Background: The occurrence of heavy metals in the environment is of important concern due to their TOXICITY and health effects on humans, including cancer. Because metals have been extensively used for centuries in commerce, environmental contamination is widespread; moreover, exposure to metals and metal compounds continues to be a significant public health problem. Electroplating sludge contains heavy metals. Solidification/Stabilization can be used to avoid LEACHING of these metals to the environment. The aim of this study was evaluating the effectiveness of the application of dicalcium phosphate (DCP) and sodium tripolyphosphate (STPP) on Cd, Co, Cu, Ni, Pb and Zn immobilization in dewatered metal plating sludge.Methods: The ratios of STPP and DCP per dry plating sludge were determined to be 0.1%, 0.2% and 0.5% by weight. Metal LEACHING from the solidified plating wastes was assessed using the TOXICITY characteristic LEACHING PROCEDURE ((TCLP)). The results showed that the concentration of metals in untreated sludge were appropriate to classify this sludge as a hazardous waste as described in The Code of Federal Regulations (CFR) 40 CFR 261.24.Results: DCP and STPP lowered the concentration of metal in the effluent. Increasing DCP concentration from 0.1 to 0.5% decreases the contaminant concentration in the effluent. F or Cd, Pb, Cu and Ni increasing the percentage of STPP in the sludge increases the contaminant’s concentration resulting from (TCLP) extraction.Conclusion: Immobilization of heavy metals was more effective through application of DCP rather than STPP. Moreover, it may minimize the potential risk of groundwater eutrophication connected with the application of highly soluble phosphate like STPP.

Two fly ashes from municipal solid waste incineration were selected to study their heavy metal LEACHING behavior. The main purpose of this research is to investigate the CHARACTERISTICS of fly ashes and compare the LEACHING of heavy metals in different LEACHING environment. pH and acid neutralization capacity analysis showed that fly ashes were highly alkaline. Fly ashes also contained a variety of heavy metals including Pb, Cu, Cr, Zn, Cd and Ni etc. LEACHING studies showed that the alkalinity of fly ashes raised the pH of LEACHING solution from acidic to basic. Ni, Cu and Zn were strongly bound to ashes and manifested low LEACHING. In contrast, Cr and Cd had high mobility but their LEACHING was inhibited by the low solubility of carbonate Cr and Cd. Pb was highly leachable in the alkaline environment with concentration in the LEACHING solution reached as high as 9.74 mg/L. In addition, the presence of EDTA in the environment also increased LEACHING. Pb concentration was raised to 16.63 mg/L. This could be attributed to the chelating capacity of EDTA which means that the presence of organics in natural environment should be taken into consideration.

Introduction: Modeling energy demand in different energy consuming sectors is a crucial measure for effective management of the energy sector and appropriate policies to increase productivity. The rising importance of energy resources in economic development is evident. Sustainable energy use is crucial for environmental protection and social progress. Understanding the factors affecting energy consumption is essential for effective energy management. Therefore, the purpose of the current study is to investigate the impact of environmental factors on household electricity consumption in Yazd city. Materials and Methods: In the present research, various environmental factors affecting electricity consumption, including air pollution, air temperature in homes, ground surface temperature, and green space were investigated. The effects of these factors on electricity consumption of subscribers were investigated with ANN and  apriori methods. Results: Among the environmental factors, the distance to the regional park, the area of the park, and the amount of vegetation at a distance of 300m have the greatest impact, respectively, and the average summer air temperature, the amount of vegetation at a radius of 500 m, the distance from the local park, and the average summer NDVI have had the smallest effect. Unlike neural network methods, apriori presents relationships between parameters affecting electricity consumption transparently in the form of rules. Conclusion: It's used to identify the most frequently occurring elements and meaningful associations in a dataset. Greenspace can be a mitigation strateegy for reduction of energy consumption.

Anguran-Zanjan lead and zinc mine is the largest producer of lead and zinc in Iran and the Middle East. The volume of tailings produced by this mine is very large, which unfortunately is accumulated in different parts of Zanjan province without any protection operations. These tailings contain a variety of heavy metals, especially cadmium, whose disposal or spread into the environment can have very hazardous effects on soil and water resources. The present study investigates the concentration, distribution, LEACHING behavior and release of cadmium from Zn-Pb mine tailings (S1 and S2). In order to investigate the distribution of cadmium among different tailings components sequential extraction method and to classify the tailings in terms of environmental risk level, LEACHING protocols include TOXICITY characteristic LEACHING PROCEDURE ((TCLP)), synthetic precipitation LEACHING PROCEDURE (SPLP), field leach test (FLT) and LEACHING extraction PROCEDURE (LEP) was used. The effect of contact time, particle size, liquid to solid ratio and pH on cadmium release from tailings was also studied. The results showed that the cadmium release was the same in different particle size ranges and with the increase in LEACHING time, the release of cadmium almost reaches a constant value. It was also found that the cadmium release behavior was cationic and solubility controls the concentration of cadmium in the LEACHING solution. Both tailings were classified as highly hazardous residues based on the mobility index. The results of the (TCLP) test also show that tailings are one of the substances that should be protected by very good management practices because they have a high potential for contaminating the soil and water resources.

