Trona ore located in Beypazari is extracted by solution mining method with well pair connected by directional drilling technology. This thesis covers the determination of the dimensions of the initial (vertical) caverns formed in underground by use of a computer modeling (trademark: WinUbro/Poland) on the basis of horizontal and vertical leaching rates. The leaching rates were determined using the trona core samples from the ore deposit. The effect of insoluble content and the thickness of trona layer and solvent temperature on the initial cavern dimension were studied. The outcome of this study showed that the better the trona layer quality from the point of view of thickness and insoluble content, the wider the vertical cavern size is. In 1 m thick trona layer with 20% insolubles, it is possible to develop caverns of 6 m width, which is the minimum size for well pair connection. On the other hand, it is determined that the effective leaching time depends mainly on solvent temperature.

The aim of this study was to investigate synthesis of lithium borides by mechanochemical synthesis from oxides. Lithium borides have promising properties in the area of high energy additives and hydrogen storage. Lithium oxide (Li2O), boron oxide (B2O3) and Mg were used to synthesize lithium borides. Experiments were conducted in a planetary ball mill under argon atmosphere. Analyses of the products were done by X-ray diffraction and scanning electron microscopy. Trilithium tetradecaboride (Li3B14) peaks were observed in the product powder. Removal of other phases that were formed during experiments was done by leaching in HCl/water solution. Leaching in 0.5 M HCl/water solution for 10 minutes was found to be sufficient to remove / iron (Fe) and magnesium oxide (MgO). Effects of ball milling parameters such as milling speed, ball to powder ratio, milling duration were investigated and milling for 20 hours with 300 rpm and 30:1 ball to powder ratio was found to be the optimum conditions. Syntheses of other lithium borides (LiB4, Li2B6, LiB13) were also experimented with the same milling parameters. Formation of LiB4, Li2B6 and LiB13 was not observed in the product powders. However, the results of LiB4 and LiB13 production experiments showed also Li3B14 peaks in the product. Li2B6 synthesis experiments resulted in Li2B9 peaks in the product powders.

ABSTRACT HIGH PRESSURE ACID LEACHING OF TURKISH LATERITES Kaya, Serif M.Sc., Department of Metallurgical and Materials Engineering Supervisor: Prof. Dr. Yavuz A. Topkaya January 2011, 91 pages The aim of this thesis study was to investigate and find the most cost effective way of extracting nickel and cobalt into the pregnant leach solution (PLS) from G&ouml / rdes lateritic nickel and cobalt ore by means of sulphuric acid leaching under high temperature and high pressure conditions.The high pressure acid leach (HPAL) experiments were conducted with nontronitic and limonitic types of G&ouml / rdes lateritic nickel ore, respectively. Leaching experiments of nontronite ore have shown that almost all of the nickel and cobalt contained in the nontronitic ore were easily extracted into the (PLS). Therefore, the rest of the experiments were concentrated on difficult to leach limonitic sample when compared with the nontronitic one, and higher nickel and cobalt extractions were aimed to be obtained. By taking economic and technical considerations into account, the basic (HPAL) process parameters for the limonitic sample were optimized as / leaching at 255 &deg / C with a particle size of 100% -850 &mu / with 0.30 sulphuric acid to ore weight ratio in 1 hour of leaching duration. The experiments were conducted with 30% solids ratio and it was found that 87.3% of nickel and 88.8% of cobalt present in the limonitic ore could be extracted into the pregnant leach solution. Nevertheless, these results were found to be below the desired values. Therefore, the possible reasons of this behavior were investigated and the presence of hematite mineral in the limonitic ore was found to be the most probable one. Therefore, in order to dissolve the nickel and cobalt present in the hematite mineral, the additions of HCl, ferrous ions, cuprous ions and sulphur were tried, respectively and they were found to be beneficial in order to increase the degree of nickel and cobalt extractions.

