Showing papers in "Particulate Science and Technology in 2013"

Organic Solar Cells: A Review of Materials, Limitations, and Possibilities for Improvement

Abstract: Significant attention has been given during the last few years to overcome technological and material barriers in order to develop organic photovoltaic devices (OPVs) with comparable cost efficiency similar to the inorganic photovoltaics (PVs) and to make them commercially viable. To take advantage of the low cost for such devices, major improvements are necessary which include: an efficiency of around 10%, high stability from degradation under real-world conditions, novel optically active materials, and development of novel fabrication approaches. In order to meet such stringent requirements, the research and development in OPVs need to improve upon the short diffusion length of excitons, which is one of the factors that are responsible for their low power conversion efficiency. This review discusses some of the most significant technological developments that were presented in the literature and helped improve photovoltaic performance, such as tandem architectures, plasmonics, and use of graphitic nanos...

Effect of Nano Hexagonal Boron Nitride Lubricant Additives on the Friction and Wear Properties of AISI 4140 Steel

Abstract: The aim of this study was to investigate the effects of nano hexagonal boron nitride(hBN) particles on the friction and wear properties of AISI 4140 steel material when the hBN particles are used as an oil additive. Nano hexagonal boron nitride powders, which were produced using a special process, were dispersed in engine oil (SAE10 W) to enhance lubrication. The amount of nano hexagonal boron nitride in the engine oil was varied from 0 to 10% by volume, and four different lubricant samples were prepared. Wear tests were conducted using ball-on-disc geometry. The worn surfaces of substrates were analyzed using scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). The experiments showed that the nano hexagonal boron nitride particles that were used as an oil additive affected the friction and wear behavior. A 14.4% improvement in the friction coefficient and a 65% decrease in the wear rate were achieved through the use of the nano hBN as an oil additive.

Air Dense Medium Fluidized Bed for Dry Beneficiation of Coal: Technological Challenges for Future

Abstract: Air dense medium fluidized bed (ADMFB) offers a better alternative approach for dry coal beneficiation. In recent years, there has been a rapid advancement in the understanding of fluidized bed behavior and a great deal of work has been done to make this process competitive with conventional wet beneficiation processes. At the same time, much information is available in the general technical literature concerning various aspects of ADMFB; however, this is often uncoordinated information and widely dispersed. So, it is necessary to provide the adequate information systematically, which offers researchers an effective and easy way to obtain specific details. This review critically evaluates the understanding of different operating parameters that affect the cleaning performance of this equipment. Then, following the discussion of different operating parameters, we describe three recent practical developments in ADMFB: the dual-density fluidized bed, vibrated fluidized bed, and magnetically stabilized fluidi...

Physical Properties for Flow Characterization of Ground Biomass from Douglas Fir Wood

Abstract: The particle size distribution and packing (loose bulk and tapped density) of a mixture of ground biomass from Douglas fir wood particles was characterized by different practical methods: sieving, digital imaging and scanning electron microscopy. The ground mixture was analyzed using a set of 14 wire mesh sieves. The calculated mean diameter of mixture was 251 µm. The mixture was divided into four size fractions of mean size ranging from 74 to 781 µm. Particle length measured by imaging technique were 3–4 times larger than the mean diameter determined by sieve analysis. Similarly, particle width was 1.0–2.5 times larger than mean particle diameter. The sphericity of particles in each of the four fractions increased with decreasing size of the sieve indicating that smaller particles also have a smaller aspect ratio. Empirical power law equations were developed to correlate the packing and flow ability of ground particles (HR) to the mean diameter, with R2 values of 0.88 and 0.91, respectively. The HR value...

Deformation and Mechanical Characteristics of Compacted Binary Mixtures of Plastic (Microcrystalline Cellulose), Elastic (Sodium Starch Glycolate), and Brittle (Lactose Monohydrate) Pharmaceutical Excipients

Abstract: This work studies the tensile strength, coherence, elastic, and plastic energy of single and bi-component compacted tablets consisting of (i) microcrystalline cellulose (MCC) PH 102 as a plastic material, (ii) (SSG) as an elastic material, and (iii) alpha lactose monohydrate as a brittle material by direct compression Compacted tablets were studied with various mass ratios formed at an ultimate compaction stress of 150 MPa The loading and unloading stages of the compaction process for the single and binary tablets were evaluated based on the energies derived from the force-displacement data obtained The resulting tablet quality was measured in terms of the tensile strength Material that exhibit predominantly plastic deformation (MCC) shows a dominant property over elastically deforming sodium starch glycolate (SSG) and brittle (lactose) materials during the loading and unloading stages of the compaction process In conclusion, the tensile strength of the formed tablets depends directly on the plastic

