Plant Tailings Research Articles

Characterization, Spatial Variation and Risk Assessment of Heavy Metals and a Metalloid in Surface Soils in Obuasi, Ghana.

Background.Soil contamination with heavy metals and metalloids has become an increasingly important issue in recent years.Objectives.The present study examines possible contamination of the environment with metals from gold mining activities in Obuasi, Ghana.Methods.Soil samples were collected from commercial and residential areas and tailing dams in Obuasi in order to investigate the extent of lead (Pb), cadmium (Cd), mercury (Hg), copper (Cu), zinc (Zn), cobalt (Co), chromium (Cr), nickel (Ni) and arsenic (As) pollution, create thematic maps showing the extent of heavy metals pollution, identify the sources of pollution, and to assess risks to humans and the surrounding ecological system.Results.Mean concentrations of metals from the study were found in the order of As > Cu > Zn > Cr > Ni > Pb > Co > Hg > Cd. The results showed that all communities were severely polluted with As, and distribution maps highlighted two hot spots at the sulfite treatment plant and Pompura treatment plant tailings dams. Additionally, the levels of Pb, Cu and Zn were elevated around the city center where vehicular traffic is very dense. Principal component analysis indicated that mining activities may have significantly contributed to metal levels in Obuasi soils. The potential ecological risk (RI) indicated that soils in 41% of the communities pose very high risks to the surrounding ecological system, 50% pose considerable risk, and 9% pose a moderate risk. Arsenic and Hg contributed 73 and 15% of the RI, respectively. The average hazard quotient due to soil As exposure was 2.51 ± 1.23 and ingestion of soils in 95% of the communities in the study area could pose non-carcinogenic health risks to children. Moreover, the average cancer risk for children from the communities was 1.13 × 10−3. Based on the United States Environmental Protection Agency (USEPA) recommendation for cancer risk of 10−6 to 10−4, the cancer risk for children (> 10−3) was higher in 45% of the studied communities.Conclusions.The central part of the study area is polluted with Pb, Zn and Cu, and As pollution is severe in all of the studied communities. The RI from all study sites revealed very high risk to the ecological system, including mammals. There could be non-cancer and cancer risks to Obuasi residents due to ingestion of As-contaminated soils, and children are particularly vulnerable.Competing Interests.The author declares no competing financial interests

Copper recovery from chalcopyrite flotation plant tailings acid leach using ion exchange resin dowtm XUS 43578.00

This study examined the feasibility of recovering copper from a sulphuric acid leach solution of chalcopyrite flotation plant tailings assaying 0.18 % copper and 0.19 % zinc using DOWTM XUS 43578.00 ion exchange resin. Zn2+cations are counter ionsto Cu2+cations during the ion exchange process. Adsorption and desorption tests were conducted on the resin with a leach solution containing26 mg Cu/L and 225 mg Zn/L,under various conditions of pH, DOWTM XUS 43578.00resin dosage, agitation time and eluant(ammonium hydroxide solution) concentration. The DOWTM XUS 43578.00resindemonstrated a high selectivity for copper over zinc, with a separation factor of 30.26 mg/g. The highcopper distribution coefficient of65L2/g2suggeststhe resin can effectively concentrate copper in leach solutions of these particular tailings.A 4M ammonium hydroxide solution yielded the highest copper recoveryat pH 3and0.6gresin dosageafter3hours of agitation. These results can be improved by a pre-treatment step to remove the zinc before the copper ion exchange process, and modifying the experiments to simulate industrial practice by having multi-stage sorption and desorption phases.

Strength Development and Microstructure Evolution of Cemented Tailings Backfill Containing Different Binder Types and Contents

The microstructure evolution and strength development of cemented tailings backfill (CTB), mixed with plant tailings and cement, is critical to a more thorough and complete understanding of its functionality as a support structure in underground mining operations. Here, an experimental study is conducted to investigate the effect of the solid contents of tailings, binder proportion, and type of cement reagent on unconfined compressive strength (UCS) and microstructure evolution with respect to a 90-day curing time. The results indicate that the mechanical strength gain is proportionally associated with increased binder and solid content. Besides, the samples prepared with 70 wt % solid content and a 25 wt % binder/tailings ratio have a maximum UCS of 6.26 MPa at a curing time of 90 days. In addition, it is also concluded that the binder proportion promotes the strength acquisition of CTB samples. Specifically, the 90-day UCS of the CTB with solid content of 68 wt % and binder content of 25 wt % is approximately twice that of the CTB with a 12.5 wt % binder proportion. Slag cement (Binder B1) and slag cement with 5 wt % NaOH (Binder B2) are used as admixture to replace the cement reagent; the results show that Binder B2 has more advantages than Binder B1 and Portland cement, and is a suitable cementing material for the CTB technology in the Daye Iron Mine. The microstructure is dominated by the network of hydration products and distribution of the pore, and hydrated material is significantly influenced by the curing time. The tailings particles are enclosed by the hydration products, and randomly disperse within their matrix at curing time of 90 days. Finally, the UCSs of CTB samples are observed to significantly increase with the increase in the curing time.

