Mathematical model for choosing the preferable range of concentrations of ligands as components of solutions for alloy electrodeposition

Based on a statistical analysis of the information on the composition of solutions for the electrodeposition of A-B alloys, a mathematical model is proposed that makes it possible to choose the preferable range of the total concentrations of ligands in solutions for alloy electrodeposition. The prediction by the model is verified by known and new experimental data.     

Modeling of a process for removal of metal ions by electromigration and electrodeposition

A mathematical model for the removal of impurities of the metal ions of Fe, Ni, and Cu from hard chromium plating solution by electromigration and subsequent electrodeposition has been developed and presented. Experimental data for the metal removal at 45°C and constant cell voltage using o‐phosphoric acid as the catholyte are presented. Up to 36% iron and 29% nickel removal is obtained over about 25 h. The copper removal rate is observed to be approximately four times greater than the rate of nickel removal. The experimental data were found to closely match results predicted from the model developed. The inherent model parameters such as mobility, diffusivity, mass transfer coefficient and metal deposition rate constants were estimated. The calculated values of these parameters are found to be in good agreement with the published data.     

混合金属离子定量萃取分离时酸度范围的探讨

提出了混合金属离子定量萃取分离时酸度范围的简便计算方法,并应用于双硫腙-CC l4溶液定量萃取分离Hg2+和Zn2+体系,所得计算结果与实验值一致。     

Calixarene-based extractants for heavy metal ions removal from aqueous solutions

The article reviews the literature on the possibility of application of the calixarene-based compounds for selective separation of toxic heavy metals from aqueous solutions by the solvent extraction and transport across liquid membranes. The specific three-dimensional structure of calixarenes and their derivatives, simple and low-cost synthesis, and ease of chemical transformation qualify these compounds for the role of selective chemical extractants of toxic heavy metal ions present in industrial wastewater. This article analyses the influence of various process factors, with the greatest emphasis on the structure of the extractants/carriers, on efficient separation of heavy metal ions, primarily those most commonly found in galvanic wastewater.     

The electrodeposition of copper-silver and copper-nickel alloy powders from aqueous ammoniacal solutions

The electrodeposition of copper-silver and copper-nickel powders from aqueous ammoniacal solutions at a continuously scraped rotating cylinder cathode is described. Ag-Cu powders can be prepared under these conditions, but the individual particles are inhomogeneous and the extent of this inhomogeneity is examined. Surface areas (from BET) and particle size distributions are reported, and the morphology is considered. Cu-Ni powders deposited under these conditions are heavily contaminated with oxide/ hydroxides and this is attributed to an increase in near-cathode pH.     

某些有机添加剂对硫酸-酒石酸盐溶液中电沉积Cu-Zn合金的作用

研究了以酒石酸钾钠、柠檬酸三钠作为络合剂的酸性硫酸盐溶液中的Cu-Zn合金镀层。探讨了电流密度、pH、温度对镀液分散能力和镀层组成的影响。在本实验条件下,添加剂的加入可以使镀液具有较好的分散能力和较高的电流效率。实验发现,在所研究的各种添加剂中,糖精、苯酚是加速剂,而硫脲、甘油是阻化剂。采用动电位极化和电化学阻抗谱方法,测定了Cu-Zn合金镀层在NaCl(φ=3.5%)溶液中的耐蚀性能。采用扫描电镜研究了添加剂对控制沉积质量的微妙作用。X-射线衍射分析表明,合金镀层的相结构是正交晶。在上述研究的基础上,提出了Cu-Zn合金电沉积的最佳组成和工艺控制参数。     

Effect of low concentrations of Pb on Sn electrodeposition in methyl sulphonic acid solutions

The influence of Pb²⁺ on the initial stages of Sn electrodeposition onto copper from methyl sulphonic acid solutions in the absence of organic additives has been investigated. Particular attention is placed on the effect of Pb²⁺ at concentrations much lower than previously reported and where no lead is detected in the resulting deposit. Linear sweep scans and i-t transients show that Pb²⁺ catalyzes Sn plating at Pb²⁺:Sn²⁺ molar concentration ratios between about 1:1000 and 20:1000. This effect can be significant, with as much as a 30% increase in the amount of tin deposited over that obtained in the absence of Pb²⁺ when the concentration ratio is 2:1000 or 5:1000. At concentration ratios above 20:1000, the effect disappears and, in fact, Pb²⁺ has an inhibitory effect on Sn²⁺ reduction. Under conditions where Pb²⁺ enhances Sn electrodeposition, it also begins to affect electrocrystallization by promoting faster nucleation and a more 2-dimensional coating that more rapidly covers the substrate. This trend continues as the Pb²⁺ concentration is further increased and the catalytic effect disappears.     