Synthesis of Bismuth Oxide Nanoparticles by Solution Combustion Method

Abstract: In this article, nano-Bi2O3 powder was synthesized by the solution combustion synthesis method using bismuth nitrate as oxidant and citric acid as fuel. The investigation was focused on the effect of calcination temperature on the size of nano-Bi2O3, phase transformation, and morphology. The β-Bi2O3 powder was synthesized at 300°C for 2 h and characterized by SEM, TEM, XRD, and TG-DTA. Bi2O3 nanoparticles as small as 10.7 nm were formed using 0.005 mol citric acid as the fuels and 0.04 g PEG-20000 as the dispersant.

Characterization of Biogenic Silica Generated by Thermo Chemical Treatment of Rice Husk

Abstract: This study presents two routes to produce amorphous silica from an Egyptian rice husk under conditions optimized for least environmental impact and low cost. The first route includes thoroughly washing of the husk sample with water, dry milling and leaching with citric acid. The leaching process was applied in two stages, that is, at 323 K for 180 min and then at 353 K for 60 min. After washing and drying, the leached sample was subjected to a heat treatment in a muffles furnace at four sequential steps. The second route includes all the previously mentioned steps, except the citric acid leaching. The final products were characterized using x-ray fluorescence analysis, carbon content analysis, x-ray diffraction, differential thermal analysis, nitrogen adsorption, mercury intrusion, and scanning electron microscopy. The results show that the citric acid leaching has many advantages with respect to silica yield and porosity as well.

Synthesis and Characterization of CuCl Nanoparticles in Deep Eutectic Solvents

Abstract: In the present work, CuCl nanoparticles were fabricated in deep eutectic solvents (DES) which is a new kind of ionic liquid with special properties. The as-prepared samples were characterized by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The effect of polyvinylpyrrolidone (PVP), the molar ratio of ascorbic acid to copper chloride and the mixing method were investigated. The optimized reaction conditions were as follows: reaction time is 1 h, reaction temperature is 25°C in the presence of PVP in deep DES. Under the optimum conditions, CuCl nanoparticles with the average size about 50 nm could be successfully prepared in DES.

Grinding of Coriander Seeds: Modeling of Particle Size Distribution and Energy Studies

Abstract: Coriander seeds were ground in an impact type hammer mill and a pin mill to study the pattern of particle size distribution and their relationship with energy consumption. The particle size distribution for all samples was best described by the Rosin-Rammler-Bennett (RRB) and model with high degree of correlation coefficient compared to the Gaudin-Shumann (GS) model and Log-normal function. Particle size distribution was also characterized by various size parameters such as: uniformity index, size range variation coefficient, mass relative span, skewness, kurtosis, size guide number, coefficient of uniformity, and the coefficient of gradation and geometric standard deviation. Energy consumption for grinding was studied based on classical grinding laws, namely, Bond's, Rittenger's and Kick's law. Bond's Work index varied from 0.5 to 4.3 kJ kg−1 depending on the size reduction ratio. Energy consumption followed a linear relationship with size reduction ratio.

Prediction of Concentration Distribution in Pipeline Flow of Highly Concentrated Slurry

Abstract: The Kaushal and Tomita's (2002a) model, which has already been found satisfactory for broadly graded multisized particulate zinc tailings slurry with moderate concentration up to 26%, flow velocity up to 3.5 m/s in 105 mm diameter pipe, mean diameter 140 μm, and geometric standard deviation of particles of 4.0, is tested for concentration distribution data collected by Kaushal et al. (2005) on two sizes of glass beads, of which mean diameter and geometric standard deviation are 440 μm and 1.2, and 125 μm and 1.15, respectively, with concentration up to 50% and flow velocity up to 5 m/s in 54.9 mm diameter pipe. Kaushal and Tomita's (2002a) model gives more asymmetric concentration distributions. A modified model is proposed by alleviating some of the restrictive assumptions used in the existing model. Comparison of experimental data by Kaushal et al. (2005), Gillies and Shook (1994), and Matousek (2009) with the proposed model is satisfactory.

