Modeling and predicting of drainage quality for sulfide mine tailings impoundments     

Kaixuan TAN Zhwngji YI Aili TAN Liangshu XIA 《中国地球化学学报》2006,25(B08):28-29

Effluent from tailings impoundments of sulfide mine is an important environmental problem. The oxidation of sulfide minerals in tailings impoundments and consequent release of acid and contaminants, including heavy metals and arsenic, to tailings pore-water can last for decades to centuries. Pollution of water bodies including surface water and groundwater occurs when infiltration of precipitation is unhindered, bottom liners are absent and no drainage collection is installed. So there is a great need to develop reliable modeling techniques for characterizing geochemical interactions taking place within the tailings and predicting potential future environmental hazard which favor further prevention and remediation of the acidic mine drainage （AMD）. In this paper, a comprehensive dynamic model for tailings-water interaction was established on the basis of considering the coupling and feedback among many factors and processes such as sulfide oxidation, gangue dissolution, oxygen diffusion, water flow and mass transport,  相似文献   

Distribution and behavior of heavy metals in a river polluted by acid mine drainage in the Dabaoshan mine area, China     

Xingchun DUAN Zhi DANG Jianmin ZHOU Xiaoyun YI 《中国地球化学学报》2006,25(B08):34-35

Acid mine drainage （AMD） has been recognized as a major environmental pollution problem over past decades. This pollutant effluent is complex and is characterized by elevated concentrations of iron and sulfate, low pH, and high concentrations of a wide variety of metals depending on the host rock geology. Massive inadvertent discharges from acid mines have given rise to dramatic cases of ecological damage. These events indicate an improved understanding of the mechanism controlling metal transport to the river is important, since the aquatic ecology will be affected, to some degree, dependent on the phase （dissolved or particulate） in which the metal is transported. In this study, polluted water samples were collected along the Hengshi River near the Dabaoshan mine, Guangdong, China, in April 2005. The concentrations of dissolved Cu, Zn, Cd and Pb have been determined using ICP-MS and the chemical speciation of those metals in suspended particles was examined using BCR methods and SEM/EDX mineralogical analysis. Combining these two sets of data, the intention was to develop geochemical concepts, which explain the behavior of Cu, Zn, Cd and Pb in particle-water interactions of heavy metals in AMD. The results show that the dissolved heavy metals exhibited non-conservative behavior in the Hengshi River. The dissolved and particulate Cu, Zn, Cd and Pb have the similar spatial distribution, which decreased gradually along the river except in the lower reaches because of the absorption-desorption between dissolved and particulate phases. Although the metal concentrations in both phases were elevated, dissolved metals were dominant and had the maximum concentrations in the low pH region.  相似文献   

Impacts of acid mine drainage on a stream in subtropical China during a major flood event     

Chuxia LIN Yonggui WU Wenzhou LU Aisheng CHEN Yong LIU 《中国地球化学学报》2006,25(B08):39-40

Field and laboratory work was carded out to investigate the chemistry and ecotoxicity of stream water affected by acid mine drainage in a tributary catchment of the Pearl River in subtropical China during a major flood event that corresponded to a return period of 100 years occurred in the study area. The results indicate that stream water was affected by acid mine drainage from the Dabaoshan Mine at least to a distance of 25 km downstream of the mine water discharge point. It appears that sulfide-H^＋ from the waste rock dumps was readily available for discharging and the amount of H^＋ being transported outwards depended on the volume of out-flowing waters. However, there was a lag time for the discharge of the metals. This may be attributed to the slower release of metals, relative to H^＋, because it might take more time for the dissolution of heavy metal-bearing compounds. Fe, Zn and Al were the major metals of potential toxicity contained in the AMD-affected stream water, followed by Mn, Cu, Pb, As, Cd and Ni. Acute toxicity tests show that the AMD-affected stream water at 3.5 km downstream of the discharge point was highly toxic to the test organisms.  相似文献   

Study on treatment of wastewater from acid in-situ leaching of uranium ore with sulfate reducing bacteria     