Optimization of role of physical parameters in the filtration processing with focus on the fluid flow from pore

Tailings management and water recovery from mineral processing tailings which contain high amount of fine and clay materials are very important and this matter presents considerable challenge. Any improvement in disposal and tailings filtration methods requires understanding of fluid flow in the cake pores and filter media, which are affected by various parameters. In this study, the effects of physical parameters on the specific cake resistance (α), cake formation rate, moisture content, and filter cloth resistance in the filtration of iron processing plant tailings have been examined by vacuum Top-Feed Leaf method. The main parameters which investigated in this work were cloth type, solid content, pressure drop, and thickness of cake. Experiments results showed that the polypropylene type B (PP-B) cloth was suitable for filtration process, because it had the least resistance to fluid flow. Increasing solid amount from 30 percent to 60 percent, increased specific cake resistance from 96 × 10+10 to 230 × 10+10 kg/m and cake formation rate was also increased from 0.18 to 0.46 mm/min and αwas between 1011 and 1013. Results also showed that the iron tailings had a moderate filtration capability, and based on the compressibility factor result (n: 0.56), the filter cake was compressible. This study clearly determined the action of physical parameters on dewatering mechanism and the fluid flow through the cake and cloth pores, and demonstrated the possibility of enhancing the water recycling in the industrial plant by choosing appropriate level for each parameters.

Kinetics and Adsorption Isotherms Study of Cyanide Removal from Gold Processing Wastewater Using Natural and Impregnated Zeolites

The extraction of gold involves using cyanide which has the potential to impact the environment. Many studies have been done to reduce the environmental effects of cyanide. In this research, the cyanide adsorption on zeolite from gold processing plant tailing dam wastewater was investigated. Results indicated that the pH of the solution, contact time duration, temperature, zeolite amount and size of zeolite particles were the most important parameters in the adsorption process. Zeolite was used in two fraction sizes; (100-300)m and (300-1000)m in two types of natural and impregnated with copper sulfates. The optimum amounts of both natural and impregnated zeolite in the solutions and the maximum cyanide adsorption percentage were determined as 30, 24g/L and 50.2, 86.1% for small fraction size, and 36, 24g/L and 39.5, 64% for large fraction size, respectively. The optimum values of pH were 10.5 and 10 for natural and impregnated types in both fraction sizes. Contact time duration in equilibrium conditions for fraction sizes of (100-300)m and (300-1000)m were 40 and 50 min, respectively. The optimum temperature in all situations was 22 oC. The adsorption process in a size of (100-300)m for natural zeolite was fit into the Freundlich model and for impregnated zeolite type there was no significant difference between two models, although, the Langmuir model was more accurate. In a fraction size of (100-300)m for two types of zeolites, the kinetic adsorption was fit into the Lagergren second-order kinetic model. In a fraction size of (300-1000)m, the adsorption kinetics for the natural type has no sensible difference between the first and second Lagergren kinetic model, but for the impregnated zeolite type it follows the second-order kinetic model. The results showed that the cyanide adsorption on impregnated zeolite was more than the natural type.

An investigation of the effect of NaCl concentration on the electrocoagulation of coal preparation plant tailings

An investigation of the effect of NaCl concentration on the electrocoagulation of coal preparation plant tailings

Removal of the residual xanthate from flotation plant tailings using modified bentonite

Xanthates are the most widely used collectors for flotation of sulfide minerals. It has been estimated that about half of the organic reagents (including xanthate) added to the flotation circuits are consumed, while the remaining half are discharged into the plant tailing. The residual xanthate in the flotation tailing can cause environmental issues through contaminating of the nearby water resources as a result of poor design of the tailings dams. In this communication two modified bentonite adsorbents, namely acid-activated (H-Be) and aluminum-pillared (Al-Be) bentonite, were synthesized and used for the removal of the residual xanthate (potassium amyl xanthate) from the synthetic and real solutions.Al-Be was found superior to H-Be in terms of adsorption performance and under optimum conditions (adsorbent dosage: 7500 mg/L; xanthate concentration: 2000 mg/L; pH = 12.2; time = 45 min) and more than 99% of the residual xanthate was removed. The kinetics data were best described by pseudo-second order model for the both adsorbents. The adsorption equilibrium isotherms were fitted by Freundlich, Langmuir, and Temkin models. The isotherm data were best-fitted to the Langmuir model, indicating monolayer adsorption of the xanthate on homogenous surfaces of the both adsorbents. The thermodynamics studies indicated that the adsorption was spontaneous, exothermic with the reducing entropy. The adsorption tests on the real samples taken from the tailing stream of a copper flotation plant (Qaleh-Zari in Iran) proved that both adsorbents are capable of removing more than 90% of the residual xanthate.

