Electrochemical Analysis of Aqueous Benzalkonium Chloride Micellar Solution and Its Mediated Electrocatalytic De-Chlorination Application

The physicochemical properties of biologically important benzalkonium chlorides (BKCs) and the effects of its structure on the de-chlorination of allyl chloride was studied by electrogenerated [Co(I)(bipyridine)3]+ (Co(I)) using an electrochemical technique. The results of [Co(II)(bipyridine)3]2+ (Co(II)) cyclic voltammetry in the presence of BKC demonstrates Co(II)/Co(III) redox couple for physicochemical analysis of BKC and Co(II)/Co(I) redox couple for catalytic application. Cyclic voltammetry over a range of scan rates and BKC concentrations revealed the BKC-bound Co(II)/Co(III) micelles showed that the identification of cmc and association of the probe Co(II) species, associated more in the hydrophobic region. In addition, change in diffusion coefficient value of Co(II)/Co(III) with BKC concentration demonstrates the association of Co(II) in micellar hydrophobic region. The beneficial effects of BKC could be accounted for by considering the benzyl headgroup-Co (II) precatalyst-volatile organic compounds (VOCs) (allyl chloride here) substrate interaction. Chromatography/mass spectroscopy (GC/MS) revealed 100% complete de-chlorination of allyl chloride accompanied by three non-chloro products. This is the first report of benzyl headgroup-induced micellar enhancement by an electrochemical method, showing that it is possible to use hydrophobic benzyl headgroup-substitution to tune the properties of micelles for various applications

Experimental aspects of combined NOx and SO2 removal from flue-gas mixture in an integrated wet scrubber-electrochemical cell system

The objective of this work was to study the effect of some operating conditions on the simultaneous removal of NOx and SO2 from simulated NO–SO2–air flue-gas mixtures in a scrubber column. The gaseous components were absorbed into 6 M HNO3 electrolyte in the scrubber in a counter-current mode, and were oxidatively removed by the Ag(II) mediator oxidant electrochemically generated in an electrochemical cell set-up. The integration of the electrochemical cell with the scrubber set-up ensured continuous regeneration of the Ag(II) mediator and its repeated reuse for NOx and SO2 removal purpose, thereby avoiding: (1) the usage of chemicals continuously for oxidation and (2) the production of secondary waste. The influences of packing material (raschig glass rings, raschig poly(vinylidene) fluoride rings, Jaeger tri-pack perfluoroalkoxy spheres), feed concentrations of NO and SO2 (100–400 ppm NO and 100– 400 ppm SO2), superficial gas velocity (0.061–0.61 m s�1) and liquid velocity (0.012–0.048 m s�1) were investigated. The raschig glass rings with high surface area provided highest NO removal efficiency. NO and NOx showed decreasing abatement at higher feed concentrations. The removal of nitrogen components was faster and also greater, when SO2 co-existed in the feed. Whereas the gas flow rate decreased the removal efficiency, the liquid flow rate increased it for NO and NOx. The flow rate effects were analyzed in terms of gas/liquid residence time and superficial liquid velocity/superficial gas velocity ratio. SO2 removal was total under all conditions

Removal of H2S using a new Ce(IV) redox mediator by amediated electrochemical oxidation process

BACKGROUND: Hydrogen sulfide (H2S) from industrial activities and anaerobic manure decomposition in commercial livestock animal operations is an offensivemalodorous and toxic gas even in small concentrations, causing serious discomfort and health and social problems. The objective of this study was to employ for the first time a novel, attractive, low cost, environmentally benign mediated electrochemical oxidation (MEO) process with Ce(IV) as the redox catalyst forH2S gas removal from anH2S–air feed mixture. RESULTS: The influence of liquid flow rate (QL) from2–4 Lmin−1, gas flow rate (QG) from 30–70 L min−1, H2S concentration in theH2S–air feed mixture from 5–15 ppm, and Ce(III) pre-mediator concentration in the electrochemical cell from 0.1–1 mol L−1 on H2S removal efficiency were investigated. Both liquid and gas flow rates influenced the removal efficiencies, but in opposite directions.Nearly 98%H2S removal was achievedwhen the concentration of Ce(IV)mediator ion in the flowing scrubbing liquid reached 0.08mol L−1. CONCLUSIONS: The new MEOmethod proved promising for H2S removal, achieving high removal efficiency. Integration of the electrochemical cell with the scrubber set-up ensured continuous regeneration of the mediator and its repeated reuse for H2S removal, avoiding use of additional chemicals. Since the processworks at room temperature and atmospheric pressure utilizing conventional transition metal oxide electrodes more commonly used in industrial applications, it is also safe and economical

