Selective nickel recovery from iron-rich solutions

This study aims to demonstrate the selective removal of iron from acidic leach solutions using an effective purification method and to convert nickel into a usable form. The method of removing iron by using CaCO₃, which is a better precipitation reagent, was optimized using Response Surface Methodology. A further evaluation was carried out on the complexation of Ni(II) ions with dimethylglyoxime to obtain a high-yield nickel-dimethylglyoxime complex from nickel remaining in the solution after iron precipitation. Taking into account nickel losses to remove iron, pH should be within the range of 3–4, and low temperatures around 25°C should be used.     

Leaching kinetics of ulexite in sodium hydrogen sulphate solutions

The aim of this study was to investigate the dissolution kinetics of ulexite in sodium hydrogen sulphate solutions in a mechanical agitation system and to declare an alternative reactant to produce boric acid. Reaction temperature, concentration of sodium hydrogen sulphate solutions, stirring speed, solid/liquid ratio and ulexite particle size were selected as parameters of the dissolution rate of ulexite. The experimental results were successfully correlated by linear regression using Statistica program. Dissolution curves were evaluated in order to test shrinking core models for solid-fluid systems. It was observed that increase in the reaction temperature and decrease in the solid/liquid ratio cause an increase in the dissolution rate of ulexite. The dissolution extent is highly increased with increase in the stirring speed rate between 100 and 700 rpm experimental conditions. The activation energy was found to be 36.4 kJ/mol. The leaching of ulexite was controlled by diffusion through the ash or product layer. The rate expression associated with the dissolution rate of ulexite depending on the parameters chosen may be summarized as: 1–3(1 − X)^2/3 + 2(1 − X) = 6.17 × C^0.97 × W^1.17 × D^−1.72 × (S/L)^−0.66 × e^(−36.4/RT)·t.     

Recovery of nickel,cobalt, copper and zinc in sulphate and chloride solutions using synergistic solvent extraction

A number of synergistic solvent extraction (SSX) systems have been developed to recover nickel, cobalt, zinc and copper from sulphuric and chloride leach solutions by the solvent extraction team of CSIRO, Australia. These in-clude (1) Versatic 10/CLX50 system for the separation of Ni from Ca in sulphate solutions, (2) Versatic 10/4PC system for the separation of Ni and Co from Mn/Mg/Ca in sulphate solutions, (3) Cyanex 471X/HRJ-4277 system for the separation of Zn from Cd in sulphate solutions, (4) Versatic 10/LIX63 system for the separation of Co from Mn/Mg/Ca in sulphate solutions, (5) Versatic 10/LIX63/TBP system for separation of Ni and Co from Mn/Mg/Ca in sulphate solutions, (6) Versatic 10/LIX63 system for the separation of cobalt from nickel in sulphate solutions by difference in kinetics, (7) Cyanex 272/LIX84 system for the separation of Cu/Fe/Zn from Ni/Co in sulphate solutions, (8) Versatic 10/LIX63/TBP system to recover Cu/Ni from strong chloride solutions, and (9) Versatic 10/LIX63 system to separate Cu from Fe in strong chloride solutions. The synergistic effect on metal separation and efficiency is presented and possible industrial applications are demonstrated. The chemical stability of selected SSX systems is also reported.     

A versatile route to synthesizing bulk and supported nickel phosphides by thermal treatment of a mechanical mixing of nickel chloride and sodium hypophosphite

Bulk and supported nickel phosphides were prepared by thermal treatment of a mechanical mixing of nickel chloride and sodium hypophosphite in a flowing N₂. The samples were characterized using thermogravimetric analysis, X-ray diffraction, and inductively coupled plasma. The effect of different aspects on the Ni₂P formation was primarily investigated. A rational mechanism was proposed for the selective formation of Ni₂P. SiO₂-supported Ni₂P exhibits excellent hydrodesulfurization (HDS) activity for dibenzothiophene (DBT).     

废电解液除杂制硫酸铜和粗镍工业试验

研究了废电解液除杂制硫酸铜和粗镍的主要工艺条件 ,在废电解液中加入CH80调节 pH值到一定范围后 ,加入CH6 4,将电解液中Fe2 + 氧化为Fe3 + ,生成Fe(OH) 3 后 ,过滤 ,将铁除去 ;然后向滤液中加入CH80 ,调节pH值 ,沉铜 ;过滤后的滤饼加入H2 SO4 ,溶解后结晶 ,便可得到CuSO4 ·5H2 O晶体 ;滤液中加入Na2 CO3 沉镍 ,过滤后的滤饼即为粗镍 (NiCO3 ) ;试验结果 :铁的去除率为 94%～ 98% ,铜和镍的回收率分别达 96 %和 90 %。     