Investigation of Grain Size Effects on Micro/Macro-Mechanical Properties of Intact Rock Using Voronoi Element—Discrete Element Method Approach

Abstract: The effects of grains and sampling sizes on macro/micro-mechanical properties and the representative elementary volume of intact rocks were determined using a Voronoi element-discrete element method approach. Voronoi element was used for generation of grain assembles of rock matrices and the discrete element method was used as the numerical tool. Micro-mechanical parameters of Voronoi models were determined using back-calculation techniques through numerical calibrations. A series of two dimensional Voronoi element with different grain size distributions for calcite based marble intact rocks of Neiriz and Baghat from two quarries in Iran with varying model sizes were generated and numerical uniaxial compression tests were performed to calculate the equivalent macro-mechanical properties of intact rocks using the universal distinct element code. The results show high size-dependency of mechanical properties of intact rocks. The side lengths of 10 cm and 6 cm were determined as the representative elementary...

Optimization of Amorphous Silica Nanoparticles Synthesis from Rice Straw Ash Using Design of Experiments Technique

Abstract: In this study, a chemical method of dissolution-precipitation was applied to produce amorphous silica nanoparticles from rice straw ash (RSA; the waste material of rice cultivation. The morphology,...

Column versus Mechanical Flotation for Calcareous Phosphate Fines Upgrading

Abstract: Froth flotation, either conventional or column, has been studied for phosphate upgrading In this study, a reverse flotation scheme using either mechanical or column flotation was applied for the beneficiation of Al-Jalamid Saudi phosphate ores It is classified as a sedimentary phosphate with calcite as main impurity (calcareous type) The effects of different operating parameters were evaluated for both conventional and column flotation A mixture of oleic acid and kerosene is used as a collector, sulfuric acid as pH regulator and sodium sulfate as phosphate depressant The results of this study revealed that both conventional and column flotation technology can be adopted for this type of ore A high grade concentrate of 35% P2O5 can be achieved at a high recovery of 95% Comparing the results of the both techniques indicates the superiority of column at fine sizes However, the mechanical cells are more suitable at high solid liquid ratios because of good particle dispersion and good mixing in the mec

Porous c.p. Titanium Using Dextrin as Space Holder for Endosseous Implants

Abstract: Porous structures are advantageous alternatives to bulk titanium for endosseous implants because the elastic modulus can be adjusted to match that of bone, preventing bone retraction. Porous titanium scaffolds were developed using corn starch dextrin powder with increased granularity to obtain larger pores. Titanium and dextrin powder mixtures in different proportions (15, 25, 35 and 40% dextrin) were die-pressed and sintered under high vacuum. The porosity of the implants was between 21.80 and 37.79%. The surface of porous titanium was characterized by SEM analysis that showed presence of pore sizes over 100 µm for all compacts, except those with 15% dextrin. For samples with 35 and 40% dextrin, the size of pores reached 200–250 µm. X-ray diffraction analysis of titanium samples revealed presence of TiOCN compound with progressive increase with dextrin content. Mechanical characteristics were investigated by compression tests. Osteoblasts adhesion and proliferation was determined by MTT assay and scannin...

Analytical Model for Pipe Wall Friction of Pseudo-Homogenous Sand Slurries

Abstract: In pseudo-homogenous pipeline flow of sand-water mixtures the measured hydraulic resistance is higher than for the flow of water, but is less than for a liquid having the same density as the mixture but a viscosity equal to that of water. A new analytical model is devised for pipe wall friction in which there is a watery viscous sublayer along the pipe wall. It is assumed that the presence of solids does not affect the viscous properties of the mixture, and that grain-stresses are negligible. A satisfying result is obtained in a particle range of 0.1 to 2 mm median grain diameter and volumetric concentrations up to about 30%. It is found that the model describes a lower bound for hydraulic resistance. The theoretical concept can be used as a basis for further developments into the heterogeneous regime, where additional physical processes come into play.

