Selection of Feasible Leaching Method for Recovery of Heavy Metals from E-waste using Analytic Hierarchy Approach

Amount of e-waste is increasing tremendously over the years, from almost getting doubled each year. 40 % e-waste consists of many metals and precious metals. The rapid growth in technology development is alarming, as a result more and more e-waste is generating. This leads to myriad problems for handling or management of e-waste. Traditional methods of disposal of e-waste such as landfilling, composting and incineration is major threat to the environment and life. In this study recovery of metals through hydro-metallurgical process such as thiosulfate (M1), iodide (M2) aqua-regia (M3) and thiourea (M4) leaching methods were compared in terms of economic feasibility, environmental impact and reagent reuse in order to find out a feasible leaching method using Analytic Hierarchy Process (AHP). The selection of feasible leaching method has been performed by applying the Saaty, ranking. From the final ranking are, thiosulfate (M1) scored = 0.09, iodide (M2) = 0.16, aqua-regia (M3) = 0.39 and thiourea (M4) = 0.39. From the result M3 and M4 are the feasible method for recovery of heavy metals from E-waste.

Improvement of the Occupational Safety by Radical Isolation of Pollution Sources during Underground Ore Mining

One of the ways to protect the health of the employees in the mining enterprises is the improvement of the mine atmosphere by strengthening safety measures in the underground mining of minerals, especially those that pose a particular hazard. The aim of the study is to develop a technology for the radical protection of the employees from specific pollution. To achieve this goal, a set of tasks is being solved, one of which is the use of technogenic waste as materials for the preparation of hardening filling mixtures. It is experimentally established that the process of increasing the strength of the tailings of various concentration plants is adequate, the structures of which can be used to control the geomechanics of the ore-bearing massif. Classification of the strengthening mixtures that allow to increase strength can occur when unloading from the crushing and grinding mills. Use of tailings for the manufacture of insulating massifs is possible after extracting the remaining metals from them, for example, using one of the leaching methods. Air pollution with specific substances during underground mining of ore deposits can be radically reduced by isolating workings with artificial insulating massifs. Possibility of using tailings for the manufacture of insulating artificial massifs is substantiated experimentally by comparing the capabilities of mills of various types. The issues of atmospheric air pollution during underground mining, mainly of ore deposits, are considered. Quantitative values of hazard for development systems are given. The results of experiments confirming the possibility of using tailings for the manufacture of concrete insulating artificial massifs are presented. Quantitative values are obtained related to the capabilities of mills for obtaining a product of the same size with different granulometric composition of the starting material when used in industry.

Two-Stage Continuous Process for the Extraction of Silica from Rice Husk Using Attrition Ball Milling and Alkaline Leaching Methods

A two-stage continuous process was developed for improved silica extraction from rice husk. The two-stage continuous process consists of attrition ball milling and alkaline leaching methods. To find the optimum conditions for the continuous process, the effects of alkaline leaching parameters, such as the alkaline solution type and reaction conditions, on the silica extraction yield were investigated in a batch process. The use of NaOH showed a slightly higher silica yield than KOH. The optimum reaction conditions were found to be 0.2 M, 80 °C, 3 h, and 6% (w/v) for the reaction concentration, temperature, duration time, and solid content, respectively. Attrition ball milling was used to make micron-sized rice husk particles and to improve the fluidity of the rice husk slurry. The two-stage continuous process was performed using optimum conditions as determined based on the results of the batch experiment. The two-stage continuous extraction was stably operated for 80 h with an 89% silica yield. During the operation, the solid content remained consistent at 6% (w/v). The obtained silica was characterized using inductively coupled plasma–optical emission spectrometry (ICP–OES), X-ray diffraction (XRD), and the Brunauer–Emmett–Teller (BET) method.

Determining and improving the analytical blank for radiocarbon analyses of small foraminifera samples using MICADAS and the gas interface system

<p>Foraminifera isolated from deep-sea sediments are among the most common materials in AMS radiocarbon analysis. These results are used to determine accurate age models for sediment sequences as well as to detect changes in deep-sea ventilation. Often, only small numbers of (monospecific) foraminifera shells can be isolated, in particular when studying benthic species in sediments from the polar regions. Therefore, these samples are often analyzed as CO<sub>2</sub> gas using MICADAS instruments, and the method can typically be used for samples of up to around 40 ka in age. For reliable results, an accurate determination and minimization of processing blanks is required.</p><p>Processing blanks for foraminifera samples may in part derive from acid hydrolysis of the carbonates. It has, however, been shown that contamination of the carbonate fossils, mainly from atmospheric CO<sub>2</sub> adsorbed on the porous surfaces of foraminifera, is the largest source of blank found in foraminifera samples. The removal of such contamination has been attempted by various leaching methods, which come at the risk of introducing additional contaminations. Alternatively, blank correction of AMS results may be achieved using fossil foraminifera from ancient deposits much beyond the range of the radiocarbon method.</p><p>Here we report results of a systematic test comparing the F<sup>14</sup>C levels obtained for fossil (>130 ka) and sub-modern monospecific planktic and benthic foraminifera samples using different blank correction approaches. Specifically, we compare leaching with dilute hydrochloric acid, blank correction relative to a leached and an un-leached fossil foraminifera standard, and blank correction relative to the IAEA-C1 certified carbonate standard. </p>

A comparison of waste leaching determination methods in the context of dewatered oil sands fine tailings

Leaching tests are an important component in assessing the potential of contaminants to leach from waste materials to the environment. Numerous leaching test protocols have been developed for different applications. In this study, we compare four different methods in the context of assessing leaching of inorganic ions from oil sands tailings. The four methods compared were: United States Environmental Protection Agency (EPA) Toxicity Characteristic Leaching Procedure; ASTM D6234; ASTM D3987; and what we refer to as the Deionized method (modified from Syncrude Analytical Aqueous Extraction of Oil Sand Method 1.7). It was found that the EPA Toxicity Characteristic Leaching Procedure generally resulted in the highest ion concentrations. The EPA method had statistically different results for three of the four tailings mixes when compared with the other three leaching methods. For Mo and Ti the EPA method always resulted in the lowest concentrations compared with the other methods, and As, Tl, and Pb sometimes resulted in the lowest concentrations. The other three leaching protocols resulted in similar dissolved ion concentrations.