Effect of Fe-Pd bimetallic nanoparticles on Sphingomonas sp. PH-07 and a nano-bio hybrid process for triclosan degradation.

In this study, we have evaluated the effect of palladium-iron bimetallic nanoparticles (nFe-Pd) on diphenyl ether (DE) degrading bacterial strain Sphingomonas sp. PH-07 as well as a sequential nano-bio hybrid process with nFe-Pd as catalytic reductant and PH-07 as biocatalyst for degradation of triclosan. Strain PH-07 grew well in the presence of nFe-Pd up to 0.1g/L in minimal salts medium with DE as carbon source. In aqueous system, TCS (17.3 μM) was completely dechlorinated within 2h by nFe-Pd (0.1g/L) with concomitant release of 2-phenoxyphenol (16.8 μM) and chloride ions (46 μM). All possible dichloro- and monochloro-2-phenoxyphenol intermediates were identified by HPLC and GC-MS analyses, and the dechlorination pathway was proposed. Addition of PH-07 cells into the reactor effectively degraded the 2-phenoxyphenol. Our results reveal that strain PH-07 survives well in the presence of nFe-Pd and nFe-Pd/PH-07 hybrid treatment could be a potential strategy for degradation of TCS.

Murugesan K ，Bokare V ，Jeon JR ，Kim EJ ，Kim JH ，Chang YS ... -  《-》

Degradation of triclosan by an integrated nano-bio redox process.

In this study, a sequential reduction-oxidation method was developed for complete degradation of triclosan (2,4,4'-trichloro-2'-hydroxydiphenyl ether, TCS) in aqueous solution. Rapid reductive dechlorination of TCS was achieved with palladized zero-valent iron nanoparticles (Pd/nFe), under anaerobic conditions, with generation of 2-phenoxyphenol as the sole dechlorination product. Sequentially, 2-phenoxyphenol was transformed into a non-toxic polymer using laccase (EC:1.10.3.2) derived from Trametes versicolor in the presence of natural redox mediator syringaldehyde (SYD). High performance liquid chromatography combined with electrospray ionization mass spectroscopy (HPLC-ESI-MS) revealed the formation of dimer and trimer products during the laccase-mediated transformation process. The efficiency of the integrated method is critically dependent on the Fe(2+) concentration, which was effectively controlled by optimizing the solution pH. To the best of our knowledge, this is the first report of a redox two-step hybrid system for the complete transformation of TCS into non-toxic products.

Bokare V ，Murugesan K ，Kim YM ，Jeon JR ，Kim EJ ，Chang YS ... -  《-》

Catalytic dechlorination of 2,4-dichlorophenol by Pd/Fe bimetallic nanoparticles in the presence of humic acid.

Pd/Fe bimetallic nanoparticles were synthesized for treatment of 2,4-dichlorophenol (2,4-DCP) in the presence of humic acid (HA), in order to understand their applicability for in situ remediation of groundwater. In this case, 2,4-DCP was catalytically dechlorinated to form the final products--phenol (P) via two intermediates, namely o-chlorophenol (o-CP) and p-chlorophenol (p-CP). We demonstrated that the carbon mass balances during the dechlorination were in the range of 82-91%, and other carbons were absorbed on the surface of Pd/Fe bimetallic nanoparticles. Our results suggest the dechlorination reaction of 2,4-DCP by Pd/Fe bimetallic nanoparticles in the presence of HA followed pseudo-first-order kinetics. HA competed for reaction sites on the Pd/Fe bimetallic nanoparticles with 2,4-DCP, and thus reduced the efficiency and rate of the dechlorination of 2,4-DCP. Efficiencies of dechlorination and phenol formations increased significantly as the Pd content increased from 0.10 wt.%, 0.15 wt.% to 0.20 wt.%, the removal percentage of 2,4-DCP increased from 70.4%, 98.4% to 99.4% within 300 min, respectively, the nitrate (NO(3)(-)) content in water also has a significant impact on 2,4-DCP dechlorination efficiency. Our results show that no other intermediates were generated besides Cl(-), o-CP, p-CP and phenol during the catalytic dechlorination of 2,4-DCP.

Zhang Z ，Shen Q ，Cissoko N ，Wo J ，Xu X ... -  《-》

Reductive dechlorination of gamma-hexachlorocyclohexane using Fe-Pd bimetallic nanoparticles.

Nanoscale Fe-Pd bimetallic particles were synthesized and used for degradation of lindane (gamma-hexachlorocyclohexane) in aqueous solution. Batch studies showed that 5mg/L of lindane was completely dechlorinated within 5 min at a catalyst loading of 0.5 g/L and the degradation process followed first-order kinetics. GC-MS analysis in corroboration with GC-ECD results showed the presence of cyclohexane as the final degradation product. The proposed mechanism for the reductive dechlorination of lindane involves Fe corrosion-induced hydrogen atom transfer from the Pd surface. The enhanced degradation efficiency of Fe-Pd nanoparticles is attributed to: (1) high specific surface area of the nanoscale metal particles (60 m(2)/g), manyfold greater that of commercial grade micro- or milli-scale iron particles (approximately 1.6m(2)/g); and, (2) increased catalytic reactivity due to the presence of Pd on the surface. Recycling and column studies showed that these nanoparticles exhibit efficient and sustained catalytic activity.

Nagpal V ，Bokare AD ，Chikate RC ，Rode CV ，Paknikar KM ... -  《-》

An integrated (nano-bio) technique for degradation of γ-HCH contaminated soil.

We have evaluated the effect of an integrated (nano-bio) technique involving the use of stabilized Pd/Fe(0) bimetallic nanoparticles (CMC-Pd/nFe(0)) and a Sphingomonas sp. strain NM05, on the degradation of γ-HCH in soil. Factors affecting degradation such as pH, incubation temperature and γ-HCH initial concentration were also studied. The results revealed that γ-HCH degradation efficiency is ~ 1.7-2.1 times greater in integrated system as compared to system containing either NM05 or CMC-Pd/nFe(0) alone. The integration showed synergistic effect on γ-HCH degradation. Further, cell growth studies indicated that NM05 gets well acclimatized to nanoparticles, showing potential growth in the presence of CMC-Pd/nFe(0) with respect to control system. This study signifies the potential efficacy of integrated technique to become an effective alternative remedial tool for γ-HCH contaminated soil. Further research in this direction could lead to the development of effective remediation strategies for other isomers of HCH and other chlorinated pesticides as well.

Singh R ，Manickam N ，Mudiam MK ，Murthy RC ，Misra V ... -  《-》