Maden Mühendisliği Bölümü Koleksiyonu

Susceptibility to cyanidation of pyrrhotite-associated gold in pyrite calcines from (non)oxidizing roasting environments

Sun, 01 Jan 2023 00:00:00 GMT

Susceptibility to cyanidation of pyrrhotite-associated gold in pyrite calcines from (non)oxidizing roasting environments Baş, Ahmet Deniz; Lukumu, David Bampolé; Larachi, Faïçal The susceptibility to leaching of pyrrhotite-associated gold in roasted pyrite calcines was studied, with emphasis on the effects of the roasting environment and galvanic contacts under cyanidation conditions. The first part scrutinized the thermal treatment of pyrite under different oxidizing and non-oxidizing atmospheres, and demonstrated that air roasting promoted the coexistence of multiple pyrrhotites, while He, CO2, and steam environments resulted in single hexagonal pyrrhotites with increasing iron deficiency and decreasing porosity. The second part employed a bilayer leach cell to control the electrochemical contacts between gold powder and raw/roasted pyrite during cyanidation, and found that the topology of pyrrhotite and iron oxides was influenced by the type of roasting treatment, which could impact the kinetics of gold dissolution, particularly in cases involving refractory gold or ore preg-robbing recalcitrance. Therefore, when it comes to extracting encapsulated gold associated with refractory pyrite that requires heat treatment, air roasting was the most effective for leaching gold from calcine, outperforming both inert and mild oxidative environments. In addition, the presence of CO2 (and/or moisture) in the roasting atmosphere to mimic the combustion of carbonaceous material could moderately enhance gold recovery regardless of whether or not there was galvanic contact with the roasted pyrite.

Phase variation and mechanical properties of waste calcium carbonate to substitute quartz in composite slab production

Sun, 01 Jan 2023 00:00:00 GMT

Phase variation and mechanical properties of waste calcium carbonate to substitute quartz in composite slab production Baş, Sedanur; Güler, Taki; Özer, Ali; Aktürk, Selçuk Owing to the fast-emerging nature and rapid advancements in the construction industry, huge volumes of marble dust (MD) are generated as reject during slab cutting in marble processing, causing significant environmental hazards. Nowadays, quartz composite slabs have increasingly been preferred in building works due to their excellent hygienic property and mechanical strength. Composite slab is produced using micronized quartz as filler, the grinding of which is an energy-intensive process. Substitution of micronized quartz with MD at different percentages was investigated in natural form and after roasting. Natural MD offered appreciable physical properties closer to those of a quartz composite slab. Physical properties slightly retrograded by quartz supplementation in the raw form. Roasting the filler led to the formation of rounded Ca–silicate. Wollastonite was the first phase formed after sintering at the lowest MD percentage and shortest roasting times. Larnite became dominating phase first by increasing MD percentage and roasting time, and then calcio-olivine formed. Physical characterization test results demonstrated that hardnesses of new phase and particle shape were the key parameters that improved slabs’ mechanical properties of. Hard rounded larnite particles improved mechanical behavior of slabs having the synergic effect of quartz, whereas wollastonite did not show a significant effect.

Combined effect of pyrometallurgical and hydrometallurgical processes on quartz ore purification

Fri, 01 Jan 2021 00:00:00 GMT

Combined effect of pyrometallurgical and hydrometallurgical processes on quartz ore purification Baş, Ahmet Deniz Recent advances in high-tech applications have highlighted the growing demand on highly pure silicates like quartz. Therefore, purification of quartz ore was determined as the subject of this study performed by pyrometallurgical followed by hydrometallurgical processes. In this research, the effect of thermal treatment (TT) followed by oxalic acid (OA) bleaching of quartz was examined to have a better understanding on the relationship between Fe remaining in concentrate and colour response. The level of TT temperature was found to have a significant effect on the purification of quartz by OA. The maximum Fe rejection rate was observed to occur both for non-treated and TT quartz up to 250°C (Fe content decreased from 624 ppm to <100 ppm, and L* value increased from 81.34 to 88.23). TT between 400°C and 900°C showed poor purification performance: decreasing L* value, and increasing a* and b* values. It is important to note that further increase in TT temperature to 1100°C resulted in the poorest bleaching: Fe rejection rate decreased, but colour response improved providing the highest L* value and the lowest a* and b* values. This finding was explained by the formation of dissolution resistant iron silicates. Moreover, the rate of Fe removal from quartz ore and differences observed in its colour response by OA bleaching were explained by changes in crystalline structure and formation of microcracks.

Advances on the fragmentation-energy fan concept and the swebrec function in modeling drop weight testing

Fri, 01 Jan 2021 00:00:00 GMT

Advances on the fragmentation-energy fan concept and the swebrec function in modeling drop weight testing Ouchterlony, Finn; Sanchidrián, José A.; Genç, Ömürden The breakage index equation (BIE), or t10 model from drop weight testing (DWT) data for rocks and ores is used in the design of crushers and mills. Such models are becoming increasingly difficult to visualize as the number of variables increases. The so-called double fan BIE, combined with the Swebrec distribution’s accurate description of the sieving curves, is applied to the modelling of drop-weight test fragmentation. The key parameters are geometric properties visible in the fan plot; slopes of straight lines and their point of convergence. The ability of the double fan BIE to reproduce DWT data had been previously established for 8 rocks with 480 DWT data sets. Here the fidelity of the double fan BIE is further evaluated for 18 new materials, based on 281 data sets. The fidelity of the double fan BIE with three fan lines is on par with the fidelity of the current state-of-the-art models for the new materials. Besides the breakage index equation, the new double fan BIE’s t10 equation produces, without additional parameters or fitted constants, the general breakage surface equation tn for an arbitrary n value as a bonus. The specific sieving curve for any combination of particle size and impact energy is also contained in the same formula. The result is an accurate, compact and transparent model.