New Composite Bone Cement Based on Hydroxyapatite and Nanosilver

Abstract: Although total joint replacement surgery has become common in recent years, problems due to bacterial infection remain a significant complication following this procedure. One approach in our study was to obtain a self-cured bone cement based on hydroxyapatite with nanosilver (Hap-Ag) and ZrO2 and polymer matrix based on 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)-phenyl]propane/triethyleneglycol dimethacrylate. New materials were tested for: in vitro silver release, compressive strength (CS), compressive modulus (CM), and radiopacity. In vitro silver release increased in time and depended of silver content in cement. The highest silver release was registered for the cement with 1.26 wt% silver content. The results reveal that the CS for bone cement was between 133.37 and 146.70 MPa and CM was between 1.68 and 1.82 GPa (p > 0.05). A slow increasing of CM was registered for samples with 1.5/1 powder/liquid ratio. Addition of nanosilver and ZrO2 increased radiopacity of experimental bone cement.

Kinetics studies of adsorption and desorption of South African fly ash for some phenolic compounds

Abstract: The extent of adsorbability and desorbability of an unclassified South African coal fly ash (SACFA) from the Lethabo power plant was evaluated in the treatment of phenol, 2-nitrophenol, and 4-nitrophenol from aqueous solutions. Batch studies were performed to evaluate the effects of various experimental parameters such as adsorbent dosage, initial pH (pHo), and contact time on the removal of these three adsorbates. The adsorption isotherm indicates that the Freundlich model correctly fits the experimental data for the adsorbates better than the Langmuir model, with fly ash having the highest adsorption capacity of 6.51 × 10−2 mg/g for 4-nitrophenol, 2-nitrophenol 6.00 × 10−2 mg/g, and phenol 6.31 × 10−2 mg/g. SACFA was found to adsorb 90.2% of phenol, 88.9% of 2-nitrophenol, and 92.6% of 4-nitrophenol at an initial concentration of 20 mg/l. The desorption of the adsorbates from the surface of the fly ash was achieved using 30 ml of distilled water at 307 K. The analyses of the results obtained revealed th...

Modeling and Analysis of Solids Friction Factor for Fluidized Dense Phase Pneumatic Conveying of Powders

Abstract: Pressure drop in pneumatic conveying is due to frictional interaction among gas, particle, and pipe wall. Fictional forces due to solids can be calculated using a solids friction factor. Many correlations have been proposed for predicting solids friction factor in dilute phase pneumatic conveying. These correlations are calculated based on value of the parameters calculated for a long pipeline or value of the parameter at the inlet of the pipeline. Pneumatic conveying in long pipelines suggests that some of the flow parameters are not constant along the length of the pipeline. This article presents a modeling technique for predicting solid friction factor taking into account of the local value of flow parameter. In this method, the solids friction factor is presented in terms of coefficient and exponents. The values of coefficient and exponents are predicted for fluidized dense phase conveying using different types of conveying materials. Values of coefficient and exponents are found to be different for d...

Particle Size Distribution of Top-Hole Drill Cuttings from Norwegian Sea Area Offshore Wells

Abstract: Measurement of top-hole drill cuttings particle size distribution in offshore drilling from floating rigs is not straightforward because these sections are drilled without a marine riser. In two drilling operations, a riserless mud return system was used, which made it possible to measure the particle size distribution. Still, because of the reactivity between loose shale and water, such measurements are not simple. A measurement method was developed in the field during the drilling of these two wells. The development of this method is described to assist and simplify similar measurements in the future. Likewise, the results are presented to allow scientist to use proper particle size distributions in offshore cuttings spreading analyses.

A New Approach for Calculating the Mass Flow Rate of Entrained Air in a Freefalling Material Stream

Abstract: This article presents the outcomes from a series of physical experiments to measure the air entrainment rates encountered within a stream of freefalling particles. The experimental work presented spans a range of particle parameters and hopper geometries. From these results a new theory for the prediction of air entrainment is developed and presented. This new method was developed specifically to facilitate a better understanding in the area of fugitive dust control associated with material handling systems, which are driven by the air entrainment during freefalling. From the work presented in this article, a better prediction capability of freefalling bulk materials in either constrained, or unconstrained systems, will allow for the optimization of either passive or active dust control strategies. This article presents several distinct sections that detail the experimental work used to determine the freefall stream parameters that were conducted to allow the development of the entrainment equations.

