Evaluation of the Bioelectrochemical Approach and Different Electron Donors for Biological Trichloroethylene Reductive Dichlorination

Trichloroethylene (TCE) and more in general chlorinated aliphatic hydrocarbons (CAHs) can be removed from a contaminated matrix thanks to microorganisms able to perform the reductive dechlorination reaction (RD). Due to the lack of electron donors in the contaminated matrix, CAHs’ reductive dechlorination can be stimulated by fermentable organic substrates, which slowly release molecular hydrogen through their fermentation. In this paper, three different electron donors constituted by lactate, hydrogen, and a biocathode of a bioelectrochemical cell have been studied in TCE dechlorination batch experiments. The batch reactors evaluated in terms of reductive dechlorination rate and utilization efficiency of the electron donor reported that the bio-electrochemical system (BES) showed a lower RD rate with respect of lactate reactor (51 ± 9 µeq/d compared to 98 ± 4 µeq/d), while the direct utilization of molecular hydrogen gave a significantly lower RD rate (19 ± 8 µeq/d), due to hydrogen low solubility in liquid media. The study also gives a comparative evaluation of the different electron donors showing the capability of the bioelectrochemical system to reach comparable efficiencies with a fermentable substrate without the use of other chemicals, 10.7 ± 3.3% for BES with respect of 3.5 ± 0.2% for the lactate-fed batch reactor. This study shows the BES capability of being an alternative at classic remediation approaches.

The high activity of step sites on Pd nanocatalysts in electrocatalytic dechlorination

The role of step sites on nanocatalysts in electrocatalytic dechlorination reaction (ECDR) is studied by using 3 Pd nanocatalysts with different density of step sites, which is decreasing on tetrahexahedral...

Reductive Dechlorination of Chloroacetamides with NaBH4 Catalyzed by Zero Valent Iron, ZVI, Nanoparticles in ORMOSIL Matrices Prepared via the Sol-Gel Route

The efficient reductive dechlorination, as remediation of dichloroacetamide and monochloroacetamide, toxic and abundant pollutants, using sodium borohydride catalyzed by zero valent iron nanoparticles (ZVI-NPs), entrapped in organically modified hybrid silica matrices prepared via the sol-gel route, ZVI@ORMOSIL, is demonstrated. The results indicate that the extent of the dechlorination reaction depends on the nature of the substrate and on the reaction medium. By varying the amount of catalyst or reductant in the reaction it was possible to obtain conditions for full dechlorination of these pollutants to nontoxic acetamide and acetic acid. A plausible mechanism of the catalytic process is discussed. The present work expands the scope of ZVI-NP catalyzed reduction of polluting compounds, first reports the catalytic parameters of chloroacetamide reduction, and offers additional insight into the heterogeneous catalyst structure of M0@ORMOSIL sol-gel. The ZVI@ORMOSIL catalyst is ferromagnetic and hence can be recycled easily.

The removal of 2,4,6-trichlorophenol in water by Ni/Fe nanoparticles

In this paper, the removal of 2,4,6-trichlorophenol (2,4,6-TCP) by synthesized Ni/Fe nanoparticles were investigated. At the same time, the factors, such as the dosage of Ni/Fe, Ni content in Ni/Fe nanoparticles, sulfate ion, HA, coexisting substances in water which affected the removal of 2,4,6-TCP by synthesized Ni/Fe nanoparticles were also investigated. Under the experimental conditions, the removal efficiency of 2,4,6-TCP by Ni/Fe nanoparticles in water was about 72% for 2 h. The dosage of Ni/Fe, Ni content in Ni/Fe nanoparticles, and Fe3+ all promoted the dechlorination reaction of 2,4,6-TCP by Ni/Fe nanoparticles. Sulfate, oxalic acid and citric acid played an inhibitory role on the removal of 2,4,6-TCP by Ni/Fe nanoparticles in water. Fe2+ had no obvious affect to the removal of 2,4,6-TCP by Ni/Fe nanoparticles in water. In addition, low initial HA concentration was favorable for the removal of 2,4,6-TCP by Ni/Fe nanoparticles, while high concentrations of HA played an inhibitory role.

In Situ Rapid Dechlorination by Microwave-Assisted Catalytic Reduction of Chlorobenzene and 1,4-Dichlorobenzene on Raney Ni-Al Alloy Catalyst

Microwave-assisted catalytic reductive dechlorination on Raney Ni-Al alloy catalyst is an efficient method for treatment of chlorobenzene (CB) and 1,4-dichlorobenzene (1,4-DCB). The result shows that the Raney Ni-Al alloy catalyst retains its high activity in this in-situ reductive dechlorination reaction. The reductive dechlorination reaction was in accordance of a psendo-second-order reaction kinetics under the microwave irradiation. The apparent reductive reaction rate constant of CB dechlorination was 0.0175 L/mol·min at 30°C and 0.114 L/ mol·min at 50°C, and the activation energy Ea was 76.24 kJ/mol. The reaction rate constant of 1,4-DCB dechlorination was 0.0376 L/ mol·min at 35 °C and 0.151 L/ mol·min at 50 °C, and the activation energy Ea was 76.66 kJ/mol. The dechlorination for CB and 1,4-DCB was rapid and complete under mild conditions. It shows that the microwave-assisted catalytic in-situ reductive dechlorination on Raney Ni-Al alloy catalyst is an effective method for dechlorination of polychlorinated organic compounds.