Effect Of Pulp Density Research Articles

Removal of Fe From Kaolin by Chemical Leaching and Bioleaching

AbstractThe use of microorganisms to remove Fe (oxyhydr)oxides from kaolins has the potential to be an effective method for upgrading the whiteness and brightness, and therefore the commercial value, of the kaolin. The purpose of the present study was to compare kaolin products obtained by currently used chemical leaching methods with a bioleaching treatment using Aspergillus niger in order to remove Fe from kaolin (from Canakkale, Turkey). The effects of pulp density, temperature, and oxalic acid concentration on the chemical leaching experiments were investigated using the ANOVA-Yates test. The greatest degree of removal of Fe from the kaolin sample (at 15% w/v pulp density, temperature of 80°C, oxalic acid concentration of 0.2 M, and a particle size of <63 µm) was found to be 94.89% in 120 min of leaching. The Fe content decreased from 1.723%) Fe2O3 to 0.088% Fe2O3. In a shake flask, bioleaching of kaolin by Aspergillus niger resulted in removal of 77.13% of the total Fe, suggesting that this strain is effective at removing Fe impurities from kaolin. The removal efficiency generally decreased with increased pulp density. The Fe content of the kaolin decreased from 1.723% Fe2O3 to 0.394% Fe2O3 (at 1% w/v pulp density, temperature of 25°C, Aspergillus niger 3 × 107 spores, and particle size of <63 µm) after 21 days of bioleaching.

Gold Bioleaching of Electronic Waste by Cyanogenic Bacteria and its Enhancement with Bio-Oxidation

This work compares gold bioleaching from e-waste containing gold and copper by Chromobacterium violaceum and Pseudomonas fluorescens. The effect of pulp density (ranging from 0.5 to 8%w/v) was examined. Although C. violaceum produced more cyanide than P. fluorescens in the absence of e-waste, P. fluorescens showed higher growth rate, cyanide production and gold leaching efficiency at all pulp densities. Pretreatment with biooxidation of the e-waste using Acidithiobacillus ferrooxidans resulted in the removal in excess of 80% of the copper present in the waste, and increased the gold/copper ratio in the residual solid. Bioleaching the biooxidised e-waste significantly improved gold recovery, especially by C. violaceum, particularly at high pulp density. For example, at pulp densities of 2 and 4% w/v, gold recovery from non-biooxidzed e-waste was 0.22 and 0.14% respectively. Higher gold recovery, at 8%, was obtained for bioleaching of the biooxidised e-waste at both these pulp densities. The ratio of gold/copper in leachates after bioleaching of the biooxidized e-waste was also found to be increased.

Iron removal from Turkish quartz sand by chemical leaching and bioleaching

The primary advantage of using oxalic acid is in the formation during leaching of soluble complexes that are both photochemically and microbiologically degradable. In this study, chemical leaching and bioleaching methods were used for quartz sand. Using the ANOVA-Yates test technique, the effects of solids rate, temperature and oxalic acid rate were investigated using chemical leaching experiments. Solids rate and temperature were effective parameters on the chemical leaching. After the tests, the removal of Fe2O3 increased to 97.02%. Finally, the iron content decreased from 0.315% Fe2O3 to 0.0094% Fe2O3 in the leached quartz sand. The effect of pulp density was investigated on the bioleaching experiments. The bioleaching of iron oxides by Aspergillus niger resulted in removal of 47. 70% of the total iron in the quartz sand, and suggested that this strain has not a good ability to remove iron impurities from quartz sand in comparison with chemical leaching. The iron content decreased from 0.315% Fe2O3 to 0.164% Fe2O3 in the bioleached quartz sand.

Leaching of manganese ores using sawdust as a reductant

In this study sawdust was used as reductant for sulphuric acid leaching of manganese ore. Effects of pulp density, amount of acid, temperature, particle size of ore and amount of sawdust were studied. Manganese extraction of ∼98% was achieved under the conditions: leaching time 8 h, 5% H 2SO 4 (v/v), 10% pulp density, 90 °C and 5% sawdust (w/w), i.e. 0.5 g/g ore. Other Mn containing materials like low grade manganese ore, manganese nodule and Mn-nodule leach residues were tested and all these materials responded well giving more than 98% Mn extraction.

