Efficient novel amphiphilic double shells layer coupled with nanoscale zero-valent composite for the degradation of trichloroethylene

Biotechnology and nanotechnology for remediation of chlorinated volatile organic compounds: current perspectives

Chlorinated volatile organic compounds (CVOCs) are persistent organic pollutants which are harmful to public health and the environment. Many CVOCs occur in substantial quantities in groundwater and soil, even though their use has been more carefully managed and restricted in recent years. This review summarizes recent data on several innovative treatment solutions for CVOC-affected media including bioremediation, phytoremediation, nanoscale zero-valent iron (nZVI)-based reductive dehalogenation, and photooxidation. There is no optimally developed single technology; therefore, the possibility of using combined technologies for CVOC remediation, for example bioremediation integrated with reduction by nZVI, is presented. Some methods are still in the development stage. Advantages and disadvantages of each treatment strategy are provided. It is hoped that this paper can provide a basic framework for selection of successful CVOC remediation strategies.

Chitin- and Chitosan-Based Derivatives in Plant Protection against Biotic and Abiotic Stresses and in Recovery of Contaminated Soil and Water

Biotic, abiotic stresses and their unpredictable combinations severely reduce plant growth and crop yield worldwide. The different chemicals (pesticides, fertilizers, phytoregulators) so far used to enhance crop tolerance to multistress have a great environmental impact. In the search of more eco-friendly systems to manage plant stresses, chitin, a polysaccharide polymer composed of N-acetyl-D-glucosamine and D-glucosamine and its deacetylated derivative chitosan appear as promising tools to solve this problem. In fact, these molecules, easily obtainable from crustacean shells and from the cell wall of many fungi, are non-toxic, biodegradable, biocompatible and able to stimulate plant productivity and to protect crops against pathogens. In addition, chitin and chitosan can act as bioadsorbents for remediation of contaminated soil and water. In this review we summarize recent results obtained using chitin- and chitosan-based derivatives in plant protection against biotic and abiotic stresses and in recovery of contaminated soil and water.

Characterization of bimetallic Fe/Ni nanoparticles supported by amphiphilic block copolymer and its application in removal of 1,1,1-trichloroethane in water

The iron and nickel bimetallic nanoparticles supported by the block copolymer polystyrene-block-poly (acrylic acid) (PS-b-PAA-nZVI-Ni) were synthesized successfully and were applied to assess the degradation of 1,1,1-trichloroethane (1,1,1-TCA) in water. An optimal dose of Ni loading was 2 wt%, while an optimal mass ratio of PS-b-PAA to Ni/Fe, i.e., 0.5:1, at which the dechlorination efficiency was a maximum. The size of PS-b-PAA-nZVI-Ni nanoparticles (average size ~ 50 nm) was three times smaller than that of nZVI-Ni due to the prevention of agglomeration of the resultant zerovalent iron nanoparticles by PS-b-PAA. In the applying aspect, the pseudo-first-order rate constant (Kobs) of 1,1,1-TCA removal by PS-b-PAA-nZVI-Ni was 0.0142 min-1 within 240 min, which was approximately five times higher than nZVI. Meanwhile, PS-b-PAA-supported nZVI-Ni nanoparticles penetrated much deeper in quartz sand columns than nZVI-Ni nanoparticles, indicating PS-b-PAA had significant influence on nZVI transport. The findings from this study suggested that PS-b-PAA-nZVI-Ni, with its high reactivity, selective screening for 1,1,1-TCA, could be one significant potential for use as remedial agent to treat chlorinated solvents in water.

Biogenic FeS promotes dechlorination and thus de-cytotoxity of trichloroethylene

Abiotic iron monosulfide (FeS) has attracted growing interests in dechlorinating trichloroethylene (TCE) in anoxic groundwater, but it is still unclear how biogenic FeS affects the dechlorination and thus the cytotoxity of TCE. In this work, a biogenic FeS was synthesized by Shewanella oneidensis MR-1 with addition of ferrihydrite and S⁰, and it was used for dechlorination of TCE in alkaline environment and the de-cytotoxicity was evaluated by the growth of Synechocystis sp. PCC6803. The results show that the biogenic FeS was of mackinawite, with a loose flower-like mosaic structure. The dechlorination of TCE by the biogenic FeS was accelerated by 6 times than that by abiotic FeS. TCE was dechlorinated mainly by hydrogenolysis to form dichloroethane (C₂H₂Cl₂), vinyl chloride (C₂H₃Cl), and finally ethylene, accompanied with transformation of both Fe²⁺ to Fe³⁺ and monosulfide to disulfide and polysulfide on the biogenic FeS surface. The concentration for 50% of maximal inhibition effect (EC₅₀) of TCE to Synechocystis was 486 mg/L and the inhibition to Synechocystis under the EC₅₀ was relieved more significantly on addition of the biogenic FeS than that of abiotic FeS. These results indicate that the biogenic FeS promoted the dechlorination and thus de-cytotoxity of TCE.

Catalytic degradation of TCE by a PVDF membrane with Pd-coated nanoscale zero-valent iron reductant

Trichloroethylene (TCE) has serious threat to ecosystem. Fe-Pd nanoparticles (NPs) are good materials for catalytic degradation of TCE but still face severe challenges including easy fouling, agglomeration, deactivation and difficult separation and reuse etc. To overcome these drawbacks, we have constructed a novel structured PVDF/Fe-Pd NPs composite membrane with nanosized surface pores to execute the TCE degradation. Results indicate the degradation shows pseudo first-order reaction kinetics and high degradation rate in the static state degradation. Furthermore, the degradation ability can be enhanced by increasing Fe and Pd contents, the degradation temperature or decreasing the degradation pH value. However, the degradation is essentially limited by the diffusion. Thus, the cross-flow degradation is further applied to promote the diffusion. By this operating model, the degradation ability of the composite membrane can be greatly improved. More importantly, the reactants always keep the purity in the membrane surface side and can be controlled to enter the membrane pore for catalytic degradation. Thus, products can be timely discharged via the membrane pores and the side reactions between reactants and products can be largely reduced. In addition, the nanosized surface pores can also prevent the Fe-Pd NPs from being fouled. In a word, the novel composite membrane shows strong degradation ability, good stability and convenient operating ability for the TEC catalytic degradation.