The aim of this thesis study was to extract nickel and cobalt from Sivrihisar limonitic nickel laterite ore by high pressure acid leaching (HPAL) method under most economical operating parameters. Optimizing the conditions to yield a saleable quality mixed hydroxide product from the pregnant leach solution (PLS) was also investigated. To extract high amounts of nickel and cobalt from the laterite matrix / leaching duration, leaching temperature and sulfuric acid/ore ratio were studied at fixed conditions of -850 &micro / limonitic ore particle size and 40% solids concentration. The Sivrihisar limonitic nickel laterite ore was found to be readily leachable. It was found that 95.4% of Ni and 91.5% of Co were extracted at the optimized conditions of 235oC, 0.23 acid/ore ratio in 60 minutes. The real pregnant leach solution produced at the optimized conditions of HPAL was purified in two iron removal stages under the determined optimum conditions. Nearly all of the Al and Cr were removed from the PLS in the two stages of iron removal. Then, nickel and cobalt were taken out from the PLS in the form of mixed hydroxide precipitates (MHP) in two stages. A MHP 1 product containing 33.41 wt.% Ni, 2.93 wt.% Co was obtained with a Mn contamination of 3.69 wt.% at the optimized conditions of pH=7, 50oC and 60 minutes. The MHP 1 product was also contaminated with Fe (2.83 wt.%) since it could not be completely removed from the PLS without the critical losses of nickel and cobalt during the two iron removal stages.

During last decade, polyurethanes (PUs) which are able to degrade into harmless molecules upon implantation have received a significant level of attention as a biomaterial in tissue engineering applications. Many studies are focused especially on development of PUs based on amino acid derivatives / however, there are only few applications of amino acid based PUs in tissue engineering. In this study, a biocompatible and biodegradable thermoplastic poly(ester-urethane) (PEU) based on L-lysine diisocyanate (LDI) and polycaprolactone diol (PCL) was synthesized and used for the preparation of two dimensional (2D) films and three dimensional (3D) scaffolds. The resulting polymer was casted as 2D films for full characterization purpose and it was found that it is highly elastic with modulus of elasticity ~12 MPa. Surfaces of 2Ds were modified via micropatterning and fibrinogen coating to check the material-cell interaction. The 3D scaffolds were obtained by salt leaching and rapid prototyping (bioplotting) techniques. The 3D scaffolds had various pore size and porosity with different mechanical strength. The bioplotted scaffolds had uniform pore size of ~450 &micro / m and exhibited higher compressive modulus (~4.7 MPa) compared to those obtained by salt leaching (~147 kPa). Salt leached 3D scaffolds had inhomogenous pore size distribution in the range of 5 &micro / m - 350 &micro / m and demonstrated greatest degradation profile compared to 2D films and 3D bioplotted samples under enzymatic condition. Rat bone marrow stem cells (BMSCs) were used to investigate the biocompatibility of the polymer and suitability of fabricated scaffolds for osteogenesis. Presence of micropatterns on 2D matrices did not show any influence on osteoblastic function, but presence of fibrinogen enhanced cell attachment and proliferation. All of the fabricated 3D PEU matrices supported proliferation, osteoblastic differentiation and extracellular matrix (ECM) deposition with highest osteoblastic activity on bioplotted scaffolds which confirmed by von Kossa staining and EDX analysis. The results indicated that the synthesized PEU based scaffolds were able to induce osteoblastic differentiation and mineralization of BMSC and therefore these scaffolds can be good candidates to be used in bone tissue engineering

