The metal indium termed as 'rare' in recent days due to its increasing demand in the formulations of electronic and energy-related gadgets and scarce supply resources. Hence, the attempts to recover indium from the secondary resources, such as recycling of the indium abundant waste materials, received increasing research focus. The major indium consumption happens in the form of indium tin oxide (ITO) that used for the fabrication of liquid-crystal displays (LCD). The end-of-life LCD screens, termed as ITO-glass hereafter, are an emerging contributor to the global e-waste load and can be an impending secondary source of indium.The present work introduces a new technique for the treatment of waste ITO-glass using aminopolycarboxylate chelants (APCs) in combination with a mechanochemical treatment process. APCs are capable of forming stable complexes with the indium deposited on the ITO-glass, whereas the rate of recovery was not substantial. The mechanochemical treatment induces the destruction of crystalline structure with which the ITO fragments are attached and facilitate the increased indium dissolution with the chelants. The increase was more prominent followed by a decrease in the cumulative processing time from 24 to 6 h when the vitrified ITO-glass was simultaneously crushed and washed with the chelants. The extraction of indium was better at the acidic pH condition, and it was further intensified when the operating temperature was raised to ≥ 120 °C. Keywords:Indium; Indium tin oxide; Liquid crystal display; Waste; Recovery; Mechanochemical treatment Microchemical Journal (In Press). DOI: http://dx.doi.org/10.1016/j.microc.2012.08.010 3 IntroductionIndium has emerged as an important strategic element in electronic and energy-related industries due to its specific applications [1,2]. The most important end use of indium in recent years is to manufacture indium-tin oxide (ITO) thin film, an optoelectronic material with the characteristics of transparency to visible light, electric conduction and thermal reflection [2,3]. ITO thin film is widely used in designing liquid-crystal displays (LCD), plasma displays and solar-energy cell [3], and consume about two-third of the global indium production [4].Indium has no ore of its own and is generally found in low concentrations in some sulphide ores of zinc, copper and lead, from which it is procured as a by-product [5]. The technology revolution created an increasing demand for indium while the boom in its price is due to the policies of the nations with indium reserves (e.g. China, South Korea). Hence, the recovery of indium from the waste resources received sincere focus from the researches [4-6].The ITO-scrap resulted from the ITO ceramic target during the conversion and application of ITO thin films on glass panels using the DC magnetron sputtering process is the most potential secondary resource of indium [2,3,6,7]. The other prospective waste resources of indium are the etching waste [1,8] and the LCD powder [6,9].The end-of-life (EoL) LCDs are a gr...

The protonation and complex formation equilibria of two biodegradable aminopolycarboxylate chelants (DL-2-(2-carboxymethyl)nitrilotriacetic acid (GLDA) and 3-hydroxy-2,2´-iminodisuccinic acid (HIDS)) with Ni 2+ , Cu 2+ , Zn 2+ , Cd 2+ and Pb 2+ ions was investigated using the potentiometric method at a constant ionic strength of I = 0.10 mol·dm -3 (KCl) in aqueous solutions at 25 ± 0.1°C. The stability constants of the proton-chelant and metal-chelant species for each metal ion were determined, and the concentration distributions of various complex species in solution were evaluated for each ion. The stability constants (log 10 K ML ) of the complexes containing Ni 2+ , Cu 2+, Zn 2+ , Cd 2+ and Pb 2+ ions followed an identical order of log 10 K CuL > log 10 K NiL > log 10 K PbL > log 10 K ZnL > log 10 K CdL when using GLDA (13.03 >12.74 >11.60 >11.52 >10.31) as when using HIDS (12.63 >11.30 >10.21 > 9.76 >7.58). In each case, the constants obtained for metal-GLDA complexes were higher in magnitude than the corresponding constants for metal-HIDS complexes. The conditional stability constants (log 10 K´M L ) of the metal-chelant complexes containing GLDA and HIDS were calculated in terms of pH, and compared with the stability constants for EDTA and other biodegradable chelants.Keywords: stability constant; biodegradable aminopolycarboxylate chelant; GLDA; HIDS; ecotoxic ions. 2Journal of Solution Chemistry, 41(10): 1713Chemistry, 41(10): -1728Chemistry, 41(10): , 2012Chemistry, 41(10): (http://dx.doi.org/10.1007 IntroductionAminopolycarboxylate chelants (APCs) have been and continue to be extensively used in a variety of industrial processes [1,2], including the treatment of toxic metal-contaminated solid waste materials [3][4][5]. APCs are commonly employed to restrict metal ions from playing their normal chemical roles through the formation of stable and water-soluble metal complexes [6,7]. Because ethylenediaminetetraacetic acid (EDTA) forms stable water- Chemistry, 41(10): 1713Chemistry, 41(10): -1728Chemistry, 41(10): , 2012Chemistry, 41(10): (http://dx.doi.org/10.1007 available [25]. The development of the new eco-friendly chelants and the study of their complexation behavior are critical for evaluating the usefulness of these chelants in specific treatment operations [26][27][28][29]. DL-2-(2-carboxymethyl)nitrilotriacetic acid (GLDA) and 3-hydroxy-2,2´-iminodisuccinic acid (HIDS) (Fig. 1) Therefore, we report on the complexation behavior of GLDA and HIDS and divalent ecotoxic ions (Ni, Cu, Zn, Cd, and Pb) in aqueous solutions, which will be useful for the design of eco-friendly waste management processes. Experimental Section InstrumentationKEM AT-610 automatic titrator (Kyoto Electronics, Kyoto, Japan), equipped with a pHcombination electrode and a temperature probe, was used for potentiometric measurements.The electrode system was calibrated with standard buffer solutions (pH 4.0, 7.0 and 9.0 prepared from buffer powders (Horiba, Kyoto, Japan) at 25 ± 0.1°C before and after each serie...

