Study on the Leaching of Mercuric Oxide with Thiosulfate Solutions

Abstract

Abstract:Mercury is receiving more concern due to its high mobility and high toxicity to human health and the environment. Restrictive legislations and world-wide efforts have been made on mercury control, especially the release and disposal of mercury-contaminated wastes. This paper describes a novel technology for detoxifying mercury-containing solid wastes with thiosulfate salts. Various parameters which may potentially influence mercury extraction from mercuric oxide with the thiosulfate leaching system-including reagent concentration, solution pH, and temperature-have been examined. The experimental results show that virtually all mercuric oxide can rapidly dissolve into the thiosulfate leaching system under optimized experimental conditions, indicating that thiosulfate is an effective lixivant for recovering mercury from mercury-containing solid waste.

Comparative Study of Mercury(II) Removal from Aqueous Solutions onto Natural and Iron-Modified Clinoptilolite Rich Zeolite

“…The pH of the suspension is one of the most important parameters that affect the sorbent surface charge as well as type of metal species. Figure 1 illustrates the distribution of mercury species in relation with pH based on the hydrolysis constants represented by Equations (21)- (23) From Figure 1 it is clear that below pH = 2.9 the dominant species is Hg 2+ , the HgOH + species exists in the range 1.5 < pH < 4.5, while Hg(OH) 3 appears at pH > 13.2. Precipitation of Hg(II) begins at pH = 2.4, and the proportion of Hg(OH) 2 increases with a further increase in pH, and pH range 4.7 < pH < 13.2 Hg(II) exists completely in the form of Hg(OH) 2 .…”

“…The main sources of mercury emissions into the environment comes from natural (volcanic emissions, mineral deposits), anthropogenic (coal combustion, mining processing), and reemitted resources (already mercury contaminated sites) where the most significant are the anthropogenic ones. From all mentioned sources, mercury is emitted into the atmosphere, soils, or water systems where it remains permanently due to its non-biodegradable properties [1][2][3]. It could appear in inorganic forms such as Hg o , Hg(I), Hg(II), as well as in organic forms such as non-volatile mono methyl-mercury (CH 3 Hg + ) and volatile dimethyl-mercury [(CH 3 ) 2 Hg].…”

“…Thus, in soils and aquatic sediments, mercury species can be trapped by clays and more often by organic matter such as fluvic and humic acids in acidic soils [2,5]. On the other hand, trapped mercury can be released into the environment and undergo complex physical, chemical, and biological transformations and distributed into the deeper layers of the soil, towards even groundwater [1][2][3]. Therefore, the World Health Organization has given a recommendation on the maximum permissible concentration of mercury in drinking water of the amount up to 1 µg/L [6].…”

Recovery and separation of silver and mercury from hazardous zinc refinery residues produced by zinc oxygen pressure leaching

“…Additionally, this has the added advantage of minimizing the solubility of impurities, whilst allowing both the selective recovery of Ag and reduced consumption of thiosulfate (Petter et al, 2014). Thiosulfate is also effective agent for Hg recovery from mercurycontaining oxides (Han et al, 2016) however, as thiosulfate does not dissolve mercury sulfides as readily as silver, the mercury tends to become more dispersed (Oraby et al, 2010). Another drawback is that thiosulfate can only work effectively under alkaline and neutral conditions, which means that for highly acidic leaching residues a large amount of alkali is required for neutralization.…”

Simultaneous Removal of Hg(II) and Phenol Using Functionalized Activated Carbon Derived from Areca Nut Waste

“…Heavy metals and phenolic compounds, which are the most common water pollutants, are found to be highly toxic towards living organisms and are difficult to eliminate from water bodies or even from the biosystem once entered [3][4][5]. Mercury has received greater environmental concern due to its high toxicity, persistence in the environment, and high bioaccumulation [6,7]. Dissolved Hg(II) in an aquatic environment is readily transformed into methylmercury, which is a highly toxic, persistent, and bioaccumulative form of mercury present in assessed for its capability to remove Hg(II) and phenol simultaneously from aqueous solutions under batch and fixed-bed adsorption systems.…”