Chemical Stabilization of Zinc Tailings via Additives of Lime, Red Mud, Cement and GGBFS

To reduce the solubility of nickel, cadmium, lead, zinc and cobalt of filter cake tailings, resulting from zinc processing, a sample of the mentioned tailings was collected from the accumulation site in Zanjan province. Their chemical properties were measured using XRF and XRD analysis. Then, these tailings were mixed with 0-10%, 0-3%, 0-2% and 0-6% of lime, red mud, cement and GGBFS, respectively, as stabilizers. In order to investigate the reduction of solubility of heavy metals, the extraction process of the samples was performed using 0.05 M EDTA solution, and the heavy metal of these extracts were measured by atomic absorption. The results demonstrate that in samples made with a combination of both lime and red mud, the solubility of all heavy metals except lead was reduced by 45 to 50%. A comparison between the XRD spectra of the control sample and that of the stabilized sample shows that the sulfate form of PbSO4 in the control sample has converted to the carbonate form of PbCO3 in the sample containing lime and red mud, which has more solubility. This change was the main factor in increasing the solubility of lead (87%) in these samples. Cement and slag have been the most effective additives in reducing lead solubility in filter cake. According to the XRD spectrum, the form of PbSO4 in the control sample decreased significantly (100%) after being mixed with cement and slag, which was the reason for the maximum reduction of the solubility of extractable lead in the sample

all pages no. 3 2006.qxd

Abstract Three marine bacteria, Pseudomonas putida PTCC 1664, Bacillus cereus PTTC 1665 and Pseudomonas pseudoalkaligenes PTCC 1666 isolated from the East Anzali wetland sediments of the Caspian Sea, were resistant to heavy metals of Cadmium (Cd), Nickel (Ni) and Vanadium (V). Pseudomonas pseudoalkaligenes PTCC 1666 was found to be resistant to all 3 metals Ni, Cd, V. Heavy metal uptake was determined in both the biomass and supernatant by the Atomic Absorption Spectrophotometer (AAS). These bacteria showed enhanced absorption and growth in the presence of Cd and Ni at 80-100 mg/l and V at 40 mg/l concentrations. The high uptake of Cd, Ni and V was directly proportional to their respective concentrations, 5-100 mg/l for Cd and Ni and 5 -40 mg/l for V. The maximum amount of heavy metal uptake occurred during stationary phase when cells were incubated at 30°C for 72h. The results revealed that these bacteria accumulated approximately 40-50% Cd, 5-6% Ni and 10-12% V. Bacterial cells Immobilized in alginate gel showed more efficiency in biosorbing heavy metals than free cells (80%). Scanning Electron Microscopy (SEM) results indicated that the marine bacteria were capable of accumulating several metals, showing that the isolated bacterial strains can be used as potential candidates for bioremediation, with respect to Cd, Ni and V removal from aqueous effluents

Material Flow Cost Accounting Modeling and Life Cycle Analysis of Zinc Smelting Industry Concentrate Unit in Iran to Reduce Environmental Pollution

