Ex situ soil washing with synthetic extractants such as, aminopolycarboxylate chelants (APCs) is a viable treatment alternative for metal-contaminated site remediation. EDTA and its homologs are widely used among the APCs in the ex situ soil washing processes. These APCs are merely biodegradable and highly persistent in the aquatic environments leading to the post-use toxic effects.Therefore, an increasing interest is focused on the development and use of the eco-friendly APCs having better biodegradability and less environmental toxicity. The paper deals with the results from the lab-scale washing treatments of a real sample of metal-contaminated soil for the removal of the ecotoxic metal ions (Cd, Cu, Ni, Pb, Zn) using five biodegradable APCs, namely [S,S]-ethylenediaminedisuccinic acid, imminodisuccinic acid, methylglycinediacetic acid, DL-2-(2-carboxymethyl)nitrilotriacetic acid (GLDA) and 3-hydroxy-2,2'-iminodisuccinic acid. The performance of those biodegradable APCs was evaluated for their interaction with the soil mineral constituents in terms of the solution pH and metal-chelant stability constants, and compared with that of EDTA. Speciation calculations were performed to identify the optimal conditions for the washing process in terms of the metal-chelant interactions as well as to understand the selectivity in the separation ability of the biodegradable chelants towards the metal ions. A linear relationship between the metal extraction capacity of the individual chelants towards each of the metal ions from the soil matrix and metal-chelant conditional stability constants for a solution pH greater than 6 was observed. Additional considerations were derived from the behavior of the major potentially interfering cations (Al, Ca, Fe, Mg, and Mn), and it was hypothesized that use of an excess of chelant may minimize the possible competition effects during the single-step washing treatments.Sequential extraction procedure was used to determine the metal distribution in the soil before and after the extractive decontamination using biodegradable APCs, and the capability of the APCs in removing the metal ions even from the theoretically immobilized fraction of the contaminated soil was observed. GLDA appeared to possess the greatest potential to decontaminate the soil through ex situ washing treatment compared to the other biodegradable chelants used in the study. KeywordsSoil remediation; Toxic metals; Ex situ washing; Aminopolycarboxylate chelants; Biodegradable; Sequential extraction 3 IntroductionSoil contamination with heavy metals derived from various anthropogenic activities, including agricultural practices, industrial activities and waste disposal is a worldwide concern. Soil washing is one of the few enduring treatment alternatives, which uses either or both physical and chemical processes, to confine the contaminants in soils (Peters, 1999;Dermont et al., 2008). Soil decontamination by washing treatment can be accomplished through either in situ or ex situ operations. Aminopolycarboxylate c...

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...

Moringa oleifera Lam. seed oil of the indigenous-cultivar of Bangladesh was extracted using n-hexane (H), light petroleum ether (LPE) (bp 40-60C) and chloroform/methanol (50:50, v/v) mixture (CM). The oil content ranged from 37.50 (H) to 40.20% (CM). The moisture, protein, ash and crude fiber contents of seed residues, and the density, refractive index, color, acidity, saponification value, iodine value, unsaponifiable matter content, oxidative state, sterols, tocopherols and fatty acid composition of the extracted oil were determined. The oil contained a high amount of oleic acid (C 18:1 ) of up to 74.41% and a high ratio of monounsaturated to saturated fatty acids with moderate oxidative stability. The results of the present study were compared with those reported in literature for different regional habitats and species variants. PRACTICAL APPLICATIONSA high-oleic oil with a good potential for edible and industrial use can be produced from Moringa oleifera Lam. (M. oleifera) oilseeds of the indigenous cultivar of Bangladesh. Thus, mature seeds of M. oleifera can be considered as an alternative source of vegetable oil in Bangladesh provided that it is cultivated on a large scale.3 Corresponding

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