Dewatering and water recycling operations in mineral concentration processes lead to not only cost-effective water use, but also less waste disposal to the environment. In this study, optimization of dewatering process in Zareshouran gold processing plant is carried out using hydrocyclone containing circuit. For this purpose, 12 experiments using 4 spigots with 2, 3, 6, 9 mm diameter, and in 3 operation state of spray discharge, transition state and rope discharge have been conducted. Dewatering capability of hydrocyclone is evaluated based on solid weight percent and solid recovery of underflow stream. The results indicate that in the same operation state, increase in spigot diameter leads to an increase in solid recovery and a decrease in solid weight percent of underflow stream. On the other hand, as the operation state tends to rope discharge solid weight percent and solid recovery of underflow increases simultaneously. Therefore, it can be stated that spray discharge pattern has a higher dewatering capability. Using a spigot with 6mm diameter in the operation state of spray discharge, solid recovery and solid weight percent reaches 75 and 61%, respectively. In this condition, if hydrocyclone is considered as the first step of dewatering process, 75% of the feed solid content can be directly transferred to tailings dam at a lower cost. On the other hand, the overflow stream carries only 25% of feed solid content. If pressure filter present in current dewatering system are considered as the second step of dewatering process, their feed slurry will be reduced by 75%. This means an overall increase in dewatering system capacity by hydrocyclone.

This paper carried out the study on removing cyanide from aqueous solutions by modified zeolite with hexadecyltrimethylammonium bromide. After determining the properties of the prepared adsorbent by the XRD, SEM, FTIR, and BET techniques, the effect of parameters such as the initial concentration of cyanide, pH, contact time, temperature, and the ionic strength of cyanide was examined by batch tests, and the effects of bed depth and flow rate on the performance of cyanide adsorption was investigated by column process. The XRD analysis showed the presence of clinoptilolite mineral in the structure of the raw zeolite, and the surface coating of raw zeolite by surfactant was detected by the SEM method. The FT-IR results confirmed the adsorption of cationic surfactant on the surface of the modified zeolite. The Langmuir, Freundlich and Tamkin adsorption models showed an excellent ability to describe the cyanide adsorption isotherm using the studied adsorbent. The adsorption capacity of cyanide by modified zeolite was 3.97 mg/g, significantly increased compared to the maximum adsorption capacity of raw zeolite cyanide (0.54 mg/g). The pseudo-second-order model has an excellent ability to describe the adsorption kinetics of cyanide contaminants using natural and modified zeolites. Maximum cyanide uptake capacity was achieved at pH value 8. Cyanide removal decreased with increasing pH and ionic strength of the stock solution and increased with an increase in solution temperature. Column study results confirmed that the adsorption capacity increased with the increasing bed depth, and decreased with increasing flow rate. Yoon-Nelson curves are closer to the experimental curves with high R2 values.

