Effect of organic and inorganic compounds on dissolution kinetics of chalcopyrite in hydrogen peroxide– Hydrochloric acid system

The addition of 2-Propanol as an organic substance and NaCl as an inorganic compound in hydrochloric acid with hydrogen peroxide as a strong leaching agent of chalcopyrite was investigated. The effects of the leaching parameters on copper extraction, such as stirring speed, H₂O₂ concentration, temperature, HCl concentration and solid/liquid ratio were studied. The maximum final copper extraction of 54.55% was obtained with 600 rpm stirring speed, 1.5 M H₂O₂, 0.5 M HCl, 600 rpm, 50 °C, 240 min of the reaction and particle size of ?106 +75 µm. Further experiments were performed when the solid-to-liquid ratio (S/L), stirring speed, temperature, HCl, H₂O₂ and leaching time were kept constant to examine the influence of NaCl and 2-Propanol concentrations in the range of 0–0.5 M and 0–3 M, respectively. The results showed that the copper extraction was increased up to 58.11% with addition of NaCl. While copper extraction yield reached 94.25% in case of addition of 2-propanol with the optimum parameters(0.5 M HCl,50 °C, 1.5 M H₂O₂, 600 rpm, particle size ?106 +75 μm, solid liquid ratio 2g/L, 3 M 2-propanol). The chalcopyrite leaching in hydrogen peroxide– hydrochloric acid system was found to be described by the interface transfer and diffusion across the product layer with activation energy of 77.14 kJ/mol. Addition of 2-propanol suggested that the reaction was under product layer diffusion control and decreased the activation energy of chalcopyrite leaching to 67.98 kJ/mol.     

Coupling on-line preconcentration by ion-exchange with microwave plasma torch-atomic emission spectrometry for the determination of cobalt and nickel

In the present work, a simple and sensitive preconcentration-microwave plasma torch-atomic emission spectrometric procedure was carried out for the determination of cobalt and nickel. The method was based upon a flow-injection system with on-line preconcentration of the metal ions on a minicolumn of a strong acid cation-exchange resin. The operation parameters including sample acidity, flow rate, loading time, and eluent concentration, flow rate were studied and optimized. Under the optimal experimental conditions the enrichment factors were calculated as 13.58 and 17.65 for cobalt and nickel, respectively. The relative standard deviations, 3.73% for cobalt and 4.23% for nickel (n = 7), and a sample throughput of 40 h^− 1 were obtained. Furthermore, the limits of detection were shown to be 1.28 and 1.80 μg·L^− 1 for cobalt and nickel, respectively. The method was applied to the determination of cobalt and nickel in tea samples and the accuracy was assessed through recovery experiments.     

Statistical Optimization of Recycled-Paper Enzymatic Hydrolysis for Simultaneous Saccharification and Fermentation Via Central Composite Design

A central composite design of the response surface methodology (RSM) was employed to study the effects of temperature, enzyme concentration, and stirring rate on recycled-paper enzymatic hydrolysis. Among the three variables, temperature and enzyme concentration significantly affected the conversion efficiency of substrate, whereas stirring rate was not effective. A quadratic polynomial equation was obtained for enzymatic hydrolysis by multiple regression analysis using RSM. The results of validation experiments were coincident with the predicted model. The optimum conditions for enzymatic hydrolysis were temperature, enzyme concentration, and stirring rate of 43.1 °C, 20 FPU g⁻¹ substrate, and 145 rpm, respectively. In the subsequent simultaneous saccharification and fermentation (SSF) experiment under the optimum conditions, the highest 28.7 g ethanol l⁻¹ was reached in the fed-batch SSF when 5% (w/v) substrate concentration was used initially, and another 5% added after 12 h fermentation. This ethanol output corresponded to 77.7% of the theoretical yield based on the glucose content in the raw material.     

Structure and magnetic properties of CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> ferrites synthesized by sol–gel and microwave calcination

CoFe₂O₄ ferrites were synthesized sol–gel with cobalt chloride, ferric chloride and citric acid as the main raw material. X-ray diffraction, vibrating sample magnetometer and simultaneous thermal analysis were applied to character the structure and magnetic properties of traditional and microwave calcined samples. The samples with pH 5 and molar ratio of citric acid to metal nitrate 1–1.2 showed the optimal structure and magnetic properties. Microwave calcination reduces the synthesis time from 2 h for conventional calcination to 15–30 min. The saturation magnetization (σ _s ) for sample microwave-calcined at 550 °C for 30 min reaches to 75.89 emu/g, much higher than that of conventional-calcined samples.     

