Quanfang Lu

Oxidative degradation of phenol in aqueous electrolyte induced by plasma from a direct glow discharge

The liquid-phase oxidation of phenol induced by plasma that was generated from direct glow discharges at the tip of a platinum anode in aqueous electrolyte was investigated. Various influencing factors such as the initial pH, the concentration of reactants and the catalytic action of Fe2+ were examined. The results suggest that the reaction is a pseudo-first-order kinetic reaction; the initial pH significantly affects the degradation velocity and ferrous ions displayed a remarkable catalytic effect on the oxidation. The major oxidation intermediates were identified with high-performance liquid chromatograph and ion chromatograph analysis. It was found that the degradation proceeded differently in the presence and absence of catalysts and consequently two degradation pathways were proposed.

Evaluation of liquid cathode glow discharge-atomic emission spectrometry for determination of copper and lead in ores samples

In this study, a liquid cathode glow discharge-atomic emission spectrometry (LCGD-AES) was constructed for simultaneously determination of Cu and Pb in digested ores samples, in which the glow discharge was produced between the needle-like Pt anode and electrolyte overflowing from quartz capillary. The stability of LCGD and the effects of discharge voltage, capillary diameter and flow rate on emission intensity were systematically investigated. The limits of detections (LODs) of Cu and Pb were compared with those measured by closed-type electrolyte cathode discharge-atomic emission spectrometry (ELCAD-AES). In addition, the measured results of LCGD were verified by ICP-AES. The results showed that the optimization analytical conditions were 675V discharge voltage, 1.0mm capillary diameter and 5.5mLmin-1 flow rate. The analytical response curves had good linearity in the range of 1-10mgL-1. The RSD was 2.05% for Cu and 1.27% for Pb. The LODs of Cu and Pb were 0.36 and 0.20mgL-1, respectively, which are in agreement with the closed-type ELCAD. The obtained results of Cu and Pb in ore samples by LCGD are consistent with the reference materials of ICP. The recovery of samples is ranged from 85.2-105.6%, suggesting that the determinated results have high accuracy. All the results indicated that the LCGD can provide an alternative analytical method for the determination of metal elements in ores samples.

A promising absorbent of acrylic acid/poly(ethylene glycol) hydrogel prepared by glow-discharge electrolysis plasma

AbstractAn acrylic acid/poly(ethylene glycol) (AAc/PEG) hydrogel was synthesized in aqueous solution by a simple one-step method using glow-discharge electrolysis plasma (GDEP) technique. The structure of AAc/PEG hydrogel was characterized by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). Factors influencing the adsorption of heavy-metal ions such as solution pH, contact time, initial heavy-metal ion concentration were examined systematically by batch experiments. Results showed that both chemical complexation and ion exchange played an important role for heavy-metal ion adsorption onto AAc/PEG hydrogel. The adsorption isothermals followed the Langmuir isotherm and the adsorption kinetics fitted the pseudo-second-order model at 25°C with a pH 6. In addition, AAc/PEG hydrogel can be also regenerated and re-used.

Determination of calcium and zinc in gluconates oral solution and blood samples by liquid cathode glow discharge-atomic emission spectrometry

A novel flowing liquid cathode glow discharge (LCGD) was developed as an excitation source of the atomic emission spectrometry (AES) for the determination of Ca and Zn in digested calcium and zinc gluconates oral solution and blood samples, in which the glow discharge is produced between the electrolyte (as cathode) overflowing from a quartz capillary and the needle-like Pt anode. The electron temperature and electron density of LCGD were calculated at different discharge voltages. The discharge stability and parameters affecting the LCGD were investigated in detail. In addition, the measured results of real samples using LCGD-AES were verified by ICP-AES. The results showed that the optimized analytical conditions are pH = 1 HNO3 as supporting electrolyte, 4.5mLmin-1 solution flow rate. The power consumption of LCGD is 43.5-66.0W. The R2 and the RSD ranged from 630 to 680V are 0.9942-0.9995 and 0.49%-2.43%, respectively. The limits of detections (LODs) for Zn and Ca are 0.014-0.033 and 0.011-0.097mgL-1, respectively, which are in good agreement with the closed-type electrolyte cathode atmospheric glow discharge (ELCAD). The obtained results of Ca and Zn in real samples by LCGD-AES are basically consistent with the ICP-AES and reference value. The results suggested that LCGD-AES can provide an alternative analytical method for the detection of metal elements in biological and medical samples.

