Dechlorination

The biotransformation of hexachlorocyclohexane isomers (HCH) by two Dehalococcoides mccartyi strains (195 and BTF08) and an enrichment culture was investigated and compared to conversion by the obligate anaerobic strain Clostridium pasteurianum strain DSMZ 525. The D. mccartyi strains preferentially transformed γ-HCH over α-HCH and δ-HCH isomers while β-HCH biotransformation was not significant. In case of the enrichment culture, γ-HCH was preferentially transformed over the δ-HCH, β-HCH and α-HCH isomers...

This study systematically compared the degradation of atrazine (ATR) with aerobic zero-valent aluminum (ZVAl/Air) and zero-valent iron (ZVI/Air) systems. By comparing the ATR degradation curves and rate in the ZVAl/Air and the ZVI/Air systems, a significant induction period was observed in the ZVAl/Air system, and the pseudo-first-order rate constant of ATR degradation in the second stage by ZVAl was 6.4 times faster than that by ZVI. The differences in ATR degradation patterns of the two systems stemmed from the different redox nature and electrical conductivity of aluminum (oxide) and iron (oxide)...

A novel bionanomaterial comprising Saccharomyces cerevisiae (S. cerevisiae) and Fe3 O4 nanoparticles encapsulated in a sodium alginate-polyvinyl alcohol (SA-PVA) matrix was synthesized for the efficient removal of atrazine from aqueous solutions. The effects of the operating parameters, nitrogen source, and glucose and Fe3+ contents on atrazine removal were investigated, and the intermediates were detected by gas chromatography-mass spectrometry (GC-MS). In addition, the synthesized Fe3 O4 particles were characterized by XRD, EDX, HR-TEM, FTIR, and hysteresis loops, and the bionanomaterial was characterized by SEM...

Layered FeII-FeIII hydroxide chloride (chloride green rust, GRCl) has high reactivity towards reducible pollutants such as chlorinated solvents. However, this reactive solid is prone to dissolution, and hence loss of reactivity during storage and handling. In this study, adsorption of silicate (Si) to GRCl was tested for its ability to minimize GRCl dissolution and to inhibit reduction of carbon tetrachloride (CT). Silicate adsorbed with high affinity to GRCl yielding a sorption maximum of 0.026 g Si per g GRCl...

The carbon-carbon triple bond (-C≡C-) is an elementary constituent for the construction of conjugated molecular wires and carbon allotropes such as carbyne and graphyne. Here we describe a general approach to in situ synthesize -C≡C- bond on Cu(111) surface via homo-coupling of the trichloromethyl groups, enabling the fabrication of individual and arrays of poly(p-phenylene ethynylene) molecular wires. Scanning tunneling spectroscopy reveals a delocalized electronic state extending along these molecular wires, whose structure is unraveled by atomically resolved images of scanning tunneling microscopy and noncontact atomic force microscopy...

The removal of recalcitrant organic pollutants in groundwater is a challenge being faced around the world. Achieving effective long-term remediation of contaminated aquifers faces a variety of significant issues such as back diffusion, tailing, and rebound. In recent years, some researchers have proposed the use of controlled release materials (CRMs) as a new approach to counteracting such issues. The novelty of CRMs lies in that they release their active products slowly, over prolonged periods of time, in order to sustain in situ treatments and long-term effectiveness...

In this study, significant synergistic degradation of antibiotic diclofenac (DCF) was demonstrated in a novel magnetic field (MF) enhanced zero-valent iron (ZVI)/EDTA Fenton-like system. Five operational parameters, namely, initial ZVI loading, pH, EDTA dosage, DCF concentration and reaction temperature, were investigated for their effects on the DCF degradation. OH was identified as the predominant reactive oxygen species for DCF degradation in ZVI/EDTA systems whether in the presence or absence of MF. DCF molecule can be oxidized by OH, attacking via the hydroxylation and substituted dechlorination of the chlorinated aromatic ring, as well as by dehydration between the N atom and the acetoxyl...

