Search

One of the Tanggamus gold ore types in Lampung Province is a refractory sulfide dominated by quartz (SiO2) and pyrite (FeS2) minerals with a 10.58% sulfur (S) content. The gold recovery will be less efficient without pretreatment and if only using the conventional method (direct cyanide leaching). An alternative method is introduced by combining physical and chemical routes to gain a preferable gold dissolution rate. This study aimed to determine the effect of pH, temperature, and percent solids on the weight of dissolved gold from various types of leaching feed. First, the gold ore was crushed and ground until the particle size was under 74 microns. Then, the two-stage pretreatment was introduced: the roasting process was conducted to form hematite (F2O3) mineral, which has high magnetic properties with a 1.301% sulfur trace-followed by low wet magnetic separation to separate ore with magnetic and non-magnetic minerals. Next, the gold ore with pretreatment was leached using thiourea solution and iron (III) as an oxidation agent in a 1000 ml reactor, completed with a hotplate-magnetic stirrer and condensing system. The highest gold dissolution was obtained from a magnetic concentrate at pH 1, the temperature of 50°C, thiourea concentration of 0.013 M, iron (III) concentration of 0.0195 M, a solid percentage of 20%, and stirring speed of 600 rpm for 10 hours. This study concluded that gold is more easily dissolved if gold is present in hematite matrices rather than quartz matrices. At low pH, thiourea could be used as an alternative to gold dissolution reagents. [ABSTRACT FROM AUTHOR]

Currently, due to the decreasing availability of sulfide ores, laterite ores are attracting much attention as nickel reserves. Laterite ore with nickel content of 1.35% can not be processed in Indonesia, therefore it is necessary to do processing in order to increase the laterite ore grade. One of nickel laterite processing is leaching in sulfuric acid solution. To produce a product with high levels of the metal nickel-metal impurities that come dissolved, particularly iron must be removed first from the results of the leaching solution. After separating the iron, nickel is deposited so that an intermediate product is produced in the form of Mixed Hydroxide Precipitate. The experiment was started by leaching using 1 M H2SO4 solvent, leaching time 6 hours, S/L 10 g/100 ml, stirring speed 400 rpm, variations in the addition of hydrogen peroxide 3, 5, 7, and 9 ml, and variations in temperature 30, 50, 70, and 90°C. The leached solution was then separated from the iron in 2 stages, namely the first stage with the addition of 25 wt.%/wt.% CaCO3 at a temperature of 90°C, a time of 2 hours, and a pH of 4.25. Then the second stage was with the addition of CaCO3 12.5 w/w with a temperature of 70°C, time of 1 hour, and pH 7. After that, nickel was deposited using MgO 20% wt.%/wt.% at a temperature of 50°C, 1 hour, and pH 9. The results showed that the highest extraction percent was achieved in 1 M H2SO4 conditions, leaching time of 6 hours, S/L 10 g/100 ml, stirring speed of 400 rpm, the addition of 9 ml of hydrogen peroxide and a temperature of 90°C is equal to 94.47%. [ABSTRACT FROM AUTHOR]

The utilization of iron sand as a steel-making resource has encountered a new challenge to utilize a by-product of TiO2. Nevertheless, there is no technology that is able to process it economically. Research is being developed towards direct reduction–magnetic separation technology to obtain high grade of titanium slag and easy to process further. In this work, the effect of temperature, and the addition of Na2SO4 on the direct reduction of iron sand, which was followed by the magnetic separation process, was investigated clearly. Before being reduced, the pellets were oxidized at a temperature of 1150°C for 60 minutes. The reduction was carried out in a muffle furnace with temperatures of 1000, 1100, and 1200°C for 120 min with various dosages of Na2SO4 as additives for 0, 3, 6, 9, and 12 wt.%. After that, a wet magnetic separation process was carried out with a 500-gauss magnet to obtain a magnetic concentrate containing metallic iron and non-magnetic tailing containing titanium dioxide. The XRF, XRD, and SEM-EDS analyses were carried out to identify the chemical composition,phase transformation, and morphology of the reduced pellets. The optimum results were obtained at a temperature of 1200°C with an additional dose of 12 wt.% Na2SO4 with metallic iron grade and recovery in concentrate were 89.119% and 94.64%, respectively, while titanium oxide grade and recovery in the tailings were 19.32% and 38.23%, respectively. [ABSTRACT FROM AUTHOR]

Gold ores in Tasikmalaya region, West Java, are commonly found in the form of sulfide ores. Sulfide minerals generally include chalcopyrite, pyrite, galena, sphalerite, and chalcocite. These sulfide minerals would obstruct the extraction of gold through cyanidation process. According to XRF test, it is obtained that Tasikmalaya ores contain 83.68% of silica. Cyanidation of gold was carried out in three conditions. The first condition was done by roasting the gold ores before cyanidation. The second one was conducted by adding H2O2 and the last one by doing cyanidation process without roasting and H2O2 addition. The cyanidation process was carried out along 48 hours with cyanide concentrations varied of 300, 500, and 700 ppm. The highest gold recovery of 95.86% was achieved through H2O2 addition with 700 ppm of cyanide concentration. [ABSTRACT FROM AUTHOR]