Screening of Variables Influencing the Clavulanic Acid Production by <Emphasis Type="Italic">Streptomyces</Emphasis> DAUFPE 3060 Strain

Clavulanic acid (CA) is a β-lactam antibiotic, which has a potent β-lactamase inhibiting activity. The influence of five variables, namely pH (6.0, 6.4, and 6.8), temperature (28°C, 30°C, and 32°C), agitation intensity (150, 200, and 250 rpm), glycerol concentration (5.0, 7.5, and 10 g/L) and soybean flour concentration (5.0, 12.5, and 20 g/L), on CA production by a new isolate of Streptomyces (DAUFPE 3060) was investigated in 250-mL Erlenmeyer flasks using a fractional factorial design. Temperature and soybean flour concentration were shown to be the two variables that exerted the most important effects on the production of CA at 95% confidence level. The highest CA concentration (494 mg/L) was obtained after 48 h at 150 rpm, 32°C, pH 6.0, 5.0 g/L glycerol, and 20 g/L soybean flour concentrations. Under these conditions, the yields of biomass and product on consumed substrate were 0.26 g_X/g_S and 64.3 mg_P/g_S, respectively. Fermentations performed in 3.0-L bench-scale fermenter allowed increasing the CA production by about 60%.     

Coupling on-line preconcentration by ion-exchange with microwave plasma torch-atomic emission spectrometry for the determination of cobalt and nickel

In the present work, a simple and sensitive preconcentration-microwave plasma torch-atomic emission spectrometric procedure was carried out for the determination of cobalt and nickel. The method was based upon a flow-injection system with on-line preconcentration of the metal ions on a minicolumn of a strong acid cation-exchange resin. The operation parameters including sample acidity, flow rate, loading time, and eluent concentration, flow rate were studied and optimized. Under the optimal experimental conditions the enrichment factors were calculated as 13.58 and 17.65 for cobalt and nickel, respectively. The relative standard deviations, 3.73% for cobalt and 4.23% for nickel (n = 7), and a sample throughput of 40 h^− 1 were obtained. Furthermore, the limits of detection were shown to be 1.28 and 1.80 μg·L^− 1 for cobalt and nickel, respectively. The method was applied to the determination of cobalt and nickel in tea samples and the accuracy was assessed through recovery experiments.     

Solvent extraction in hydrometallurgy: the role of organophosphorus extractants

Solvent extraction (SX) has come to be one of the most important separation processes in hydrometallurgy. Phosphorus-based extractants have proved to be of particular importance, especially for the separation of cobalt from nickel. However it was not until the dialkyl phosphinic acid reagent, CYANEX 272, and its dithio analogue CYANEX 301, became available that liquors containing very low Co:Ni ratios of at least 1:40 to even >1:100 could be treated. This has opened the way to the direct application of SX for the separation of Co from Ni in liquors derived from the leaching of nickel mattes from the smelting of nickel sulphide ores and from the pressure acid leaching of nickel laterite ores. This paper describes the development of the range of Cytec extractants and, in particular, discusses the development of their application for the separation of cobalt from nickel. Examples of actual industrial operating plants will also be given and individual flowsheets discussed.     

Analysis of trace‐level nitrated polycyclic aromatic hydrocarbons in water samples by solid‐phase microextraction with gas chromatography and mass spectrometry

A solid‐phase microextraction coupled with gas chromatography and mass spectrometry method has been developed for the determination of ten nitrated polycyclic aromatic hydrocarbons in water samples. Five different kinds of commerical fibers were used to compare the extraction efficiency, including 65 μm polydimethylsiloxane/divinylbenzene, 100 μm polydimethylsiloxane, 30 μm polydimethylsiloxane, 7 μm polydimethylsiloxane, and 85 μm polyacrylate fibers. Five factors were also selected to optimize conditions, including extraction temperature, time, stirring speed, salt concentration, and headspace volume. Taguchi design was applied to design the experiments and obtain the best parameters. The results show that 65 μm polydimethylsiloxane/divinylbenzene fiber directly immersed into aqueous solution for 35 min at 55°C with a constant stirring rate of 1150 rpm were the optimal conditions. Under these conditions, the limits of quantification were 0.007–0.063 μg/L, and the relative standard deviation based on six replicates ranged from 2.8 to 9.5%. The spiked recoveries ranged from 69.1 to 110.1%. Intra‐ and inter day relative standard deviations at three concentration levels were less than 12%, and the recoveries were 66.4–111.5%. The proposed method is reliable for analyzing nitrated polycyclic aromatic hydrocarbons in different water samples.     