In this study, various techniques of hydrometallurgy and ultrasound-assisted solvent extraction were used to recover the platinum group metals (PGM¡¦s) from a composite sample of honeycomb-type autocatalysts. After they were removed from the converter casings, the autocatalyst substrates were first crushed and then ground by a ball mill. The recovery procedures employed are shown as follows: (1) dissolve PGM¡¦s from ground spent autocatalyst by aqua regia leaching; (2) separate PGM¡¦s from base metals in the aqua regia leachate by metal cementation using zinc powder so that PGM¡¦s can be precipitated out; (3) the PGM¡¦s precipitate was first dissolved by aqua regia, then proceed to remove nitrate and hydrochloride within. The residue was further dissolved in hydrochloride acid as a preparation step for solvent extraction; (4) the PGM¡¦s pregnant solution of hydrochloride acid was treated by solvent extraction and stripping to separate and purify each component of PGM¡¦s. Effects of ultrasound agitation on the efficiency of solvent extraction was also evaluated in this work. Results of aqua regia leaching experiments have shown that the quantity of dissolved PGM¡¦s increased as the solid-to-liquid ratio decreased. The maximum dissolved quantity of PGM¡¦s could be obtained by a 3-hr leaching time. At this stage, the PGM¡¦s recoveries are 80-90% for platinum and rhodium and greater than 99% for palladium. The result of a preliminary test has indicated that acetic acid can not effectively separate the PGM¡¦s and base metals. Thus, the method of cementation by zinc powder was employed to separate PGM¡¦s from base metals. Before cementation, the aqua regia leachate was diluted and pH-adjusted to greater than 2. In so doing, an almost complete cementation (>99%) could be obtained by the least quantity of zinc powder. In addition, the base metals occurred with the PGM¡¦s precipitate have been minimized except lead and zinc. While palladium was extracted by di-n-octyl sulfide (DOS), ultrasound assistance has rendered a complete extraction within a few minutes. At this stage, the extraction efficiency was found to be independent of the HCl concentration. It was found that platinum and rhodium were not extracted by DOS. When platinum was extracted by tri-n-octylamine (TOA) and assisted by ultrasound, rhodium will be extracted at the HCl concentration higher than 4M. Thus, TOA is not an effective chemical for selective extraction of platinum. TOA was then replaced by tributyl phosphate (TBP). Experimental results have indicated that the extraction of platinum using TBP was affected by the HCl concentration. The best result was obtained when the HCl concentration was 5M. Extraction by TBP was found to be fast. It took only 20-30 seconds to reach the equilibrium even with no ultrasound assistance. But multi-stage extractions are generally required to extract platinum completely. Rhodium was found to be not extracted by TBP. After palladium and platinum were extracted, only rhodium was remained in the reffinate. In summary, solvent extraction using DOS and TBP has made it possible to separate palladium, platinum, and rhodium effectively. In the palladium stripping solution almost no base metals was determined. However, zinc and lead were found in the platinum stripping solution and the rhodium-containing raffinate. These base metals should be removed to achieve a better purity for each precious metal. The TCLP (i.e., a leaching test for toxicity) result of the autocatalyst substrate after aqua regia leaching has found to be non-hazardous. However, several streams of wastewater and acid gas generated in the recovery process should be properly managed to avoid the secondary pollution.

