Determination of poisonous metals in wastewater collected from paint manufacturing plant using laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) system was developed for determination of toxic metals in wastewater collected from local paint manufacturing plant. The plasma was generated by focusing a pulsed Nd:YAG laser at 1064 nm on the solid residue from wastewater collected from paint industry. The concentration of different elements of environmental significance like, lead, copper, chromium, calcium, sulphur, magnesium, zinc, titanium, strontium, nickel, silicone, iron, aluminum, barium, sodium, potassium and zirconium, in paint wastewater were 6, 3, 4, 301, 72, 200, 20, 42, 4, 1, 35, 120, 133, 119, 173, 28 and 12 mg kg⁻¹, respectively. The evaluation of potential and capabilities of LIBS as a rapid tool for paint industry effluent characterization is discussed in detail. Optimal experimental conditions were evaluated for improving the sensitivity of our LIBS system through parametric dependence study. The laser-induced breakdown spectroscopy (LIBS) results were compared with the results obtained using standard analytical technique such as inductively coupled plasma emission spectroscopy (ICP). The relative accuracy of our LIBS system for various elements as compared with ICP method is in the range of 0.03-0.6 at 2.5% error confidence. Limits of detection (LOD) of our LIBS system were also estimated for the above mentioned elements.     

Low-pressure membrane filtration of secondary effluent in water reuse: Pre-treatment for fouling reduction

Fouling in the low-pressure membrane filtration of secondary effluent for water reuse can be severe due to the complex nature of the components in the water. Pre-filtration, coagulation and anion exchange resin were investigated as pre-treatments for reducing fouling of microfiltration (MF) and ultrafiltration (UF) membranes in the treatment of activated sludge-lagoon effluent. The key fouling components were determined using several analytical techniques to detect differences in the organic components between the feed and permeate.Pre-filtration (1.5 μm) enhanced the permeate flux for MF by removing particulates, but had little effect for UF. Marked flux improvement was obtained by coagulation pre-treatment at 5 mg L⁻¹ Al³⁺ with internal membrane fouling being substantially alleviated. Anion exchange resin removed >50% of effluent organic matter but did not improve the flux or reduce irreversible membrane fouling. These results, together with detailed organic compositional analyses, showed that the very high-molecular weight organic materials (40–70 kDa) comprised of hydrophilic components such as soluble microbial products, and protein-like extracellular matter were the major cause of membrane fouling.     

Study of Cathodic Polarization Curves During Pulse Plating of Chromium

A study has been made of the cathodic polarization curves during the pulse plating of chromium from an aqueous chromic acid bath containing 250 g/L CrO3 and 2. 5 g/L H2SO4 at 22℃ over the range of pulse periods from 1 ms to 50 ms. The duty cycle was kept at 50%. The methods of potentiostatic pulse potential control and galvanostatic pulse current control were used to determine the polarization curves of a platinum and a copper rotating disk electrode in the chromium plating solution. The results indicated that pulse potential and pulse current inhibited the formation of a cathode film and shifted the potential of the hydrogen evolution reaction toward the positive direction by about 500 mV. The potential and current pulses behaved as a depolarter of H reduction reaction. The present results agreed with a previous experimental observation that the coulombic efficiency of the chromium deposition reaction was reduced and the coulombic efficiency of the hydorgen evolution reaction was increased in pulse p     

Analysis of Trace Levels of Volatile Organic Contaminants in Municipal Drinking Water by Glass Capillary Gas Chromatography Using Simultaneous Flame Ionization and Electron Capture Detection

Abstract

A glass capillary gas chromatographic system using simultaneous flame ionization (FID) and electron capture (ECD) detection has been employed for the analysis of trace volatile organic pollutants in a municipal drinking water supply. The use of dual detectors with glass capillary columns allows resolution and detection of both halogenated and non-halogenated compounds simultaneously at less than microgram per liter (ppb) concentrations. By using diethyl ether as a solvent in preparing standard solutions of volatile organic compounds, standardization is made more accurate due to a reduction in solvent masking of early eluting peaks of interest. Additionally, ether shows promise for use in an internal standard method for quantification of VOA. These techniques were found to alleviate problems previously encountered in the analysis of purgeable organics and are described.     

