A composite strong-acid cation exchanger was developed for use in high-flow-rate metal recovery systems by coating a porous silica support with a styrene-divinylbenzene copolymer and subsequently introducing sulfonic acid groups. The purpose of this study was to clarify how structural factors of the composite exchanger affect adsorption-desorption performance under dynamic flow conditions relevant to compact and high-throughput recovery processes. A series of samples with different crosslinking ratios, sulfonation feed ratios, and particle sizes was prepared, and their adsorption properties were evaluated using Ni(II) and Cu(II) as model metal ions. Batch adsorption tests were carried out to examine adsorption rates and distribution behavior, while column experiments were performed to investigate breakthrough behavior, elution characteristics, recovery efficiency, scale-up performance, and cyclic stability. The results showed that the sample prepared with a crosslinking ratio of 15%, a sulfonation feed ratio of 2 equiv., and a particle size of 250-500 μm exhibited the most favorable overall performance among the materials examined. This sample showed rapid adsorption, sharp breakthrough and elution behavior, high recovery rates for both metal ions, and stable operation in scale-up and repeated adsorption-elution cycle tests. In addition, under high-flow-rate conditions, the optimized composite exchanger exhibited superior recovery behavior compared with the reference commercial resin. These findings demonstrate that systematic optimization of the resin structure and particle size is essential for maintaining efficient ion-exchange performance at high flow rates, and that the developed composite cation exchanger is a promising separation material for compact metal recovery systems.
The effects of Cl-, gelatin and Sb(III) additions on the current efficiency and crystal morphology of Zn electrodeposition from the electrowinning solutions were investigated. When Cl-(300 mg/L), gelatin (1 mg/L) and Sb (5 mu g/L) were added individually, the current efficiency increased by 1-1.5% compared with the additive-free case. When two of these additives were used in combination, the current efficiency also increased compared with the additive-free condition, with the largest improvement observed for the combination of Cl-and gelatin. This is attributed to the complementary effects of Cl-, which promotes Zn deposition, and gelatin, which suppresses hydrogen evolution. When Cl-coexisted with either gelatin or Sb, the grain size of the deposited Zn became larger than in the cases where gelatin or Sb was added alone. Since the addition of Cl-reduces the overpotential for Zn deposition, it is considered that the nucleation rate decreases, leading to an increase in grain size. The number of bubble marks on the deposited Zn increased with the addition of Cl-, but decreased when gelatin or Sb was present together with Cl-. These results suggest that an increase in the nucleation rate of Zn reduces the formation of bubble marks.
The objective of this study was to develop a method for quantitatively characterizing tetravalent Ru complexes, namely [RuCl6]2− and [Ru2OCl10]4−, in concentrated hydrochloric acid by ultraviolet-visible absorption spectroscopy. To obtain the standard spectra of each complex, measurements on K2RuCl6 and K4[Ru2OCl10] dissolved in hydrochloric acid containing an oxidizing agent were performed. Test solutions were prepared by fusing Ru with NaOH and Na2O2, followed by dissolving in hydrochloric acid. Using cuvettes with appropriate pass lengths for each solution, the spectra were measured over a wide range of Ru concentrations, from 0.000323 to 0.0321 mol･dm−3. Then the spectra of the test solutions were separated into the contributions of [RuCl6]2− and [Ru2OCl10]4− to quantify the Ru complexes. Among the tests conducted, [RuCl6]2− was mainly formed in hydrochloric acid when the amount of Ru added was relatively small, whereas [Ru2OCl10]4− was more likely to be formed when the amount of Ru was large. [RuCl6]2− and [Ru2OCl10]4− coexisted at comparable concentrations at the intermediate condition. Heat treatment on the Ru solution to improve the accuracy of the analysis was also demonstrated.
This study examines the effects of rock spalling on support elements in order to prevent cracking and to ensure the integrity of the support system and safety during shaft sinking. When the ventilation shaft at the Horonobe Underground Research Center reached a depth of more than 250 m, severe rock spalling occurred, and cracks developed in the concrete lining immediately above the spalling zone. Therefore, a three-dimensional numerical analysis of the shaft was conducted to estimate changes in the stress distribution within the concrete lining caused by the spalling. The simulation results indicated that the vertical tensile stress in the concrete lining increased as the spalling progressed. By integrating the analytical results with field observations and considering various support patterns to prevent further rock spalling, a flowchart for selecting the optimal support pattern was developed. Shaft sinking was subsequently completed to a depth of 500 m without significant damage to the concrete lining or excessive spalling. The flowchart developed in this study will contribute to the selection of optimal support patterns for future shaft sinking projects.