Ferrite process (denoted by FP) has been used for treating the waste-liquid containing heavy metal for many years. Related researches have shown that this method could catch the heavy metal regulated by environmental law into the structure of spinel, and sludge from FP also conformed the standards of toxicity characteristic leaching procedure in EPA of Taiwan. On comparing with neutral precipitation of conventional method, spinel¡¦s sludge produced in FP had an ease separation of solid-liquid and no need of solidification in further treatment. These spinel, belonged to the magnetic material, could be used for applications such as brick of blinder guide, magnetic symbol, absorber of electric wave and adsorbent. Therefore, this method has a great potential for treating the waste containing heavy metal in laboratory. This study was to investigate the optima conditions in removal of heavy metal in waste liquid in laboratory by using the FP of conventional, two and three stage. All experiments, including one ion and ten ions heavy metal mixed in a solution, were conducted in a batch- type reactor for total concentration of 2000 mg/L heavy metals. The major parameters included temperature, ferric ion dosage, aeration intensity and pH. The performance of treatment in FP was judging by that the concentration of all heavy metals in filtered solution and the heavy metal containing in sediment sludge should be below the regulations of effluent standards and TCLP standards. In conventional one stage of FP experiments performed at constant temperature and pH, the residual concentration of heavy metals in filtered solution was below the effluent standards except of Cd and of Hg; in results of TCLP showed that higher dissolvion of Cd, Cu and Pb leached from sediment and the rest ions of heavy metal passed the regulations. Thus, we conducted individually for Cd, Cu and Pb to find the optimal conditions. The optimal pH of 7 and temperature above 70 ¢J for Cd and Pb and the optimal pH of 10 and temperature above 80 ¢J for Cu were obtained. They were be used for combination of process in various stage to achieve the goal of treatment performance. After the combination of two and three stage reactions, three stage reactions in series was the only selection in removal of ten heavy metals performed by FP. As a result, the sequences were in the following: (1) 70¢J, pH=9 (2) 90¢J, pH=9 (3) 80¢J, pH =10 , and the reaction period was 40 min for each stage.

One of the most toxic environmentally mobile compounds found in water is arsenic. It has been used as a pesticide to control insects, fungi, weeds and rodents since the early part of this century because of its high toxicity. Sorption of toxic metals onto a metal oxy-hydroxide is the most popular and practical arsenic removal method from contaminated water. Water treatment with oxy-hydroxides creates arsenic containing residuals, which are usually disposed of in landfills. To prevent leaching, stabilization of the solid residuals is required. It has been reported that calcium may inhibit arsenic desorption and/or benefit arsenic sorption. The objective of this investigation is to assess arsenic leaching in the presence of calcium and phosphate ions at extreme pH. Two hypotheses have been identified to explain the decrease in soluble arsenic in the presence of calcium. One explanation is that arsenic reacts with calcium to form calcium arsenic solids. The second hypothesis is that calcium affects the surface properties of the oxy-hydroxide solid in solution. Results show that calcium enhances the removal by iron oxides and prevents the leaching of arsenic from the residuals. Isotherm experiments show that arsenic adsorption can be described as occurring on nonporous powders or powders with pore diameters larger than micro-pores. Physically, with increase in adsorbate concentration, second and more layers are completed until saturation when the numbers of adsorbed layers becomes infinite. Further, experimental data were fitted to a Brunauer, Emmett and Teller isotherm (BET) model which assumes the initial layer can act as substrate for further adsorption. Finally, calcium-arsenic and calcium-phosphate solids were predicted to be formed by Visual MINTEQ modeling program. Nevertheless, from the x-ray diffraction output calcium-arsenic or calcium-phosphate solids were not identified. Because no calcium arsenate solids were found it was concluded that calcium affects the surface properties of the oxy-hydroxide solids in solution. Increasing the pH produces negative surface charge, which in turn increases repulsion between the negatively charged hydrated arsenate ions and the Fe(OH)3 surface. Calcium’s positive charge might neutralize this effect enhancing the sorption of arsenic onto the oxy-hydroxide. Also, it was concluded that the competition between arsenic and phosphate was reduced by the same mechanisms.

