Greener Chelators for Recovery of Metals and Other Applications

Abstract

Furthermore, industries generate a variety of wastes which contain heavy metals [7]. Electroplating and mining companies generate large amounts of mercury, lead, cadmium, silver, copper, and zinc ions [8,9]. More so, papers, metals, electrical and electronic equipment wastes contain precious metals like Ag, Au [10]. And some of these metals are regarded as technology metals [11,12]. Unfortunately, the reserves of highgrade ores of these metals are depleting [7]. Therefore, there is a need to recycle and recover these metals from the environment. Moreover, some heavy metals can be hazardous even at low concentrations [9,13]. According to Nagajyoti et al. [14] heavy metals such as Cd, Cu, Pb, Cr and Hg are major environmental pollutants, particularly in areas with high anthropogenic activities. Thus, when these metals are in bioavailable forms and at excessive levels, they have the potential to become toxic to plants and consequently the environment [14]. In addition, there are usually trace amounts of iron, copper, manganese, calcium, and other metals found naturally in many raw materials [15,16]. These metal ions are normally found in processing water as well, and may infiltrate processing [15]. Moreso, presence of metal ions in a process or product can bring about scaling, chemical degradation, discoloration, precipitation, emulsion instability, rancidity, and reduce; quality, consumer appeal, shelf-life and ultimate value [15,17,18].Fortunately, chelating agents have been used to eradicate these problems by binding metal ions via N, O, S atoms as the case may be [19]. When metal ions are bonded to chelant, the metal becomes blocked from undesired interaction [20].

Metabolomics and lipid profile analysis of Coccomyxa melkonianii SCCA 048

“…Levels of threonic acid as housekeeping metabolite in C. melkonianii might correlate with its adaptation to harsh habitats (Malavasi et al 2016). Moreover, malic acid and citric acid that are time-correlated with the growth of C. melkonianii are also known to be able to chelate metals (Perpetuo et al, 2011;Asemave 2018) Furthermore, myo-inositol is required for the cell growth and development, being involved in the phosphatidylinositol signaling pathway that takes part in auxin transport, cell wall biosynthesis, phytic acid biosynthesis, and the production of stress-related compounds (Cho et al 2015). Consistently, malic acid, succinic acid, citric acid, and fumaric acid, all involved in TCA cycle, increased during algal growth.…”

A General Fruit Acid Chelation Route for Eco-friendly and Ambient 3D Printing of Metals

“…As binding agents, nature-based chelators, which are crucial to ensure eco-friendliness of metal 3D printing, were used. Unlike polymer binding agents, which are hazardous, the chelators utilized here are food-grade organic materials because they are salts of nature-based fruit acids (e.g., of fruits such as lemons, cherries, and grapes) 37 . For example, citric acid derived from citrus fruits has three carboxyl groups, and it transforms into sodium citrate upon replacement of the hydrogens in these groups with sodium ions through a salt-formation reaction (Figure 1d) 38 .…”

Modification of bio-based β-diketone from wheat straw wax: synthesis of polydentate lipophilic super-chelators for enhanced metal recovery

“…Based on the method previously reported by Asemave et al 22 Into a 15 mL microwave vial, 14,16-hentriacontanedione (HTD) (0.010 g, 0.02 mmol) was added; followed by a known amount of KF/alumina. The heterogeneous catalyst was well dispersed among the HTD.…”

“…3), and a more detailed discussion following our rst report of this modication is contained herein. 22 Initially, methyl acrylate (MA), methyl methacrylate (MMA), dimethyl itaconate (DMI) and trimethyl aconitate (TMA) were included as Michael acceptors, but the low yields obtained by MMA and TMA meant they were not included for the remainder of this investigation. It is thought that the steric hindrance on TMA prevented the reaction from occurring, and electron-donation from the methyl group to the alkene of MMA reduced its electrophilicity.…”