Determination of ultra trace amounts of cobalt and nickel in water samples by inductively coupled plasma-optical emission spectrometry after preconcentration on modified C18-silica extraction disks

A highly sensitive and accurate method for preconcentration and determination of ultra trace amounts of cobalt and nickel ions in water samples is proposed. The preconcentration is achieved using C₁₈-silica extraction disks modified with 5-(6-methoxy-2-benzothiazoleazo)-8-aminoquinoline (MBTAQ). The retained ions on the prepared solid phase was eluted with 10 ml of 0.01 M nitric acid and measured by inductively coupled plasma-optical emission spectrometry (ICP-OES). The influence of the type and amount of eluent used, pH, sample and eluent flow rates, amount of MBTAQ and the effect of other ions on extraction efficiency were investigated. The limits of detection of the method were 0.08 and 0.06 μg l^− 1 for cobalt and nickel, respectively, and provide an enrichment factor of 100. The results obtained on 10 successive extractions and elution cycles revealed relative standard deviations of 1.5 and 1.0% for cobalt and nickel, respectively. The proposed method has been applied to the determination of ultra trace amounts of cobalt and nickel ions in natural and synthetic water samples with satisfactory results.     

Extraction of cobalt (II) and nickel (II) by a solvent impregnated resin containing bis(2,4,4-trimethylpentyl)monothiophosphinic acid

In the present work, studies have been conducted on the equilibrium distribution of cobalt (II) and nickel (II) between aqueous hydrochloric solution and macromolecular resin impregnated with bis(2,4,4-trimethylpentyl)monothiophosphinic acid (Cyanex302, HL). Effects of extraction time, pH values, metal ion concentration, and temperature were investigated. Analysis of the results shows that the extraction of the two metal ions can be explained assuming the formation of metal complexes in the resin phase with a general composition ML ₂. An extraction reaction is proposed and the equilibrium constants of the complexes were determined. The Freundlich isotherm and thermodynamic quantities, i.e., ΔG, ΔH and ΔS were also obtained. Both of the extraction reactions of cobalt (II) and nickel (II) are endothermic ones. The efficiency of the resin in the separation of cobalt (II) and nickel (II) is provided according to the separation factors. Under the experimental conditions employed, pH₅₀ values for cobalt (II) and nickel (II) are 3.76, 5.01, respectively. The logarithmic value of separation factor was calculated as 2.50.     

Simultaneous determination of alkali,alkaline earth and transition metal elements in uranium and thorium based nuclear fuel materials by single column ion chromatography

A single-column ion chromatography (SCIC) for the simultaneous determination of alkali, alkaline earth and transition metal elements in UO₂, ThO₂ powders and sintered (Th, U) O₂ pellet is described in this paper. Metrosep cation 1-2 analytical column containing poly butadiene-maleic acid (PBDMA) coated silica has been applied to the ion chromatographic separation of 12 cations (copper, lithium, sodium, ammonium, nickel, potassium, zinc, cobalt, manganese, magnesium, calcium and strontium) using an isocratic elution with tartaric acid and oxalic acid as mobile phase with non-suppressed conductivity detection. Mobile phase composition was optimized to 1 mM tartaric acid and 0.75 mM oxalic acid for the baseline separation of 12 cations. The calibration plots were linear in the range of 0.05–40 mg L⁻¹ with regression coefficients better than 0.998. The relative standard deviations (RSDs) of the retention time, peak area and peak height were less than 1, 2.8 and 3.0%, respectively. The recoveries of the spiked samples for the cations were 94–110%. The method developed was validated by comparison with certified standards of UO₂ and ThO₂ powders.     

Influence of the thermal treatment in the crystallization of NiWO4 and ZnWO4

NiWO₄ and ZnWO₄ were synthesized by the polymeric precursor method at low temperatures with zinc or nickel carbonate as secondary phase. The materials were characterized by thermal analysis (TG/DTA), infrared spectroscopy, UV–Vis spectroscopy and X-ray diffraction. NiWO₄ was crystalline after calcination at 350 °C/12 h while ZnWO₄ only crystallized after calcination at 400 °C for 2 h. Thermal decomposition of the powder precursor of NiWO₄ heat treated for 12 h had one exothermic transition, while the precursor heat treated for 24 h had one more step between 600 and 800 °C with a small mass gain. Powder precursor of ZnWO₄ presented three exothermic transitions, with peak temperatures and mass losses higher than NiWO₄ has indicating that nickel made carbon elimination easier.     

