Extraction of gold from agricultural drones' waste components through Thiourea leaching

Improved thiourea leaching of gold from a gold ore using additives

Ecological and human health risk assessments at active and abandoned metal mines require accurate geochemical data for earth materials, including soils, sediments, dusts, and mine wastes. Reliable data on metal(loid) concentrations are also important for establishing geochemical baselines and to support environmental monitoring activities. However, the reported concentration for an element in a given sample can be affected by many factors, including mineralogy, grain size, laboratory digestion conditions (reagents, temperature, time), and the instrument(s) used for elemental analysis. In particular, aggressive multi-acid digestion methods used to provide 'near-total' data for some metals of environmental interest (e.g. chromium (Cr), uranium (U)) may result in the loss of other elements (e.g. antimony (Sb), arsenic (As), sulfur (S)) through volatilization prior to analysis. When comparing data from different studies or sampling periods, it is crucial to ensure that the analytical protocols used are consistent and that changes in element concentrations over time are not simply due to variations in sample processing or laboratory procedures. The purpose of this study is to compare common digestion protocols used in the analysis of geological materials and provide recommendations on the most appropriate techniques for use in environmental risk assessments. We analyzed samples of lake sediments, stream sediments, soils, and mine tailings collected at metal mine sites across Canada. These samples were digested using two of the most commonly employed procedures in exploration and environmental geochemistry: a modified aqua regia digestion and a 4-acid digestion. All solutions were analyzed using ICP-ES/MS, and certified reference materials (CRMs) and duplicate samples were used to monitor analytical accuracy and precision. The concentration of elements (e.g. Cr) hosted in relatively insoluble mineral phases are consistently higher following 4-acid digestions as compared to digestions using aqua regia, but generally lower than total values measured using direct methods of analysis (e.g. Instrumental Neutron Activation Analysis). In contrast, the concentrations of As are often higher in samples following aqua regia versus 4-acid digestions and generally in good agreement with total values in CRMs. The behaviour of other elements (e.g. Sb, copper (Cu), lead (Pb), S, zinc (Zn)) was more variable and for many samples, the results following 4-acid and aqua regia digestions were statistically indistinguishable. Variations in the mineralogy of different samples play a key role in determining the fraction of different metal(loid)s released by these digestion techniques. This poster highlights some of the advantages and disadvantages of using each of these digestion protocols for risk assessment and environmental monitoring purposes, and provides recommendations for using geochemical data to help guide environmental decision-making at both active and abandoned metal mines.

Processing technologies for gold-telluride ores

Pongkor Gold Mining has been operated for almost twenty years and produced more than 50 ton of gold. One of important process to in gold processing plant at PT Antam (Persero) Tbk. Pongkor Gold Mining Business Unit is CIL (Carbon In Leach) Process which cyanidation process occur. Pongkor has epithermal low sulfide and clay ore which have its own difficulty to process to get high gold extraction levels. There are many several variables in cyanidation process that can be optimized to increase gold extraction. Variables like free cyanide concentration, dissolved oxygen level, viscosity, and residence time had play role in on gold dissolution rate and gold extraction. Optimization has done gradually and not simultaneously in 2013, some improvements done in Pongkor are decreasing level of viscosity and increasing dissolve of oxygen in CIL circuit by choosing and adding effective materials to increase gold dissolution rate and stabilize residence time for maximizing gold leaching time. Decreasing level. of viscosity and increasing dissolve oxygen means higher dissolution rate will achieved and will give higher gold extraction levels and also impact on getting higher throughput. By that improvements, average gold extraction in 2013 is increase 2.5 - 4 % compare to average gold extraction in 2012. This successful project will be utilized over 300,000 dmt ore/year.

