Onuralp Yucel

Silver Recovery from Waste Radiographic Films by Cementation and Reduction

Abstract Waste radiographic films can act as potential source materials for the recovery of valuable silver. In this study, a chemical processing scheme was adopted to recover silver metal from waste radiographic films. The films were dissolved in 1 M nitric acid (HNO3) solution for 3 hours at 70°C to convert silver into silver nitrate (AgNO3(aq)). Subsequently, the silver nitrate solution was treated using two different methods. The first involved cementation with fine iron powder and with fine zinc powder. These two well-known cementators were compared to each other with respect to purity of the final product and the recovery efficiency. The second method was sodium hydroxide (NaOH) precipitation. The treatment with Fe powder and Zn powder resulted in the formation of metallic silver powder in just one step. Ag2O obtained via NaOH precipitation was then treated using two different methods: a treatment with a mixture of glucose (C6H12O6) and NaOH to yield metallic silver and a heat treatment, in which Ag2O was converted to silver metal at 500°C. TGA analysis revealed that at 400°C Ag2O decomposes into silver and oxygen. With the exception of the powder produced by glucose reduction, all the powders would easily find industrial application. In addition, by using relatively inexpensive chemicals these applied processes show promise for further scaling up.

Production of 150 cm wide AZ31 magnesium sheet by twin roll casting

Abstract 150 cm wide AZ31 magnesium alloy sheet was produced by twin roll casting. The sheets of 6 mm thickness were cast. The sheet material was characterized using various techniques including metallography and XRD. The mechanical properties were investigated by tensile tests and hardness measurements. The procedures were developed for thermomechanical treatment of cast sheet material. The products of these procedures were characterized and the results were discussed for possible potential applications.

The preparation of ferroboron and ferrovanadium by aluminothermic reduction

The processes for the production of ferroboron and ferrovanadium from indigenous resources by open aluminothermic reduction have been described. The influence of process parameters such as charge composition, particle size, and the use of fluxes on the yield and composition of the ferroalloys obtained are discussed. In the case of ferroboron, it has been possible to obtain a recovery of 60% of boron as Fe-15B while restricting the residual aluminium content in the product to approximately 2% by using 90% of stoichiometric aluminium in the charge. In the case of ferrovanadium, it has been possible to achieve a recovery of 70% of vanadium as Fe-75V by using 5% excess aluminium in the charge, with the same percentage remaining as residual aluminium in the product.

The fabrication of boron carbide-aluminium composites by explosive consolidation

Abstract The technique of explosive consolidation was used to prepare cermets of boron carbide with aluminium and 7075 aluminium alloy. Compacts were produced by application of 10–12 GPa pressure which was induced by explosive detonation. The compacts obtained exhibit high hardness-increasing with an increase in the boron-carbide content, integrity and close to theorical density. Hardness, fracture toughness and flexural strengths of the composites produced indicate extensive shock hardening of the metal (or alloy) matrix during consolidation.

Spark plasma sintered Al2O3–YSZ–TiO2 composites: Processing, characterization and in vivo evaluation

Al2O3 and Al2O3-YSZ composites containing 3 and 5 wt.% TiO2 were prepared by spark plasma sintering at temperatures of 1350-1400°C for 300s under a pressure of 40 MPa. The grain growth of alumina was suppressed by the addition of YSZ. Al2O3-YSZ composites showed higher hardness than monolithic Al2O3. There was not a considerable difference in hardness values for Al2O3-YSZ composites containing 10 and 20 vol.% YSZ and the addition of TiO2 decreased the hardness of the composites. The fracture toughness of Al2O3 increased from 2.8 MPa·m(1/2) to 4.3 MPa·m(1/2) with the addition of 10vol.% YSZ, further addition resulted in higher fracture toughness values. The fracture toughness values were increased with TiO2 addition and the highest value of fracture toughness, 5.3 MPa·m(1/2), was achieved with the addition of 20 vol.% YSZ and 5 wt.% TiO2. Preliminary in vivo tests demonstrated the biocompatibility and osseointegration of the composites after 6 week post-implantation in femur of Wistar rats.