Stability of the electrodeposition process for CoPt alloy formation

The stability of the process for electrodeposition of CoPt alloys from ammonium citrate electrolytes containing [Pt(NO₂)₂(NH₃)₂]⁰ as the source of Pt was studied. Voltammetric monitoring of the anodic oxidation of the electrolyte and deposition of CoPt on the cathode showed the effect of the changes of the nature of the Pt complex on the performance of the plating bath. Anodic oxidation of the Pt complex was shown to involve mainly the oxidation of and to some extent NH₃ ligands. The cathodic process is accompanied by reduction of free The reduction of this anion in the bound form is highly inhibited. In contrast, its oxidation at the anode proceeds almost as readily in the bound form as that in the free form.     

Effect of electrodeposition parameters on the hydrogen permeation during Cu-Sn alloy electrodeposition

The Cu-Sn alloy coatings were synthesized on 27SiMn steel by direct current (DC), pulse current (PC) and pulse reverse current (PRC) electrodeposition techniques from pyrophosphate-based electrolyte. The hydrogen permeation behaviors during the electrodeposition by different techniques were investigated using Devanathan-Stachurski method. The results demonstrated that the hydrogen permeation amount of different electrodeposition techniques decreased in the order: DC > PC > PRC. Frequency and duty cycle have great effect on the sub-surface concentration C_o of atomic hydrogen and hydrogen permeation amount. The minimum of hydrogen permeation amount was observed at the frequency of 1000 Hz or 2500 Hz and the duty cycle of 40%. It indicates that the amount of permeated hydrogen in the steel during deposition can be reduced due to the decrease of C_o by PC and PRC methods.     

Adequacy of a stochastic model for choosing ligands for alloy electrodeposition from solutions of mixed-ligand and multivalent ion complexes

The adequacy of a stochastic model for choosing ligands which makes it possible to determine the regions of allowable values of the stability constants of complexes, the reduction of which occurs with the formation of an alloy, and choose ligands on the basis of these data is verified. Experimental data for alloy electrodeposition from solutions with complexes of different ligands and complexes of multivalent ions that are in published data show a good agreement with predictions by this model, which made it possible to formulate an important-for-practice condition of choosing ligands for joint reduction of complexes and the formation of an alloy.     

The influence of metal ions on the aggregation and hydrophobicity of dyes in solutions

The effect of the addition of metal ions to dye solutions in promoting dye aggregation and in changing dye association in solution has been studied. Experimental findings indicate that the promoting effects of calcium and magnesium ions are greater than that of sodium ions. It is expected that any change in dye hydrophobicity would have a direct influence on the extent of dye aggregation. Under acid conditions, a higher concentration of metal ions would result in an increase in dye aggregation with a reduction in dye hydrophobicity. On the other hand, while the dye aggregation is increased under alkaline conditions under the influence of metal ions, hydrophobicity was shown to increase. These changes in dye hydrophobicity could be used to explain the dyeing behaviour of reactive dyes in the dyeing of silk.     

锡-铁合金电沉积工艺的优化

通过正交试验对电镀Sn-Fe合金的镀液配方进行优化,研究了电流密度和镀液p H对Sn-Fe合金镀层微观结构、显微硬度、光泽和耐蚀性的影响,得到最优镀液配方和工艺条件为:葡萄糖酸钠120 g/L,硫酸亚锡40 g/L,硫酸亚铁20 g/L,H3BO320 g/L,聚氧乙烯-聚氧丙烯-聚氧乙烯嵌段聚醚(EPE4600)30 mL/L,pH 4,温度25℃,电流密度2.0 A/dm2。在该条件下可电镀得到表面光亮、结晶细致、耐蚀性良好的Sn-Fe合金镀层。     

Preferential occupancy of metal ions in the hydroxyapatite solid solutions synthesized by hydrothermal method