Little is known about the diversity and succession of indigenous microbial community during debromination of polybrominated diphenyl ethers (PBDEs). This study examined the diversity and dynamics of microbial community structure in eight saline (mangrove and marine) and freshwater sediment microcosms exhibiting different debrominating capabilities for hexa-BDE 153, a common congener in sediments, using terminal restriction fragment length polymorphism (T-RFLP) and clone library analyses. The results showed that microbial community structure greatly differed between the saline and freshwater microcosms, likely leading to distinct variations in their debrominating capabilities and pathways...

Dehalococcoides mccartyi ( D. mccartyi ) strains differ primarily from one another by the number and identity of the reductive dehalogenase homologous catalytic subunit A ( rdhA ) genes within their respective genomes. While multiple rdhA genes have been sequenced, the activity of the corresponding proteins has been identified in only a few cases. Examples include the enzymes whose substrates are groundwater contaminants such as trichloroethene (TCE), cis -dichloroethene (cDCE) and vinyl chloride (VC). The associated rdhA genes, namely tceA, bvcA , and vcrA , along with the D...

Mechanochemical degradation (MCD) is employed for the dechlorination of polychlorinated dibenzo-p-dioxins (PCDD) and -furans (PCDF) in filter ashes from municipal solid waste incinerators, respectively with the assist of six additive systems. The evolution of PCDD/F-signatures in all eleven samples are systematically monitored and studied at the level of individual congeners, and special attention is paid to CP-route congeners, 2,3,7,8-substitution, 1,9-substitution, and 4,6-PCDF. The PCDD/F-isomers distribution follows an analogous pattern, indicating the similar acting mechanism for all additives: additives transfer electrons to attack the CCl bond and then expulse chlorine...

We report an allyl-decorated and hydrazine-connected covalent organic framework (COF-AO, 1) which could support Pd nanoparticles (Pd NPs) to generate (Pd@COF-AO, 2). The incorporation of 2 with thiol side chain-attached polysiloxane (PSI-SH) via photoinduced thiol-ene click reaction provided the stand-alone and elastic membrane. The obtained COF-involved and Pd NPs loaded covalently linked membrane is robust, permanently porous, uniform, processable and water permeable, and it can be used to build highly efficient catalytic membrane-based microreactor for continuous-flow operation to catalyze CBs dechlorination in water at room temperature...

Non-metallic graphene oxide (GO) and carbon nanodots (CDots) co-doped BiOBr ternary system (GO/CDots/BiOBr) were successfully synthesized via a simple one-step solvothermal process. The compositional characterization, optical and electrical properties of photocatalysts were investigated in detail. The prepared ternary photocatalysts possessed the excellent visible-light driven photocatalytic 4-chlorophenol (4-CP) degradation. Additionally, the 4-CP removal efficiencies decreased in the order of GO/CDots/BiOBr (88...

A novel Pd/CNTs-Ni foam composite catalyst was developed for catalytic hydrodechlorination of chlorophenols by using CNTs-Ni foam as support. Characterizations including FESEM, TEM/HRTEM, HAADF-STEM and element mapping revel that the composite catalyst with 2 wt.% Pd loading possesses high porous micro-network structure and high dispersed active Pd nanoparticles (5.81 nm) on CNTs surface. The HDC of chlorophenols over Pd/CNTs-Ni foam composite catalyst has been studied in continuous-flow packed bed reactor...

Polychlorinated dibenzo-p-dioxins (PCDDs), as a group of notorious anthropogenic environmental toxicants, are arguably ubiquitous in nature. In this study, we investigated the photocatalytic reductive dechlorination of 2-chlorodibenzo-p-dioxin (2-CDD) over Pd/g-C3 N4 catalysts under UV-vis irradiation. The g-C3 N4 and a series of Pd/g-C3 N4 catalysts were prepared by thermal polymerization and mechanical mixing-illumination method and characterized by XRD, TEM, BET, SEM and UV-vis DRS analyses. Among all the samples, the Pd/g-C3 N4 (5 wt%) yielded the optimal dechlorination activity with a total 2-CDD conversion of 54% within 4 h, and 76% of those converted 2-CDD were evolved to dibenzo-p-dioxin (DD)...

