Cementation Reaction Research Articles

Investigation of the Bimodal Leaching Response of RAM Chip Gold Fingers in Ammonia Thiosulfate Solution.

Oxidative thiosulfate leaching using Cu(II)-NH3 has been explored for both mining and recycling applications as a promising method for Au extraction. This study seeks to understand the dissolution behavior of Au from waste RAM chips using a Cu(II)-NH3-S2O3 solution. In the course of this work, bimodal leaching and Au loss were observed in a manner that we have not identified in the literature. Identification of the existence of a specific Au-Ni-Cu lamellar structure in the gold fingers from RAM chips by scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS) revealed the possibility of interference between Au recovery and the existence of Cu and Ni. During leaching, the co-extraction of Ni was found to predict a negative impact on the Au recovery, as a result of chemical interactions from the Au-Ni-Cu interlayer. Decopperization as a pretreatment was found necessary to remove the pre-existing Cu and promote Au leaching. As part of the study parameters, such as Cu(II) concentration, aeration rates, thiosulfate and ammonia concentrations, particle sizes, and temperatures, were investigated. A satisfactory Au recovery of 98% was achieved using 50 mM Cu(II), 120 mL/min aeration rate, 0.5 M (NH3)2S2O3, and 0.75 M NH4OH (i.e., AT/AH ratio of 0.67) for 4 h residence time at room temperature (25 °C). However, there were several high recoveries prior to Au loss from the lixiviant. It was revealed that the main cause of lower Au recovery was due to a precipitation or cementation reaction that included a sulfur species formation. Because of the bimodal leaching, a composite response comprised of the time to Au loss and maximum recovery was developed, termed leaching proclivity, to facilitate statistical analysis. Furthermore, this study explores the interactions between Au-Ni-Cu and provides suggestions for improving Au thiosulfate leaching under the interference of co-existing metals from waste PCB materials.

Rheological and Aging Properties of Vegetable Oil-Based Polyurethane (V-PU) Modified Asphalt.

To study the rheological and aging properties of vegetable oil-based polyurethane (V-PU) modified asphalt, V-PU terminated with an -NCO group was synthesized from renewable castor oil, and liquefied MDI-100LL and 10-40 wt% V-PU modified asphalts were prepared. Temperature classification, multiple stress creep recovery (MSCR), and linear amplitude scanning (LAS) tests were carried out. The results showed that the modulus, the creep recovery rate (R), and the yield stress and yield strain of the V-PU modified asphalts significantly increased in the order: 0 wt% < 10 wt% < 20 wt% < 40 wt% < 30 wt%, while the phase angle and the unrecoverable creep compliance (Jnr) changed in the opposite order, and the high temperature grade of 30 wt% V-PU modified asphalt was 4 grades higher than that of the base asphalt, which indicated that the addition of V-PU enhanced the fatigue, permanent deformation, and recovery deformation resistance. The 30 wt% sample exhibited phase inversion had the best performance. Comprehensive FTIR, GPC, and fluorescence microscopy analyses showed that the molecular weight significantly increased and the V-PU molecules agglomerated after aging. The excess -NCO groups of V-PU prepolymer react with water in the air and the active hydrogen in the asphalt system and finally form a cross-linked three-dimensional network structure with the asphalt to improve performance. The mechanism of intramolecular cementation reaction and the aging process of V-PU modified asphalt was creatively derived.

Activation and Application of Wet Shotcrete Concrete with Coal Gasification Slag Aggregate

By analyzing the shortcomings of the existing dry shotcrete process in the coal mines and the shortage of natural sand and gravel resources, it is proposed to use coal gasification slag to replace all natural sand and gravel in the preparation of wet shotcrete. Coal gasification slag has alkali-activated cementitious activity, and its strength as an aggregate in cement mortars still shows significant growth after 28d of age. First of all, the gasified slag aggregate cement mortar was mixed with calcium carbide residue to further stimulate its activity, and the effect law of different amounts of calciumcarbide residue on mortar strength was studied. The results showed that the mortar strength increased continuously with the increase of calcium carbide residue admixture, and the mortar strength increased slowly after the admixture reached 8%. With 8% admixture, the flexural strength at 90d age increased by 58.9%, and compressive strength increased by 13.6% compared with 28d age. MIP, XRD and SEM microscopic analyses showed that the incorporation of CCR promoted the alkali-activated cementation reaction of the gasified slag aggregate, eliminated the oriented aggregation of calcium hydroxide at the cement-aggregate interface, improved the interfacial bonding, and significantly reduced the percentage of harmful pores (50-200 nm) and more harmful pores (>200 nm) in the mortar, which explained the microscopic mechanism of the significant increase in mortar strength. Then the mining wet shotcrete was prepared with coal gasification slag as aggregate and calcium carbide residue as cementing material, and the 28d compressive strength reached 34.8MPa, which significantly improved the concrete strength and ensured the stability of the coal mine roadway support.

