Nowadays, environmental minerals represent one of the most important problems in coal mine and coal cleaning factory contamination. Zirab coal cleaning factory in Mazandaran Province is one of the largest and the oldest in the coal concentration of the Central Alborz Coal Basin. So, annually, a huge amount of coal tailing will be left. The sampling of environmental secondary surface minerals, drainage water from coal tailing, the factory's waste water, and river water have been carried out.Hydrogeochemical studies demonstrate that drainage and seepage water from tail dumps are of the (Na-Ca-Mg) -SO4 type. Gibbs diagram indicates that lithology is the most important factor in increasing the ionic concentration in drained and seepage water from tailing and river water. In arid seasons due to the evaporation of hydro-sulfate solution, blodite and secondary minerals are formed on the tailing dump surfaces. This drainage water from tailing and Zirab coal cleaning factory into the adjacent river has caused the precipitation of hematite, calcite and amorphous iron oxide.Hydrogeochemical modeling has shown that hematite goethite and iron hydroxides along with carbonate minerals (calcite, dolomite and aragonite) are present.The rate of SO4, PO4, Ca, Sr, Sb, and Bi in seepage water from tailing and coal cleaning factory are higher than the standard values, which can cause both surface and groundwater pollution in this region.

This study mostly investigated the environmental impact of acid mine drainage (AMD) on the tailing of coal cleaning factory in Mazandaran province. This factory is one of the largest and the oldest in the coal concentration in Central Alborze Coal Basin. So, annually huge amounts of coal tailing will be left. The sampling of coal, coal tailing, drainage water from coal tailing, factory's waste water, secondary surface minerals and river water have been carried out in summer in 2005. On the basis of geochemistry and mineralogy results indicate that the amount of Fe2O3, SO3 and heavy metal have decreased strongly in coal tailing of Zirab coal cleaning factory compare to homogenate coals. This is an indication of oxidation of pyrite and acidic environment formation. This acid reacts with calcite and dolomite and increase the value of pH. The process also decreases the amount of CaO, MgO and MnO in coal tailing. Hydrogeochemical studies demonstrate that drainage and seepaged water from tail dumps are of (Na-Ca-Mg)-SO4 type. In arid seasons, due to evaporation of hydro-sulfates solution, blodite and secondary minerals are formed on the tailing dump surfaces. This drainage water from tailing and Zirab coal cleaning factory into adjacent river has caused the precipitation of hematite, calcite, amorphous iron oxide. Hydrogeochemical modeling proved that hematite goethite and iron hydroxides along with carbonate minerals (cacite, dolomite and aragonite) are forming. According to Gibbs diagram, indicates that lithology is the most important factor in increasing the ionic concentration in drained and seepage water from tailing and river water. The rate of SO4, PO4, Ca, Sr, Sb, and Bi in seepage water from tailing and coal cleaning factory are more than the standard value, which can cause the surfaces and groundwater pollution in this region. By keeping the coal waste material in vicinity of the river, so for prevention of pollution, it is necessary to collect and transform the tailing to a place with a sufficient drainage and treatment systems.

Screening experiments were carried out to isolate bacterial strains capable of solubilizing coal tailings for use in biofuel production from these byproduct wastes. Using enrichment in medium containing coal as sole carbon source, seven bacterial strains able to grow on coal hydrocarbons were isolated. The bacterial consortium was then cultured in mineral salt liquid media containing 1% (w/v) hard coal or coal tailings and incubated for 15 days at 25 degree centigrade on an orbital shaker (150 rpm). Spectrophotometric analysis of supernatants resulted from centrifugation of cultures showed 1.475 increases in absorbance at 450 nm for coal tailing and 0.832 for hard coal, compared to blank lacking bacteria. Gravimetric measurements also performed wich confirmed the solubilization of coal by bacteria.

Background: Human activities such as mining enhance the radioactivity levels above normal background which can lead to an incremental increase in the radiation risk to the population. Materials and Methods: 20 tailing enriched soil samples collected around Maiganga coal mine, Gombe, Northeast Nigeria were assessed for their 226Ra, 232Th and 40K contents using HPGe gamma-ray detector. Results: The mean activity values of 11. 90± 3. 0, 17. 72± 3. 6 and 70. 44± 20. 4 Bq kg-1 were obtained for 226Ra, 232Th and 40K respectively. These values were below the world average values documented by UNSCEAR. The ratio of 232Th: 226Ra obtained was 1. 5, which showed that 232Th activity was higher than the activity of 226Ra while 40K recorded the highest activity concentration in the studied samples. Statistical analysis identified strong positive relationships among all radiological parameters and confirmed that 226Ra, 232Th and 40K were the major contributors to radiation dose. Radium equivalent activity (Raeq), absorbed gamma dose rate (DR), annual effective dose (AEDE), activity utilization index (AUI), external and internal hazard indices (Hex and Hin), gamma representative index (Iγ r), annual gonadal dose (AGDE) and excess lifetime cancer risk (ELCR) were calculated to quantify the radiation risk to the public from exposure to 226Ra, 232Th and 40K in the studied samples. The mean values of these hazard parameters were within the acceptable limits provided for human safety and environmental protection. Conclusion: The use of the tailing enriched soil samples of Maiganga coal mine for any purpose whatsoever does not therefore pose any immediate radiological risk to the coal workers or the general public.