Treatment of dye and cadmium solutions using asymmetric kaolin porous tubular support

Kaolin porous support ceramic was prepared from kaolin. The characterization of the porous properties and structure of the support synthesis was carried out by scanning electron microscopy (SEM), absorption rate, shrinkage rate and Hg-porosimetry methods. The pore size distribution showed a unimodal pore size distribution with an average pore size of about 0.9 µm. The reliability of support was measured by filtration tests and removal of heavy metals.Filtration studies using porous tubular supports were performed for solutions containing methylene blue and Evans blue. The study of the liquid filtration and flow through these supports showed that the methylene blue rejection rate was 99% while the Evans blue rate reached 90% for a 90 minute filtration time under a pressure of 2 bar. We beforehand tested the flow rate for each support with distilled water and the results show that the support of kaolin gave a flux for distilled water of 31.0 L/h at the pressure of 2 bar. At a pressure of 3.5 bar an increase in the distilled water flux through the support was observed.The rejection rate of cadmium ions was more significant. A rejection rate of 99.99% using a 10^− 4 mol/L solution of this heavy metal for two-hour treatment time was obtained.     

Removal of nickel(II) from aqueous solutions using iminodiacetic acid functionalized polyglycidyl methacrylate grafted-carbon fibers☆

Iminodiacetic acid functionalized polyglycidyl methacrylate grafted-carbon fibers (PGMA-IDA/CFs) were prepared for Ni(II) removal from aqueous solutions. The effects of solution pH value, temperature and adsorption time were investigated. The maximum adsorption capacity of Ni(II) on PGMA-IDA/CFs is 0.923 mmol·L?1 · g?1 at pH 5.2 and 50 °C. Kinetic data indicate that the adsorption process matches the pseudo-second-order model and Elovich kinetic model. Thermodynamic data suggest that the adsorption process is endothermic spontaneous reaction.     

Effect of organic extractants on the electrocrystallization of nickel from aqueous sulphate solutions

The effect of the presence of commercial organic extractants LIX 84I, Cyanex 272, D2EHPA, Versatic 10 and TBP with or without Mg²⁺ on various electrodeposition parameters for nickel deposition on stainless steel cathode from aqueous sulphate solutions was investigated. The parameters included cathodic current efficiency, deposit morphology, crystal orientation and cathodic polarization. There was no significant variation in the current efficiency in the presence of these additives, but changes were observed in the deposit morphologies and crystal orientations even though all the deposits were bright, smooth and coherent. Changes were also observed in the cathodic polarization behaviour during nickel electrocrystallization in the presence of these additives. The effect of the additives on the electrokinetic parameter, exchange current density (i ₀) has also been investigated.     

Retention of cadmium ions from aqueous solutions by poly(ammonium acrylate) enhanced ultrafiltration

Cadmium removal from aqueous solution by polyelectrolyte enhanced ultrafiltration (PEUF) with relatively low transmembrane pressure was investigated at varying conditions of polyelectrolyte and cadmium concentrations, transmembrane pressure, ionic strength and pH. The poly(ammonium acrylate), with two average molecular weights (8000 and 15 000 Da) were used as polyelectrolyte. Flux declines during ultrafiltration of polyelectrolyte solutions. An effort has been made to evaluate these resistances independently at different operating conditions. The hydraulic membrane resistance is higher for processing solutions of PAmA₈ than solutions of PAmA₁₅. The study of ionic strength effect demonstrates that it decreases the retention of cadmium ions and increases the permeate flux. More than 99% of cadmium was retained for a NaNO₃ feed concentration less than 5 × 10⁻² mol L⁻¹. The pH effect study on the cadmium recovery revealed a maximum retention around 98% for pH 4.     

High-temperature removal of cadmium from a gasification flue gas using solid sorbents

In this work, the retention capacity of solid sorbents for cadmium species present in coal gasification flue gases at high temperature was investigated. The influence of HCl(g) on the gas atmosphere was also evaluated. The study was carried out in a laboratory scale reactor, using synthetic gas mixtures with the sorbent as fixed bed. The sorbents tested were kaolin, limestone, alumina and fly ashes. The results obtained were compared with data from the works of other authors, who used similar solid sorbents in typical coal combustion flue gases. Whereas in the combustion atmospheres described in the literature, kaolin, limestone and alumina showed high retention capacities for cadmium compounds (0.5-40 mg g⁻¹), in the coal gasification atmospheres studied in the present work, the amount of cadmium captured by these solid sorbents was negligible. Fly ashes were found to be the most efficient for retaining cadmium in gasification atmospheres, their maximum retention capacity in the conditions studied being approx 0.75 mg g⁻¹.     