In recent years there has been growing interest in bio-mineral processing due to its low operating costs and its application in processing lean-grade ores. Bioprocessing is a good alternative to conventional hydrometallurgy process in mineral processing. In recent times microorganisms have been used as surface modifiers in processes such as froth flotation and flocculation. The surface properties of microbes and minerals such as zeta potential and surface hydrophobicity play a major role in determining adhesion of microorganisms to minerals and hence, the efficiency of flocculation and flotation. These properties also depend on solution conditions such as pH and ionic strength. Adhesion of microorganisms to mineral surfaces can alter the surface properties of the minerals. Such surface modification imparting hydrophobicity or hydrophilicity is used in flocculation and flotation of fine particles. In this research work the effect of ionic strength and pH in deteraiining the surface properties and hence adhesion of the bacterium Bacillus polymyxa to minerals such as hematite, quartz and coal has been studied in detail. The effect of the ionic strength and pH on the electrokinetics of the minerals and bacteria and its subsequent effect on adhesion and flocculation were investigated in detail. Contact angle measurements along with the zeta potential results were used to calculate the interaction energies between the mineral and the microorganism to establish a mechanism for the interaction. The following major conclusions can be drawn from this study. Results indicate that increase in the ionic strength significantly changes the zeta potential of hematite and bacteria without varying the isoelectric point. Increase in the ionic strength caused very little change in the zeta potential of quartz and coal. The adhesion of bacterial cells on to the minerals was found to be dependent on pH, ionic strength and conditioning time. Adhesion of bacterial cells was found to be more on hematite and coal when compared to quartz. The adsorption isotherms of Bacillus polymyxa cells with respect to all the three minerals were found to obey Langmuir isotherm. Flocculation studies demonstrated that the settling rate of hematite and coal was enhanced in presence of bacterial cells and electrolyte. However quartz settled much slower under the same conditions indicating that the quartz particles are being dispersed. Thus, selective flocculation of hematite and coal is possible which can be used in separating them from quartz effectively. The different components of total interaction energy arising from Lifshitz-van der Waal forces, acid/base forces and electrostatic forces were calculated using the van Oss approach. Calculation of the components of the acid base free energy showed that coal and hematite were hydrophobic compared to quartz and the bacterium. From total interaction energy calculation based on the extended DLVO theory, hematite and coal were found to have a net negative interaction energy in acidic pH values and hence attractive forces are predominant. Quartz was found to have a net repulsive energy at all the pH values at low ionic strengths but increase in ionic strength the interaction energy become attractive. The AGLW values of quartz was found to be attractive which is probably responsible for bacterial adhesion onto quartz.

<p>There are several incentives for using bottom ash from municipal solid waste incineration (MSWI bottom ash) as a construction material, such as for road construction. These incentives include decreased disposal of material on landfills and a reduced amount of raw material extracted for road building purposes. However, one of the main obstacles to utilising the material is uncertainties regarding its environmental properties. The overall objective of this thesis is to describe the potential environmental impacts of utilising MSWI bottom ash in constructions and to improve the tools for environmental assessments.</p><p>An environmental systems analysis (ESA) approach based on a life cycle perspective was outlined and used in a case study, with the aim of describing the differences in resource use and emissions that can be expected if crushed rock in the sub-base of a road in the Stockholm region in Sweden were to be substituted by MSWI bottom ash. The whole life cycle of the road was taken into account and the alternative disposal of the bottom ash was included. It was found that the studied alternatives would cause different types of potential environmental impact; whereas the conventional alternative with only crushed rock in the road’s sub-base would lead to larger use of energy and natural resources, the alternative with MSWI bottom ash in the sub-base would lead to larger contaminant leaching. It was concluded that a life cycle approach is needed in order to include both resource use and emissions in the comparison between the two alternative scenarios. The leaching of metals turned out to be the most important environmental aspect for the comparison and in particular the difference in copper (Cu) leaching was shown to be large.</p><p>However, a large amount of Cu may not pose an environmental threat if the Cu is strongly bound to dissolved organic carbon (DOC). In order to improve the basis for toxicity estimates and environmental risk assessments, and thereby provide better input values for ESAs, the speciation of Cu to DOC in MSWI bottom ash leachate was studied. It was found that Cu to a large extent was bound to DOC, which is consistent with previous research. The results also suggest that the hydrophilic fraction of the MSWI bottom ash DOC is important for Cu complexation and that the pH-dependence for Cu complexation to MSWI bottom ash DOC is smaller than for natural DOC. This implies that models calibrated for natural DOC may give inconsistent simulations of Cu-DOC complexation in MSWI bottom ash leachate.</p>