Solid-phase extraction of trace Au（Ⅲ） with SDG and determination by the catalytic spectrophotometric method

The new catalytic kinetic spectrophotometric method for Au(III) determination was developed and validated. It was based on the catalytic effect of gold on the oxidation of sudan red III by ammonium peroxodisulfate ((NH4)2S2O8) with nitrilo triacetic acid as an activator in mi- croemulsion and H2SO4 medium. Under optimum conditions, there was the linearity of the calibration curve in the concentration range from 0 to 20 μg/L Au(III) at 520 nm. The relative standard deviation was 3.0% with a correlation coefficient of 0.9986. The detection limit achieved was 9.75 × 10-5 μg/mL. A new method using a column packed with sulfhydryl dextrose gel (SDG) as a solid-phase extractant has been developed for the preconcentration and separation of Au(III) ions. The method has been applied to the determination of trace gold with satisfactory results.     

Analysis of trace mercury in water by solid phase extraction using dithizone modified nanometer titanium dioxide and cold vapor atomic absorption spectrometry

A new method for analysis of trace mercury in water samples was developed, based on the combination of preconcentration/separation using dithizone-modified nanometer titanium dioxide (TiO2) as a solid phase extractant and determination by cold vapor atomic adsorption spectrometry (CVAAS). Dithizone was dissolved with alcohol and loaded on the surface of nano-sized TiO2 powders by stirring. The static adsorption behavior of Hg2 on the dithizone-modified nanoparticles was investigated in detail. It was found that excellent adsorption ratio for Hg2 could be obtained in the pH range of 7-8 with an oscillation time of 15 min, and a 5 mL of 3.5 mol·L-1 HCl solution could quantitatively elute Hg2 from nanometer TiO2 powder. Common coexisting ions caused no obvious influence on the determination of mercury. The mechanisms for the adsorption and desorption were discussed. The detection limit (3σ) for Hg2 was calculated to be 5 ng·L-1. The proposed method was applied to the determination of Hg2 in a mineral water sample and a Zhujiang River water sample. By the standard addition method, the average recoveries were found to be 94.4%-108.3% with RSD (n = 5) of 2.9%-3.5%.     

Catalytic spectrophotometric determination of trace vanadium in fly ash and coal gangue by Triton X-100 enhancing effect

Trace V(V) catalyzes mightily the decolorization reaction of arsenazo Ⅲ(AsA Ⅲ) by oxidizing with H2O2 in a pH 4.0 HAc-NaAc buffer solution, and the addition of Triton X-100 can further increase the sensitivity of the reaction and its catalytic extent is linear with the content of V(V). A catalytic spectrophotometric procedure for determining trace V(V)was developed. The results show that the maximun absorption of the color solution is at 560 nm and the detection limit of the method for V(V) is 0.014 mg.L-1. Beer's law is obeyed for V(V) in the range of 0.00-0.20 mg.L-1. The recoveries are 99.0%-104.6%, and the relative standard deviations (RSD) are 2.7%-3.7%. Combined with ion-exchange resin, the method has been applied to the determination of trace vanadium in fly ash and coal gangue with satisfactory results.     

Catalytic spectrophotometric determination of trace vanadium in fly ash and coal gangue by Triton X-1O0 enhancing effect

Trace Ⅴ(Ⅴ) catalyzes mightily the decolorization reaction of arsenazo Ⅲ(AsA Ⅲ) by oxidizing with H2O2 in a pH 4.0 HAc-NaAc buffer solution, and the addition of Triton X-100 can further increase the sensitivity of the reaction and its catalytic extent is linear with the content of Ⅴ(Ⅴ). A catalytic spectrophotometric procedure for determining trace Ⅴ(Ⅴ)was developed. The results show that the maximun absorption of the color solution is at 560 nm and the detection limit of the method for Ⅴ(Ⅴ) is 0.014 mg.L^-1. Beer‘s law is obeyed for Ⅴ(Ⅴ) in the range of 0.00-0.20 mg.L^-1.The recoveries are 99.0%-104.6%, and the relative standard deviations (RSD) are 2.7%-3.7%. Combined with ion-exchange resin, the method has been applied to the determination of trace vanadium in fly ash and coal gangue with satisfactory results.     