Qingliang WANG 《中国地球化学学报》2006,25(B08):180-180

Synthetic surfactants are among the most widely used chemicals in the world （around 10 millions of tons are produced per year）, mainly as key components in detergent formulation, apart from other applications such as wetting agents or emulsifiers. Coastal ecosystems receive large quantities of these compounds and, after a relatively fast partial degradation in water, the remaining quantities end up in the sediments due to their high affinity for organic carbon in the particulate phase. We therefore focused our studies on sediments because they can be assumed to play an important environmental role acting as a sink for these contaminants. Moreover, because of their widespread use and source specificity, surfactants can usefully be employed as molecular indicators in sediments for more general contamination caused by human activities. This work deals with the vertical distribution in sediment cores of the main anionic surfactants, both linear alkylbenzene sulfonates （LAS） and alkyl ethoxysulfates （AES）, and non-ionic surfactants, including nonylphenol polyethoxylates （NPEOs） and alcohol polyethoxylates （AEOs）. In the case of LAS their degradation metabolites sulfophenyl carboxylic acids （SPCs） are also studied. The processes considered are degradation, sorption and diffusion occurring along the sedimentary column for the different homologues contained in the commercial surfactant mixtures. The most hydrophobic surfactants such as NPEOs and AEOs remain strongly attached to the particulate phase whereas polar metabolites such SPCs tend to be present in the pore water. Highest values of surfactants are found near the surface and, in most cases, there is a decrease in their concentration down the sediment core. Furthermore, the reduction in the average length of the ethoxylated chain in polyethoxylated surfactants, as well as the increase in the concentrations of SPCs at depths showing redox potential from -300 to -400 mV, suggests that surfactants may be degraded anaerobically in the sediment. In the case of LAS, these field results are compared with the data from laboratory experiments carried out in order to determine sorption capacity and anaerobic degradation.  相似文献   

Dissolution of hydrous Th （Ⅳ） oxide in aqueous Na^＋-H^＋-OH^——NO3^——H2O^- solutions in the presence of citrate, EDTA and oxalate     

Ziya S. Cetiner Scott A. Wood 《中国地球化学学报》2006,25(B08):245-246

Data on the hydrolysis of Th （Ⅳ） and solubility of ThO2 in the presence of organic ligands are of critical importance to the safe disposal and treatment of high-level nuclear waste. Such data are required to predict reliably thorium behaviour in high-level waste repositories where organic anions may be present. In addition, recent studies of the performance of thorium-based fuels report that these fuels can be used to reduce concerns related to potential proliferation of nuclear weapons and disposal of the current uranium dioxide fuel waste. Because several reactor concepts based on thorium fuel cycles are under consideration, it is important to have thermodynamic data to predict how such fuel and its waste form will behave in the environment. To establish the effect of pH and organic ligands on the hydrolysis of Th （Ⅳ）, experiments on the solubility of hydrous ThO2 in aqueous solution at room temperature were performed, covering a wide range of pH （pH=3.0 to 12.0） in 0.1 molal NaNO3 solutions. Experiments also were conducted in the presence of citrate, EDTA and oxalate with a concentration range 100 to 500 μmol. Approach to equilibrium was from supersaturation. Slopes of straight lines fit to plots of log mTh vs. pH were approximately -4 at the acidic region and near 0 at neutral and alkaline region for experiments conducted at constant ionic strength （I=0.1）, implying that the dominant Th species should be Th4^＋ and Th （OH）4（aq） The←→Th^4＋＋2H2O ThO2＋2H2O←→Th （OH）40 as follows： ThO2＋4H^＋ solubility of ThO2 decreases with increasing pH （pH 3 -6） and remains near the detection limit of ICP-MS （in the order of 10^-9 M to 10^1- M） in the range of pH 6-12. These values are in accordance with data in the literature.  相似文献   

Modeling humic acids transport in a bauxite profile: Los Pijiguaos, Venezuela     

T. Tosiani  W. Melndez  F. Vivas 《Journal of Geochemical Exploration》2006,88(1-3):246

Los Pijiguaos bauxite deposit is located in Southern Venezuela, in a tropical rain forest environment. Among the various impurities during the bauxite processing (Bayer process), organic matter compounds present in Bayer liquor can slow the rate of alumina precipitation, and reduce product yield and quality. Soil samples were taken from a 37-m-deep core and the distribution of organic carbon (OC) was investigated as well as its relationship with major oxides Al₂O₃, Fe₂O₃, SiO₂ and with the mineral phases gibbsite, hematite, kaolinite and quartz. Each sample was subjected to an adsorption process of humic acids by interaction with solutions of known concentrations. Maximum adsorption capacity was also studied in each mineral separately, which allowed calculation of the theoretical adsorption capacity of each soil sample. Even if concentrations of OC were higher in the first 5 m of the profile (0.2–0.5%), samples exhibited a low adsorption capacity (0.02%), while at depth between 10 and 37 m, samples showed lower OC concentrations (0.03–0.05%), and a larger OC adsorption capacity (0.08%). The model for the adsorption capacity only works between 10 and 30 m of depth, since in the first 10 m the bauxitic profile seems to be saturated in OC, because the concentration of OC is higher than the maximum predicted by adsorption experiments.  相似文献   