The aim of this research was to use a variety of LEACHING methods to see how different parameters affected the amount of lead LEACHING from tailings. Synthetic precipitation LEACHING PROCEDURE, TOXICITY characteristic LEACHING PROCEDURE, leachate extraction PROCEDURE, and field leach test protocols were utilized to assess the TOXICITY of the tailings. The impact of the liquid-solid ratio, particle size, contact time, and pH on lead release from tailings was also investigated. According to the findings, pH entirely effects on the release of lead from the tailings, and amphoteric LEACHING behavior was observed. The tailings were classified as hazardous material as a result of the (TCLP) LEACHING protocol's findings. S1 and S2 samples had lead mobility indexes of 51% and 5.6%, respectively. The solubility process influenced the discharge of lead from the tailings. In the particle size ranges of 0.3-0.5 mm and 0.6-1.0 mm, respectively, the maximum amount of lead was released from S1 and S2 samples. Various experiments have shown that the interaction between different factors will have complex and strong effects on the LEACHING process. To that end, managing of tailings and preventing lead emission into the environment necessitates a unique technique. Leachability is affected by a number of factors and often multiple factors can produce synergistically different releases than would be predicted by each factor alone. However, validation of the LEACHING approaches to field-collected and monitored cases indicates that combined effects are either captured by the test data or can be considered through fate and transport modeling.

Sirri Island is one of the most important islands in Iran where contains massive amounts of crude oil reservoirs and is a crude oil exporting and storage spot. Petroleum sludge wastes produced by the refineries are deposited in outdoor 2-ha open pits.30 sludge samples from different depot locations were conducted in 3-time intervals and mixed with each other to form one homogenized sample. The sample was treated by solvent extraction method using methyl ethyl ketone as an efficient polar solvent in order to recover the valuable hydrocarbon and oil. About 99.8% of the oil was recovered and determined to reach almost the same quality as the exportable crude oil of Sirri Island. The sediments were also tested for size distribution range and titled as fine-grained soil. TOXICITY CHARACTERISTICS LEACHING PROCEDURE test was conducted on the residuals to determine whether the waste is categorized as toxic and hazardous.The industrial waste evaluation model used in the current work suggested different leachate concentrations (10%, 30%, 50%, 70% and 90% of total leachate) based on TOXICITY CHARACTERISTICS LEACHING PROCEDURE for different probable LEACHING scenarios. The surface and subsurface regional conditions such as depth to underground water table, climate condition, subsurface pH, soil texture and material were defined to the model as well. Then, the model simulated 10000 possible runs considering the LEACHING PROCEDURE, contaminant concentrations, maximum contaminant limits and surface and sub-surface conditions. The final outcomes regarding heavy metals results showed that nickel, chromium and vanadium were protective under composite liner while cobalt and lead were not safe under such liner and need proper treatment before landfilling. As the final step, the size and details of landfill were designed. The landfill was selected as a square with side and depth of 55m and 3m respectively. The composite liner consisted of 1.5mm high density polyethylene layer with 50cm compacted clay liner of 10-7 cm/s hydraulic conductivity underneath.

Solidified samples of fuel oil combustion bottom ash with two sets of Ordinary Portland Cement (OPC) and Pozzolan added OPC were investigated with three sets of chemical LEACHING tests. TOXICITY characteristic LEACHING test ((TCLP)) results classified waste material and its solidification products as hazardous. Although Ni and Cr have over-leached, but their close examination with Sequential Chemical Extraction (SCE) test revealed new insights as follows. Nickel fixation in cement matrix has shifted over 20% of leachable Ni from first 4 fractions of SCE test to residual fraction with less likelihood of LEACHING. Chromium fixation in matrix has made shifts on leachable fractions that are not generally in favor of a successful fixation in matrix. In the case of Cd LEACHING, the only obvious finding from SCE test is that solidification processes have made a slight shift between fractions in bound to Iron and Manganese oxide and fraction in bound to carbonates. Compared to (TCLP) results for different mixtures, it can be concluded that Cd fixation has been done properly and significant change in LEACHING probability was not caused by solidification processes. Results of “Alkalinity, Solubility and Release as a function of pH” test indicate over regulation in the case of Pb and Cr LEACHING in different pHs. Results indicate need for more delicate interpretation of (TCLP) test results when several management scenarios are available and practical.

