Papers by Keyword: Leaching

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Authors: Ye Qing Li, Huan Zhong Wang, Jiang Zhang, Song Bai Yu, Wen Juan Miao
Abstract: The national general survey manifests that the Chinese soil is suffering from serious contamination, mainly arising from heavy metals (HM). Due to the large amount of heavy metal waste, many researchers have performed the feasibility studies on co-processing this kind of waste in cement kilns. In this paper, we review these results from the perspectives of national standards, the crystal structure of clinker, and the volatility of metals in cement kiln system. The crystal structure of clinker mineral offers physical possibility for the solidification of HM atoms. The volatility studies also indicate that most of the metals will not emit from the kiln system. For the incorporated metals in clinker, their release ratio is very low, and the leaching HM atoms can be immediately enclosed by the cement hydration products. Based on these theoretical results, we measured the HM in the raw materials and in the cement product for 1 year in a cement plant. The bag filter dust contained high level of Tl with an average of 219.30 ppm. The other metals were almost solidified by the clinker. With the vaporization of Tl in the raw materials, the circulation pattern causes the accumulation and buildup of Tl in the system. The incorporation capacity of clinker on HM is predicted in this paper, but the incorporation ratio of HM from contaminated soil, the circulation pattern of HM in cement kiln system, and the emission of HM is currently not clear and further work is in progress.
Authors: Muhammad Raisul Abedin, Shamsul Abedin, Md. Hasib Al Mahbub, Nandini Deb, Mohidus Samad Khan
Abstract: This study addresses the recovery of recovery of zinc (Zn) and manganese (Mn) from spent dry cell (Zn-C battery) batteries using a hydrometallurgical approach. Every year, a significant number of Zn-C dry cell batteries are consumed and disposed worldwide. Zn-C dry cell batteries constitute more than 60% of Zn and Mn together. Higher amount of Zn and Mn present in Zn-C dry cells shows an industrial interest in recycling and recovering Zn and Mn. In this study the recovery of Zn and Mn from spent dry cells was investigated through an energy efficient hydrometallurgical route. Zn-C batteries were manually dismantled to collect the battery paste. Neutral leaching was carried out to remove potassium and non-metal contents. The battery powder was leached in sulfuric acid medium with glucose as reducing agent. The experiments were conducted according to ‘24 full factorial design’. The purpose of the design was to identify the most effective and optimum condition for Zn and Mn recovery from spent Zn-C batteries. Using the optimum operating condition, up to 86.54 % of Mn and 82.19% of Zn were recovered from the original battery powder.
Authors: Yu Jian Wang, Hongyu Li, An Wei, Da Ping Li
Abstract: Iron chemical-biological process was widely applied in desulfurization and hydrometally. 9K medium is used usually in this process. However, 9K medium is regarded as an optimal medium for suspended A. ferrooxidans culture. Iron oxidation rate is slow and some precipitation would be formed when the medium is used in this process. In this paper, a novel liquid mixture for iron chemical-biological process was reported: (NH4)2SO4 1 g/L, K2HPO4 0.2 g/L, KCl 0.15、iron 17 g/L with initial pH 1.8. A verification test indicated that Fe2+ oxidation rate was 6.1 g/(L•h), which was better than the results obtained in previous experiments. At the same time the precipitation formed is very small compared with all the experiments. So the liquid mixture may apply in this chemical-biological process better.
Authors: Dan Dan Wu, Shu Ming Wen, Jing Yang, Yi Jie Wang, Chao Lv
Abstract: In this paper, the leaching effect of zinc oxide ore was investigated using ammonium sulfate solution as leaching agent. The effects of temperature, concentration of ammonium sulfate, average particle size and stirring speed on the leaching of zinc oxide ore were studied. The leaching rate increased with increasing solution temperature, concentration, and stirring speed as well as with decreasing average particle size. Ammonium sulfate solution can therefore be used as an effective leaching agent for zinc extraction from zinc oxide ore.