The beneficiation of coal tailings is usually difficult by common oily collectors in the flotation process, so it is necessary to use a suitable method for clean coal recovery from coal tailing dams. Thus, this study was aimed to investigate the behavior of dissolved air flotation by zero prewetting time for the clean coal recovery and to optimize the conditions of zero prewetting time for an effective flotation. In this regards, the effects of the process parameters, i. e., pH, frother type, collector type on the rougher flotation recovery of coal tailings were assessed and optimized. Additionally, Fourier transform infrared (FTIR) spectroscopy was used to understand the functional groups of oily collectors on the surface of floated products. The findings indicated that the frother type and the interactive effects between the type of frother and collector had the most effect on the performance of flotation. It was also found that under the optimal conditions (150 g/t Methyl isobutyl carbinol, 1500 g/t gas oil, and pH 4), the combustible recovery, yield reduction factor, and flotation efficiency index of coal reached to 67. 79%, 0. 056%, and 37%, respectively. Meanwhile, the FTIR analysis confirmed that the less adsorption of gas oil collector occurred in the presence of SDS (Sodium dodecyl sulfate) as frother due to the interaction of SDS and collectors

One of the major coal mines in the eastern part of Iran is Agh-Darband mine which is located in Sarakhs. Agh-Darband plant works with a content of less than 37% ash at inputs and about 12% ash in the product. Due to the equipment being depreciated and the lack of optimal conditions for the processing system, a large amount of the coal in feed is entered to the tailing part so that ash content in the tailing is about 75%. The purpose of this research is to investigate whether the flotation method can process the mine tailing with 75% ash content and reduce it to return to the processing circuit. For this purpose, various flotation tests were performed on 70 kg of tailing of Agh-Darband mine. The optimum conditions was obtained at neutral pH with 2000 g/t of oil collector, 30 g/t of pine oil as a frother, and a solid content of 18%, which the ash content of coal and recovery were 34% and 45%, respectively. In addition, using the experimental design software (DX7), the mechanical parameters of the cell such as mixer circulating speed, the distance of the mixer from the bottom, the aeration rate, skimmer circulating speed, and cell volume were optimized. Optimal values of parameters were mixer circulating speed= 1227.2 rpm, the distance of the mixer from the bottom= 0.13H, the aeration rate= 1 (completely open), skimmer circulating speed= 8.49 seconds, and the cell volume= 1 L, which resulted in the percentage of ash= 35.34% and the recovery= 52%.

Positioning of the phreatic surface in a dam body plays a critical role in the stability of tailing dams.Soil-atmosphere interaction effects, such as precipitation, runoff, interception, infiltration, and evaporation, on the one hand, and unsaturated soil effects, such as capillary rise, on the other, cause significant changes in the situation of the phreatic surface.In this paper, first, different mechanisms that affect the phreatic line level in the tailing dams and their corresponding equations are studied, and a computer program is developed for calculating the uctuations of the phreatic line. Then, for evaluating the usefulness of the program in real time problems, the stability of “Sarcheshmeh” copper mine tailing dam in Rafsanjan city, Iran, has been studied. Plaxis software Ver.8.0 has been used for modeling this tailing dam. Necessary parameters for modeling this dam have been obtained from the results of different laboratory tests on tailing materials, and information available from synoptic stations of the meteorological organization of Iran in the area. After determining the amount of change in the phreatic level for a special period of time, the stability of the dam was studied, based on calculating the factor of safety under different conditions.The results show that by constructing new dikes, the safety factor decreases. Also, the results show that those parameters that increase the phreatic level reduce the safety factor, and the stability of the tailing dam will be threatened. Among different parameters affecting the phreatic level, capillary rise was found to be the most significant factor in regard to tailing dam stability when constructed in arid areas.

Summary: The aim of this research is stability analysis of coal pillars in inclined coal seams (the variable pillar width and the variable seam dip) using the finite difference method software (FLAC2D). This aim is achieved by assessing the vertical and shear stresses distribution and their influence on the coal pillar.Introduction: In some mining method such as longwall, room and pillar and stope and pillar, the design of mine is done in such a way that the pillars are left in the seam gradient. Therefore in this case the effect of seam dip must be considered on the stability of pillar. Pillars in dipping strata are under in compression and shear load and therefore require consideration of a failure criterion that accounts for compression and shear load. The stability analysis of coal pillar can be performed by empirical, analytical, statistical and numerical methods.Since the existing empirical methods developed to pillar design have some limitations, the application of numerical methods was widely increasing to optimize pillar size in all mining methods. Applying numerical methods, it is possible to consider seam dip on the stability of coal pillar.Methodology and Approaches: In this study, six numerical models were analyzed in FLAC2D software for 30, 45 and 60 degree steeply coal seams with 10 and 15 m pillar width. It should be noted that 90 m width are considered for stopes in all numerical models. Moreover, exploitation has been started at the first stope and then continued to the second stope. In each step of the analyses, the model is run to equilibrium before creating the second stope.Results and Conclusions: The numerical modeling result on 30, 45 and 60 degree steeply coal seams with 10 and 15 m pillar width showed that the vertical stresses on the pillar decreased by increase of coal seam dip and coal pillar width. Moreover, the shear stresses increased by increases of coal seam dip. Finally, according to the numerical modeling result the pillar width of 15 m on a dip of 30 degree is stable.