compare the power efficiency of the GDP process with atmospheric pressure corona discharge. Results suggest that the cost of power for PCP conversion by glow discharge was less than that of atmospheric pressure corona discharge. Additionally, the operating cost for PCP destruction in aqueous solution using UV based advanced oxidation technologies was found to be comparable with power costs for PCP conversion using GDP.

Promotion of crystal growth rate in aqueous solution by direct contact with gas corona discharge

“…To achieve these processes, highly-reactive gas radicals induced by reactions of accelerated electrons with gas molecules are important. Among them, water purification using gas discharge [8][9][10][11][12] is noteworthy because this process utilizes such gas radical species to produce aqueous short-lived species. In this report, we suggest these discharge-induced aqueous species can be used as anti-solvents to promote crystal growth processes.…”

Corona discharge influences ozone concentrations near rats

“…Singlet oxygen, generated by corona discharge, oxidized both NADH and NADPH at a much greater rate than controls . Hemoglobin in vitro was not only oxidized, but destroyed by corona discharge , probably by a similar mechanism to that by which corona destroys chlorinated cyclic hydrocarbons [Sharma et al, 2000], organic dyes [Goheen et al, 1992], and carbon tetrachloride [Sharma et al, 1997].…”

“…The electron attachment step produces O 2 À , O À , H À , and OH À [Mukkavilli et al, 1988;Kossyi et al, 1992]. We have observed O 3 production near a grounded water source [Goheen et al, 1984;Goheen et al, 1985;Sharma et al, 1997;Sharma et al, 2000], but have identified no specific plausible surface or bulk reaction of ions with ground state molecules contributing to O 3 production. A reaction O 2 À þ H 2 O !…”

Plasma Chemistry in Pulsed Electrical Discharge in Liquid

“…Direct chemical measurements reveal the presence of hydrogen peroxide, hydrogen and oxygen. Electrical discharges in water produced by pulsed high voltage have been known to degrade various chemicals, such as phenols [2,3] polychlorinated biphenyls [4], aniline [5] and monochlorophenols [6,7]. In all of these studies, it has been shown that the species responsible for the degradation of molecules is the hydroxyl radical.…”