Effect on Copper Recovery by Ultrasonic Energy during Cementation Reaction from Copper-contained Waste Etching Solution

Effect on Copper Recovery by Ultrasonic Energy during Cementation Reaction from Copper-contained Waste Etching Solution

Recovery of “Hard-to-Recover” Selenate Ions in Sulfuric Acid Solutions during Polarization of Titanium Electrodes by Industrial Alternating Current

The article is devoted to the study of selenium (VI) reduction processes in sulfuric acid solutions when titanium electrodes are polarized by alternating current of industrial frequency (50 Hz). It was found that selenate ion reduction occurs on the surface of titanium electrodes in the cathode half-cycle of alternating current (practically at the cathode) by reaction: SeO42−+ 6e + 8H+ → Se + 4H2O. In addition, the recovery is carried out by titanium (III) ions: 6Ti3+ SeO42−+ 8H+ → Se + 6Ti4+ + 4H2O. It has been established that titanium (III) ions are products of dissolution of titanium during polarization by alternating current, so they can be formed by reaction: 2Ti + 6H+ → 2Ti3+ + 3H2. Reduction in selenate ions during polarization by alternating current can also occur due to the cementation reaction with titanium: 3Ti + 2SeO42− + 16H+ → 2Se + 8H2O + 3Ti4+. It was shown for the first time that the selenate ion is reduced to form a dispersed selenium powder with a high current efficiency. Depending on the conditions, both amorphous and crystalline selenium modifications are produced.

Experimental and Theoretical Investigation of the Copper (II)/Co Cementation Reaction

Cobalt is a potential candidate as an adhesion layer in the copper metallization for its low resistivity and high thermal stability.(1) The electrodeposition of copper onto the cobalt substrate is a promising technique for the next generation interconnects. However, the cementation reaction of copper (II)/Co creates an irregular interface, and it’s not possible to apply the mature copper damascene plating technique.(2) In this work, we studied the Copper (II)/Co cementation reaction using a rotating disk electrode (RDE) and developed a continuum model to gain insight into the copper (II)/Co cementation reaction.Experimental section: a thin film of cobalt is firstly plated on the Pt RDE in a three-chamber cell filled with the electrolyte containing 50 mM CoSO4 and 0.5M H3BO3 (pH =2.6). A constant current is applied for a certain period of time (0.7 mA, 20 s) while the electrode is rotating at 700 rpm. The electrode is designated as Co/Pt electrode. After the deposition, the Co/Pt electrode is washed by ultrapure water and dried by nitrogen before it’s moved to another three-chamber cell. The electrode is immersed into the electrolyte containing 10mM CuSO4 and 50mM Na2SO4 while rotating at 900 rpm. The open-circuit potential is recorded in the whole process to identify the species and possible relations on the electrode surface.Figure 1 is the chronopotentiogram of a cobalt film reacting with copper(II) solution. As shown, fresh cobalt is replaced by the Cu in stage a, and a temporary equilibrium is reached in stage b, where the surface is a layer of newly formed metallic copper. A phase transition between copper and copper oxide is observed in stage c, and stage d represents a layer of CuOx, which is a dark color. (3) The intercept between stage and stage b will be used to extract the rate constant of the cementation reaction for modeling study. H.-S. Lu, J.-X. Wang, X. Zeng, F. Chen, X.-M. Zhang, W.-J. Zhang and X.-P. Qu, Electrochemical and Solid-State Letters, 15, H97 (2012).W.-Z. Xu, J.-B. Xu, H.-S. Lu, J.-X. Wang, Z.-J. Hu and X.-P. Qu, J Electrochem Soc, 160, D3075 (2013).J. Xiong and I. M. Ritchie, Hydrometallurgy, 16, 301 (1986). Figure 1