Introduction: Contamination caused by tailing dams of mineral processing plants is one of the most important problems facing the mineral industry and that causes many environmental problems. Among these, we can point out to the contamination caused by the tailing dams of gold processing plants. This wastewater contains significant amounts of cyanide and its compounds. So far, various biological and chemical methods have been investigated for eliminating cyanide in gold processing waste. One of the methods used by researchers is the use of natural absorbents such as activated charcoal, due to the ease of use and the its reusability.Materials and methods: In this research, the adsorption of cyanide of the tailing dam wastewater of the Zarshuran gold processing plant (35 km from Takab, West Azarbaijan Province) using Shahin Dezh coal mine (about 100 km from the plant) was investigated. Cyanide adsorption experiments were performed on a laboratory scale under two modes of using crude charcoal and processed charcoal. First, the charcoal sample was poured into the cylinder up to the height of 75 mm. In the next step, the effluent containing cyanide was added to the cylinder (up to 100 mm) and the cyanide output flow rate was measured. After the experiments, charcoal samples were dried in open air, and ash percentage analysis was performed for each of them. The resultant solution of each test was filtered with Whatman paper No.75 and analyzed for cyanide content.Results and discussion: According to the results of the experiments, the granulation fraction of -2±1 mm had the highest output flow rate of 8.16 mL.min-1 and the lowest flow rate was related to particles less than 1 mm in size. The highest output flow rate for processed charcoal was obtained at 10.61 mL.min-1 in the granulation fraction of -2±1 mm. Based on analysis of the amount of ash, after the cyanide adsorption operation, the amount of ash in fractions of –4.75 and+4.75 ± 2 mm decreased by 0.7 and 3.7%, but, after cyanidation, the amount of fractions+1 mm increased by 11.8%. In all experiments, cyanide adsorption using crude charcoal has thehighest absorbance value for grain size in the range of -2±1 mm. The amount of cyanide adsorbed in this fraction for crude coal, processed coal and coal mixed with cyanide using a mechanical stirrer is 42.3, 31.78 and 21.88%, respectively. In this study, isotherm adsorption models of cyanide on charcoal were also studied based on Langmuir and Freundlich. The absorption process in all granulation fractions matched most closely the Freundlich model, indicating that that adsorption of cyanide follows a multi-layer adsorption onto the heterogeneous surface of the charcoal. The adsorption phenomenon occurs in different absorbent intake regions as a result of various forces, both physical and chemical.Conclusion: The results of this study indicate that processing the charcoal does not have any effect on the absorption of cyanide, and physical properties such as particle size and the specific surface area of coal are the most important factors in the absorption of cyanide. The results of this study indicate that the use of coal from the Gozlu mine Shahin Dezh, located a few kilometers from the tailing dam, with a grain size of -2±1 mm, in the form of crude in the bed and bottom of the dam, can significantly reduce the cyanide contamination of underground water resources.

The basic purpose of this research was the investigation of cyanide adsorption on talc mineral surface from tailing dam water in Aghdareh-Takab gold processing plant. Then in this work, talc was used for adsorbing the cyanide from the tailing dam water. Solution pH, adsorption time, amount and size of talc and temperature are some importani parameters in the adsorption mechanism. Talc was used in two fraction (100-300) and (300-1000) microns in tests in two type (natural and impregnated) conditions. Optimum amounts talc for natural and impregnated types and maximum percent of cyanide adsorbed in (100-300)m are about 30 and 24(g/L) and 50.2% and 86.1% (300-1000)m are about 36 and 24(g/L) and 50.2% and 86.1% respectively. In any fractions optimum values of pH are 10.5 and 10 for natural and impregnated types respectively. Contact time in equilibrium conditions for each types of (100-300)m and (300-1000)m is 40 and 50 min respectively. In (100-300)m adsorption isotherm follow natural type from Frondlich and impregnated type of Longmuir models amount of cyanide adsorption on impregnated talc more than natural type.

The effluent from Zarshouran gold mineral processing plant contains high quantities of arsenic, antimony, mercury, and bismuth. These metals and metalloids are soluble in water and very toxic when they enter the environment. Their solubility in water causes the polluted area to extend beyond their point of origin. In this article, different methods of antimony removal from water and wastewater were reviewed and the zero-valent iron nanoparticles coated on Bentonite were selected as an effective and low cost material for removing antimony from wastewater. For the purposes of this study, zero-valent iron nanoparticles of 40-100 nanometers in size were synthesized by dropwise addition of sodium borohydride solution to an Iron (III) aqueous solution at ambient temperature and mixed with nitrogen gas. To avoid particle agglomeration and to enhance the product’s environmentally safe application, the nanoparticles were coated on Bentonite and characterized by SEM/EDAX and BET. The experiments were carried out by intense mixing of the adsorbent with 10ml of real/synthtic wastewater samples in 20ml bottles. The effects of pH, contact time, temperature, and adsorbent dosage on antimony removal efficiency were investigated under intense mixing using a magnetic mixer. Finally, the effluents were filtered upon completion of the experiments and used for atomic adsorption analysis. The results of the experiments showed that the adsorption isotherms of the synthesized nanoparticles obeyed the Langmuir and Freundlich models. The experiments carried out on real samples showed that antimony adsorption capacity for B-nZVI was 2.6 mg/g of the adsorbent and that the highest antimony removal efficiency was 99.56%.

