Sharif Digital Repository

In this study, effects of solid concentration, temperature, and initial Fe2+ concentration on bioleaching of sulfide mineral (chalcopyrite) obtained from Sarcheshmeh Copper Mine in the region of Kerman located in the south of Iran were investigated. A mesophilic iron oxidizing bacterium, Acidithiobacillus ferrooxidans has been isolated from a typical chalcopyrite copper concentrate of the mentioned mine. Bioleaching experiments were carried out in two batch air-lift bioreactors with recycling stream. One reactor contained 2 liters of medium and 10% (v/v) inoculum while in the other reactor, control bioleaching tests were carried out with sterilized concentrate without inoculum by the... 

In this paper, we describe a carbon dioxide mineralization process and its associated solid products. These solid products include amorphous silica, iron hydroxides and magnesium carbonates. These products were subjected to various characterization tests, and the results are published here. It was found that the iron hydroxides from this process can have different crystalline properties, and their formation depended very much on the pH of the reaction conditions. Different forms of magnesium carbonate were also obtained, and the type of carbonate precipitated was found to be dependent on the carbonation temperature. Hydromagnesite was obtained mainly at low temperatures, while dypingite was... 

This research concerns fundamentals of spontaneous transport of saltwater (1 mol·dm-3 NaCl solution) in nanopores of calcium carbonates. A fully atomistic model was adopted to scrutinize the temperature dependence of flow regimes during solution transport under CaCO3 nanoconfinement. The early time of capillary filling is inertia-dominated, and the solution penetrates with a near-planar meniscus at constant velocity. Following a transition period, the meniscus angle falls to a stabilized value, characterizing the capillary-viscous advancement in the calcite channel. At this stage, brine displacement follows a parabolic relationship consistent with the classical Lucas-Washburn (LW) theory.... 

Researchers and practicing engineers have come to this realization that different mixtures should be used for different climate and traffic conditions. Rutting is one of the main performance related types of distress in areas where the asphalt pavement is subjected to heavy axle loads and high temperature. In this research various types of SMA mixtures were tested to evaluate their effectiveness for inhibiting rutting. The variables in the laboratory tests were aggregate gradation  

The use of a draft tube fluidized bed bioreactor (DTFBB) has been successfully demonstrated for the bioleaching of a chalcopyrite concentrate (Mousavi, et. al., 2005). In the present paper this technique was used for the bioleaching of zinc from a sphalerite bearing low-grade ore. A strain of the thermophilic bacterium, Sulfobacillus, has been isolated from the Kooshk lead and zinc mine near the city of Yazd (Iran) and is tested at temperatures 47 °C-72 °C. This is compared to leaching with a strain of the mesophile Acidithiobacillus ferrooxidans, which has been adapted to the high levels of zinc and the presence of the low-grade ore, and which was tested at temperatures 18 °C-42 °C. The... 

The principal objective involved in this research is to explore the mechanical behaviour of the binder using different mineral fillers such as stone dust (SD), brick dust (BD) and fly ash Class F (FA). Currently, a large quantity of roads is being constructed under the China-Pakistan Economic Corridor (CPEC) project. It is a major concern for quality of road to with stand heavy loads. For the investigation of the quality of roads, it is mandatory to evaluate the behaviour of mineral fillers addition in asphalt mastic. Fatigue cracking, thermal cracking and permanent deformation have been found a major common distress in the construction of road networks. In this study, the behaviour of... 

The present study examined the sorption capacity and sorption kinetics of four-type perlite for oil spills clean up. These four types are different on their porous space, expansion ability and special surface area. The tests were done both in static and dynamic methods. Experiments showed that the perlite spread on oil spill rapidly and floated on the surface of oil spill because of its low density (80-180 kg/m3). Scanning Electron Micrograph (SEM) of a typical structure of expanded perlite showed that it of high porous space. Sorption kinetic of oil spill into porous expanded perlite was evaluated by weight increase of crude oil with sorption time. According to kinetic study sorption of oil... 

The effects of several variables on zinc recovery in column bioleaching have been investigated. The ore contained sphalerite and pyrite as the main sulfide minerals and chalcopyrite and galena as minor minerals. Tests were carried out using a bench-scale column leach reactor which was inoculated with mesophilic (Acidithiobacillus ferrooxidans) and thermophilic (Sulfobacillus) iron oxidizing bacteria; initially isolated from the Sarcheshmeh chalcopyrite concentrate (Kerman, Iran) and Kooshk sphalerite concentrate (Yazd, Iran), respectively. In the inoculated column, jarosite and elemental sulfur were formed. The leaching rate of sphalerite tended to increase with dissolved ferric ion... 