Cementation of Copper on Zinc in Agitated Vessels Equipped with Perforated Baffles as Turbulence Promoters

In this work, the possibility of intensifying the cementation process in stirred vessels was studied by using the perforated baffles as turbulence promoters; the cementation reaction of Cu+2 on Zn was selected as a model. Zn was used in the form of a sheet lining the inner wall of an agitated vessel. Parameters considered are initial concentration of Cu+2, solution temperature, impeller rotation speed, and impeller geometry. Within the present range of parameters studied, the rate of cementation was found to increase with increasing initial concentration of Cu+2, solution temperature, and impeller rotation speed. At the same rotational speed, a flat turbine gave a higher rate of cementation than a 45° pitched turbine. The present suggested that baffles’ geometry gave superior performance in terms of mass transfer of copper cementation compared to the conventional baffle geometry. All parameters that affect the rate of cementation were correlated in the form of dimensionless equations suitable for the design and performance prediction of the agitated vessel. Potential applications of the obtained results in the field of hydrometallurgical processes and wastewater treatment were discussed.

Comparative Study Between Geopolymer and Cement Waste Forms for Solidification of Corrosive Sludge

Two waste forms, namely cement and geopolymer, were investigated and tested in this study to solidify the corrosive sludge generated from the surface and precipitates of the tubes of steam generators in nuclear power plants. The compressive strength of the cement waste form cured for 28 days was inversely proportional to waste loading (24.4 MPa for 0wt% to 2.7 MPa for 60wt%). The corrosive sludge absorbed the free water in the hydration reaction to decrease the cementation reaction. When the corrosive sludge waste loading increased to 60wt%, the cement waste form showed decreased compressive strength (2.7 MPa), which did not satisfy the acceptance criteria of the repository (3.45 MPa). Meanwhile, the compressive strength of the geopolymer waste form cured for 7 days was proportional to waste loading (23.6 MPa for 0wt% to 31.9 MPa for 40wt%). The corrosive sludge absorbed the free water in the geopolymer when the water content decreased, such that a compact geopolymer structure could be obtained. Consequently, the geopolymer waste forms generally showed higher compressive strengths than cement waste forms.

Gold Cementation Kinetic Features Using Dendritic Zinc Powders

Gold cementation kinetic features from cyanide solutions using zinc powders of various origins were studied. The first powder was obtained by distillation and is currently used in the vast majority of industries (traditional powder). The second powder was obtained by electrochemical reduction from alkaline solution (electrolytic powder). The main distinguishing feature of these powders is specific surface area. This indicator for the electrolytic powder is 2.6 times higher than for the traditional one (3.02 and 1.16 m2/g, respectively), which is associated with dendritic form of electrolytic powder. For cementation studies, a solution with a gold content of 50.8 μmol/dm3 and 0.04 mol/dm3 sodium cyanide (NaCN) was taken. Studies have shown the presence of a depassivation period associated with oxide film dissolution on the powder surface and overcoming diffusion difficulties. The depassivation period of a traditional powder (10–15 seconds) exceeds the depassivation period of an electrolytic powder (5–8 seconds). Values of cementation reaction experimental rate constants are determined for the process using traditional and electrolytic powders at different ratios of zinc and gold masses in solution. Experimental reaction rate constants for electrolytic powder under the studied conditions are 1.3–1.6 times higher than the experimental rate constants for traditional powder. Zinc oxidation rates are compared under these conditions for various ratios m(Zn)/m(Au). Powder dissolution rates referred to specific surface area (taken in initial period) practically do not differ. The electrolytic powder’s absolute dissolution rate at the initial time is almost two times greater. As powder reacts with an alkaline solution, absolute dissolution rates of electrolytic and traditional powders are equalized.