Effects of Mill Speed on Kinetic Breakage Parameters of Four Different Particulate Pumices

Abstract: In this study, the effect of mill speed was investigated on different particulate pumice samples at batch grinding conditions based on a kinetic model For this purpose, S i and B i,j equations were determined from the size distributions at different grinding times, and the model parameters (S i , a T , α, γ, and φ j ) were compared for three different mill speed (fraction of mill critical speed; 65%, 75%, and 85%) The effect of fraction of mill critical speed (φc) on the grinding for model parameter a T found to be different for four different pumices Additionally, in this study it was found that optimum grinding occurs at φc = 85% for all pumice samples, in contrast to the 75% of critical speed of the ball mill

Effect of SiC Nanoparticles Content and Mg Addition on the Characteristics of Al/SiC Composite Powders Produced via In Situ Powder Metallurgy Method

Abstract: In the present study, the effect of the nanosized SiC particles loading and Mg addition on the characteristics of Al/SiC composite powders produced via a relatively new method called “in situ powder metallurgy” (IPM) was investigated Specified amounts of SiC particles (within a size range of 250 to 600 µm) together with SiC nanoparticles (average size of 60 nm) were preheated and added to aluminum melt This mixture was stirred via an impeller at a certain temperature for a predetermined time The liquid droplets created by this process were then subsequently cooled in air and screened through 250 µm sieve to separate micron-sized SiC particles from solidified aluminium powder particles containing nanosized SiC particles Results of SEM and TEM studies together with microhardness measurements revealed that the commercially pure (CP) Al could not embed as-received SiC particles However, the nanosized particles were distributed uniformly in the Al-1 wt% Mg powders The process yield and microhardness of t

Controlling Conformational Transition of Silk Fibroin Microspheres by Water Vapor for Controlled Release Drug Delivery

Abstract: In the present study, preparation of silk fibroin (SF) microspheres with controllable conformational transition by water-vapor treatment for drug delivery was investigated. The SF microspheres with and without drug encapsulation were prepared by a water-in-oil emulsion solvent diffusion method. Average sizes of drug-free and drug-loaded SF microspheres were 158 and 167 µm, respectively, as measured by light scattering analysis. They were spherical shape and smooth surface with high drug loading efficiency (83%). The water-vapor treatment with 90% relative humidity at ambient temperature induced SF conformational transition from random coil to β-sheet form. Dissolution of the SF microspheres decreased as the treatment time increased. In vitro release of blue dextran model drug from the SF microspheres depends on the treatment time. It is considered that these water-vapor-treated SF microspheres have the potential to be developed further as drug delivery systems.

Integrated Population Balance Model Development and Validation of a Granulation Process

Abstract: This study is concerned with the development of an integrated three-dimensional population balance model (PBM) that describes the combined effect of key granulation mechanisms that occur during the course of a granulation process. Results demonstrate the importance of simulating the different mechanisms within a population balance model framework to elucidate realistic granulation dynamics. The incorporation of liquid addition in the model also aids in demarcating the dynamics in different regimes such as premixing, granulation (during liquid addition) and wet massing (after liquid addition). For the first time, the effect of primary particle size distributions and mode of binder addition on key granule properties was studied using an integrated PBM. Experimental data confirms the validity of the overall model as compared to traditional models in the literature that do not integrate the different granulation mechanisms.

Experimental Evidence of Mixture Segregation by Particle Size Distribution

Abstract: In this study, we discuss experimental segregation results obtained for two industrial cases, namely, ammonium perchlorate and a polymeric resin. These results show a segregation effect due to particle size distribution rather than particle size itself. We used a heap-pouring device as a tester, for which a visual knowledge of the segregation state was observed. The analysis of segregation is based on various coefficients of variations related to the size fractions or particle size distribution's global characteristics, indicating heterogeneities in the heaps formed. Both cases indicate that wide particle size distributions, as opposed to narrow ones, are limiting segregation risks. This collective, and maybe astonishing, effect is extremely marked for the cases studied, and demonstrates again the mesoscopic nature of granular media.

Predicting Transition Velocities from Bubbling to Turbulent Fluidization by S-Statistics on Vibration Signals

Abstract: Vibration signatures as the representatives of the fluidized bed nonlinear hydrodynamics were measured in a lab-scale fluidized bed of sand particles operated at ambient conditions. The experiments were carried out for three particle sizes, different velocities, and three probe heights. The S-statistic method was applied to the vibration signatures for the chaotic attractor comparison. The measured signatures of two different consecutive velocities in similar conditions were compared based on null hypothesis that they have same origin. According to this method, when the value of S is larger than 3, the null hypothesis is rejected with the confidence level of 95% indicating that the two signals are originated from different hydrodynamics. The results are compared with results obtained from common statistical methods and it is shown that attractor comparison can be a reliable method for detecting regime transition velocity.