Simultaneous Removal of NOxand SO2: A Promising Ag(II)/Ag(I) Based Mediated Electrochemical Oxidation System

The present study is a first attempt towards utilizing a Ag(II)/Ag(I) based mediated electrochemical oxidation (MEO) system for the simultaneous clean-up of NOx and SO2 gases in simulated flue gas-air mixtures on a laboratory-scale scrubber column integrated with an electrochemical reactor, and to rationalize the efficient application of the MEO process for flue gas abatement and pollution control. Experiments were carried out with individual gas components followed with the mixture, and the effect of input NO and input SO2 concentrations was examined on the NOx and SO2 removal efficiencies at 208C. Complete oxidation of NO to NO2 with 100% NO removal efficiency and 80% NOx removal efficiency was achieved along with 100% SO2 removal efficiency, highlighting the potentially far greater efficiency of the Ag(II)/Ag(I) based MEO system in functionality and selectivity. Significant research work in this direction can be anticipated in the near future

Studies on Effective Generation of Mediators Simultaneously at Both Half-Cells for VOC Degradation by Mediated Electroreduction and Mediated Electrooxidation

Of the several electrochemical methods for pollutant degradation, the mediated electrooxidation (MEO) process is widely used. However, the MEO process utilizes only one (anodic) compartment toward pollutant degradation. To effectively utilize the full electrochemical cell, an improved electrolytic cell producing both oxidant and reductant mediators at their respective half-cells, which can be employed for treating two pollutants simultaneously, was investigated. The cathodic half-cell was studied first toward maximum [Co^I(CN)₅]^4– (Co⁺) generation (21%) from a [Co^II(CN)₆]^3– precursor by optimizing several experimental factors such as the electrolyte, cathode material, and orientation of the Nafion324 membrane. The anodic half-cell was optimized similarly for higher Co₃(SO₄)₂ (Co³⁺) yields (41%) from a Co^IISO₄ precursor. The practical utility of the newly developed full cell setup, combining the optimized cathodic half-cell and optimized anodic half-cell, was demonstrated by electroscrubbing experiments with simultaneous dichloromethane removal by Co⁺ via the mediated electroreduction process and phenol removal by Co³⁺ via the MEO process, showing not only utilization of the full electrochemical cell, but also degradation of two different pollutants by the same applied current that was used in the conventional cell to remove only one pollutant

Surface Related Emission in CdS Quantum Dots. DFT Simulation Studies

In general, organic capping molecules are applied to passivate the surface of semiconductor nanomaterials to modulate the optical properties of these nanostructures. In this work, two alkylamines (<i>n</i>-butylamine (<i>n</i>-BA) and <i>n</i>-hexylamine (<i>n</i>-HA)) and oleic acid (OA) were used to modify the surface of moderately high luminescent CdS quantum dots (QDs). From the photoluminescence (PL) spectra and the quantum yield (QY) analyses, we observed that the PL QY of the CdS QDs decreased after introduction of the alkylamine and oleic acid molecules. The PL decay kinetics for these CdS-capping molecule systems were followed by time-resolved photoluminescence (TRPL), and the spectra were analyzed in terms of a biexponential model identifying two lifetime values, shorter lifetime (τ_S) and longer lifetime (τ_L). Compared to bare CdS QDs, for the CdS QDs surface modified by alkylamine or fatty acid, both the shorter and the longer excited state lifetimes were decreased; the fractional contribution by the longer-lifetime component became reduced and the shorter-lifetime component accounted for most of the total PL. Density function theory (DFT) simulation was employed using a Cd₃S₅ cluster to model the adsorption of organics to calculate the binding energy and the charge on Cd and S of CdS. By comparing the elemental charges of the bare CdS with those of the CdS modified by the organic molecules, it is suggested that <i>n</i>-BA, <i>n</i>-HA, and OA could decrease the surface related radiative charge-recombination process and the PL-QY of the CdS QDs