Evaluating the Strength and Performance of Backfill Support in Deep Level Gold Mines

The backfill operations at the deep level gold mine consist of a Cyclone Classified Tailings (CCT) Plant as well as a Full Plant Tailings (FPT) Plant with both producing cemented backfill. Due to the high demand of backfill at the mine, including a backlog of voids that need to be filled, both the CCT and FPT Plants are being operated at the moment. The mine will require an increased capacity of backfill going forward, with monthly throughputs in the order of 200 000 to 250 000 tonnes being required. The current mining methods includes destress cuts, long hole stoping as well as drift and fill mining with cemented backfill as a support medium. These concerns have led to the review of the entire backfill operations of the mine with a need for optimising, reducing costs and reducing operational complexity going forward. The research provides strength test work (solids density, particle size distribution, slurry pH, temperature, conductivity, freely settled bed packing concentration, permeability, particle micrographs, water quality, mineralogy, boger slump tests, cement mortar tests (ISO bars), and unconfined compressive strength (UCS) tests) and audit the current backfill operations at the mine. The data showed that both materials had similar top particle sizes of approximately 500 μm. The CCT has a d30 and d10 of 63.4 and 18.2 μm, respectively, compared to the FPT with a d30 and d10 of 13.1 and 3.1, respectively, which is significantly finer. The freely settled bed packing concentration by volume was calculated from the volume of the freely settled bed formed by a known volume of solids. A slurry sample was allowed to settle for 24 hours in a measuring flask. The actual solids volume was determined from the dry mass of material and the solids density. The results were as follows: CCT 45.2 %v (69.1 %m) and FPT 40.0 %v (63.8 %m).

Characterization of Flocs in Dewatering of Coal Plant Tailings

Characterization of Flocs in Dewatering of Coal Plant Tailings

Evaluation of the environmental impact of Dzhidinsky wolfram–molybdenum plant tailings

Evaluation of the environmental impact of Dzhidinsky wolfram–molybdenum plant tailings

Recovery of Phosphate Minerals from Plant Tailings Using Direct Froth Flotation

Wastes produced from the phosphate industry presents many challenges due to the high economic and environmental impacts involved with their disposal. However, the relative scarcity of high-grade phosphate ores has driven researchers to recover and recycle these valuable wastes (secondary sources). The goal of this study was to investigate the possibility of upgrading the P2O5 content in tailings produced from a phosphorous production plant using direct froth flotation. Characterization assays, including X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence (XRF), and mineral liberation analysis (MLA), were first conducted to identify the mineralogical and morphological characteristics of tailings samples and grain properties to better understand the behavior of the flotation feed. Flotation experiments were conducted using Denver D-12 in a 1-L flotation cell in the presence of sodium silicate (dispersant) and sodium oleate (collector). Several parameters, such as the solids content of the flotation pulp, pulp pH and flotation time, were investigated to optimize the recovery and grade of the concentrate products. Results obtained from this study indicated that the P2O5 content in plant tailings could be upgraded from 21.57% to 28.4% at >73% recovery.

Preparation of synthetic carnallite and amorphous silica from chromite beneficiation plant tailings

Abstract In this paper, synthetic carnallite (MgCl2 ∙ KCl ∙ 6H2O) and amorphous silica (SiO2) preparation possibilities were investigated by utilizing chromite beneficiation plant tailings which contain 3.44% chromite (Cr2O3) and 30.55% magnesium oxide (MgO) by weight. Firstly, laboratory scale high intensity wet magnetic separator was applied for removing the magnetic materials such as chromite, iron (II ) and manganese (II ) minerals in the tailings. About 85.75% of chromite, 91.22% of MnO and 64.71% of Fe2O3 were removed by single stage magnetic separation. After the magnetic separation, hydrometallurgical recovery was initiated by leaching of the tailings with hydrochloric acid (HCl). Amorphous silica particles and the other solids were separated from the leach solution by filtration. Impurities were precipitated from the leach solution by elevating the solution pH via magnesium hydroxide (Mg(OH)2) adding. The purified magnesium chloride (MgCl2) solution was mixed with potassium hydroxide (KOH ) at stoichiometric ratio. According to the XRD and chemical analysis, the synthetic carnallite was synthesized by controlled heating of this solution at 90-100°C. Also, the amorphous silica with 96.5% SiO2 content and 84.38% recovery yield was obtained by additional magnetic separation treatment.

