Field application of glycerol to enhance reductive dechlorination of chlorinated ethenes and its impact on microbial community.

Chlorinated ethenes (CEs) are common and persistent contaminants of soil and groundwater. Their degradation is mostly driven by a process of bacterial reductive dechlorination (also called organohalide respiration) in anaerobic conditions. This study summarizes the outcomes of the long-term in-situ application of glycerol for the enhanced reductive dechlorination of CEs on a highly contaminated site.

Discovering the potential of an nZVI-biochar composite as a material for the nanobioremediation of chlorinated solvents in groundwater: Degradation efficiency and effect on resident microorganisms.

Abiotic and biotic remediation of chlorinated ethenes (CEs) in groundwater from a real contaminated site was studied using biochar-based composites containing nanoscale zero-valent iron (nZVI/BC) and natural resident microbes/specific CE degraders supported by a whey addition. The material represented by the biochar matrix decorated by isolated iron nanoparticles or their aggregates, along with the added whey, was capable of a stepwise dechlorination of CEs. The tested materials (nZVI/BC and BC) were able to decrease the original TCE concentration by 99% in 30 days.

Reduction of chlorinated hydrocarbons using nano zero-valent iron supported with an electric field. Characterization of electrochemical processes and thermodynamic stability.

Electric field assisted remediation using nano iron has shown outstanding results as well as economic benefits during pilot applications (Černíková et al., 2020). This method is based on donating electrons to the zero-valent iron that possess an inherently strong reductive capacity.

Combining nanoscale zero-valent iron with electrokinetic treatment for remediation of chlorinated ethenes and promoting biodegradation: A long-term field study.

Nanoscale zero-valent iron (nZVI) is recognized as a powerful tool for the remediation of groundwater contaminated by chlorinated ethenes (CEs). This long-term field study explored nZVI-driven degradation of CEs supported by electrokinetic (EK) treatment, which positively affects nZVI longevity and migration, and its impact on indigenous bacteria. In particular, the impact of combined nZVI-EK treatment on organohalide-respiring bacteria, ethenotrophs and methanotrophs (all capable of CE degradation) was assessed using molecular genetic markers detecting Dehalococcoides spp.

Combination of nZVI and DC for the in-situ remediation of chlorinated ethenes: An environmental and economic case study.

Over the past two decades, the use of nanoscale zero-valent iron (nZVI) has emerged as a standard method of contaminated groundwater remediation. The effectiveness of this method depends on key intrinsic hydrogeological parameters, which can affect both reactivity of the nanoparticles and their migration in the aquifer. In the case of low hydraulic permeability, the migration of nanoparticles is limited, which negatively influences remediation.

Electric-field enhanced reactivity and migration of iron nanoparticles with implications for groundwater treatment technologies: Proof of concept.

The extensive use of nanoscale zero-valent iron (nZVI) particles for groundwater treatment has been limited, in part, because of their non-selective reactivity and low mobility in aquatic environments. Herein, we describe and explore progressive changes in the reactivity and migration of aqueous dispersed nZVI particles under an applied DC electric field. Due to the applied electric field with an intensity of about 1 V cm, the solution oxidation-reduction potential (ORP) remained as low as -200 mV for at least 32 days, which was in agreement with the persistence of the reduced iron species (mainly Fe(II)), and led to substantially prolonged reactivity of the original nZVI.

Coupled extensional vibrations of longitudinally polarized piezoceramic strips.

A system of one-dimensional equations for coupled length-extensional, width-stretch, and symmetric width-shear vibrations of piezoceramic strips polarized in the length direction is derived from the two-dimensional, second-order plate equations by averaging the mechanical displacement and the electrostatic potential over the strip thickness. The boundary conditions correspond to the case of electrically forced vibrations. Theoretical values are compared with results of a previous analytical model and with experimental data.

High-frequency extensional vibrations of piezoelectric ceramic bars polarized in the longitudinal direction.

The approximate 1-D governing equations for coupled length-extensional, width-stretch, and symmetric width-shear vibration modes in rectangular finite piezoelectric bars with 6 mm hexagonal symmetry are presented. The bars polarized in the longitudinal direction with electrodes on the faces perpendicular to the length are considered. The system of equations is used to study the frequency spectrum of piezoelectrically forced vibrations of bars made of hard ceramics.

Determination of the electromechanical coupling factor of gallium orthophosphate (GaPO4) and its influence on resonance-frequency temperature dependencies.

The quartz homeotype gallium orthophosphate (GaPO4) is a representative of piezoelectric single crystals of large electromechanical coupling factor. It is known that its coupling factor kappa26 associated with the resonators vibrating in the thickness-shear mode is approximately two times greater than that of quartz. This property increases the spacing between the series and parallel resonance frequencies of resonators, as well as the difference between the resonance frequency temperature dependencies of the fundamental and harmonic resonance frequencies of resonators vibrating in the thickness-shear mode.

Contribution to the electromechanical and nonlinear properties of GaPO4 crystals.

In the last decade, much attention has been given to piezoelectric crystals with large electromechanical coupling coefficient. The quartz homeotypes berlinite and gallium orthophosphate (GaPO4), along with the calcium gallo-germanates such as langasite are representative of these crystals. The coupling coefficient k26 associated with thickness-shear mode resonators is two times greater than that of quartz, increasing the spacing between the series and parallel resonance frequencies of resonators suitable for the frequency range from 1 to 100 MHz.

A precise measurement of some nonlinear effects and its application to the evaluation of nonlinear elastic constants of quartz and GaPO4.

This paper deals with a precise measurement of amplitude frequency and intermodulation effects, and its application to the evaluation of nonlinear elastic constants of quartz and gallium orthophosphate (GaPO4). An evaluation is based on the methods used previously concerning determination of the higher-order material constants in the quartz. Using a measurement of the intermodulation products and measurement of drive level dependence of resonant frequency of quartz resonators, we have determined some effective elastic constants of fourth order.