Kinetic features of gold cementation using dendritic zinc powders

The study covers kinetic features of gold cementation from cyanide solutions using two zinc powders of various origins. The first one was obtained by distillation and is currently applied in gold cementation from cyanide solutions (traditional powder). The second one was obtained by electrochemical reduction from the alkaline solution (experimental, electrolytic powder). The main distinguishing feature of these cementation powders is their specific surface area. This indicator for the electrolytic powder is 2.6 times higher than for the traditional one (3.02 m2/g and 1.16 m2/g, respectively) due to its dendritic form. The studies used a solution with a gold content of 50.8 μmol/dm3and a sodium cyanide content of 0.04 mol/dm3NaCN was taken. Cementation revealed a powder depassivation period associated with oxide film dissolution and overcoming diffusion difficulties. The traditional powder depassivation period (10–15 sec) exceeds that of the electrolytic powder (5–8 sec). Experimental rate constants of the cementation reaction were determined for the process involving both powders under study at different ratios of zinc and gold masses in the solution. Experimental reaction rate constants for the electrolytic powder under the studied conditions were 1.3– 1.6 times higher than that for the traditional powder. It was found that oxidation rates of zinc powders compared at different ratios of zinc and gold masses are virtually the same. At the same time, absolute rates of electrolytic powder dissolution in the initial period are nearly 2 times greater. As the powder reacts with the alkaline solution, absolute dissolution rates of electrolytic and traditional powders are equalized.

Wood Bottom Ash and GeoSilex: A By-Product of the Acetylene Industry as Alternative Raw Materials in Calcium Silicate Units.

The main objective of this research was to obtain calcium silicate units from alternative raw materials, such as the bottom ashes from the combustion of wooden boards (WBA), as a source of silica, and GeoSilex (G), a by-product with low energy and environmental costs generated in the manufacture of acetylene, as a source of lime. Once the raw materials were physically, mineralogically and chemically characterized, calcium silicate units were obtained by mixing different amounts of WBA residue (90–20 wt%) and G by-product (10–80 wt%). The mixtures were compressed at 10 MPa and cured in water for 28 days. The calcium silicate units were subjected to a wide experimental program that included the determination of physical properties (bulk density, apparent porosity and water absorption), mechanical properties (compressive strength), and thermal properties (thermal conductivity). Optimum values are obtained for calcium silicate units that contain a 1/1 WBA/G weight ratio, which have an optimal amount of SiO2 and CaO for the cementation reaction. The 50WBA-50g units have compressive strength values of 46.9 MPa and a thermal conductivity value of 0.40 W/mK. However, all calcium silicate units obtained comply with the European Standard EN 771-2: 2011 to be used as structural building materials.

Recovery of indium from extractants of waste indium tin oxide (ITO) by aluminum cementation

Due to the wide applications, limited supply, and high demand, sustainable utilization of indium has become an important task. In this study, the recovery of indium from acidic extractant solutions of ITO scraps using aluminum (Al) powder was investigated. The cementation reaction of indium from HCl solution was completed within 10 min and it could be described by pseudo-first-order kinetic model. Effective recovery of indium (91.69%) at aluminum dose of 5 g/L and 25 °C was found in HCl solution. Recovery efficiency increased with aluminum dose. Results from cyclic voltammetry were used to provide information why cementation reactions did not work in H2SO4 or HNO3 solutions. Indium recovery by aluminum cementation could be an alternative process, which is simple and efficient. However, there are some drawbacks, e.g., cementation reaction was not specific as tin was recovered simultaneously with indium from solutions. Furthermore, removal and separation of indium deposit on aluminum surfaces could be another issue.

Effect of nettle plant extract on the overconsumption diminution of zinc as sacrificial metal during cementation of copper

In this work, we study the cementation reaction of copper by zinc in acid sulphate media in the presence of nettle plant extract (Urtica dioica L.). The effect of some parameters, namely concentration of nettle extract, temperature and initial copper ions concentration have been studied. This extract obtained by refluxed technique in water, has proved to be a good inhibitor of the parasitic reactions of hydrogen and dissolved oxygen that accompanied the cementation process in acidic media. These reactions are the main causes of the zinc overconsumption and the decrease of copper recovery efficiency. The results showed that the maximum of copper recovery efficiency (85.2%) was obtained at the optimal concentration of nettle extract, equal to 1.5 g·L−1. At this concentration, we recorded a decrease in zinc overconsumption of about 43.5% compared to the solution without additives. The rate of the cementation reaction increases with increasing temperature up to 37 °C and this effect is more pronounced when the extract is present in solution.