Quantitative determination of triclocarban in wastewater effluent by stir bar sorptive extraction and liquid desorption–liquid chromatography–tandem mass spectrometry

Triclocarban is an antimicrobial and antibacterial agent found in personal care products and subsequently is a prevalent wastewater contaminant. A quantitative method was developed for the analysis of triclocarban in wastewater effluents using stir bar sorptive extraction–liquid desorption (SBSE–LD) followed by liquid chromatography–tandem mass spectrometry (LC–MS/MS) by means of an electrospray interface. A stir bar coated with polydimethylsiloxane (PDMS) is placed within a vial containing wastewater effluent and is stirred for an hour at room temperature. The PDMS stir bar is then placed in a LC vial containing methanol and is desorbed in a sonicator bath. The methanol is evaporated to dryness and reconstituted in 75% methanol. Spike and recovery experiments in groundwater that did not contain native concentrations of triclocarban were performed at 0.5 μg/L and were 93 ± 8%. Recoveries in wastewater effluent that were corrected for the background levels of triclocarban were 92 ± 2% and 96 ± 5%, respectively, when spiked with 0.5 and 5 μg/L of triclocarban. The precision of the method as indicated by the relative standard error was 2%. The limit of quantitation was 10 ng/L. The SBSE–LD–LC/MS/MS method was applied to wastewater effluent samples collected from northeast Ohio. Triclocarban was quantitated in all five effluent samples, and its concentration ranged from 50 to 330 ng/L. The described method demonstrates a simple, green, low-sample volume, yet, sensitive method to measure triclocarban in aqueous matrices.     

电刷镀含钛合金非晶态镀层的晶化动力学(II)

用热分析仪研究非晶态材料的晶化动力学有两大类方法：等温法和变温法．变温法测定动力学参数的优点是简便，需要的样品量少，能在反应开始到结束的整个温度范围内连续计算动力学参数．晶化反应是一种相变反应．反应前后没有重量的变化，因此，只能采用差热分析法D’fA或差示扫     

Kinetic speciation of nickel in mining and municipal effluents

This study presents the results of kinetic speciation of nickel in undiluted mining and municipal effluents and effluents diluted with receiving freshwaters from the surrounding environment. The dilution ratios used for the dilution of the effluents were arbitrarily chosen, but were representative of the prevailing mining practices. The purpose of the this dilution was to mimic dilution with natural waters that result from dilution of the mining and municipal effluents with receiving freshwaters, so that this study would reveal environmental realities that are of concern to the managers and regulators of water resources. Ligand exchange kinetics using the competing ligand exchange method (CLEM) was studied using two independent techniques: graphite furnace atomic absorption spectrometry (GFAAS) with Chelex 100 resin as the competing ligand, and adsorptive cathodic stripping voltammetry (AdCSV) with dimethylglyoxime (DMG) as the competing ligand to determine the percentage of Ni metal released from Ni(II)–DOC complexes and the rate of dissociation of Ni(II)–DOC complexes. Using a sample containing a mixture of 30% Copper Cliff Mine effluent, 40% Sudbury municipal effluent and 30% Vermillion River water, both techniques gave results showing that the dilution of the effluent samples increased the percentage of nickel released from Ni(II)–DOC complexes. This increase in the release of nickel from the Ni(II)–DOC complexes may be of concern to managers and regulators of water resources. Agreement between the results of these two techniques has enhanced the validity of the competing ligand exchange method used by both techniques.     

Numerical study of the adsorption of dyes from textile effluents

The textile industry is one of the greatest generators of liquid effluents, due to the high quantities of water used in the dyeing process. Fixed bed adsorption columns using activated carbon have been widely used in industrial processes for the removal of contaminants from textile effluents. In this study we present the modelling of an adsorption process applied to textile dyes, using fixed bed columns. This model permits the prediction of the dye concentration at the adsorption column outlet, considering the influence of various operational parameters. The adsorption isotherms of the dye Basic Green 4, over granular activated carbon at 25 °C in an aqueous solution, were determined experimentally through a comprehensive series of tests. The Langmuir and Radke–Prausnitz models gave the best results for the adsorption isotherms. Tests were carried out in fixed bed columns to determine the breakthrough curves, with variations in feed rate, feed concentration, diameter of the column and mass transfer coefficient. The experimental conditions were simulated using a transient mathematical model. The data obtained numerically and experimentally were compared to validate the mathematical model proposed.     

The effect of plating on magnetron sputtering: Residual stress and scratch behavior of Au/NiCr/Ta multi-layers

Au/NiCr/Ta multi-layers were deposited on Al₂O₃ substrate by magnetron sputtering and plating. The effect of plating technique on magnetron sputtering film in residual stress, crystal orientation and scratch resistance behavior was investigated. The all magnetron sputtering and plating films were highly textured with dominant Au-(1 1 1) orientation or a mixture of Au-(1 1 1) and Au-(2 0 0) orientation and the (1 1 1)/(2 0 0) intensity ratio were increased after plating. The residual stress in magnetron sputtering films at different substrate temperature was tensile stress with 155-400 MPa and it decreased approximately to 50 MPa after plating. The scratch resistance could be affected by the film thickness, and it increased approximately linearly with the increase of the thickness of metallic films after plating.