Mathematical model for reactive transport of heavy metals in soil column: Based on PHREEQC and HP1 simulators

Mining activities play a significant role in environmental pollution by producing large amounts of tailings which comprise heavy metals. The impressive increase in mining activities in recent decades, due to their high influence on the industry of developing countries, duplicates the need for a substantial effort to develop and apply efficient measures of pollution control, mitigation, and abatement. In this study, our objective was to investigate the effect of simulation of the leachate, pH and inflow intensity of transport of Pb2+, Zn2+, and Cd2+ through Lakan lead and zinc plant tailings, in Iran, and to evaluate the modeling efficiency by comparing the modeling results and the results obtained from previous column studies. We used the HP1 model and the PHREEQC database to simulate metals transport through a saturated soil column during a 15 day time period. The simulations assumed local equilibrium. As expected, a lower pH and inflow intensity increased metal transport. The retardation of heavy metals followed the order Zn2+>Pb2+>Cd2+ and the removal concentrations of Cd, Pb, and Zn at the inflow intensity critical scenario, and Cd and Pb at inflow acidity critical scenario exceeded the allowable EPA and Iranian\'s 1053 standard thresholds. However, although the simulation results generally agreed well with the results of the column study, improvements are expected by using multi-dimensional models and a kinetic modeling approach for the reactions involved. The results of such investigations will be highly useful for designing preventative strategies to control reactive transport of hazardous metals and minimize their environmental effects.

Intensive removal efficiency and mechanisms of carbon and ammonium in municipal wastewater treatment plant tail water by ozone oyster shells fix-bed bioreactor − membrane bioreactor combined system

Residual carbon and ammonium in municipal wastewater treatment plant (WWTP) tail water lead to membrane fouling, and prejudice the operation and life time of reverse osmosis (RO) membrane. In this study, a new combined treatment system of ozone oyster shells fix-bed bioreactor (OFBR)-membrane bioreactor (MBR) was developed and pilot scale was tested for 110days to intensify the removal of residual carbon and ammonium in WWTP tail water. This results showed that the mean maximum COD, ammonium and TP removal efficiencies were achieved by 73%, 99% and 43%, under the optimum ozone dosage of 70mgL−1 and HRT of 25h. The single contribution of OFBR and MBR was 62% and 38% to COD removal, 94% and 6% to ammonium removal, 63% and 37% to TP removal, respectively. High throughput sequencing data showed that there were rich bacterial populations (>2800 species), and Deinococcus-Thermus, Firmicutes, Actinobacteria and Planctomyctes were dominant in both reactors. After addition of ozone, Deinococcus-Thermus and Planctomyctes species bacteria increased significantly in OFBR, and Firmicutes, Actinobacteria and Planctomyctes species bacteria increased remarkably in MBR, which might mainly contribute to carbon removal in OFBR and MBR, respectively. Aerobic ammonia-oxidizing bacteria, nitrite-oxidizing bacteria, and denitrifying bacteria were all existed in both reactors, which might be the main reasons for high removal efficiency of ammonium in OFBR-MBR system.

Environmental and geochemical assessment of surface water streams in the impact area of the Urupsky mining plant tailings

Surface water is contaminated by trace elements in mining areas. A complex study was carried out on the state of water and bottom sediments of two rivers in the area of the tailings of Urupsky’s mining plant. The impact of tailings on the content of elements in the water, suspensions and bottom sediments was estimated. The main pollutants of the surface water and bottom sediments and also their element’s forms were revealed.

A new process for the production of medium quality fuels from coal washing plant coarse tailings

ABSTRACT Turkey’s proven bituminous coal reserve is very low, and it is about 1.3 billion tons. The annual bituminous coal production is 2 million tons, and the annual import amount is 30 million tons. Turkey is a foreign-dependent country in its bituminous coal requirement. In this respect, the highest recycling of coarse and fine plant tailings is important in respect of the efficient use of limited natural resources. In this study, a novel process was developed for medium quality fuel production from coarse plant tailings. By the developed process, from coarse plant tailings with an ash content of 78.21%, medium quality fuel was produced which has ash content between 29.20 and 44.38% and which has economic value in the current market. The upper calorific values of these fuels change between 5620 and 4350 kcal/kg. The developed process basically includes the stages of micronized grinding and then froth flotation applied to the obtained powder tailing material.

