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Papers by David Bampole

Engineering Journal, Sep 30, 2018

Silicon dioxide is a compound containing two of the most abundant elements in Earth's crust. One ... more Silicon dioxide is a compound containing two of the most abundant elements in Earth's crust. One of the main obstacles for upright solvent extraction in a copper (bio)-hydrometallurgical production chain relates to the high silica content and solid colloidal particles in the pregnant leach solution (PLS) during the treatment chain. This study assesses by way of laboratory tests the removal performance of silica and fine colloidal particles in the bioleachate solution. Their concentration requirement at solvent extraction stage could not exceed 500 ppm and 75 ppm respectively. The contact time and three ratios (coagulant/PLS): 1/2; 1/1 and 1/3 settled. The removal method from coagulation with Magnafloc (set #1597) was performed by varying its concentration in contact with the bioleachate solution. The coagulation tests consisted of finding optimal conditions with the coagulant from 0.50 to 1000 ppm, while outcomes related to the interaction of bioleached solution with coagulant consisted of the search for the optimal ratio (volume ratio). From the above, the outcomes of coagulation tests revealed a removal optimisation of silica and solid colloidal particles from bioleachate solution, which has to be greater than 200 ppm, either 300 ppm and up, keeping a volume ratio of 1/1, for a recovery rate of 68% and 58% respectively for a removal efficiency of SiO2 and solids in suspension. A reduction of the phase separation time in aqueous continuity was observed from 230 to 148 seconds. It can be noted from the results mentioned above that the removal method will promote an effective copper solvent extraction stage, affecting the operating cost and greener environment with the possibility for recycling the organic wastes.

Journal of Sustainable Metallurgy, 2018

Most of the surface reserves of copper minerals are oxidized while underground mining leads to ri... more Most of the surface reserves of copper minerals are oxidized while underground mining leads to rich silica–chalcopyrite–pyrite ore. Based on the challenges of the twenty-first century, the (bio)-hydrometallurgy processing is suggested as an alternative route to replace conventional techniques. However, the search for a sustainable metallurgy and/or more effective method to decrease impurities for efficient solvent extraction led to a comparative study of the removal performances of silica and solid colloidal particles from bioleachate solution by comparing the techniques using Shellsol set #2325 and Magnafloc set #1597, respectively. Three ratios (thinner/aqueous) or/and (coagulant /aqueous) of 1/2, 1, and 3/2 were assessed, along with the disengagement time and the required absorbed dose of Magnafloc 1597. The search for the alternative route also sought to ensure that the requirements in terms of concentration values at solvent extraction stage did not exceed 500 and 75 ppm, respectively. Findings show that the diluent/wash method is less efficient in terms of the removal performances of silica and solid colloidal particles from the bioleachate solution, but the phase disengagement time was similar, being comparatively around 150 s. The results of Magnafloc 1597 coagulation tests show removal performances of silica and colloidal particles from the bioleachate solution to be greater than 300 ppm, with a volume ratio of 1/1 for recovery rates of 68 and 58%, respectively, for SiO2 and colloidal solids in suspension. In comparison, the employment of Shellsol 2325 achieved silica removal efficiencies of 20.92 and 40%, respectively, of SiO2 and colloidal fine particles in suspension. A decreased phase separation time in aqueous continuity from 245 to 148 s has been recorded with a ratio of 1/1 (thinner or coagulant/aqueous). On the other hand, coagulant concentration of 300 ppm was retained. Hence, it could be assumed that the coagulation showed better results than the washing method.