ICP-AES法测定红土镍矿中镍、钙、钛、锰、铜、钴、铬、锌与磷的含量

建立了ICP-AES法测定红土镍矿中Ni;Ca;Ti;Mn;Cu;Co;Cr;Zn和P含量的方法。样品用HCl、HNO3溶解,加入HF和HClO4,加热至HClO4烟冒尽,用HCl溶解盐类,过滤,采用ICP-AES法同时测定滤液中Ni、Ca、Mn、Cu、Co、Zn、P;残渣经灼烧、挥硅、K2S2O7熔融、HCl浸取,所得溶液与滤液合并,测定溶液中Cr和Ti含量。方法检出限:P为0.022μg/mL,其它元素在0.0032～0.0085μg/mL之间,方法的精密度(n=7)在1.4%～2.9%之间。分析结果与分光光度法、XRF法和AAS法分析结果的相对误差:Ni、Cu、Co、Cr小于5%,Ti和Mn小于10%,Zn小于15%,Ca和P小于19%。     

Effects of stirring prior to starting emulsion polymerization of styrene with nonionic emulsifier on particle formation and its incorporation

Emulsion polymerization of styrene with a nonionic emulsifier (polyoxyethylene nonylphenyl ether, E911) and potassium persulfate as initiator was carried out at different stirring rates (240–500 rpm) at 70 °C, which was started by the addition of initiator after stirring for 100 min at 70 °C. Resulting polystyrene (PS) particles at 240 rpm were 70-nm-sized, spherical particles and incorporated only 5 wt.% of total E911. On the other hand, particles at 500 rpm were 1-μm-sized, nonspherical particles, which were formed by coagulation of small particles, and incorporated above 70 wt.% of E911 in the inside. Before starting emulsion polymerization, E911 and styrene, respectively, transferred from an aqueous phase to a styrene phase and from the styrene phase to the aqueous phase (water and micelles) faster at 500 rpm than 240 rpm. At 240 rpm, there were a lot of almost empty micelles (ca. 5 nm) in the aqueous phase, on the other hand at 500 rpm, 70 wt.% of total E911 transferred to the styrene phase and the micelles were swollen with much monomer (ca. 40 nm) even if the number was smaller. Stirring prior to starting the emulsion polymerization greatly affected partitionings of monomer to the aqueous phase and the nonionic emulsifier to the styrene phase, resulting in the differences in the particle formation and the incorporation of the nonionic emulsifier inside PS particles.     

An influence of thermal treatment conditions of hydrotalcite-like materials on their catalytic activity in the process of N<Subscript>2</Subscript>O decomposition

Hydrotalcite-like materials containing apart from magnesium and aluminum also copper, cobalt, nickel, and iron were prepared by a co-precipitation method. Thermal transformations of hydrotalcite-like materials were studied by thermal analysis methods as well as XRD, UV–vis–DRS, and XPS measurements of the samples calcined at various temperatures (600, 700, and 800 °C). Calcined hydrotalcites, especially those containing cobalt and copper, were found to be active and selective catalysts of N₂O decomposition. It was shown that an increase in the calcination temperature significantly activated the Co-containing catalysts. Promotion of the samples with potassium resulted in activation of the hydrotalcite-based catalysts.     

Preparation of non-spherical hollow carbon nanocapsules from nickel nanoprecursors

Hollow carbon nanocapsules (NCs) are prepared from nickel nanoplate precursors through carburizing, decomposition, and leaching steps. The carburizing step was carried out by heating the nickel nanoplates in oleylamine at 250 °C for 4 h. Decomposition was then performed in a nitrogen atmosphere at 530 °C for 3 min. Characterization of the resulting product of the first two steps shows the intermediates to be Ni₃C/Ni–C alloy and Ni/C core–shell nanostructures. Hollow carbon NCs are recovered from the products by leaching the Ni/C core–shell nanostructures in concentrated nitric acid. The NCs are found to have a high specific surface area (1081 m² g⁻¹) and a mesoporous structure (i.e., a pore volume of 2.81 cm³/g and a narrow pore size distribution of 2.9–3.4 nm). In addition, it is found that the hollow carbon NCs retained the same morphology as the original nickel precursors; demonstrating the robustness of the nickel templates and the ability of the carbon shells to maintain a non-spherical shape.     

