China 
Africa 
Explore chapters and articles related to this topic
Synthesis of Zinc, Copper, Cadmium, and Iron Sulfides and Their Sorption Properties
Published in D.S. Sofronov, K.N. Belikov, M. Rucki, S.N. Lavrynenko, Z. Siemiątkowski, E. Yu. Bryleva, O.M. Odnovolova, Synthetic Sorbent Materials Based on Metal Sulphides and Oxides, 2020
D.S. Sofronov, K.N. Belikov, M. Rucki, S.N. Lavrynenko, Z. Siemiątkowski, E. Yu. Bryleva, O.M. Odnovolova
SEM images of cadmium sulfide particles synthesized in presence of glycine and alanine are shown in Figures 1.20–1.23. When the synthesis was conducted at the temperature 20°С and glycine content 0.005–0.01 М, large spherical particles resembling flowers were formed with diameters ca. 5 μm, irrespective of thiourea concentration, as it is seen in Figures 1.20a–f. In general, this additive plays no significant role in the cadmium sulfide precipitation process. When the concentration was 0.05 M, morphology of the particles changed dependent on the proportion of cadmium to thiourea CCd/CТh. When CCd/CТh was 1:1, the sediment was formed as small spherical particles with diameters ca. 100 nm (Figure 1.20g). When CCd/CТh was 1:2, small plates were formed (Figure 1.20h), When CCd/CТh was 1:4, large, dense spherical particles appeared, with dimensions between 10 and 20 μm (Figure 1.20i).
The prospects for an alternative gold leach reagent: Thiourea
Published in Gülhan Özbayoğlu, Çetin Hoşten, M. Ümit Atalay, Cahit Hiçyılmaz, A. İhsan Arol, Mineral Processing on the Verge of the 21st Century, 2017
Thiourea (H2NCSNH2) is an organic compound, the crystals of which dissolve in water to yield an aqueous form stable in acidic solutions. Thiourea in an acidic medium forms a single cationic species with gold according to the following reaction (Preisler & Berger, 1947; Groenewald, 1976; Huyhua et. al. 1988). () Au°+2CS(NH2)2⇔Au(CS(NH2)2)2++e
Conventional Metal Recycling Techniques
Published in Hong Hocheng, Mital Chakankar, Umesh Jadhav, Biohydrometallurgical Recycling of Metals from Industrial Wastes, 2017
Hong Hocheng, Mital Chakankar, Umesh Jadhav
Cyanide is being used predominantly as a leaching agent for the recovery of metals (Au, Ag, etc.) from mines and secondary sources because of its high efficiency and low cost. Dilute solutions of sodium cyanide (100–500 ppm) are used in tank and heap leaching processes. Cyanide ions (CN–) play a major role in the dissolution of metals present in complexes with other materials. This dissolution is an electrochemical process and can be given by general Equations 3.1 and 3.2 (Dorin and Woods 1991, Marsden and House 1992, Cui and Zhang 2008, Syed 2016). However, a series of environmental accidents at various gold mines that resulted in severe environmental contamination has spread concern over the use of cyanide as a leaching agent (Hilson and Monhemius 2006). Halide leaching (Equations 3.3 and 3.4) employs various halides such as fluorine, chlorine, bromine, iodine, and astatine in metal dissolution (La Brooy et al. 1994). In thiourea leaching, thiourea ((NH2)2CS) dissolves metals in acidic conditions by forming a cationic complex (Equation 3.5) (Yannopoulos 1991). However, successful leaching using thiourea depends on the optimization and control of pH, redox potential, thiourea concentration, and leaching time. Alkaline thiosulfate dissolves metals slowly (Equations 3.6 and 3.7) and the rate of dissolution is affected by thiosulfate concentration, dissolved oxygen, and process temperature, and can be enhanced by adding copper ions (Yannopoulos 1991, Kuzugudenli and Kantar 1999). The process can be enhanced in the presence of ammonia using copper(II) as an oxidant (Abbruzzese et al. 1995, Aylmore 2001). In spite of the potential environmental benefits of thiosulfate, the slow process and high reagent consumption render its use uneconomical (Feng and Van Deventer 2002).
Hydrometallurgical processes for heavy metals recovery from industrial sludges
Published in Critical Reviews in Environmental Science and Technology, 2022
Viraj Gunarathne, Anushka Upamali Rajapaksha, Meththika Vithanage, Daniel S. Alessi, Rangabhashiyam Selvasembian, Mu. Naushad, Siming You, Patryk Oleszczuk, Yong Sik Ok
Thiourea leaching was developed as an alternative to the well-known cyanide leaching as the latter may be detrimental to the environment (Birich et al., 2019); however, thiourea is 25% more expensive than cyanide (Boboev et al., 2019). Thiourea (SC(NH2)2) is a sulfur-based complexing agent that has the ability to form soluble, cationic complexes with targeted metals, in contrast to other anionic complexes. The leaching rate of this complex extends up to 99%, making it readily soluble in the solvent medium. Thus, thioureation is one of the most widely used leaching techniques for recovering precious metals from industrial waste sources. The following equation, which utilizes thiourea as the leaching agent and Fe(III) ions as the oxidant, represents the complexation of Ag from Ag2S using thiourea (Bernaola-Flores et al., 2019; Bruckard et al., 1993):
A DFT study on the addition and abstraction reactions of thiourea with hydroxyl radical
Published in Journal of Sulfur Chemistry, 2018
Mwadham. M. Kabanda, Kemoabetswe R. N. Serobatse
Thiourea (SC(NH2)2) is an organo-sulfur compound in which a carbon atom is double bonded to a sulfur atom and two amino groups [1]. It has a wide range of uses, including production of pharmaceuticals (e.g. sulfothiazoles [2]), pesticides [3], as an additive to some plastic materials [2] and utilization in textile processing [4]. It also possesses a variety of biological activities which include anti-HIV, antiviral, antibacterial and analgesic [5–9]. Thiourea derivatives such as dimethylthiourea, phenylthiourea, benzoyl thiourea and 1-phenyl-3-benzoyl-2-thiourea have been reported to possess biological activities such as analgesic [10], antitumor [11,12], anti-HIV [9], antimicrobial [13,14] and antioxidant [15–17]. Thiourea (TU) also possesses electrochemical properties [18,19] and photochemical properties.
Growth and genetic analysis of Pseudomonas BT1 in a high-thiourea environment reveals the mechanisms by which it restores the ability to remove ammonia nitrogen from wastewater
Published in Environmental Technology, 2022
Jingxuan Deng, Zhenxing Huang, Wenquan Ruan
The nitrification-denitrification process is usually used for biological nitrogen removal from wastewater, which transfers nitronate ammonium to nitrite using ammonium-oxidizing bacteria (AOB) and is then reduced to N2 by anammox bacteria [1]. However, thiourea, which is widely used in various industries and is common in wastewater [2–4], can inhibit the nitrification system in sewage treatment plants by covalently bonding with the copper of AOB [5]. Even at a low concentration, thiourea can still significantly impact the activated sludge in sewage treatment systems [6]. In addition, thiourea can also cause some health problems for humans, such as occupational allergic contact dermatitis [6], blood diseases, and even death [7].