Ultrasonic-Assisted Acid Leaching of Indium from Blast Furnace Sludge
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BLAST furnace sludge is a hazardous industrial waste generated during pig iron production, from which we can recover some metals such as indium, zinc, etc. Indium is a rare and dispersed element, which is widely spread in the Earth’s crust in very low concentration estimated to be 0.11 lg/g. There is seldom an indium ore deposit. In fact, indium often enters into zinc ore, lead ore, etc.[1] As an important element, indium is extensively used in liquid crystal displays,[2, 3] semiconductors,[4–6] infrared detectors,[7, 8] catalytic agents,[9–11] and so on. However, the source from which indium can be produced is becoming scarce. So, it is important to find new sources for extracting indium. Recently, indiumbearing wastes, such as etching waste,[12,13] spent catalysts,[14] zinc oxide flue dust,[15,16] indium-tin oxide (ITO) scrap,[17–19] alloy wire scrap,[20] and so on,[21,22] have been used as raw material for recovering indium. Due to small amounts on Earth, indium is worthy of recovery when its content in industrial wastes reaches 0.002 pct. Therefore, blast furnace sludge, which contains a few percent of indium, can be a raw material for extracting indium. The hydrometallurgical recovery of indium usually starts from the leaching process, and sulfuric acid, hydrochloric acid, and nitric acid are mainly used as leachants.[19,23] Li et al.[24] have reported that temperature and sulfuric acid concentration significantly influenced XINGMEI SHEN, Lecturer, LIAOSHA LI, Deputy Director, ZHAOJIN WU, Professor, HUIHONG LU¨, Associate Professor, and JIA LU¨, Postgraduate, are with the AnHui Province Key Laboratory of Metallurgy Engineering & Resources Recycling, Anhui University of Technology, Ma’anshan 243002, Anhui, P.R. China. Contact e-mail: [email protected] Manuscript submitted November 19, 2012. Article published online September 10, 2013. 1324—VOLUME 44B, DECEMBER 2013
the leaching rate of indium from sphalerite concentrate during pressure acid leaching, and 92 pct indium extraction was achieved under optimal conditions. And, the above scientists have also studied the oxidative pressure leaching of sphalerite concentrate with high indium content.[25] The kinetics of indium extraction from indium-bearing zinc ferrite were studied by Zhang et al.,[26] and they found that an increase in temperature and sulfuric acid concentration significantly enhanced the leaching rate of indium. However, few studies have focused on the leaching of indium from blast furnace sludge. According to previous work, extraction of indium was relatively low by traditional acid leaching, and ultrasonic-assisted acid leaching had been demonstrated[27–30] to be an effective way to increase extraction efficiency. Bese[31] has reported that ultrasonic energy increased extraction efficiency of Cu, Zn, Co, and Fe in copper converter slag. Ultrasonic-assisted leaching and conventional leaching of Cu, Pb, Ni, Zn, and Mn from sediments were also compared by Elik,[32] and the results showed that ultrasonic-assisted leaching method reduced the time required f
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