Bromine leaching

The ICP scan data is presented to indicate certain metals reactivity towards acidic bromine/bromide. The acidic bromine leach was carried out to determine the dissolution of impurity elements and to provide a competitive environment for gold loading onto the adsorbents. 

Choi K-I, Lee S-H, Osako M (2009) Leaching of brominated flame retardants from TV housing plastics in the presence of dissolved humic matter. Chemosphere 74(3) 460-466. doi 10.1016/j. chemosphere.2008.08.030... 

Simple anions in soil are the halogens, chlorine (Cl ), and bromine (Br ). If present, the other halogens—fluoride, F, and iodide, I-—will also occur as simple anions. Because the compounds of these anions are generally soluble, they readily leach out of the soil and so are present at low concentrations. Exceptions occur in low-rainfall regions where significant, sometimes deleterious (to plants and animals), levels of simple anions can be found. 

Incubation in soils showed that polybrominated biphenyls were resistant to degradation, but were apparently not taken up by plants or leached into groundwater [261]. Commercial formulations of brominated aromatic flame retardants had variable composition some contained highly brominated phenols, but no evidence of contamination with dibenzodioxins and dibenzofurans was found [198]. 

However, especially brominated flame retardants are creating problems when electronic and electrical equipment reach end of life. If landfilled, toxic brominated flame retardants may slowly leach ont into the groundwater, where they persist for several years or they can evolve into the air. If waste materials are burned toxic polybrominated dioxins and furans can be formed [53, 50]. 

There have been numerous attempts to use trace-element concentrations in coal as indicators of depositional environments. Most commonly, these studies have sought evidence of a marine influence on the coal (Goodarzi, 1987, 1988 Swaine, 1983 Chou, 1984 Hart and Leahy, 1983). The elements cited as indicators of marine influence include molybdenum, magnesium, boron, chlorine, bromine, sodium, yttrium, and uranium. However, problems such as mixing in brackish environments, the reworking of sediments, and postdepositional enrichment or leaching, make the data equivocal, and there is no consensus regarding reliable indicators. 

The final use of chemical products can result in the release of hazardous substances affecting man and the environment. Chemicals can be released from products used in the indoor environment, released to the atmosphere when a product is used outside, and released to groundwater if the chemicals leach out of a product in a landfill. Data are extremely limited on how many chemical products there are on the market today, on their chemical content, and on whether - and how - they may be releasing hazardous substances to the environment. Recent studies have shown that, in some cases, the majority of emissions released during the entire lifecycle occur during the service life of the product, rather than during production. A study conducted by TNO estimated that over 75 percent of total emissions to the environment from phthalates in plastics, brominated flame retardants in plastics, and zinc from tires occurred during the service life (TNO, 2001). 

The PBDEs are of particular concern. They are incorporated into polymer matrices, but are not covalently bonded and readily leach out of substrates holding them. These compounds are similar in structure to PCBs, are persistent organic polluters (POPs), and are resistant to environmental degradation and metabolism. They can be absorbed via inhalation, ingestion, and dermal contact. The less-brominated PBDE species (tetra-, penta-, and hexa- moieties) have been found in human blood, adipose tissue, and breast milk. These bioaccumulate in human adipose tissues. 16 ... 

The sample containing Re is sintered at 600-700°C for 2-3 h with CaO and Ca(N03)2, then the sinter is leached with hot dilute bromine water. Most metals (including molybdenum, which is then present as CaMo04) remain in the solid residue while ReOT ions pass into solution [16]. 

The gold leaching experiments in Stabilized Bromine were conducted by leaching a gold bearing ore in a suitable size reactor equipped with an overhead stirrer. The gold analyses were performed using the Fire Assay method. 

Gold adsorption isotherm and regeneration of bromine from leach liquor... 

Leaching of gold bearing material achieved 89-93% gold extraction using an acidic (pH 2 with sulphuric acid) lixiviant with the composition of 47-48 g/L bromine and 10 g/L bromide. The leach test results are presented in Table 11. The ICP scan data for major elements are shown in Table 12. 

Table 13 Bromine regeneration from leach barren solution...

A further objective was to prove the feasibility of regenerating the bromine in a continuous manner. To accomplish this task RIL and CIL experiments were conducted, providing some additional data on gold recovery under the harsh conditions of leaching. 

The CIL and RIL experiments were carried out on a similar feed material but using more diluted bromine lixiviant compared to previous leaching tests. The gold recoveries were 82% and 81.1% for CIL and RIL experiments, respectively. The leaching data are presented in Table 15. 

The results indicate that production of bromine at targeted 15 g/L from leach barren solution is feasible under the continuous experimental conditions adopted. 

Dry, M., O Day, J., Manimaran, M, Melashvili, M., Fleming, C., 2015. Evaluation of stabilized bromine technology for gold leaching. Alta 2015 proceedings. 

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