Efficient extraction of bismuth from hydrochloric acid solution by copper powder

An efficient method for extracting bismuth (Bi3+) from a hydrochloric acid (HCl) system by cementation with copper (Cu0) powder was proposed in this work. The thermodynamic properties of cementation were investigated via cyclic voltammetry measurement and thermodynamic calculation. Then, the effects of reaction temperature, Cu0/Bi3+ molar ratio, stirring rate, HCl concentration, and competing ions on the cementation efficiency of bismuth were systematically investigated. Results showed that the cementation reaction between bismuth and copper powder was thermodynamically spontaneous. A Bi recovery of 99% could be achieved with copper powder under an optimized cementation condition (6 mol L−1 HCl, 60 °C, Cu0/Bi3+ molar ratio of 4, stirring rate of 500 rpm, and reaction time of 30 min). Kinetics study revealed that Cu0-Bi3+ cementation followed a first-order reaction law in the range of 20 °C–60 °C. The activation energy of bismuth cementation was 8.58 kJ mol−1. The generated cuprous ions can be recovered as copper sulfides by sulfuration after Bi3+ was extracted. This finding indicated that Cu0 powder cementation showed potential for Bi3+ extraction.

Cementation Reaction of Lithium Powder Electrodes for Improving the Electrochemical Performances of Lithium-Metal Batteries

Lithium metal is of particular interest for higher energy density Lithium Metal Batteries (LMBs) for example all-solid-state batteries, lithium/sulfur or lithium/oxygen batteries.1 Furthermore, there are several challenges to overcome, such as lithium dendrite growth, volume changes of the electrodes or low Coulombic efficiency, before reaching commercialization. With respect to these points, the initial morphology of the lithium metal could play an important role in suppressing the formation of lithium dendrites. However, the use of lithium powder is mainly limited to the prelithiation of high capacity electrodes.2 Using a common slurry casting method with polyisobutylene (PIB) as a binder3 allows the preparation of electrodes that preserve the spherical shape of lithium-powder particles. However, these lithium-powder electrodes suffer from poor active material utilization which is caused by the electronic isolation of such particles during lithium electrodissolution. In literature, studies could show an increase in mechanical surface stability after implementation of Li-rich composite alloy films on lithium electrodes.4 This approach (cementation reaction with ZnI2) was adapted to be suitable for lithium powder modification with the goal of the improvement of active lithium loss. The resulted growth of a Li-Zn alloy phase within the bulk lithium-powder electrodes and on their surface was found to improve the electronic contact between the lithium-powder particles. With this method, an increase in active material utilization could be achieved, resulting in enhanced cycling performances of LMBs with lithium powder anodes. Betz, J.; Bieker, G.; Meister, P.; Placke, T.; Winter, M.; Schmuch, R. Advanced Energy Materials 2018, 1803170.Holtstiege, F.; Schmuch, R.; Winter, M.; Brunklaus, G.; Placke, T. Power Sources 2018, 378, 522.Heine, J.; Rodehorst, U.; Qi, X.; Badillo, J. P.; Hartnig, C.; Wietelmann, U.; Winter, M.; Bieker, P. Electrochimica Acta 2014, 138, 288.Liang, X.; Pang, Q.; Kochetkov, I. R.; Sempere, M. S.; Huang, H.; Sun, X.; Nazar, L. F. Nature Energy 2017, 2, 17119.

The Power of Stoichiometry: Conditioning and Speciation of MgCl2/AlCl3 in Tetraethylene Glycol Dimethyl Ether-Based Electrolytes.

In many Mg-based battery systems, the reversibility of Mg deposition and dissolution is lowered by parasitic formation processes of the electrolyte. Therefore, high Coulombic efficiencies of Mg deposition and dissolution are only achieved after several "conditioning" cycles. As this phenomenon is especially reported for AlCl3-containing solutions, this study focuses on the "conditioning" mechanisms of MgCl2/AlCl3 and MgHMDS2/AlCl3 (HMDS = hexamethyldisilazide) in tetraethylene glycol dimethyl ether (TEGDME)-based electrolytes. Electrochemical (cyclic voltammetry) and spectroscopic investigations (27Al nuclear magnetic resonance spectroscopy, Raman spectroscopy, inductively coupled plasma optical emission spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy) reveal that cationic AlCl2+ species in TEGDME-based electrolytes with an AlCl3/MgCl2 ratio higher than 1:1 corrode the Mg metal. According to a cementation reaction mechanism, the corrosion of Mg is accompanied with Al deposition. In effect, the consumption of Mg results in low Coulombic efficiencies of Mg deposition and dissolution during the electrolyte "conditioning". After understanding the mechanism of this process, we demonstrate that a careful adjustment of the stoichiometry in MgCl2/AlCl3 and MgHMDS2/AlCl3 in TEGDME formulations prevents Mg corrosion and results in "conditioning"-free, highly efficient Mg deposition and dissolution.