A novel indicator system for catalytic spectrophotometric determination and speciation of inorganic selenium species (Se(Ⅳ), Se(Ⅵ)) at trace levels in natural lake and river water samples

A novel catalytic kinetic method is proposed for the determination of Se(Ⅳ), Se(Ⅵ), and total inorganic selenium in water based on the catalytic effect of Se(Ⅳ) on the reduction of Celestine blue by sodium sulfide at pH 7.0 phosphate buffer. The fixed-time method was adopted for the determination and speciation of inorganic selenium. Under the optimum conditions, the two calibration graphs are linear with a good correlation coefficient in the range 2-20 and 20-200 μg·L-1 of Se(Ⅳ) for the fixed-time method a...     

Determination of trace amounts of silver(I) in the presence of an activator with a kinetic method

A simple and sensitive kinetic-spectrophotometric method was developed for the determination of trace amounts of silver, based on its catalytic effect on the oxidation of azocarmine G by peroxydisulfate in sulfuric acid medium and at 30 °C in the presence of 1,10-phenantroline as activator. The absorbance was measured at 525 nm with the fixed-time method. The optimization of the operating conditions regarding concentrations of the reagents, temperature, ionic strength, and interferences was also investigated. The calibration curve is linear over the concentration range 0.3–50.0 ng ml-1of silver with good precision and accuracy, and the detection limit is down to0.125 ng ml-1. The relative standard deviation for a standard solution of 25.0 ng ml-1of silver is 1.36 %(n = 10).The proposed method proves to be highly sensitive,selective, and relatively rapid for the assay of silver at lowlevel range of 0.3–50.0 ng ml-1without any pre-concentration and separation step. The method was applied for the determination of silver in river water and white photographic film. The analytic results of the real samples are in excellent agreement with atomic absorption spectrometry analysis. The analytical results obtained are satisfactory.     

Catalytic activity of Au/Fe-PILC and Au/Fe-oxide catalysts for catalytic combustion of formaldehyde

Iron polymeric hydroxygroups pillared clays （Fe-PILC） were prepared by Na^＋-montmorillonite with iron pillaring agent. 2.01Au/Fe-PILC catalyst was obtained by deposited-precipitation （DP） method. 2.52Au/Fe-oxide catalyst was prepared by co-precipitation method. The catalytic activity of these catalysts was measured by catalytic combustion of formaldehyde. The catalyst of 2.01Au/Fe-PILC exhibits the high catalytic activity. The catalytic combustion reaction of formaldehyde proceeds at considerable rates at 20 ℃ and complete burn-off of formaldehyde is achieved at 120 ℃. The structure of catalysts, the valence state of gold and the size of gold particles were investigated by means of X-ray powder diffractometry, X-ray photoelectron spectroscopy and transmission electron microscopy. The results show that gold atoms with partially positive charge exist in the catalyst and play an important role in the catalytic activity. In addition, nano-sized, well-dispersed gold particles and good adsorption properties of support are necessary to obtain high activity Au catalysts for catalytic combustion of formaldehyde.     

Determination of trace gadolinium by catalytic kinetic fluorimetry

There was a significant catalytic effect of trace Gd(III) ions on the oxidative reaction of potassium persulfate with Saffron T in the acetic acid–sodium acetate buffer solution. Thus, a catalytic kinetic fluorimetry method for the determination of trace Gd(III) ions was established. The factors such as acidity, concentration of reagents, reaction time, and temperature as well as influence of coexisting ions were discussed. The optimum reaction conditions were established. The apparent rate constant and apparent activation energy of the reaction were determined. The linear range is 0.02–0.10 lgáml-1,and the detection limit is 7.27 9 10-4lgáml-1. This method was used for the determination of gadolinium in the samples of lanthanum acetate with RSD of 0.9 %–3.1 %.     