The removal of sodium,cadmium and chromium ions from dilute aqueous solutions using foam fractionation

Cationic metallic ions such as sodium, cadmium and chromium were flotated from aqueous solution by using foam separation or foam fractionation technique in a continuous flow system. Experimental results showed a considerable difference between mono- or divalent and trivalent metallic ions in their affinity to neutralize the negatively charged surface layer formed at the gas-liquid interface. This was verified by use of the Gouy-Chapman diffuse double-layer theory, except for the case of high concentration of the co-existing collector which formed miscellaneous metal-collector complexes.     

Effect of nickel coating on carbon for adsorption of cadmium from aqueous solutions

Nickel was coated on carbon and it was characterized by SEM and XRD. Sorption of Cd(II) ions onto carbon and nickel‐coated carbon (Ni/C), effect of acids, pH, shaking time, loading capacity, and adsorbent weight has been investigated. Acids reduce sorption and maximum sorption takes place from deionized water and R_d values for carbon and Ni/C in deionized water are 212.9 ± 0.9 and 232.5 ± 2.5. The sorption data followed the Freundlich, Dubinin–Radushkevich (D–R), isotherms and different parameters have been calculated. Sorption free energy values have been calculated and are 12.56 ± 0.19 and 14.84 ± 0.196 for carbon and Ni/C and indicate that adsorption process is chemisorption. Increase in adsorption shows the increase in catalytic activity of the adsorbent. The variation of sorption with temperature has been used to calculate the values of ΔH, ΔS, and ΔG for Cd(II) sorption. These values show that adsorption of Cd(II) ions on the adsorbents is endothermic, spontaneous, and entropy driven. Coating of carbon with nickel has improved its adsorption properties. Adsorption behaviour provides useful information for the catalytic activity of catalysts.     

Biosorption of cadmium(II) and lead(II) from aqueous solutions using Pleurotus ostreatus immobilized on bentonite

The purpose of this work was to evaluate the potential of a white rot fungi (P. ostreatus) immobilized on bentonite, in a continuous flow removal of trace heavy metals. The procedure is based on the biosorption of Cd(II) and Pb(II) ions on a column of bentonite loaded with dried, dead fungi components prior to their determination by atomic absorption spectroscopy (AAS). Cd(II) and Pb(II) were determined with a relative error of less than 5%. Various parameters such as “pH, amount of adsorbent, eluent type and volume, flow rate of the solution and matrix interference effect” on the retention of the metal ions were investigated. This procedure was applied to Cd(II) and Pb(II) determination in aqueous solutions, including tap water system. The optimum experimental parameters were determined to be pH 5, concentration of 10 mg/L, contact time of 30 min and 0.2 g of adsorbent for a quantitative adsorption of the metals. The optimum flow rate was found to be 2.5 mL/min for all metal ions. Each column can be used up to 20 successive analyses without considerable change in recoveries of metal ions.

The proposed method is excellent as regards simplicity, sensitivity, selectivity, precision, accuracy and column stability.     

硫化钠沉淀法从含铑溶液中富集铑工艺研究

用硫化钠作沉淀剂,从含铑强酸性水溶液中沉淀富集铑金属。通过实验确定了影响铑沉淀率的诸多因素,如沉淀剂加入量、沉淀温度、沉淀剂硫化钠加料速度、陈化时间及搅拌速度等。结果表明,当沉淀剂硫化钠与铑的物质的量比为10、沉淀温度为100 ℃、硫化钠加入速度为5 mL/min、陈化时间为1 h、搅拌速度为600 r/min时,铑沉淀率达到最大,铑沉淀率最高为99%以上。富集后溶液铑含量低于1 mg/kg,铑富集效果明显。     

Studies on precipitation of highly dispersed silica from sodium metasilicate–sodium hydrogencarbonate system

A novel procedure is presented for precipitation of highly dispersed silica from sodium metasilicate solution using sodium hydrogencarbonate. In the course of silica precipitation, hydrophobicity‐inducing agents were introduced to the reactor, including derivatives of saturated and unsaturated higher fatty alcohols and nonylphenylpolyoxyethyleneglycol ethers. Silicas of variable physicochemical characteristics were obtained. Analysis of the principal physicochemical properties of the silicas was performed, their surface morphology was examined using scanning electron microscopy while particle size distribution, polydispersity and tendency to form the agglomerate structures were estimated by the dynamic light scattering technique. The zeta potential was also measured by estimation of electrophoretic mobility. Sodium hydrogencarbonate solution was found to be a very good silica‐precipitating agent in solutions of sodium metasilicate. The hydrated silica obtained demonstrated low bulk density and a high capacity to absorb paraffin oil. © 2002 Society of Chemical Industry     