Gold recovery enhancement from a refractory flotation concentrate by sequential bioleaching and thiourea leach

Gold recovery from a refractory pyrrhotite ore by biooxidation

Microwave-assisted aqua regia digestion for determining platinum, palladium, rhodium and lead in catalyst materials

In Tadzhikistan the volume of gold-containing waste converted to gold is 18 tons. This waste is products of amalgamation and cyaniding processes., and with respect to end component content they may be classified as a very rich type of raw material since they contain 1.7–8.5 g/ton of gold, whereas the average gold content in ores extracted for processing in one of the richest deposits of the republic, i.e., Tarror, comprises 2.4 g/ton. In addition, treatment of these dumps does not require crushing and refining since they have adequate coarseness of a finished class. In view of this the research object is goldcontaining waste of Tarror ore and a number of other adjacent deposits that have been accumulated over a long time. Results are provided for the raw material substance composition of the test raw material and the possibilities of using thiourea leaching for processing them. The main process parameters are optimized and the degree of gold extraction at the level of 80% is demonstrated. A fundamental production scheme is presented for processing dumps, including the following operations: preliminary acid treatment; sorption thiourea leaching; desorption; reactivation; electrolysis; melting.

As a highly accurate quantitative method of determining the contents of heavy metal in soil, aqua regia digestion is a standard method in Taiwan, and the control standards of soil in Taiwan is primarily based on this method. X-ray fluorescence spectrometer (XRF) is a fast and low cost screening method widely used in situ for real-time investigation approach. 294 high concentration soil samples (Cr & Ni) formed from serpentine in east Taiwan and 127 contaminated samples from rice paddy were analyzed in both aqua regia deigestion and XRF methods. The results were compared and discussed using statistical method. The results of both methods were highly correlated in rice paddy samples ( R2=0.95 and 0.98, P<0.01). In contrast, the correlation of Cr concentration in serpentine soil samples were not significant (R2=0.64, P<0.01) whereas the conc. of Ni were highly correlated (R2=0.94, P<0.01). Concentration of Cr in rice paddy samples is under estimated with XRF methods while the Ni is over estimated. In the case of serpentine soil samples, XRF method is over estimated in both elements. Consequently, the application of XRF screening method in the investigation of contaminated rice paddy could largely decrease the amounts of laboratory analysis, and thus reduce the cost.

Sample inhomogeneity is a severe issue in printed circuit boards especially when we are comparing the bioleaching efficiency. To avoid the ambiguous results obtained due to inhomogeneity in PCBs, 12 similar cell phone chargers (of renowned company) having same make and batch number were collected from scrap market. PCBs obtained from them were used in present studies. Out of these 12, three PCBs were used separately for chemical analysis of PCBs with prior acid digestion in aqua regia. It was found that, 10.8, 68.0, and 710.9mg/l of Zn, Pb, and Cu were present in it, respectively. Six PCBs were used for bioleaching experiment with two variations, pulverized and non-pulverized. Though the pulverized sample have shown better leaching than non-pulverized one, former has some disadvantages if overall recycling of e-waste (metallic and nonmetallic fraction) is to be addressed. At the end of leaching experiments, copper was recovered using a simple setup of electrodeposition and 92.85% recovery was attained. The acidophiles involved in bioleaching were identified by culture dependent and culture independent techniques such as DGGE and species specific primers in PCR.

Using cattle hair to assess exposure to essential trace elements in volcanic soils

Recent years have witnessed intensification of road traffic and, with it, the amount of substances emitted by vehicles. Such emissions need to be monitored for public health purposes. The aim of this study was to evaluate the impact of the highway traffic on the total content and bioavailability of Zn, Cu, Ni, Cd, Cr and Pb in nearby soils as well as influence of an acoustic screen on spatial distribution of the metals. The material included 40 soil samples collected from 15 research points located 5, 10, 25 and 50 m away from the road acoustic screen and from 4 points between the screen and the highway. Additionally, 5 research points were located next to the metal barrier. Selected physicochemical properties of soils were determined: soil texture, soil pH, TOC and CaCO3 content. The total content of heavy metals in the soils was determined by AAS after digestion in aqua regia and bioavailable forms in 1 M diethylenetriaminepentaacetic acid. The research found low impact of the highway traffic on the content of heavy metals in soils; however, due to a very short period of this potential impact (5 years), the moderately polluted category of geo-accumulation index of cadmium and high bioavailability of lead indicate the need of repeating the research within the next several years. Furthermore, the road acoustic screen significantly influenced spatial distribution of the metals in soils.