Determination of ultra trace amounts of cobalt and nickel in water samples by inductively coupled plasma-optical emission spectrometry after preconcentration on modified C18-silica extraction disks

A highly sensitive and accurate method for preconcentration and determination of ultra trace amounts of cobalt and nickel ions in water samples is proposed. The preconcentration is achieved using C₁₈-silica extraction disks modified with 5-(6-methoxy-2-benzothiazoleazo)-8-aminoquinoline (MBTAQ). The retained ions on the prepared solid phase was eluted with 10 ml of 0.01 M nitric acid and measured by inductively coupled plasma-optical emission spectrometry (ICP-OES). The influence of the type and amount of eluent used, pH, sample and eluent flow rates, amount of MBTAQ and the effect of other ions on extraction efficiency were investigated. The limits of detection of the method were 0.08 and 0.06 μg l^− 1 for cobalt and nickel, respectively, and provide an enrichment factor of 100. The results obtained on 10 successive extractions and elution cycles revealed relative standard deviations of 1.5 and 1.0% for cobalt and nickel, respectively. The proposed method has been applied to the determination of ultra trace amounts of cobalt and nickel ions in natural and synthetic water samples with satisfactory results.     

A study on Zn-based catal-sorbents for the simultaneous removal of hydrogen sulfide and ammonia at high temperature

To simultaneously remove hydrogen sulfide and ammonia from hot coal gases, the ammonia decomposition abilities of various metal oxide catalysts were tested in the absence/presence of hydrogen sulfide, at 650 °C. Cobalt oxide, molybdenum oxide, and nickel oxide have high ammonia decomposition abilities (>95%) in the absence of hydrogen sulfide, but such abilities rapidly decreased during the reaction in the presence of hydrogen sulfide. To improve the simultaneous removal abilities of metal oxides, Zn-based catal sorbents were prepared via impregnation with various metals, such as cobalt, nickel, and molybdenum, on zinc oxide. The CZ-30 (promoted with 30 wt% cobalt oxide on zinc oxide) and NZ-30 (promoted with 30 wt% nickel oxide on zinc oxide) catal sorbents showed excellent sulfur removal capacities, which, calculated until the breakthrough point, were 0.35 and 0.39 g S/g catal sorbent, respectively, while MZ-30 promoted with molybdenum showed a low sulfur removal capacity of 0.08 g S/g catal sorbent. The ammonia decomposition ability of CZ-30, however, increased more than 18 times compared with Co₃O₄, whose ammonia decomposition ability was more than 95% until 465 min, even though the ammonia decomposition ability of NZ-30 sharply decreased after 30 min. The CZ catal sorbent is a good candidate for the simultaneous removal of ammonia and hydrogen sulfide.     

Preparation and characterization of twisted periodic mesoporous ethenylene-silica nanorods

Twisted periodic mesoporous ethenylene-silica nanorods were prepared using cetyltrimethylammonium bromide in concentrated aqueous ammonia solutions at the stirring rate of 600 rpm. The pore channels run along the long axis of the nanorod. The helical pitches are about 1.2 micrometers. Small-angle X-ray diffraction pattern was indexed to the p6 mm hexagonal symmetry. The morphologies of the ethenylene-silicas are sensitive to stirring conditions. For example, twisted nanorods and spiral nanofibers combined with nanospheres were obtained under static condition. With increasing stirring speed, both the length and helical pitch of the nanorod increased slightly. With decreasing the concentration of ammonia, the particle lengths decreased, while the particle diameters increased. Chiral mesostructures were obtained when the ammonia concentration was ≥ 20 wt%. The formation of the twisted mesoporous ethenylene-silica nanorods was studied by taking TEM images after different reaction time.     

微波消解–火焰原子吸收光谱法测定红土镍矿中氧化镁含量

以盐酸、硝酸、氢氟酸溶解红土镍矿样品,加入高氯酸冒烟除去硅和氟,在稀盐酸和氯化锶溶液介质中,于原子吸收光谱仪波长285.2 nm处,使用空气–乙炔火焰,测定样品中氧化镁的含量。在最佳实验条件下,镁的质量浓度在0.20~1.00 mg/L与吸光度呈线性关系,其检出限为0.036 mg/L。该方法用于红土镍矿中氧化镁含量的测定,相对标准偏差小于1.2%,加标回收率为99.1%~100.3%。氧化镁质量分数在0.15%~5.00%范围内的重复性及再现性方程分别为r=0.023m+0.037和R=0.133m–0.028。该方法适合于测定氧化镁含量在0.15%~5.00%的红土镍矿。