Aminopolycarboxylate chelants (APCs) are extremely useful for a variety of industrial applications, including the treatment of toxic metal-contaminated solid waste materials.Because non-toxic matrix elements compete with toxic metals for the binding sites of APCs, an excess of chelant is commonly added to ensure the adequate sequestration of toxic metal contaminants during waste treatment operations. The major environmental impacts of APCs are related to their ability to solubilize toxic heavy metals. If APCs are not sufficiently eliminated from the effluent, the aqueous transport of metals can occur through the introduction of APCs into the natural environment, increasing the magnitude of associated

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The incineration fly ash (IFA), molten fly ash (MFA), thermal power plant fly ash (TPP-FA), and nonferrous metal processing plant ash (MMA) have been screened in terms of the following rare-termed metal contents: B, Ce, Co, Dy, Eu, Ga, Gd, Hf, In, Li, Lu, Mn, Nb, Nd, Ni, Pr, Rb, Sb, Se, Sm, Sr, Ta, Tb, Te, Ti, Tm, V, W, Y, and Yb. The pseudo-potential for recycling of the waste ashes, as compared to the cumulative concentration in the crust (mg kg -1 ), was determined as follows: MMA > IFA > MFA > TPP-FA. The comparison with the crude ore contents indicates that the MMA is the best resource for reprocessing. The recovery of the target metals using aminopolycarboxylate chelants (APCs) has been attempted at varying experimental conditions and ultrasound-induced environment. A better APC-induced extraction yield can be achieved at 0.10 mol L -1 concentration of chelant, or if the system temperature was maintained between 60 to 80 °C. Nevertheless, the mechanochemical reaction induced by the ultrasound irradiation has been, so far, the better option for rare metal dissolution with chelants as it can be conducted at a minimum chelant concentration (0.01 mol L -1 ) and at room temperature (25±0.5 °C).Keywords: Rare metals; Recovery; Fly ash; Solid waste; Aminopolycarboxylate chelant; Ultrasound irradiation 2Water, Air, & Soil Pollution, 225(9): 2112 The original publication is available at: http://dx.doi.org/10.1007/s11270-014-2112-9 IntroductionThe consumption rates of the metals are continually increasing due to the diversification in applications. On the contrary, the supply of metals becomes more and more limited because the resources are nonrenewable (Guinée et al. 1999). The natural deposits of some metals, which have been increasingly consumed as a key material in clean energy applications or in designing alluring daily life gadgets, are unevenly distributed in the world and have an unsteady supply chain or fluctuating market price according to the policy of the resource country (Dodson et al. 2012, Massari & Ruberti 2013. The terminology, rare metal, is thus introduced to interpret such metals, which is not an academically defined one, and there is no consensus on which element it pertains (AIST Rare Metal Task Force 2008, Kooroshy et al. 2010). For example, in Japan, 31 ores, including the rare earth elements as a group, have been designated as rare metals in terms of the concern in securing a stable supply of resources (Kawamoto 2008). Consequently, other than the refinery production, the reclaim processing of rare metals from secondary resources, such as process discards from the rare metal-consuming manufacturing schemes (Hsieh et al. 2009, Liu et al. 2009, Kang et al. 2011, Li et al. 2011, Park 2011, Virolainen et al. 2011, Hasegawa et al. 2013b or end-oflife electronic products (Shimizu et al. 2005, Cui & Zhang 2008, Rabah 2008, Bertuol et al. 2009, Binnemans et al. 2013, Hasegawa et al. 2013c, Hasegawa et al. 2013a, received sincere focus from the researchers.Municipal solid waste (MSW) manageme...