Platinum uptake from chloride solutions using biosorbents

Present work investigates platinum uptake from synthetically prepared, dilute platinum-bearing solutions using biomass residues, i.e. pistachio nut shell and rice husk, which are abundant in Turkey, and provides a comparison between these two biosorbents. Effects of the different uptake parameters, sorbent dosage, contact time, temperature and pH of solution on platinum uptake (%) were studied in detail on a batch sorption. Before the pistachio nut shell was activated, platinum uptake (%) was poor compared to the rice husk. However, after the pistachio nut shell was activated at 1000 °C under an argon atmosphere, the platinum uptake (%) increased two-fold. The pistachio nut shell (original and activated) and rice husk were shown to be better than commercially available activated carbon in terms of adsorption capacity. These two sorbents have also been characterized by FTIR and SEM. Adsorption equilibrium data best complied with the Langmuir isotherm model. Maximum adsorption capacities, Qmax, at 25 °C were found to be 38.31 and 42.02 mg.g - 1for the activated pistachio nut shell and rice husk, respectively. Thermodynamic calculations using the measured ∆H°, ∆S° and ∆G° values indicate that the uptake process was spontaneous and endothermic. The experimental data were shown to be fit the pseudo-second-order kinetic model.

Preparation and Characterization of UV-Cured Hybrid Polyvinyl Alcohol Nanofiber Membranes by Electrospinning

/N=N nanofiber membranes were synthesized. These membranes were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric-differential thermal analysis, and Brunauer–Emmett–Teller analysis. According to results, fine polymeric nanofibers were obtained in the size range of 100-200 nm for pure PVA nanofibers and 150-250 nm for PVA/SiO

Determination of the Optimum NiS Fire Assay Parameters for Pt, Pd, and Rh in Automotive Exhaust Catalytic Converters

This work investigates the performance of the nickel sulfide fire assay (NiS-FA) for the pyrometallurgical analysis of platinum group elements (PGEs) from mixtures of automotive exhaust catalytic converters (e.g., gasoline, diesel, and diesel particular filter) by assessing the effects of various flux materials and reaction parameters on platinum, palladium, and rhodium recovery. Inductively coupled plasma mass spectrometry and atomic absorption spectroscopy (AAS) are used for the analysis of the NiS-FA beads. We found that the optimum recovery (at least 99.0%) was achieved with reaction of 11.5 g of flux (0.53 w/w ratio, sodium tetraborate:sodium carbonate), 1 g nickel, and 0.84 g sulfur (1.2 w/w ratio, Ni:S) per gram of sample for 90 min at 975°C. Reference standards (NIST SRM 2557) were used to compare efficiencies and identify the optimum conditions. The results are consistent with certified values and PGEs could be recovered within the 95% confidence level. The precision (<4.0% RSD) of all measurements, expressed as percentage relative standard deviation (SD), ranged up to 3.0%.

SORPTION OF GOLD FROM ELECTRONIC WASTE SOLUTIONS BY A COMMERCIAL SORBENT

In this work, sorption of gold from electronic waste solutions using a commercial sorbent, Lewatit TP 214, was investigated. The effects of the different parameters on gold sorption (%) were studied in detail. Sorbent dosage, contact time, temperature, and solution pH were selected as sorption parameters. Additionally, the gold sorption by Lewatit TP 214 is a diffusion-controlled process with activation energies of 12.28 kJ/mol. The thermodynamic values such as ΔG°, ΔH°, and ΔS° were calculated by experimentally obtained results. The reaction was spontaneous and endothermic. The gold sorption capacity for the sorbent was 100.1 mg gold per gram. XRD patterns revealed that the gold was in its metallic form. The results indicated that Lewatit TP 214 can be effectively used for the sorption of gold from waste solution.

Carbothermal recovery of zinc from brass ash

Abstract Brass ash of composition (wt-%) 59·67Zn-9·22Cu-1·45Pb-2·61SiO2-0·36Cl was treated by carbothermal reduction in a temperature controlled tube furnace. The aim of the work was to collect zinc in the form of metal and/or zinc oxide in the gaseous phase. Treatment temperature (950-1200°C) and time (15-180 min) were varied. At 1200°C and 60 min, recovery of zinc was 92·5% and zinc content in the remaining residue was found to be 12·8 wt-%. Kinetic analysis of the experimental results showed that initially the reaction was under chemical control with an activation energy of 90·1 kJ mol-1. Subsequently the development of a sintering structure caused the reaction mechanism to change to diffusion control.