Engineering Journal, 2018

IOSR Journal of Applied Chemistry, 2017

Transactions of Nonferrous Metals Society of China, 2019

Abstract This paper elaborated on the sustainability of the copper extraction process. In fact, a... more Abstract This paper elaborated on the sustainability of the copper extraction process. In fact, an alternative copper extraction route from mixed sulphide ores, chalcopyrite and chalcocite using mesophilic biomass consortium at 33.3 °C and ferric leaching process were attempted. Bioleaching experiments were settled with a fraction size of −75+53 µm. Bacteria were used as the catalyst. A copper yield of 65.50% was obtained. On the other hand, in ferric leaching process, with a fraction size of −53+38 µm, when the temperature was increased to 70 °C, the copper leaching rate increased to 78.52%. Thus, comparatively, the mesophilic bioleaching process showed a more obvious advantage in copper extraction than leaching process with a high temperature. However, it has been resolved from the characterization performed using SEM−EDS, FTIR and XRD observations coupled with different thermodynamic approaches that, the indirect mechanism is the main leaching mechanism, with three transitory mechanisms (polysulphide, thiosulphate and elemental sulphur mechanisms) for the mixed chalcopyrite−chalcocite ore. Meanwhile, the speciation turns into Cu2S−CuS−Cu5FeS4−Cu2S before turning into CuSO4. While ferrous oxidation and the formation of ferric sulphate occur, and there is a formation of strong acid as bacteria digest sulphide minerals into copper sulphate at low temperature, which is why this copper production scenario requires a redox potential more than 550 mV at room temperature for high copper leaching rate.

American Scientific Research Journal for Engineering, Technology, and Sciences, 2017

SN Applied Sciences

This research focuses on the extraction and characterisation of chitin and chitosan from fungal b... more This research focuses on the extraction and characterisation of chitin and chitosan from fungal biomass, Termitomyces titanicus, by immersing it in a solution of sodium hydroxide, followed by deacetylation in a basic medium using the full two-level factorial design (2 2) to obtain chitosan as a residual. The obtained chitosan was characterised by basic conductimetric titration and viscometry to determine the degree of deacetylation and the average molecular weight, respectively. The extraction of chitin was carried out under the following operating conditions: particle size less than 2.5 mm; hydrolysis time of 120 min; concentration 3 M of the NaOH solution; and temperature of 100 °C. The extraction yield of chitin was 38.04%, and the degree of deacetylation of chitosan was 69.50%, an intrinsic viscosity of 0.6822 dL/g, and a viscosimetric average molecular weight of 985.88 kDa. This research therefore shows that fungus specie called T. titanicus can serve as an alternative chitin and chitosan source. In addition, the mathematical model established for deacetylation degree that, based upon the extra process time, it would be possible to increase the purity of chitosan.

Energy, Ecology and Environment

It is well known that thermophile bacteria (40-60°C) are indicated for leaching chalcopyrite. How... more It is well known that thermophile bacteria (40-60°C) are indicated for leaching chalcopyrite. However, it is a long bioleaching process and this kind of bacteria is not available in indigenous areas. On the other hand, mesophilic bacteria (20-40°C) are easily found in many acidic drainage mines, which could be an opportunity to decrease investment costs as well as operation cost during the treatment. However, to achieve that mesophilic bacteria are able to leach chalcopyrite, it is necessary to select the appropriate conditions such as the choice of an adequate substrate, the pulp density, the pH, and oxidation reduction potential. In addition, a decrease in the latency period during bacterial adaptation and bioleaching process is necessary. Accordingly, the objective of this research is to study the bacterial adaptation of stocks in three culture media containing various sources coming from local sites of acidic drainage mines (Kipushi, Kisenda, Kamoto)at Katanga copperbelt (Democratic Republic of Congo, D.R.C) in order to develop bacterial species that are able to leach a sulphide refractory ore such as chalcopyrite. The three media consisted of a media containing gray sulphur, another with yellow sulphur and a third one with pyrite. At the end of several tests, the pyrite media was retained as the best culture medium, with an optimum pulp density of 2 % w/v, since a more rapid oxidation was observed, and the pyrite removed the lag phase. In addition, it had positive influence on the growth of cells, mostly when the pulp density is low, allowing availability of oxygen for bacterial action. Furthermore, a sharp loading of solid or again the coarse particle size during bioleaching process would lead to acid consumption by the gangue, which inhibits the growth of cells by probably damaging the cells.