Dual-wavelength dual-indicator catalytic kinetic spectrophotometry for determination of trace Ru(III)

A new dual-wavelength dual-indicator catalytic kinetic spectrophotometric method for the determination of trace Ru(III)was studied.This method was based on Ru(III)-catalyzing oxidation of Arsenazo I and indigo carmine by potassium bromate in sulfuric acid.The absorbances of the catalytic and noncatalytic systems were measured at 510 and610 nm,respectively.Under the optimum conditions,the linear range of determination is 0–0.12 lgáml-1and the detection limit is 1.21 9 10-4lgáml-1.The method was applied for the determination of trace Ru(III)in ore samples with satisfactory results.     

Solid-phase extraction gold from alkaline cyanide solution with quaternary ammonium surfactant

The solid-phase extraction(SPE) technique applied to the extraction of organic compound was creatively used as the extraction of inorganic gold in the paper.Two types of techniques were proposed and explored,namely the SPE and the liquid–liquid extraction(LLE) of the quaternary ammonium surfactant [cetytrimethyl ammonium bromide(CTMAB),cetyl pyridine bromide(CPB),benzyl dimethyl dodecyl ammonium chloride(BDMDAC),and dodecyl trimethyl ammonium chloride(DTMAC)].The surfactant could react with Au(CN)_2~-to form the ionic complex,and the compound could be extracted by SPE column of reversed-phase bonded silica gel.Hence,a new method of SPE was proposed to extract gold with these features of the high selectivity,the reliability,and the simplicity.The experimental result shows that the recovery rate of gold is more than 98 %,and the solid-phase extraction column is not easily damaged and it can be repeatedly used.The new method can be used as the extraction process of gold from alkaline cyanide solution as well.Besides,the paper also puts forward a new process of gold extraction.     

ENERGY DISTRIBUTION OF BACKSCATTERED ELECTRONS FROM HEAVY METALS

The full energy distribution of backscattered electrons from the elastic peak down to the true-secondaty electron peak for heavy metals, Ta, W, Pt and Au, in Auger electron spectroscopy in the EN(E) mode has been studied with a Monte Carlo simulation method, which includes cascade-secondary-electron production. The simulation model is based on the use of a dielectric function for describing inelastic scattering and secondary excitation, and on the use of Mott cross sections for elastic scattering. A systematic comparison between the calculated and experimental spectra measured with a cylindrical mirror analyzer has been made for primary energies ranging from 1 to 5keV. Excellent agreement was obtained for these heavy metals on the backscattering background at primary energies in the keV region. A significant contribution of cascade secondary electrons to the measured spectra on the low-energy side was found.     

Studies on Determination of Ge in Au Alloys by Potassium Iodate Potentiometric Titration Method

The paper presents a new method of determining Ge in gold alloys by potassium iodate potentiometric titration rather than by traditional distillation separation. The influences of conditions such as the reduction acidity, dosage of sodium hypophosphite and reduction time on the determination of Ge were studied. Comparison was made between the influences of end-point indication for potential method and starch method on accruracy and precision of the analysed results, stability and sensitivity of end-point, selectivity of method and so on. The possibility of reaction in an electrochemical way was discussed. Ge in the alloys such as AuGe 12 , AuGeNi 12 2 , AuAgGe 18.8 12.5 and AuAgGeNi 43.8 6 0.2 was measured, respectively, with the relative standard deviation of 0.10%~0.31% and the recoveries of added standard Ge in sample of 99.40%～100.40% when the reduction acidity was 0.40~0.80 mol/L HCl and 3.3 mol/L H 3 PO 4, 15 g sodium hypophosphite and reduction time 40 min. The new method presented is high accuracy and precision in results, good stability and sensibility in end point, easy operation and strong selectivity of determination. When it is applied to analyse actual samples, satisfactory results are achieved.     