Fractions and Release Risk of Phosphorus in Surface Sediments of Three Headwater Streams with Different Styles of Water Supply

From May to September 2015, seasonal sediment samples were collected from three headwater streams and ditches which were discharged from sewage plant tail water, food processing wastewater and agricultural drainage-groundwater seepage, respectively, in Hefei, Chaohu Lake basin. The stream-bed sediments were analyzed for phosphorus fractions. The risk assessment on phosphorus release from sediments was conducted using the phosphorus sorption index (PSI), degree of phosphorus saturation (DPS) and the phosphorus release risk index (ERI). Moreover, nonparametric tests method was used to explore the difference among the three studied streams and ditches. Study results showed that:1 Guanzhenhe Distributary and Taochong Stream were seriously damaged by phosphorus pollution both in waters and stream-bed sediment, and the phosphorus pollution levels could be arranged in the order of Guanzhenhe Distributary >Taochong Stream >Modian Stream. The mean content of total phosphorus (TP) in sediments in Guanzhenhe Distributary was 1376.95 mg·kg-1, which was 2.94 and 1.91 times as high as those of Modian Stream and Taochong Stream, respectively. 2 Significant differences and different sort orders in contents of phosphorus fractions were found for each of the three streams. 3 Obvious seasonal variations existed in PSI for the three streams, and all the sampling points in the same stream had similar changing law, namely, the maximum content emerged in autumn, followed by winter, and the minimum occurred in spring or summer. 4 The same conclusions were drawn in phosphorus release risk according to the PSI, DPS and ERI, and the risk ranked as follows:Guanzhenhe Distributary >Taochong Stream >Modian Stream. 5 According to the difference analysis, significant differences existed in almost all of the indexes among the three streams.

Treatment of artificial secondary effluent for effective nitrogen removal using a combination of corncob carbon source and bamboo charcoal filter

Nitrogen from secondary effluents has endangered the aquatic environment and human health. A new experimental setup combining a corncob carbon source and bamboo charcoal filter (BCF) was used to effectively purify artificial sewage treatment plant tail water that had high nitrate and nitrogen content, and a low carbon to nitrogen (C/N) ratio. The nitrogen concentration in the reactor's effluent was below the limit of 15 mg/L when the influent COD concentration was 20 mg/L–60 mg/L, the influent NO3−-N concentration was 15 mg/L–30 mg/L, and the hydraulic retention time (HRT) was 1 h–4 h. The reactor's maximum volumetric load of total nitrogen was 0.585 kg/(m3 d). The COD and NO3−-N balances of the reactor indicated that 4.77 g corncob was required to remove 1 g NO3−-N and 2 g corncob was required to release 1 g COD.

REE, Uranium (U) and Thorium (Th) contents in Betula pendula leaf growing around Komsomolsk gold concentration plant tailing (Kemerovo region, Western Siberia, Russia)

The article deals with the research findings of peculiarities of REE, Uranium and Thorium distribution in the territory surrounding the tailing of former Komsomolsk gold concentration plant according to the data from Betula pendula leaf testing. In the leaf element composition the slight deficiency of MREE and substantial excess of HREE are presented. In the nearest impacted area around the tailing, La, Yb, U and Th content, and Th/U ratio are lower than in the distant buffer area. It is shown, that value of Th/U ratio and REE can be an indicator for geochemical transformations of technogenic landscapes in mining districts. The results of the research can be used for biomonitoring of the territory around the tailing.

Simulation Model for Feasibility Studies on Bioremediation of Uranium Mill Tailings using Hyper Accumulator <i>Chrysopogon zizanioides</i>

Contamination of environment by uranium is expected in places where mining of uranium ore and processing, nuclear testing and reactor operations when the control measures are not effective. The daughter radionuclides of the ores, chemical additives and residual uranium are the maincomponents of processed waste from uranium industries. The bioremediation of contaminated areas using plant species or group of the plant may offer a cheap, renewable and promising approach to ensure long-term protection to the environment. In view of this, experiments were carried out to study the uranium immobilization potential of vetiver grass (Chrysopogon zizanioides (L.) Nash) under simulated conditions using the complex tailings. The vetiver plants were planted in simulation tanks at Health Physics Unit (HPU), Jaduguda, Jharkhand, India and periodic samplings were carried out to investigate the extent of uranium uptake. The acid aliquot of ashed plant samples, soil and tailings were subjected to solvent extraction followed by UV-Fluorimeter for estimation of uranium. The studies indicated that the plant species could bioremediate up to 49% of the uranium at 90th day of the experiment and the uranium remediation efficiency of vetiver increased with time and uranium was predominantly localized in the roots of the plant.