Biosorption studies on shelled Moringa oleifera Lamarck seed powder: Removal and recovery of arsenic from aqueous system     

Pushpa Kumari  Parul SharmaShalini Srivastava  M.M. Srivastava 《International Journal of Mineral Processing》2006

The present study explores the unexploited sorption property of the shelled Moringa oleifera seeds (SMOS) for decontamination of arsenic from water bodies. Sorption studies (batch experiments) result into the standardization of optimum conditions for removal of 60.21% As(III) and 85.60% As(V) as follows: biomass dosage (2.0 g), metal concentration (25 mg/L), contact time (60 min) and volume of the test solution (200 ml) at pH 7.5 and 2.5, respectively. The adsorption data are fitted with Langmuir isotherm. Surface area has been measured using BET surface area analyzer. Morphological changes observed in scanning electron micrograph of native and treated SMOS indicates the existence of biosorption process. Fourier transform infrared spectrometry of exhausted seed biomass highlights protein/amino acid–arsenic interactions responsible for sorption phenomenon. Regeneration has also been attempted for several cycles with a view to restore the sorbent to its original state. The sorption capacity of the regenerated biomass remained almost constant after three cycles of sorption process, suggesting that the lifetime cycle was sufficient for continuous application. The findings open up new avenues in the decontamination of arsenic using SMOS from arsenic contaminated water, as domestic and environment-friendly safe technology.  相似文献   

Dissolution kinetics of natural magnesite in lactic acid solutions     

Feray Bakan  Oral LaçinBahar Bayrak  Hanifi Saraç 《International Journal of Mineral Processing》2006

In this study, the dissolution of magnesite particles in aqueous lactic acid solutions was investigated in a batch reactor employing the parameters of stirring speed, particle size, temperature and acid concentration. The shrinking core model was evaluated to determine the effect of particle size, temperature and concentration. It was also found that the stirring speed did not change the dissolution. Consequently, it was determined that the dissolution rate is controlled by surface chemical reaction. The activation energy of the process was determined to be 50.3 kJ mol^− 1.  相似文献   

Beneficiation of sillimanite by column flotation—a pilot scale study     

S. Prabhakar  G. Bhaskar RajuS. Subba Rao 《International Journal of Mineral Processing》2006

A fully automated semi-commercial flotation column incorporating state of the art instruments was designed to study the amenability of flotation column for the beneficiation of different minerals. In the present study, beneficiation of sillimanite was investigated by installing the flotation column in the flotation circuit of Orissa Sands Complex, Indian Rare Earths Limited, Chatrapur, Orissa. The effect of process parameters on sillimanite grade and recovery was investigated. At optimum conditions, the flotation column was operated continuously with a feed rate of one ton per hour and demonstrated the efficiency of the technology for the beneficiation of sillimanite. The results show that a concentrate assaying 96% sillimanite at 90% recovery can be obtained in a single column flotation stage.  相似文献   

滩涂沉积物中腐殖酸对Cr（Ⅲ）的吸附平衡实验     

李英李树源  杨洪年 《岩石矿物学杂志》2006,25(2):157-161

近海滩涂是一类集中反映人类活动对地区环境影响的特定环境系统，其沉积物中腐殖质对排入重金属的迁移规律有显著影响。本文以渤海近岸滩涂沉积物为分析对象，提取其中腐殖酸，对Cr（Ⅲ）进行吸附性能实验分析，结果表明：0．1g的腐殖酸在室温条件下（20～25℃），pH值在4～5之间，在Cr（Ⅲ）的浓度达到800μg/mL时可达到饱和吸附，吸附量为6．5mg/g；腐殖酸对Cr（Ⅲ）的吸附符合Langmuir等温吸附方程。  相似文献