We report a facile, inexpensive and green method for the preparation of Pd nanoparticles in aqueous medium stabilized by anionic sulfonated surfactants sodium 1-dodecanesulfonate 1a, sodium dodecylbenzenesulfonate 1b, dioctyl sulfosuccinate sodium salt 1c and poly(ethylene glycol) 4-nonylphenyl-3-sulfopropyl ether potassium salt 1d simply obtained by stirring aqueous solutions of Pd(OAc)2 with the commercial anionic surfactants further treated under hydrogen atmosphere for variable times. The aqueous Pd nanoparticles solutions were tested in the selective hydrogenation reactions of aryl-alcohols, -aldehydes and -ketones leading to complete conversion to the deoxygenated products even in the absence of strong Brønsted acids in the reduction of aromatic aldehydes and ketones, in the controlled semi-hydrogenation of alkynes leading to alkenes and in the efficient hydro-dechlorination of aromatic substrates...

Class I benzoyl-coenzyme A (BzCoA) reductases (BCRs) are key enzymes in the anaerobic degradation of aromatic compounds. They catalyze the ATP-dependent reduction of the central BzCoA intermediate and analogues of it to conjugated cyclic 1,5-dienoyl-CoAs probably by a radical-based, Birch-like reduction mechanism. Discovered in 1995, the enzyme from the denitrifying bacterium Thauera aromatica (BCRTar ) has so far remained the only isolated and biochemically accessible BCR, mainly because BCRs are extremely labile and their heterologous production has largely failed, so far...

A falling film dielectric barrier discharge (DBD) plasma reactor combined with adsorption on activated carbon textile material was optimized to minimize the formation of hazardous oxidation by-products from the treatment of persistent pesticides (alachlor, diuron and isoproturon) in water. The formation of by-products and the reaction mechanism was investigated by HPLC-TOF-MS. The maximum concentration of each by-product was at least two orders of magnitude below the initial pesticide concentration, during the first 10 min of treatment...

Graphene may affect fate of organic contaminants due to its strong adsorption properties, which is very crucial for accurately assessing ecological risk of graphene and concurrent contaminants, while the current information remains largely unknown. Here, we firstly explored the adsorption characteristics of sulfonated graphene (SG) for a widespread polychlorinated biphenyl 2,4,4'-trichlorobiphenyl (PCB28) (0.5-100 μg L-1 ). Subsequently, the influence of SG on the uptake, translocation, and metabolism of PCB28 in maize seedlings was investigated through hydroponic exposure experiment...

To address the challenges of low hydrodechlorination efficiency by non-noble metals, a CuNi bimetallic cathode with nanostructured copper array film was fabricated for effective electrochemical dechlorination of trichloroethylene (TCE) in aqueous solution. The CuNi bimetallic cathodes were prepared by a simple one-step electrodeposition of copper onto the Ni foam substrate, with various electrodeposition time of 5/10/15/20 min. The optimum electrodeposition time was 10 min when copper was coated as a uniform nanosheet array on the nickel foam substrate surface...

2,4-dichlorophenoxyacetic acid (2,4-D) is one of the most applicable herbicides in the world, its residue in aquatic environment threatens the human health and ecosystems. In this study, for the first time, inexpensive Fe-C after pre-magnetization (Pre-Fe-C) was used as the heterogeneous catalyst to activate persulfate (PS) for 2,4-D degradation, proving that Pre-Fe-C could significantly improve the degradation and dechlorination. The results indicated the stability and reusability of Pre-Fe-C were much better than pre-magnetization Fe0 (Pre-Fe0 ), while the leaching iron ion was lower, indicating that using Pre-Fe-C not only reduced the post-treatment cost, but also enhanced the removal and dechlorination efficiency of 2,4-D...