BioMinE: An integrated project for developing biohydrometallurgy in Europe—Executive summary of its activities and outputs after three years

Biohydrometallurgy is the offspring of the unexpected union of biotechnology and metallurgy. From specific properties of some extreme biotopes, active principles of interactions between microbial metabolisms and minerals have been extracted to be used as efficient metallurgical processes. Many profitable industrial operations based on these bioprocesses have been running to recover copper, gold, uranium or cobalt for instance and many other applications have been designed. Europe was quite active in this area in the past, but currently the leadership is in South Africa, America and Australia. BioMinE （Biotechnology of Metal-bearing material In Europe） is a large integrated project launched with the support of the European Commision. It is aimed at stimulating synergies between the most relevant universities, research and industrial organizations to develop new concepts in this technical field that allow a better exploitation of the mineral resources in the future. The European non-ferrous metals mining industry has initiated and developed the BioMinE project as they identified the need to find new processes for metal extraction from resources of today and of tomorrow.     

Micellar sensitized catalytic kinetic spectrophotometry for highly accurate and reproducible determination of V（IV） and V（V）

A highly accurate and reproducible micellar sensitized kinetic method was proposed for determination of V（VI）. The method is based on its catalytic effect on the oxidation of Coomassie brilliant blue R 250 （CBB＋） by bromate at pH 2.0. The reaction was monitored spectro- photometrically by measuring absorbance change with a fixed-time method of 5 min at 594 and 552 nm with and without surfactant. The variables influencing the calibra- tion sensitivity were extensively investigated, and the optimal conditions were established. The linear calibration range was 10-1,600 μg.L-1 with a relative SD ranging from 0.35 % to 3.35 % （for five replicate measurements of 75, 500, 1,000, and 1,500 μg.L-1） and a detection limit of 3.8 μg.L-1. The selectivity was also investigated, and greatly enhanced by suitable masking agents. The method was successfully applied to the analysis of V（IV） in pre- sence of excess V（V） up to 25 fold in environmental waters with the recoveries of 100.0 %-102.8 % for V（IV） and 95.7 %-99.7 % for total V. Its accuracy was validated by analysis of certified reference material via the present kinetic method and standard flame atomic absorption spectrometric method after extractive preconcentration with good agreement between certified and found values.     

Fluorescence determination of platinum with dibromohydroxyphenyl-fluorone in microemulsion after separation and enrichment by sulfhydryl dextrose gel

A new fluorescence quenching method has been developed for the determination of platinum in nonionic mieroemulsion medium.This method is based on the fact that platinum can form a stable chelate with dibromohydroxyphenyl-fluorine (DBHPF) when they are in the molar ratio of 12 in the nonionic microemulsion medium.Under optimum conditions,the system,having the maximum excitation and emission wavelengths at 468 nm and 532 nm,respectively,shows constant fluorescence intensity in the pH range of 3.5-4.0 and high selectivity and sensitivity as well as low interference from foreign ions.Furthermore,this fluorescence intensity is a linear function of Pt(Ⅳ) concentration in the range of 0.002-1.00 μg·mL-1 and the limit of detection is 2.90 ng·mL-1.     

Modeling of Reversible γ／α Transformations of Low Carbon Steels in the Intercritical Temperature Range

A phenomenological kinetic model has been developed for the prediction of non-isothermal reversible incomplete transformations in low-carbon hypoeutectoid steels. The theoretical basis of the proposed method has its origin in a possible extension of the traditional Austin-Rickett kinetic differential equation. To critically assess the applicability of the model, a number of experiments based on computer simulations have been performed to predict the austenite/ferrite proeutectoid transformation in the temperature range of Ae1 to Ae3 on plain carbon hypoeutectoid steels. A comparison with published experimental data has verified that the model developed is reasonable both quantitatively and with respect to well-established trends. Extension of the method of prediction appears promising when the non-isothermal reactions occurring during heat treatment (such as carbide precipitation and dissolution) can be assumed to proceed in a reversible manner.     

