Non-ferrous smelting dust, especially lead-smelting dust (LSD), contains percent levels of indium and thus constitutes a novel indium resource. The main difficulty in recovering indium from LSD is the coexisting presence of lead and zinc. In this study, a unique indium separation process was designed, combining techniques that involve washing with a chelant, leaching with acid and precipitation as hydroxide. The majority of the Pb in the LSD was selectively separated during chelant-assisted washing with ethylenediaminedisuccinate (EDDS), while the residual Pb was diminished through an acid leaching treatment with a mixed solution of sulfuric acid and hydrochloric acid. The chelant washing step also ensures a decrease in the raw LSD weight at a ratio of approximately 82 % due to the removal of lead and counterions such as sulfate, and the washing step also minimizes the consumption of corrosive acids in the subsequent step. Selective indium separation from LSD is further complicated by the similarity of the behavior of zinc during the acid leaching step. Therefore, hydroxide precipitation at pH 5 has been introduced as the final step, ensuring the maintenance of zinc as a soluble species in the supernatant and the selective separation of indium (∼ 88 %) as a hydroxide precipitate. KeywordsIndium recovery; Selective separation; Lead-smelting dust; Chelant-assisted washing; Acid leaching, Hydroxide precipitation Chemical Engineering Journal, 277: 219-228, 2015 The original publication is available at: http://dx.doi. org/10.1016/j.cej.2015.04.112 3 IntroductionThe metal indium, particularly as ITO (indium-tin-oxide) thin film, is an industrially important component because ITO is necessary for building electronic devices [1]. ITO is widely utilized for manufacturing liquid crystal displays, plasma displays and solar energy cells [2], which consume approximately two-thirds of the global indium production [1]. One of the resource materials for raw indium is non-ferrous metal ore [3], which is obtained as a by-product of the smelting process of the non-ferrous metal ore [4]. Raw indium deposits are region-specific (i.e., China, Korea, and Russia) [5]. Discrepancies in demand, supply and price are therefore observed. The search for alternate sources of raw indium is vital from the point of view of resource strategy, and this search is focused mostly on the processing of indium-laden waste materials, e.g., ITO scrap [2, 6-8], end-of-life liquid crystal displays [6,[9][10][11] and etching waste [12][13][14].The residue and flue dust from the smelting of non-ferrous metals, such as lead, termed lead smelting dust or LSD hereafter, also includes indium [15] and is expected to be a novel indium resource. Acid leaching is commonly employed for metal smelting from waste resources [16][17][18].Indium recovery from waste material has been reported through the use of acid leaching and hydroxide or sulfide precipitation [2,6,7,[19][20][21]. This approach is frequently criticized both in terms of overall efficiency d...

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The accumulation behaviors and solid phase partitioning patterns of stable cesium, which have been recognized as an indicator of the long-term movement of radioactive cesium ( 137 Cs or 134 Cs) in ecosystems, were studied in typical and natural soils of Japanese origin, namely, red clay, leaf-mold and andosol soils. The retention and migration of soil-phase cesium have been explained relative to various factors, such as soil organic matter contents, competitive cation concentrations and the adsorption ratio of Cs to the solid phase. Cesium was adsorbed nearly quantitatively in the leaf-mold type soil, and the rate of Cs absorption increased as the particle size decreased in the red clay and andosol soils. The distributions of Cs within the soil solid phases were defined using the selective sequential extraction scheme and were used to explain its relative incorporation in the soil fractions. Solid phase fractionation indicated that nearly half of the total cesium concentrations in the soils were in the 'residual' fraction (representing the metal that was incorporated within the crystalline lattice of the soil and was difficult to extract). These findings are expected to provide information regarding suitable conditions for remediation, immobilization or the recovery of cesium from contaminated soils with excess cesium concentrations. KeywordsCesium; Accidental exposure; Soil contamination; Solid-phase distribution; Sequential fractionation; Temporal variation 2 Microchemical Journal, 118: 158-165, 2015 The original publication is available at: http://dx.doi.org/10.1016/j.microc.2014.09.006 IntroductionWaste disposal operations or accidental releases due to nuclear-technology-related activities have resulted in the release of large amounts of radionuclides into the environment. Among the radioactive materials, the dispersion of radiocesium at elevated concentrations evokes concern due to its extended solubility characteristics as an alkaline metal ion, its comparatively longer half-life, and its easy incorporation into living beings [8][9][10] The objective of this study is to investigate the cesium distribution in the operationally defined physico-chemical and particle size fractions of soils to understand the temporal variations of cesium after being released at an uncharacteristic rate. Experimental InstrumentsThe atomic absorption spectroscopy (AAS) technique was used to determine the stable cesium concentration in solution. An AAnalyst 600 (PerkinElmer, Waltham, MA) was used that was equipped with a transverse heated graphite atomizer with an integrated, pyrolytic graphite coated platform and a longitudinal Zeeman-effect background corrector. The light source was an electrodeless discharge lamp (EDL) that was powered by an EDL System II that was operated at 18 mA. The wavelength was set at the 852.1 nm resonance line and the monochromator spectral bandpass was set at 0.7 nm. In addition, a baseline offset correction time at 2.0 s was used with a read delay of 0.0 s. Argon was used as the purg...