Background and Objectives: Zn-Pb mine tailings of Zanjan (province of Iran) contain high concentrations of toxic metals, especially arsenic that can potentially release into the surrounding soils and water pathways. These tailings create leachate due to their connection with water, which is very dangerous to the environment and to the masses of animals and human beings. Unfortunately the geochemical and mineralogical processes that control arsenic release from tailings are not fully studded. Therefore this research aimed to assess the LEACHING CHARACTERISTICS of arsenic under different environmental conditions to recognize the parameters and factors controlling its concentration in the leachate. Materials and Methods: LEACHING of arsenic from Zn-Pb mine tailing was investigated in various environmental scenarios. In order to determine the amount of leached arsenic in different conditions, four LEACHING protocols, including TOXICITY LEACHING PROCEDURE test ((TCLP)), synthetic precipitation LEACHING PROCEDURE test (SPLP), field leach test (FLT) and leachate extraction PROCEDURE (LEP) were used. Also, to study the effect of various factors such as pH, contact time, particle size and solid to liquid ratio on LEACHING of arsenic from Zn-Pb mine tailings batch LEACHING experiments were carried out. Risk assessment code (RAC) based on fractionation method was also applied to evaluate the environmental risk of arsenic mobility. Results: The results indicated that in both samples of tailings, the highest amount of arsenic was measured in the residual fraction that is relatively stable under natural environmental situations. According to RAC index, the tailings in term of arsenic placed in the low-risk tailings group. In (TCLP), LEP, FLT and LEP test the concentrations of leached arsenic were low and the highest LEACHING concentration of arsenic occurred in the LEP test and sample S1. According to SPLP analysis, Zn-Pb tailings will have a high potential for contamination of surface and underground water. The mobility of arsenic in the tailings was entirely influenced by pH, contact time, particle size and solid to liquid ratio. The LEACHING of arsenic enhanced in acidic and alkaline condition and the amount of arsenic leached in acidic condition was much higher than that leached in alkaline condition. In fact, pH-dependent LEACHING behavior of arsenic from Zn-Pb mine tailing was amphoteric. Actually pH-dependent LEACHING behavior of arsenic from Zn-Pb mine tailings was amphoteric. In sample S1, the highest amount of arsenic was released from particles with the size of 500-600 µ m, while in the sample S2 particles with the size of 150-250µ m released the highest amount of arsenic. Conclusion: By considering the results of LEACHING protocols, and arsenic fractionation and also with regards to factors affecting the concentration of arsenic in leached water, reducing the pore water and contact time, and controlling the pH and preventing the spreading of tailings in the environment are the most important factors in preventing and managing the spread of pollution in the environment.

Investigating the LEACHING amount of trace elements from environmental pollutants such as tailings is very crucial for determining the risk of these materials and sustaining environmental quality. This research was carried out to determine the concentration, risk level and LEACHING behavior of lead from Zn-Pb mine tailing of Zanjan. For this purpose, two composite samples (0-20 cm) were taken from both types of tailings from the Zn-Pb mine and the pH, time, particle size and liquid to solid ratio was determined using a batch LEACHING test. Determination of elemental composition and mineralogical characterization of mine tailings were performed using x-ray fluorescence (XRF) and x-ray diffraction (XRD) analytical techniques respectively. The morphology of tailing particles was determined by scanning electron microscope (SEM). For evaluation of tailings risk level, LEACHING protocols such as Field LEACHING Test (FLT), Synthetic Precipitation LEACHING PROCEDURE (SPLP), TOXICITY Characteristic LEACHING PROCEDURE ((TCLP)) and LEACHING Extraction PROCEDURE (LEP) were used. Also, for identification of lead distribution among different fractions of tailings, the sequential extraction method was applied. The concentration of lead in all extracts was measured by ICP-OES. The results showed that the time, particle size, pH and the liquid to solid ratio are more effective on the concentration of lead LEACHING from tailings and the maximum concentration of lead discharged from the tailings occurred in a different range of particle size. The maximum amounts of lead in the studied tailings were respectively observed in residual, carbonaceous, exchangeable, organic, iron and manganese oxides and solution parts. The results of the LEACHING protocols also made it clear that both types of waste have great environmental effects and are considered to be hazardous waste residues. Therefore, special measures should be taken to safely store these substances in the environment and prevent lead LEACHING.

Stabilization/solidification (S/S) process is routinely used for the final treatment of the hazardous wastes prior to land disposal. This process is used for treatment of hazardous waste especially heavy metals sludge. In this study cement and silica fume were used to stabilize hexavalent chromium present in the electroplating sludge. The degree of chromium stabilization was evaluated using the TOXICITY Characteristic LEACHING PROCEDURE ((TCLP)) Test and Compression Test. The specimens were prepared based on various cr+6 concentration in sludge (12, 6, 1 gr/l) and ASTM C109/C 109M-95 standard. The results show that the Cr contaminated in LEACHING solution for 12 and 6 g/l Cr+6 in sludge is more than maximum contaminated level (5 mg/l) in (TCLP) test after 28 days curing but the results of Cr+6 fixation percent show that the mean percent of Cr+6 fixation is 87% and this percent seems to be acceptable for the present situation of electroplating sludge disposal in Iran. Another obtained data showed that the partial replacement of cement with 10% silica fume increase the efficiency of Cr+6 fixation and compensate any negative effects caused by sludge on Cement hydration. It should be mentioned that the Compressive strength amount of all samples are more than the minimum EPA compressive strength for stabilized material (3.5 kg/Cm2).