A simple, rapid, atom economy and highly efficient procedure has been developed for thiolysis of epoxides by aromatic and aliphatic thiols under solvent-free conditions. A high regioselectivity in favor of nucleophilic attack at the benzylic carbon atom of aromatic epoxides, such as styrene oxide, is observed. However, aliphatic unsymmetrical alkenyl oxides undergo selective nucleophilic attack at the sterically less hindered carbon atom. A variety of β-hydroxy sulfides were obtained in short reaction time and excellent yields with nearly complete regioselectivity. © 2005 Elsevier B.V. All rights reserved  

Enhanced Oil Recovery from carbonate reservoirs is a major challenge especially in naturally fractured formations where spontaneous imbibition is a main driving force. The Low Salinity Water Injection (LSWI) method has been suggested as one of the promising methods for enhanced oil recovery. However, the literature suggests that LSWI method, due to high dependence on rock mineralogy, injected and formation water salt concentration, and complexity of reactions is not a well-established technology in oil recovery from carbonate reservoirs. The underlying mechanism of LSWI is still not fully understood. Due to lack of LSWI study in free clay dolomite fractured reservoir, and to investigate of... 

Sharding, i.e. splitting the miners or validators to form and run several subchains in parallel, is known as one of the main solutions to the scalability problems of blockchains. The drawback is that as the number of miners expanding each subchain becomes small, it becomes vulnerable to security attacks. To solve this problem, a framework, named as Ployshard, has been proposed in which each validator verifies a coded combination of the blocks introduced by different subchains, thus helping to protect the security of all subchains. In this paper, we introduce an attack on Ployshard, called the discrepancy attack, which is the result of malicious nodes controlling a few subchains and... 

Researchers and practicing engineers have come to this realization that different mixtures should be used for different climate and traffic conditions. Rutting is one of the main performance related types of distress in areas where the asphalt pavement is subjected to heavy axle loads and high temperature. In this research various types of SMA mixtures were tested to evaluate their effectiveness for inhibiting rutting. The variables in the laboratory tests were aggregate gradation, nominal maximum aggregate size, asphalt binder content, and the type of binder thickener. Two types of asphalt binder thickener, namely mineral fiber and crumb rubber were used. The results of this investigation... 

Cryptocurrency mining device (CMD) is a plug-and-play device installed by any low-voltage customer to convert electrical energy to digital money. Recently, the significant increase in the price of digital currencies has persuaded residential customers in many countries to employ CMDs to obtain quick and easy profit. However, these rapidly evolving loads can cause a substantial increase in the coincident peak load of distribution networks. Therefore, it can threaten the safe and reliable operation of the network. A straightforward way to restrict the penetration rate of these home-based miners is to increase the electricity price such that this business becomes unprofitable; however, this... 

The leaching kinetics of stibnite in basic solution has been investigated. Spherical pellets of antimony sulphide were dissolved in 1 molar sodium hydroxide solutions at different temperatures. It was found that the shrinking core with ash layer model could satisfactorily explain the dissolution process. Using this model, it was found that initially the rate controlling step was a chemical reaction with activation energy of 10.2 kJ/mol. As the ash layer built up, diffusion through the ash layer became the rate controlling step. The activation energy for this step was found to be 33.4 kJ/mol. It was also observed that smaller particle size, larger solid to liquid ratio, and higher NaOH... 

Plasma impulse technology (PIT) is one of the most innovative methods among the oil recovery enhancement (EOR) jobs. Although the low cost and persistent effects of this method has attracted researchers attentions to its self, the governing mechanisms of reservoir remediation in this method are still shrouded in mystery. This study presents a brief discussion on probable thermal mechanisms which govern the interaction between reservoir formation and plasma impulse jet. Minerals dissociation, opening the fused pathway and organic deposits melting seem to be of the most important thermal effects  

Blockchain technology brings about an opportunity to maintain decentralization in several applications, such as cryptocurrency. With the agents of a decentralized system operating independently, it calls for a consensus protocol that helps all nodes to agree on the state of the ledger. Most of the existing blockchains rely on Proof of Work (PoW) as the underlying consensus algorithm, resulting in a significant amount of electricity power consumption. Furthermore, it demands the miner to buy specific computation devices. Besides, a protocol to gather the society-related taxes such as public education funding and charities is lacking in existing consensus algorithms. In response, this paper... 

In this paper, preparation of polyethylene/clay nanocomposites (PECNC) by in situ Ziegler-Natta catalyst polymerization was investigated. A Ziegler-Natta catalyst was first supported on montmorillonite (MMT) type clay and subsequently used for polymerizing ethylene. Clay and clay supported catalyst were characterized by Fourier transmission infrared and ICP method. X-ray diffraction (XRD) and transmission electron microscopy results show that silicate layers of the mineral clay in prepared nanocomposites were intercalated and exfoliated in the polymeric matrix. Differential scanning calorimetry results show that the prepared nanocomposites have higher crystallization temperature than pure...