Utilizing cyanide compounds in mining and chemical industry is one of the most important environmental issues due to the acute toxic properties of many cyanide compounds to humans and aquatic life. Cyanide tends to react readily with most other chemical elements, producing a wide variety of toxic, cyanide related compounds. This research was aimed at investigating a feasible and economical technique for the detoxification of cyanide from the tailing effluent of Muteh gold mine in Isfahan, Iran. In this research cyanide detoxification was achieved through the oxidation of cyanide by hydrogen peroxide using various hydrogen peroxide solutions at pH levels between 7-13 and temperatures between 12-65 °C using copper sulfate as a catalyst. The optimum pH and dose of hydrogen peroxide for complete cyanide removal in the presence of 30 mg/L copper sulfate as a catalyst were determined as 9.7 and 9.98 g/L, respectively. At high temperatures > 35°C, cyanide was completely removed perfectly at constant pH = 9.7 which was mainly due to cyanide evaporation in the form of HCN.

Nugget effect is a common feature of many vein-style gold deposits. This style of mineralization results in complication in many exploitation stages including resource and average grade estimation, representative sample selection, ore characterization as well as processing. Accurate and reliable ore characterization is a vital stage in any mineral processing project. Ore characterization in high nugget effect gold ores is so complex due to uncertainties associated with representativity of the selected sample. The main challenge is to provide a representative sample for identification of each process mineralogy parameter such as average grade, liberation, grinding size, mineral association, floatability, etc. Here, different protocols are collected and compared to draw a comprehensive picture of the available methods. The results are examined on a high nugget effect gold ore from Northeast of Iran, Azghad mine. Processing experiments were conducted to develop a process suitable for Azghad gold mine. To investigate the feasibility of pre-concentration, gravity methods using a Nelson separator was applied on the oxide sample as the main gold vein. 43. 3% of total gold was concentrated in the gravity concentrate with only 2% weight recovery, suggesting gravity concentration can be considered as an efficient method in this ore. Gold preg-robbing experiments were performed for Shale sample due to the organic matter, clay minerals and mica. Preg-robbing potential of the shale ore was determined to be 1. 1 ppm. Optimization of operating parameters was performed by central composite design method for the combined oxide and shale samples.

The tailings come from Chadormalu iron ore processing plant is beneficiated by flotation method. The obtained apatite concentrate is dissolved in acidic media and used to produce phosphoric acid. The chemical analysis shows that the phosphoric acid solution contains 75 ppm of arsenic (As) and 313 ppm of Rare Earth Elements (REE). To identify the source of As and REE, the samples taken from flotation feed (tailings of high intensity magnetic separator), flotation tailings, and apatite concentrate were characterized mineralogically using XRD, XRF, ICP-OES, and scanning electron microscopy (SEM) equipped with EDX and WDX. The results revealed that the concentrate containing 35.6% P2O5 is mainly composed of fluorapatite mineral and a small amount of dolomite and calcite. ICP analysis showed that the As and REE contents in the apatite concentrate are 345 ppm and more than 5000 ppm, respectively. Through the SEM studies, it was identified that some parts of REE have been placed in the fluorapatite lattice as substituting for calcium, and the other part is in the form of monazite minerals with dimensions finer than 20 microns. It was also revealed that As is probably substituted for phosphorus (P) in the lattice structure of fluorapatite and monazite minerals. Thus, it will not be possible to recover REE and As before dissolving the apatite concentrate. Therefore, REE must be recovered firstly from the solution by an appropriate method and then As to be separated from the solution by the precipitation method.