Aqueous p-nitrotoluene oxidation induced with direct glow discharge plasma

A plasma induced degradation process has been studied to treat 4-nitrotoluene (4-NT) present as an aqueous pollutant. The plasma was locally generated from a glow discharge around a tip of a platinum anode in an electrolytic solution. The influence of initial pH and Fe2+ on the degradation was examined. Major intermediates resulting from the degradation process were identified. Amongst the aromatic intermediates, p-hydroxybenzoic acid was the predominant degradation product. The formation of oxalic acid, malic acid was also observed. The final products of degradation were NH4+, NO3− and CO2. Based on the analysis of intermediates and the kinetic considerations, the degradation was shown to follow a pseudo-first order reaction hence, a possible reaction pathway was proposed.

Determination of the limits of detection for aluminum-based alloys by spatially resolved single- and double-pulse laser-induced breakdown spectroscopy

A comparative study of laser-induced breakdown spectroscopy (LIBS) with spatially resolved single- and double-pulse configurations is performed to investigate the capability of simultaneous multi-element detection in aluminum-based alloys. The spatially resolved technique is used to obtain the LIBS spectra at 6 different positions along the plume expansion (axial) direction. The experimental parameters, including delay time, inter-pulse delay time and gate width, are optimized to achieve sensitive elemental detection. Under these optimized conditions, the limits of detection for Fe, Cu, Mg, Mn, Zn, Sn, Pb, Ni, Ti, Cr, Sr and Ca are obtained with the single- and double-pulse configurations. It is observed that an improvement of the detection capability is achieved in the spatially resolved double-pulse experiments. Moreover, the dependence of the limits of detection on the selection of atomic and ionic lines is discussed.

Liquid Cathode Glow Discharge as a Microplasma Excitation Source for Atomic Emission Spectrometry for the Determination of Trace Heavy Metals in Ore Samples

ABSTRACT A novel liquid cathode glow discharge (LCGD) was designed as a microplasma excitation source for atomic emission spectrometry (AES) and used for the determination of Pb, Cu, and Cd in digested ore samples. The operating parameters and stability of LCGD-AES were investigated in detail. The statistical analysis (t-test) was used for comparing the results of ore samples using LCGD-AES and inductively coupled plasma atomic emission spectrometry (ICP-AES). The results showed that the optimized analytical conditions are 650 V discharge voltage, 4.5 mL min−1 solution flow rate, and pH 1 HNO3 as the supporting electrolyte. The limits of detection for Pb, Cu, and Cd were 0.019, 0.47, and 0.37 mg L−1, respectively. The correlation coefficients and relative standard deviations were 0.9985 and 1.19% for Pb, 0.9868 and 2.37% for Cu, and 0.9960 and 3.98% for Cd. The power consumption was below 65 W. The recoveries were in the range from 79.1 to 115.1%. Moreover, the measurement results of ore samples by LCGD-AES are comparable to the values obtained by ICP-AES. Therefore, the LCGD-AES may be developed as a portable analytical instrument for the direct determination of trace heavy metals.

High-Sensitivity Determination of K, Ca, Na, and Mg in Salt Mines Samples by Atomic Emission Spectrometry with a Miniaturized Liquid Cathode Glow Discharge

An atomic emission spectrometer (AES) based on a novel atmospheric pressure liquid cathode glow discharge (LCGD) as one of the most promising miniaturized excitation sources has been developed, in which the glow discharge is produced between a needle-like Pt anode and the electrolyte (as cathode) overflowing from a quartz capillary. Lower energy consumption (<50 W) and higher excitation efficiency can be realized by point discharge of the needle-like Pt. The miniaturized LCGD seems particularly well suited to rapid and high-sensitivity determination of K, Ca, Na, and Mg in salt mines samples. The optimized analytical conditions of LCGD-AES were pH = 1 with HNO3 as electrolyte, 650 V discharge voltage, and 3 mL min−1 solution flow rate. The limits of detections (LODs) of K, Ca, Na, and Mg were 0.390, 0.054, 0.048, and 0.032 mg L−1, respectively. Measurement results of the LCGD-AES are in good agreement with the comparison value obtained by inductively coupled plasma (ICP) and ion chromatography (IC). All results suggested that the developed portable analytical instrument can be used for on-site and real-time monitoring of metal elements in field with further improvement.