A series of experimental intermittent bottle roll tests was conducted on various content of gold and silver on oxide and sulfide ores at PT Bumi Suksesindo. The ores content variation that was used are high gold with low silver content, low gold with high silver content, both high gold and high silver content, and both low gold and low silver content for each oxide and sulfide ores. The intermittent bottle roll test was carried out at 33% of solids with the initial concentration of NaCN in the solution is 1,000 ppm and maintained at a concentration of 750 ppm. The sample size fraction that was used is -25.0 +0.6 mm with a P80 of 12.5 mm. The pregnant leach solutions were analyzed for the gold and silver concentrations using AAS (Atomic Absorption Spectrophotometer) and also analyzed for the NaCN concentrations by the titration method using AgNO3 (Silver Nitrate). Besides, the remaining solids (tail) were also analyzed for the gold and silver concentrations by the acid digest method (using aqua regia) to determine the metal extraction. The results showed that the highest gold extraction was obtained on the high gold and low silver content of 79.0% for the oxide ore samples and 82.8% for the sulfide ore samples. The gold extraction on the oxide ores tends to be lower than the sulfide ores, and the gold extraction is dependent on the total amount of gold and silver in the ores. The greater the total amount of gold and silver on the ores, the lower the gold extraction obtained for both oxide and sulfide ores. The average NaCN consumption for the sulfide ores is 1.33 kg/t, which almost three times more than the NaCN consumption for the oxide ores, which are on average of 0.46 kg/t.

EDTA-enhanced cyanidation of refractory bio-oxidised flotation gold concentrates

A sample of Sludge Batch 7b (SB7b) was taken from Tank 40 in order to obtain radionuclide inventory analyses necessary for compliance with the Waste Acceptance Product Specifications (WAPS). The SB7b WAPS sample was also analyzed for chemical composition including noble metals and fissile constituents. At the Savannah River National Laboratory (SRNL) the 3-L Tank 40 SB7b sample was transferred from the shipping container into a 4-L high density polyethylene bottle and solids were allowed to settle over the weekend. Supernate was then siphoned off and circulated through the shipping container to complete the transfer of the sample. Following thorough mixing of the 3-L sample, a 558 g sub-sample was removed. This sub-sample was then utilized for all subsequent analytical samples. Eight separate aliquots of the slurry were digested, four with HNO{sub 3}/HCl (aqua regia) in sealed Teflon vessels and four with NaOH/Na{sub 2}O{sub 2} (alkali or peroxide fusion) using Zr crucibles. Two Analytical Reference Glass ? 1 (ARG-1) standards were digested along with a blank for each preparation. Each aqua regia digestion and blank was diluted to 1:100 mL with deionized water and submitted to Analytical Development (AD) for inductively coupled plasma ? atomic emission spectroscopy (ICP-AES) analysis, inductively coupled plasma ? mass spectrometry (ICP-MS) analysis, atomic absorption spectroscopy (AA) for As and Se, and cold vapor atomic absorption spectroscopy (CV-AA) for Hg. Equivalent dilutions of the alkali fusion digestions and blank were submitted to AD for ICP-AES analysis. Tank 40 SB7b supernate was collected from a mixed slurry sample in the SRNL Shielded Cells and submitted to AD for ICP-AES, ion chromatography (IC), total base/free OH{sup -}/other base, total inorganic carbon/total organic carbon (TIC/TOC) analyses, and Cs-137 gamma scan. Weighted dilutions of slurry were submitted for IC, TIC/TOC, and total base/free OH-/other base analyses. Activities for U-233, U-235, and Pu-239 were determined from the ICP-MS data for the aqua regia digestions of the Tank 40 WAPS slurry using the specific activity of each isotope. The Pu-241 value was determined from a Pu-238/-241 method.