Authors: Paula C. Oliveira, M.C. Rosa, Lucinda Gonçalves, Maria A. Trancoso, Carlos A. Nogueira
Abstract: Sludges generated in leather tanning processing are very complex wastes with potential deleterious effect on the environment and its management constitutes a high cost for the companies. In this work, sludges from a Portuguese tanning company were characterized and leached with acid solutions in order to evaluate the metals removal yields. The sludges contain, as main metals, 15% Ca, 5% Fe and 2.2 % Cr, in a dry basis. Other minor elements namely Al, Ti, Zn, Pb and Cu were also detected. The leaching experiments were carried out with two types of acids – hydrochloric and sulfuric – and the effects of the reaction time, temperature and leachant concentration were evaluated. The reaction conditions strongly affected the chromium leaching yields, being temperature and acid concentration highly significant (confidence level above 99.9%). About 90% of Cr was leached using the higher levels of the factors (4h, 80°C and 2M H+, with both acids). Concerning the other major metals, iron leaching was very efficient (yields usually above 90%) whatever the conditions tested while calcium behaviour was quite different, depending on the type of acid used for the same H+ concentration: H2SO4 leaching efficiency was generally lower than HCl, probably due to the formation of less soluble calcium sulfate. The maximum calcium removal achieved was near 75%. The leaching process developed can be useful not only as a decontamination step of the tanning sludges, but also as a process for metals recovery to be potentially applied in an integrated recycling system, where several metal wastes from different sources could be processed.
Authors: Leonardo Martins da Silva, M. Nascimento, I.O. Mota, E.M. Oliveira, J.A. Castro
Abstract: Heating iron ore fine particles using microwave energy has been effective due to the different interactions between minerals and gangue in the magnetic field generated by the microwave. In this way, this paper proposes to use microwave energy to heat the particles of iron ore to promote micro cracks and fissures, which would facilitate the comminution and pulverization process to produce pellet feed. It was analyzed different conditions of heating and cooling in the comminution step. By using techniques of scanning electron microscopy (SEM) and image analysis it was possible to assess and quantify the micro cracks and subsequent analysis of the energy and size fragmentation in the comminution step of ultrafine particles.
Authors: Li Li Yu, Jin Zhen Cao, Zhen Zhong Tang
Abstract: Chinese fir (Cunninghamia lanceolata Hook.) and Mongolian Scots pine (Pinus sylvestris Linn. var. mongolica Litv.) with dimension of 19.019.0450.0 mm were treated with two concentrations of amine copper quat-type D (ACQ-D) solutions (0.5%, 1.0%) respectively and post-treated with three different methods including humidity chamber, drying oven and hot water bath. The effects of these variables on copper leaching from ACQ-D treated wood were investigated according to the leaching test of AWPA E11. The results showed that post-treatment could improve the leaching resistance of ACQ-D treated wood effectively compared to the specimens those were leached immediately after impregnation. After some promising post-treatments, copper leaching from the treated wood was not only associated with the joint effects of retentions, wood species and different locations in the treated wood, but also influenced by the special fixation mechanisms in different post-treatments.
Authors: Man Jian Wu, Wu Yao, Wei Wang, Yong Qi Wei
Abstract: A new method involving the extraction of various ions from hardened cement pastes by anhydrous ethanol is presented to determine the pH value and ionic concentration during the first 28 days. The volume content of pore solution extracted by ethanol in the leachate reached 12% or above and the pH values calculated by alkali ions are more than 12, even up to 12.73. The results were compared with those from parallel, conventional pore water expression experiments. All of these comparisons verified the feasibility of the proposed method. However, the application of this method to pore solution analysis needs further improvement.
Authors: Kui Liu, Xue Mei Su
Abstract: A ferruginous nickel laterite was leached by sulfuric acid at atmospheric pressure. Nickel extraction was largely dependent on sulfuric acid concentration and leaching temperature. Besides these two factors, leaching time and liquid/solid ratio also influenced cobalt extraction significantly. Nickel was easier to be extracted than cobalt. About 95% nickel and cobalt could be extracted when leaching with 5mol/L sulfuric acid for 2h at 100°C, and the acid consumption was 1.417kg H2SO4/kg dry ore.
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