The solid solutions in the systems of Ca-Cd HAp [Ca_10−xCd_xHAp (x = 0–10)], Ca-Sr HAp [Ca_10−xSr_xHAp (x = 0–10)] and Ca-Pb HAp [Ca_10−xPb_xHAp (x = 0–10)], were successfully synthesized at 200 °C for 12 h under hydrothermal conditions. The site of the metal ions in the solid solutions was analyzed by the Rietveld method. The results of the Rietveld analysis indicated that the metal ions of Pb²⁺, Sr²⁺, and Cd²⁺ all preferentially occupied M (2) sites in the apatite structure. The preferential occupancy of the metal ions in M (2) sites were explained mainly by their ionic radius and electronegativity.     

金刚石工具专用电沉积铁铜合金的研制

采用双阳极动态阴极电解槽以电沉积的方式制备铁铜合金Fe70Cu30,通过工艺试验、添加试验测定铁铜合金的性能及应用性能研究。研究结果表明:Fe70Cu30本身即具有良好的热压烧结性能和很好的冷压性能;研究表明电沉积铁铜合金能够降低烧结温度,硬度没有大的变化,抗弯强度普遍有不同程度提高。根据应用试验结果,我们认为电沉积铁铜合金在某些方面具有无法替代的作用。     

Synthesis of a carbamide-based dithiocarbamate chelator for the removal of heavy metal ions from aqueous solutions

This study was carried out to develop a carbamide-based dithiocarbamate (CDTC) chelator for the removal of heavy metal ions from wastewater. Its structural properties were characterized by FT-IR, ¹H NMR and ¹³C NMR. Results confirmed the functional groups of HNC(S)S existed. The adsorption isotherms showed CDTC had a high adsorption capability for Zn (119.8 mg/g) and Cu (63.1 mg/g). It exhibited a distinctive selectivity for the removal of metal ions (Cu²⁺ > Zn²⁺ > Cr³⁺ > Pb²⁺ > Cd²⁺) as they coexisted. The influence of initial pH of wastewater for the removal efficiency of metal ions was also investigated and a pH > 7 was preferred.     

New sorbent hydrogels for removal of acidic dyes and metal ions from aqueous solutions

Summary Poly(N-hydroxymethylacrylamide), PHMA, hydrogels were prepared by using N-hydroxymethylacrylamide, HMA, monomer and polyethyleneglycol(400)diacrylate as a crosslinking agent in aqueous medium and then amine groups were incorporated onto PHMA hydrogels by amination reaction with different diamines. The obtained hydrogels were characterized by determination of amine value, hydroxymethyl group content and FTIR spectra. The amine value of hydrogels changed from 2.23 to 4.64 mmol/g by depending on the amine compounds used in amination reaction. Their swelling degree increased at acidic pH values and they showed pH dependent swelling behaviour. They were used as sorbent for removal of indigo carmine and Cu(II) ion, as a model dye molecule and metal ion, respectively, from aqueous solutions. The adsorption properties of the hydrogels were investigated by depending on pH, time and initial indigo carmine or Cu(II) ion concentration. It was seen that the amine group incorporated hydrogels have quite high adsorption rate and adsorption capacity, and their adsorption capacities changed with pH of the solution. Langmuir isotherm model was the best fit for adsorption of both indigo carmine and Cu (II) ion.     

Mechanism of nickel-molybdenum alloy electrodeposition in citrate electrolytes

The kinetics of the induced codischarge of Mo with Ni in citrate-ammonia electrolytes was investigated by means of polarization and a.c. impedance measurements. Three potential ranges were considered. At low polarization, hydrogen evolution resulting from citrate reduction is the main reaction. The impedance plots exhibit a large capacitive loop with a small high frequency inflection characteristic of the development of a porous layer and a low frequency inductive feature. At intermediate polarization, the partial currents for Ni and Mo discharge increase in the same proportion; the hydrogen evolution is first constant and then rapidly decreases. Then a large low-frequency capacitive feature is observed on the impedance plots, whose size decreases with increasing polarization. At still higher polarization, the Mo discharge becomes increasingly controlled by diffusion which generates an additional capacitive loop. A reaction scheme is proposed which accounts for the polarization data and the major impedance features.