Efficient Reductive Dechlorination of Monochloroacetic Acid by Sulfite/UV Process

Abstract

Most halogenated organic compounds (HOCs) are toxic and persistent, and their efficient destruction is currently a challenge. Here, we proposed a sulfite/UV (253.7 nm) process to eliminate HOCs. Monochloroacetic acid (MCAA) was selected as the target compound and was degraded rapidly in the sulfite/UV process. The degradation kinetics were accelerated proportionally to the increased sulfite concentration, while the significant enhancement by increasing pH only occurred in a pH range of 6.0-8.7. The degradation proceeded via a reductive dechlorination mechanism induced by hydrated electron (e(aq)(-)), and complete dechlorination was readily achieved with almost all the chlorine atoms in MCAA released as chloride ions. Mass balance (C and Cl) studies showed that acetate, succinate, sulfoacetate, and chloride ions were the major products, and a degradation pathway was proposed. The dual roles of pH were not only to regulate the S(IV) species distribution but also to control the interconversion between e(aq)(-) and H(•). Effective quantum efficiency (Φ) for the formation of e(aq)(-) in the process was determined to be 0.116 ± 0.002 mol/einstein. The present study may provide a promising alternative for complete dehalogenation of most HOCs and reductive detoxification of numerous toxicants.

Treatment of Aqueous Bromate by Superparamagnetic BiOCl-Mediated Advanced Reduction Process

“…Obviously, UV/BiOCl-HAPSM/formate was more resistant to common electron acceptors than the typical hydrated electron based-ARPs. For example, 95 μM NO (5.9 mg·L −1 ) induced a 75% inhibition of MCAA degradation by typical ARP UV/SO [51]. Besides O2, NO , and Fe 3+ , residual chlorine (also an electron acceptor) is usually found in the drinking water to depress the microorganism growth.…”

“…•− [51]. Besides O 2 , NO − Fe 3+ , residual chlorine (also an electron acceptor) is usually found in the drinking water to depress the microorganism growth.…”

Ex-Situ Remediation Technologies for Environmental Pollutants: A Critical Perspective

“…The more sophisticated microbial dehalogenation types involve the use of microwave-induced and UV-photolytic process (Li et al 2012a ), nanoparticle iron (Zhuang et al 2011 ), and ZVI (Xiu et al 2010 ). In most cases, metals as such or in the form of nanoparticles or biocells are used as electron donors in dehalogenation processes as summarized in Table 6 .…”

Hydrated electron (e aq − ) generation from p -benzoquinone/UV: Combined experimental and theoretical study

“…The behavior of eaq  is just like an anion, and the size of the anion is similar to that of the iodide ion [12]. Through a one-electron transfer process [2,8,12], eaq  can react with many substrates, which have more positive standard reduction potentials, with considerable rate constants [12]. The rate constants vary with a range from 10 1 L·mol 1 ·s 1 up to the diffusion controlled limit [12].…”