Gravity Separation of Silica Sands for Value Addition

Abstract: A representative white sand sample was investigated for glass industry. Complete characterization of the sample was conducted. Chemical analysis of the sample showed that iron and alumina oxides reached 0.046% and 0.044%, respectively. Dry sieving was carried out to reject +0.6 mm and −0.10 mm fractions from the sample. The classified −0.6 + 0.1 mm product was directed to attrition scrubbing. The effect of pulp density, attrition impeller speed, attrition time and mode were studied. The attrition sand product was further subjected to gravity separation using “Wilfley” shaking table. Different working conditions of table separation i.e., sand feeding rate, stroke length, deck inclination, and dressing water flow rate were optimized. Results showed that the classified −0.6 + 0.106 mm sand product contained 0.039% Fe2O3 and 0.041% Al2O3 matched the specifications for the fourth-quality sand for sheet and plate glass industry. However, iron and alumina oxides contents were further decreased to 0.025% and 0.01...

Influence of Material Moisture on the Tribocharging Process of Plastic Granules

Abstract: The control of the triboelectrification factors is the key for a successful application of electrostatic separation to the recycling of mixed plastics waste. This article focuses on the influence of material moisture on the tribocharging process of three granular materials: polyamide (PA), polyvinyl chloride (PVC), and polyethylene terephthalate (PET). Different values of moisture content were obtained by immersing the material in water or drying it in a laboratory oven. Afterward, the granular material was tribocharged on the tray of a vibratory feeder and the accumulated charge was measured by an electrometer. The maximum charge/mass ratio was obtained for the three plastic materials at different values of moisture content: 0.27% for PA, 0.12% for PET 0.1% for PVC. Series of 5 consecutive tribocharging experiments performed on the same sample, show that the first contributes with the greater amount of granules charge while the other four only slightly increment this value. The graphical representation o...

Investigating Straight-Pipe Pneumatic Conveying Characteristics for Fluidized Dense-Phase Pneumatic Conveying

Abstract: This article presents results from an investigation into the pneumatic conveying characteristics (PCC) for horizontal straight-pipe sections for fluidized dense-phase pneumatic conveying of powders. Two fine powders (median particle diameter: 30 and 55 µm; particle density: 2300 and 1600 kg m−3; loose-poured bulk density: 700 and 620 kg m−3) were conveyed through 69 mm I.D. × 168 m, 69 mm I.D. × 148 m, 105 mm I.D. × 168 m and 69 mm I.D. × 554 m pipelines for a wide range of air and solids flow rates. Straight-pipe pneumatic conveying characteristics obtained from two sets of pressure tappings installed at two different locations in each pipeline have shown that the trends and relatively magnitudes of the pressure drops can be significantly different depending on product, pipeline diameter and length and location of tapping point in the pipeline (indicating a possible change in transport mechanism along the flow direction). The corresponding models for solids friction factor were also found to be different...

Parametric Effects on Leaching Behavior of Nickel-Copper Matte in Ammonia

Abstract: Leaching, which is described as the extraction of soluble constituents from a solid by means of a solvent, is an important separation technique in the refining of precious metals from their matte. It is, therefore, important to investigate the extraction behavior of metals from the matte, which is the focus of this study. This study reports the influence of concentration of the solvent (ammonia), leaching temperature, leaching time, and pH on the recovery of nickel and copper from the matte. The elemental composition analysis of the matte indicated that it contains 23% copper, 37% nickel and 1.1% ferrous compound. The analysis also showed that the major mineral phases present in the matte were heazlewoodite (Ni3S2), chalcocite (Cu2S), djurleite (Cu1.9S), and nickel alloy. The leaching parameters studied were concentration of ammonia (1.5, 2.0, 2.5, and 3.0 M), leaching time (0–270 min, at 15 min sampling interval), leaching temperatures (50°C, 60°C, and 70°C), and pH (9.3–11.2). The results obtained revea...