Multi-objective optimization of process parameters during low-pressure die casting of AZ91D magnesium alloy wheel castings

Multi-objective optimization has been increasingly applied in engineering where optimal decisions need to be made in the presence of trade-offs between two or more objectives. Minimizing the volume of shrinkage porosity, while reducing the secondary dendritic arm spacing of a wheel casting during low-pressure die casting(LPDC) process, was taken as an example of such problem. A commercial simulation software Pro CASTTM was applied to simulate the filling and solidification processes. Additionally, a program for integrating the optimization algorithm with numerical simulation was developed based on SiPESC. By setting pouring temperature and filling pressure as design variables, shrinkage porosity and secondary dendritic arm spacing as objective variables, the multi-objective optimization of minimum volume of shrinkage porosity and secondary dendritic arm spacing was achieved. The optimal combination of AZ91 D wheel casting was: pouring temperature 689 °C and filling pressure 6.5 kPa. The predicted values decreased from 4.1% to 2.1% for shrinkage porosity, and 88.5 μm to 81.2 μm for the secondary dendritic arm spacing. The optimal results proved the feasibility of the developed program in multi-objective optimization.     

Cloud point extraction and flame atomic absorption spectrometry analysis of palladium, platinum, and gold ions from industrial polluted soil

Cloud point extraction (CPE) with Tergitol TMN-6 was applied for the extraction of trace amounts of palladium (Pd(Ⅱ)),platinum (Pt(Ⅳ)),and gold (Au(Ⅲ)) in the soil of industrial sewage.Ammonium pyrolysine dithiocarbamate (APDC) was adopted as the chelating agent prior to CPE and then was detected by atomic absorption spectrometry (AAS).Different parameters such as the concentration of surfactants,chelating agent and salt,sample pH,equilibration temperature and time,centrifugation time and rates,and the effect of foreign ions were studied.Under optimum conditions,the low limits of detections are 1.4,2.8 and 1.2 ng.ml-1 and the enrichment factors are 21,12,and 24 for Pd(Ⅱ),Pt(Ⅳ),and Au(Ⅲ),respectively.The relative standard deviations vary from 0.6％ to 1.0％ (n=11).All correlation coefficients of the calibration curves are ＞0.9960.The proposed method was successfully applied for the determination of Pd(Ⅱ),Pt(Ⅳ),and Au(Ⅲ) in the real soil of industrial sewage samples.     

A new method to improve surface morphology of Ni-Fe-Mo-Co alloy electrode and its catalytic activity for HER

A new pretreatment method has been developed to improve the catalytic activity of the Ni-Fe-Mo-Co alloy elec- trode for hydrogen evolution reaction (HER). The procedure involves pre-electrolyzing the Ni-Fe-Mo-Co alloy electrode in 30% KOH solution containing 10% potassium sodium tartrate at 70°C for 2 h, until some of the Mo and Fe elements are leached out. The surface morphology of the Ni-Fe-Mo-Co alloy demonstrates a unique hive-like structure after the pre- treatment, which has the pore size in a nanometer range (about 50 nm), a very large real surface area, and good stability. The results of the electrochemical studies show that compared to other similar electrode materials and the treated Ni-Fe-Mo-Co electrode by leaching method, the pre-treated Ni-Fe-Mo-Co electrode has a much lower overpotential and much higher exchange current density for HER. In addition, a long-term continuous electrolysis test with a current interrup- tion shows that the Ni-Fe-Mo-Co alloy has excellent catalytic stability.     

Standardization of New Sliver Probe for Cooling Power Test of Polymer Quenchant

Technical committee for Japanese industrial standard of heat treating oils has studied on the new method for testing cooling power of aqueous quenchants. This method employed the cooling curve test of a new sliver rod probe,which has a metal-sheathed thermocouple at its geometrical center. The experimental study has clarified that this probe has the higher sensitivity and excellent durability. In order to standardize this probe for cooling power test of aqueous quenchants, the repeatability and reproducibility of test results etc. have been studied. D.O.P. (Di-2-ethylthexyl Phthalate)was used as reference quenching fluid for initial calibration and for periodic calibration verification of the probe and system.In addition, 10% brine was used to check the response capability of the probe and system to the sudden change of temperature. These procedures are established according to the experimental investigation. This new test method is going to be built in the revised version of JIS K 2242 “Heat treating oils” as the cooling power test method for aqueous quenchants.