Introduction: In developing countries, Material Flow Cost Accounting (MFCA) offers numerous benefits, including the identification of hidden costs, waste reduction, improved environmental outcomes, enhanced product quality and competitiveness, and increased process and resource productivity. The zinc mining industry and related activities, such as concentrate production and zinc smelting, require process life cycle analysis due to the extensive pollution they generate, including contamination of surface and underground water from heavy elements in the leachate. Through the use of MFCA modeling, it is possible to accurately evaluate the inputs and outputs of current processes in this field and analyze them for environmental effects.Materials and Methods: This study involved visits to industrial smelting units, expert opinions, and integration with the Sima Pro software database to prepare a life cycle model and network of the product life cycle and its environmental effects. By analyzing the life cycle of Iran's zinc smelting industry, green product productivity was used to calculate the cost-material flow in the selected sample unit, track the material flow, and present a model for the life cycle of zinc. This involved utilizing information from Iran's zinc smelting industry, data from the Sima Pro software database, and the implementation of the MFCA model on information related to zinc smelting and concentrate products. In this model, zinc smelting and zinc concentrate production processes were treated as input and greenhouse gas emissions as output.* Corresponding Author’s email: [email protected]  Results: Based on the material balance relationship, the combination of calcine with sulfuric acid produces leach cake, silver, lead, and air pollution. The research estimates that for the production of one ton of zinc ingot, the amount of air pollution generated is 7 kg. MFCA analysis of the leaching unit of the industrial research complex indicates that the cost of 5070 kilograms of input materials is 12,350,000 Tomans, the cost of the system is 30,000,000 Tomans, and the cost of energy is 1,950,000 Tomans. The study also found that 3549 kg of product is obtained for 9,100,000 Tomans, while 1536 kg of waste is produced at the cost of 3,250,000 Tomans. This highlights the input values, the primary product, and the secondary product.Discussion: Through the provision of comprehensive life cycle models for the zinc smelting process, especially the zinc smelting concentrate process, the inputs and outputs of the production chain were evaluated. By accurately determining the flow cost of these materials, the process of zinc smelting concentrate production can be optimized to minimize losses, reduce environmental pollution, lower direct costs, and increase economic output, thereby leading to the growth and development of the industrial complex

Phytoremediation of hydrocarbon-contaminated soils with emphasis on the effect of petroleum hydrocarbons on the growth of plant species

To date, many developing countries such as Iran have almost completely abandoned the idea of decontaminating oil-polluted soils due to the high costs of conventional (physical/chemical) soil remediation methods. Phytoremediation is an emerging green technology that can become a promising solution to the problem of decontaminating hydrocarbon-polluted soils. Screening the capacity of native tolerant plant species to grow on aged, petroleum hydrocarbon-contaminated soils is a key factor for successful phytoremediation. This study investigated the effect of hydrocarbon pollution with an initial concentration of 40 000 ppm on growth characteristics of sorghum (Sorghum bicolor) and common flax (Linum usitatissumum). At the end of the experiment, soil samples in which plant species had grown well were analyzed for total petroleum hydrocarbons (TPHs) removal by GC-FID. Common flax was used for the first time in the history of phytoremediation of oil-contaminated soil. Both species showed promising remediation efficiency in highly contaminated soil; however, petroleum hydrocarbon contamination reduced the growth of the surveyed plants significantly. Sorghum and common flax reduced TPHs concentration by 9500 and 18500 mg kg‑1, respectively, compared with the control treatment.À ce jour, plusieurs pays en voie de développement, comme l’Iran, ont presque complètement abandonné l’idée de décontaminer les sols pollués par le pétrole à cause des coûts élevés reliés aux méthodes conventionnelles (physiques/chimiques) de décontamination des sols. La phytoremédiation est une nouvelle technologie verte qui peut s’avérer une solution prometteuse au problème posé par la décontamination des sols pollués par des hydrocarbures. Évaluer la capacité d’espèces indigènes tolérantes à croître sur des sols âgés et pollués par des hydrocarbures de pétrole représente l’une des étapes clé de la phytoremédiation. Au cours de la présente étude, l’effet de la pollution aux hydrocarbures sur les caractéristiques de croissance du sorgho (Sorghum bicolor) et du lin cultivé (Linum usitatissumum) a été évalué à partir d’une concentration initiale de 40 000 ppm. À la fin de d’étude, des échantillons de sols dans lesquels des plantes avaient obtenu un bon taux de croissance ont été analysés à l’aide d’un appareil CG-DIF afin de déterminer les taux d’hydrocarbures pétroliers (THP) totaux enrayés des sols. Le lin cultivé a été utilisé pour la première fois dans l’histoire de la phytoremédiation de sols contaminés par le pétrole. Les deux espèces ont fait preuve d’une efficacité prometteuse dans les sols fortement pollués. Cependant, la pollution par les hydrocarbures de pétrole a réduit de façon significative la croissance des plantes à l’étude. Le sorgho et le lin cultivé ont réduit la concentration en THP de 9 500 et 18 500 mg kg‑1, respectivement, comparativement au traitement témoin