Chlorophenols reductive dechlorination

Dolfing, J. (1995). Letter to the editor Regiospecificity of chlorophenol reductive dechlorination by Vitamin B12s. Applied and Environmental Microbiology, 6l, 2450-1. 

Utkin I, C Woese, J Wiegel (1994) Isolation and characterization of Desulfitobacterium dehalogenans gen. nov, sp. nov., an anaerobic bacterium which reductively dechlorinates chlorophenolic compounds. Int J Syst Bacteriol 44 612-619. 

Sun B, JR Cole, RA Sanford, JM Tiedje (2000) Isolation and characterization of Desulfobvibrio dechlorace-tivorans sp. nov., a marine dechlorinating hacterium growing hy coupling the oxidation of acetate to the reductive dechlorination of 2-chlorophenol. Appl Environ Microbiol 66 2408-2413. 

Bell (1956) reported that the composition of photodegradation products formed were dependent upon the initial 2,4-D concentration and pH of the solutions. 2,4-D undergoes reductive dechlorination when various polar solvents (methanol, butanol, isobutyl alcohol, ferf-butyl alcohol, octanol, ethylene glycol) are irradiated at wavelengths between 254 to 420 nm. Photoproducts formed included 2,4-dichlorophenol, 2,4-dichloroanisole, 4-chlorophenol, 2- and 4-chlorophenoxy-acetic acid (Que Hee and Sutherland, 1981). 

Table 8.3. Bacteria that reductively dechlorinate chlorophenols...

Lin CH, Tseng SK. Electrochemically reductive dechlorination of penta-chlorophenol using a high overpotential zinc cathode. Chemosphere 1999 39 2375-2389. 

Lin, C.H. and Tseng, S.K. (2000) Electrochemically reductive dechlorination of chlorophenol using nickel and zinc electrodes. Water Sci. Technol. 42, 167-172. 

Reductive Dechlorination. Such reduction of chlorinated aliphatic hydrocarbons, eg, lindane, has been known since the 1960s. More recendy, the dechlorination of aromatic pesticides, eg, 2,4,5-T, or pesticide products, eg, chlorophenols, has also been documented (eq. 10) (20). These reactions are of particular interest because chlorinated compounds are generally persistent under aerobic conditions. 

Biological. 2,4,5-T degraded in anaerobic sludge by reductive dechlorination to 2,4,5-trichlorophenol, 3,4-dichlorophenol and 4-chlorophenol (Mikesell and Boyd, 1985). An... 

As an example of the technique, we may consider the reduction of penta-chlorophenol (PCP). The reactor consisted of two compartments, each 10 cm long, 2 cm wide and 0.5 cm deep, the cathode being a packed bed of carbon fibre, which was separated from the anode by a cation-exchange membrane (Nation 426). In the batch-recycle mode, constant current (10 A) electrolysis of 1 dm of 50 mg dm PCP in 0.1 mol dm " Na2S04 plus 0.1 mol dm NaOH removed PCP to a level < 0.5 mgdm within 30 min. The overall current efficiency for complete dechlorination was approximately 1 %, the energy consumption being 36 kWhm"l... 

The use of chitosan-Pd nanocomposites for heterogeneous catalytic reactions is the most extensively studied system and reported in the literature. For example, aUylic substitution reactions of ( )-cinnamyl ethyl carbonate by morpholine was reported by Quignard et al. (2000) using a chitosan-supported palladium complex. Dechlorination reaction of chlorophenol to phenol, degradation of nitrophenol, and reduction of chromate were studied by Vincent et al. (2002, 2003, 2004). Hydrogenation of nitrobenzene to aniline by chitosan-impregnated palladium composites was also reported by Jin et al. (1994). Excellent review of chitosan-based materials used in the heterogeneous catalytic reactions... 

---