The Effects of Milling and pH on Co, Ni, Zn and Cu Bioleaching from Polymetallic Sulfide Concentrate

Acid bioleaching of a low-grade and polymetallic sulfide concentrate was studied, in order to determine suitable feed material particle size and pH for efficient leaching of valuable metals. The sulfide concentrate consisted of pyrite (50 wt %), pyrrhotite (31 wt %), quartz (10 wt %) and lower amounts of cobalt, nickel, zinc and copper (each <1 wt %). After adaptation of microorganisms in shake flasks, stirred tank tests were conducted at different pH levels and supplementing feed material at different particle sizes (milled to d80 < 150 µm, <50 µm, <28 µm, <19 µm). The operation at pH 1.8 was seen prone to iron precipitation, while this was not observed at a pH between 1.3 and 1.5. Additional milling to decrease particle size from the initial d80 < 150 µm had a major positive effect on cobalt- and nickel-leaching yields, proposing that at least d80 < 28 µm should be targeted. The best leaching yields for the main economic elements, cobalt and nickel, were 98% and 94%, respectively, reached with d80 < 19 µm at pH 1.3. However, it was considered that at pH 1.5, similar results could be obtained. This research sets the basis for continuing the experiments at a continuous pilot scale.

Preparation and Characterization of Nimesulide Nanoparticles For Dissolution Improvement

Nimesulide is one of the types of non-steroidal anti-inflammatory drugs, widely used as analgesic and antipyretic. It is classified as class II drugs according to BCS guidance because of low solubility in water that leads to decrease in dissolution rate. So, the objective of this study was to decrease particle size, increase solubility and dissolution rate of nimesulide by preparation of nimesulide nanoparticles using solvent/antisolvent precipitation method by addition of organic solution of drug onto the solution of stabilizer. The size of nimesulide nanoparticles were studied and considered by particle size analyzer, drug content and loading efficiency. The freeze-dried nanoparticles were characterized by field emission electron microscope, X-Ray powder diffraction, differential scanning calorimetry and saturated solubility measurement. Tablet was manufactured by direct compression. The tablets were evaluated for drug release to measure the effect of nanoparticles on the dissolution improvement of drug.

Surface Modification of TiO2 Nanoparticles by Grafting with Silane Coupling Agent

Titanium dioxide (TiO2) possesses excellent photocatalytic activity and provides UV protection for polymeric materials. The nanosized TiO2 particles with larger surface area to volume ratio and an increased surface reactivity shall impart better photocatalysis and UV protection efficiency to the rubber compounds, compared to the use of conventional micron-sized particles. Direct incorporation of TiO2 nanoparticles (n-TiO2) into non-polar rubbers faces incompatibility problem between the two phases. One of the solutions to overcome this problem is to treat the nanoparticle surface by using silane coupling agent such as bis-(3-triethoxysilylpropyl) tetrasulfide (TESPT). This work prepared n-TiO2 from commercial micron sized-TiO2 by ultrasonication technique. Particle size of TiO2 was measured by laser light scattering particle size analyzer. The morphology of TiO2 nanoparticles was characterized by field emission scanning electron microscope (FESEM). The grafting reaction of silane on TiO2 nanoparticles surface was studied at varying reaction temperatures and times. The purified grafted materials were characterized by energy dispersive X-ray analysis (EDX), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). The characterization data confirm a presence of grafted silane on the TiO2 nanoparticles surface. The result shows that ultrasonication technique can effectively decrease particle size and the grafting reaction of silane coupling agent onto TiO2 nanoparticles can be successfully carried out at 140°C for 8 h.

Hydrogen Generation of Al-La-Bi Alloy in Aqueous Inorganic Salt Solutions

A method for obtaining hydrogen from Al-La-Bi alloy in different solutions was investigated for the production of inexpensive, pure, and safe hydrogen for micro-fuel cells. The hydrogen generation amount and rate could be regulated by changing composition design or salt solutions. Combined with X-ray diffraction (XRD), scanning electron microscopy (SEM) and hydrogen generation experiments, the hydrolysis byproduct La(OH)3 and inorganic salt solution stimulated the hydrolysis reaction of Al-La-Bi alloy and water, which was mostly based on micro galvanic cell between Al and Bi in the previous work. Increasing La content led to decrease particle size in the milling process which led to large special surface area and contact area of aluminum and water. Using inorganic salt solution such as Na2SnO3 solution might produce metal Sn which covered on Al surface and functioned as a cathode of a micro galvanic cell. The Al-13 wt%La-10 wt%Bi alloy yielded 1113 ml/g hydrogen with 100 % efficiency with 60 min at 343 K.

Sonochemical Synthesis and Characterization of Hydroxyapatite Nanoparticles

Hydroxyapatite (HA) is a bioactive ceramic, employed mainly in bone tissue engineering since it exhibits superior biocompatibility and osteoconductivity. Attempts have been made to synthesize HA nanoparticles with chemical composition, morphology, crystallinity and Ca/P ratio similar to that of natural bone. While wet chemical methods are becoming more popular for synthesis of HA nanoparticles, ultrasound irradiation has shown to be an effective method to increase the rate of production and also to decrease particle size. However, process variables must be carefully selected. In the present study, HA nanoparticles with desirable characteristics have been synthesized by the aid of ultrasound irradiation and characterized by powder X-ray diffraction (XRD) and electron microscopy techniques.

A Literature Review of Ultrasound Technology and Its Application in Wastewater Disinfection

In recent years, there has been an increase in the application of ultraviolet (UV) light as an alternative to chemical disinfection technologies. However, in the case of poor quality effluents, the practical limit of UV disinfection of wastewater is dictated by disinfection-resistant, particle-associated bacteria. Although these particles may be removed by filtration, an alternative method to reduce the impact of suspended particles on disinfection efficiency is to decrease particle size using ultrasound technology. Mechanical forces exerted on particles due to the collapse of cavitation bubbles created by sonication break suspended particles into small fragments. In this paper, a critical review of ultrasound application for wastewater treatment is presented with emphasis on disinfection. Much of the work in this area remains at the laboratory scale. As a result, there is a need for fundamental information regarding the effect of sonication on the kinetics of disinfection and interaction of ultrasound with suspended particles. Such information is necessary for process engineering, design, and scale-up of ultrasound systems.