Rheological Properties of Asphaltite−Water Slurries

In this study, the rheological characteristics of asphaltite−water slurries (AWSs) were investigated with respect to some of the most important parameters in the preparation of slurries. The effects of pulp density, chemical addition, pulp pH, and particle size on the rheological behavior and viscosity of AWSs were studied. The role of demineralization of asphaltite was also investigated, and rheological properties of raw and relatively demineralized asphaltites were compared. Results showed that viscosity of the AWSs was negatively influenced by increases in the pulp density and as the mean particle size decreased from 104.81 to 15.39 μm. Increases in pH provided reduced viscosity values. The effects of dispersing and stabilizing agents were studied with a chemical mixture including 90% polystyrene sulfonate (PSS) as the dispersant and 10% Na-carboxylmethylcellulose (Na-CMC) as the stabilizer. The change in the viscosity was also investigated as a function of the dosage of the chemical mixture used. Mini...

2P-0614 How does the time of treatment of effect the long term prognosis of patients with acute myocardial infarction treated with PCI?

The direct leaching of Australian ilmenite ore samples with HCl was found to be much more effective with high chloride (Cl−) concentration (~ 500 g/L) in the feed solution. The presence of CaCl2 was more effective for leaching than that of MgCl2 and NaCl due to its higher solubility. The effects of pulp density, retention time, HCl concentration, CaCl2 concentration and temperature were examined to optimise the leaching conditions. The optimum conditions for leaching ilmenite in this study were found to be 5–7.5 M HCl solution with a total Cl− concentration of ~ 500 g/L, 3.3% (w/w) pulp density, 70–80 °C and 4–6 h of retention time. Under these conditions, the optimum leaching efficiencies were ~ 98–99% Ti and 96% Fe for ilmenite ore A and 94% Ti and 93% Fe for ilmenite ore B. One of the advantages of the HCl–CaCl2 direct leach process is that the HCl–CaCl2 solution can be recycled back to leaching after Ti recovery. The leach residue containing mainly unleached rutile and pseudorutile can be used as a feed for synthetic rutile production.

Bioleaching capacity of an extremely thermophilic culture for chalcopyritic materials

A thermophilic culture specific to bioleaching chalcopyritic materials has been obtained from a typical chalcopyritic copper concentrate of the Spanish Pyritic Belt. This paper shows the effect of pulp density (w/v) on bioleaching culture capacity with respect to this copper concentrate. The results of the batch tests show that it is possible, operating at 10% of pulp density to attain copper extraction of 94% in 10 days and, at higher pulp densities (20%), to attain good copper extraction (80%) in only 14 days. In the same way, the culture has been amply tested with different chalcopyritic ores and copper concentrates. The results obtained with four of these materials, two refractory gold ores and two copper concentrates are also presented. These results show a varying and versatile bioleaching capacity of this bacterial culture. A model of bacterial attack of this culture to leach chalcopyrite is postulated.

Laboratory studies on ball wear in the grinding of a hematite-magnetite ore

Marked-ball grinding tests were carried out under different grinding conditions and environments. Three types of balls were used, namely, cast hyper steel, high chrome cast iron and EN-31 (forged), which cover a wide range of chemical composition, microstructure and media hardness. The effect of pulp density on ball wear and grinding efficiency was also studied. Relative pulp viscosities at different percent solids for the ore slurry were also determined. As the Kudremukh ore contained about 0.2% pyrite, the effect of addition of pyrite on ball wear was studied separately. Results of marked-ball grinding tests indicated that ball wear increased with time and showed a sharp increase for wet grinding over dry grinding. Ball wear under wet grinding conditions was also influenced by the gaseous atmosphere in the mill. At 70% solids, the best results in terms of reduced ball wear coupled with satisfactory grinding efficiency were obtained. The influence of oxygen on the corrosive wear of grinding balls was increasingly felt only if sulphide minerals such as pyrite were also present in the ore. The various ball materials could be arranged in the following order with respect to their overall wear resistance: high chrome cast iron > EN-31 (forged) > cast hyper steel. Possible ball wear mechanisms involved in the grinding of Kudremukh ore are discussed.