Thermodynamics and Kinetics on the Cementation Reaction of PbCl2 in the 50 mol%ZnCl2–50 mol%KCl Melt with Solid Zinc at 673 K

Removal of PbCl2 from the 50 mol%ZnCl2–50 mol%KCl melt by the cementation reaction with solid zinc at 673 K was investigated in terms of thermodynamics and kinetics to develop a new recycling process of zinc from the electric arc furnace dust. A chloride sample (50 mol%ZnCl2–50 mol%KCl containing PbCl2 as an impurity) in a glass container was heated to 673 K, and zinc powder was added into the melt to remove PbCl2 by the reduction with zinc. In the equilibrium experiments by the addition of largely excess zinc, the limitation of PbCl2 removal by the cementation reaction at 673 K was measured. In the kinetic experiments by the addition of slightly excess zinc, the concentration of lead in the 50 mol%ZnCl2–50 mol%KCl melt at 673 K decreased rapidly from 2.91 to about 0.2 mass%Pb in 5 min, and finally reached about 0.04 mass%Pb after a 240-min reaction. The SEM/EDS analysis showed that the lead-rich phase was formed around the zinc phase. Finally, the reaction mechanism was discussed by applying the unreacted core model.

Lithium-Powder Based Electrodes Modified with ZnI2 for Enhanced Electrochemical Performance of Lithium-Metal Batteries

Lithium-powder electrodes, prepared via paste casting method using lithium powder and polyisobutylene (PIB) as a binder, were investigated for their electrochemical properties in lithium-metal cells. The electrode paste casting method allows preserving the spherical shape of lithium-powder particles during processing to electrodes. However, these lithium-powder based electrodes suffer from poor active material utilization, as electronic isolation of lithium particles during the lithium electrodissolution process was observed to occur. In order to improve the lithium inter-particle contact as well as the contact with the current collector, a simple and effective chemical modification of the lithium-powder based electrodes was considered. Using a cementation reaction with ZnI2, the growth of a Li-Zn intermetallic (“alloy”) between the lithium-powder particles and the surface of the lithium powder, lead to an increase of the active material utilization and overcame the side reactions due to lithium electrodissolution. Besides increasing the active material utilization, such simple chemical modification of the lithium-powder based electrodes improved the electrochemical performance resulting in more stable cycling behavior with low polarization and longer cycle life in both Li||Li-symmetric and Li||NMC 622 cells.

Conformal Deposition of RuO2 on Cu via a Galvanic Cementation Reaction

We develop a seedless wet chemical process to deposit uniform RuO2 on a Cu substrate. Our approach entails the synthesis of volatile RuO4 colloids in a pH 9 aqueous solution from the oxidation of RuCl52− by ClO−, followed by a galvanic cementation reaction in which the Cu undergoes a mild oxidation in conjunction with the reduction of RuO4 to produce a dense and conformal RuO2 thin film on the Cu surface. The nature for the chemical reactions and constituents involved are investigated by UV-Vis, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy. Both as-deposited and annealed RuO2 films are characterized by scanning electron microscope and X-ray diffractometer. The as-deposited RuO2 film, with a thickness of 199 nm, reveals an amorphous structure and after an Ar annealing, becomes crystalline in rutile phase. In between the RuO2 and Cu, there are presence of CuO from the displacement cementation reaction, and Cu2O from the parasitic Cu corrosion as expected from the Pourbaix diagram. These Cu oxides, with a thickness of 330 nm, provide sufficient adhesive bonding between RuO2 and Cu.

A Study on the Cementation Reaction of Cadmium by Zinc Powders from Leaching Solution of Waste Nickel-Cadmium Batteries

A Study on the Cementation Reaction of Cadmium by Zinc Powders from Leaching Solution of Waste Nickel-Cadmium Batteries