海藻酸钠/明胶混合水溶液的流变性能

借助旋转黏度计考察了海藻酸钠/明胶混合水溶液的流变性能,发现混合溶液具有剪切变稀的非牛顿假塑性流体特征;随体系中明胶含量的增加,相应混合溶液的稠度系数增大而黏性指数下降,同时溶液的触变性能得以增强,该混合溶液体系具有协同增效性。     

Removal of chromium (III) and cadmium (II) from aqueous solutions

Chromium and cadmium are toxic heavy metals present in wastewaters from a variety of industries. A strong cationexchange resin, Amberlite IR 120, was used for the removal of chromium and cadmium. The resin was prepared in two different cationic forms, as Na⁺ and H⁺. The optimum conditions were concentration, pH, stirring time and resin amount. The concentration range was between 2–50 mg/L, pH range between 2–10, stirring time between 5–60 min, and the amount of resin was from 50–1000 mg. Exchange capacities, moisture content and optimum conditions of this resin were determined in a batch system. The stirring speed was 2000 rpm during all of the batch experiments. The initial and final chromium and cadmium amounts were determined by atomic absorption spectrophotometry. The optimum conditions were found to be a concentration of 20 mg/L, pH of 5.5, stirring time of 20 min and 100 mg of resin. The results obtained show that the Amberlite IR 120 strong cation-exchange resin performed well for the removal and recovery of chromium and cadmium.     

Preparation of poly(acrylic acid)/starch hydrogel and its application for cadmium ion removal from aqueous solutions

In this paper, potassium bromate/thiourea dioxide redox system was used to initiate the graft copolymerization reaction of acrylic acid onto maize starch. The so obtained polyacrylic acid/starch graft copolymer was crosslinked by further treatment with alkaline epichlorohydrin to get three dimensional hydrogel. This crosslinked hydrogel was used for the removal of the heavy element, Cd²⁺ from its aqueous solution by adsorption. All factors which are expected to affect the adsorption process, like adsorbent concentration, immersion time, graft yield of the adsorbent, Cd²⁺ concentration and adsorption temperature were extensively studied and reported in the text. The study and investigations demonstrated that the adsorption efficiency is affected by the adsorbent graft yield and the adsorption medium temperature. In addition, on fitting the data obtained from the adsorption process, it was found that the adsorption obeys both Langmuir and Freundlich adsorption isotherms but the Langmuir isotherm shows better mathematical fitting for the equilibrium data than does Freundlich model, based on the higher R² value for the Langmuir isotherm.     

Removal of lead,cadmium and zinc from aqueous solutions by precipitation with sodium Di‐(n‐octyl) phosphinate

Sodium di‐(n‐octyl) phosphinate (NaL) was used as a precipitating agent to remove heavy metals from aqueous nitrate solutions. Cadmium, zinc and mixtures of lead, cadmium and zinc were precipitated in the form of PbL_2(s), CdL_2(s), and ZnL_2(s). Lowering the pH of the feed solution reduced the removal of the metals as some of the phosphinate precipitated in the acid form as HL_(S). The removal of lead, cadmium, and zinc, from a solution containing the three metals gave a selectivity in the order Zn > Pb > Cd. Predictions of an equilibrium‐constant model, using measured solubility products of the precipitates and literature values of stability constants, gave metal removals, loss of precipitating agent, and equilibrium pH in good agreement with measured values.     

Formulation and statistical optimization of multiple-unit ibuprofen-loaded buoyant system using 2-factorial design

This present investigation deals with the development and optimization of buoyant beads containing ibuprofen by emulsion-gelation method for gastroretentive delivery. The effect of three independent process variables like amount of sodium alginate, magnesium stearate, and liquid paraffin on drug entrapment, density, and drug release of buoyant beads containing ibuprofen was optimized using 2³ factorial design. The observed responses were coincided well with the predicted values, given by the optimization technique. The optimized beads showed drug entrapment efficiency of 83.07 ± 3.25%, density of 0.89 ± 0.11 g/cm³, cumulative drug release of 35.02 ± 1.24% after 8 h, and floated well over 8 h in simulated gastric fluid (pH 1.2) with 4.50 min buoyant lag-time. The average size of all buoyant beads ranged from 1.43 ± 0.05 to 1.82 ± 0.14 mm. The buoyant beads were characterized by SEM and FTIR spectroscopy for surface morphology and excipients–drug interaction analysis, respectively. All these beads showed prolonged sustained release of ibuprofen over 8 h in simulated gastric fluid (pH 1.2). The ibuprofen release profile from these buoyant beads followed Korsmeyer–Peppas model over a period of 8 h with anomalous (non-Fickian) diffusion mechanism for drug release.