The use of sulphuric acid-carbonization products of sugar beet pulp in Cr(VI) removal

A carbon rich adsorbent prepared from the reaction of sugar beet pulp with sulphuric acid and gas formed during carbonization process have been studied for Cr(VI) removal from aqueous solutions. The SO(2) rich gas was shown to be an excellent Cr(VI) reductant. The equilibrium and kinetic studies were conducted by using the carbonaceous adsorbent derived from sugar beet pulp. The lower pH favoured Cr(VI) adsorption but substantial Cr(VI) reduction was observed. The Langmuir and Freundlich isotherm models were applied and the Langmuir model best fit the equilibrium isotherm data. The maximum adsorption capacity of chromium calculated from Langmuir isotherm is about 24 mgg(-1) for 25 degrees C. The adsorption of Cr(VI) is an endothermic process and follows the pseudo-second-order rate kinetics. The sulphuric acid-carbonization is an economical method for particularly chromium removal because the gas generated during carbonization exhibits good Cr(VI) reduction properties and carbonaceous material obtained is an efficient Cr(VI) adsorbent.     

Leaching of Chalcopyrite Concentrate with Hydrogen Peroxide and Sulfuric Acid in an Autoclave System

In this study, leaching of chalcopyrite concentrate was investigated in an autoclave system using hydrogen peroxide and sulfuric acid. By decomposition of hydrogen peroxide, the active oxygen formed can provide both high oxidation potential and high pressure in a closed vessel for leaching. Preliminary studies showed that hydrogen peroxide can be used as an oxidant instead of oxygen gas in the autoclave. Central composite design (CCD) was used to examine the effects of the experimental parameters on the copper and iron extraction as a response. The proposed model equation using CCD showed good agreement with experimental data, the correlation coefficients R ² for copper and iron being 0.84 and 0.86, respectively. The optimum conditions to obtain the main goal of maximum copper and minimum iron extraction from chalcopyrite were determined as to be sulfuric acid concentration of 2.5 M, hydrogen peroxide concentration of 2.3 M, leaching time of 24 minutes, chalcopyrite amount of 3.17 g (in 50-mL solution), stirring speed of 630 rpm, and leaching temperature of 351 K (78 °C). Under the optimum condition, 76 pct of copper and 9 pct of iron were extracted from chalcopyrite concentrate. Extraction yield results of metals indicate that selective leaching of chalcopyrite can be achieved using hydrogen peroxide and sulfuric acid in an autoclave system.     

The effects of Facebook and WhatsApp on success in English vocabulary instruction

The purpose of this study is to determine the effects of Facebook and WhatsApp on success in English vocabulary instruction and the learners' opinions about the implementation process. In the study, mixed method model, which combines both quantitative and qualitative data, was used. The success of the students in Facebook, WhatsApp, and control group showed a significant difference between the pretest and posttest, meaning that the learning environments had different effects on the increase of success of students. The analysis revealed that the difference in the mean scores of the students in WhatsApp, Facebook, and control group was significant, and WhatsApp has been more effective in the increase of the success. Although more increase in the mean scores of Facebook group was observed compared with control group, this increase was not found significant. Furthermore, students expressed their willingness to go on the practice not only in their present course, but also in their other courses as well. They also opined positive opinions that learning could also take place unconsciously. However, a few students reacted negatively against the unnecessary messages and the timing of some messages. The results indicated that, compared with Facebook, WhatsApp is more effective in teaching vocabulary.     

Hexavalent chromium removal by ferrochromium slag

The aim of this study is to demonstrate the potential of Cr(VI) generation during jigging operation applied for ferrochrome recovery from slag. The Cr(VI) concentrations of water contacted with ferrochromium slag (W/FS=10) in a closed cycle after 50 batches were found as 0.61 mg/l. Also, reduction of Cr(VI) to Cr(III) and a subsequent precipitation of Cr(III) by using ferrochrome slag (FS) in a model solution has been aimed. The effects of amount of acid, contact time, FS dosage, initial Cr(VI) concentration and temperature on the Cr(VI) reduction have been studied through the batch runs. The amount of acid has been found to be the most effective parameter affecting the Cr(VI) reduction. A 10 g/l FS dosage and 3.5 ml/l H2SO4 (5M) are sufficient to reduce all Cr(VI) in the model solution containing 10mg/l Cr(VI) and for contact time of 60 min at 25 degrees C. In reduced solutions, precipitation of metal ions has been studied by using extra FS. A 60 g/l dosage of fresh FS can precipitate all Cr(III) and Fe ions in the reduced solution. Thus, it has been demonstrated that the treatment of jigging water stream to be generated in a ferrochrome plant containing Cr(VI) can be accomplished by using ferrochromium slag and sulphuric acid. Also, it has been determined that solid residues of the process are environmentally stable by applying TCLP test.     

Investigation of the some physical properties of Ge-doped ZnO thin films deposited by thermionic vacuum arc technique

We exhibit the first nano-crystalline Ge–ZnO thin films deposited on glass and PET substrates by a thermionic vacuum arc technique. The effect of Ge doping on the structural, morphological and optical properties of ZnO:Ge films were investigated. An X-ray diffraction (XRD), atomic force microscopy, field emission scanning electron microscopy (FESEM) and UV–Vis spectrophotometer were used for the analysis. XRD patterns show the polycrystalline structure of the films in the range of 20°–80°. The roughness value for the ZnO:Ge on PET substrate was increased due to agglomeration of the grains. The results are in a good agreement with the FESEM images. Using Filmetrics F20 tool, the thickness values of the deposited thin films were obtained as 60 and 80 nm on glass and PET substrates, respectively. The optical properties of the films such as transmittance, absorbance, refractive index, and reflectance were determined. The band gap values were obtained as to be 3.43 and 3.38 eV glass and PET substrates, respectively. It was found that band gap variation of ZnO is very small with Ge doping.     

Dissolution kinetics of colemanite in potassium dihydrogen phosphate solution (KH2PO4)

Colemanite is rich in boron, and it is a common raw material used to produce boron components. The first step in this process is the dissolution of colemanite using different leaching solutions. The main aim of this study was to investigate the dissolution kinetics of colemanite in potassium dihydrogen phosphate (KH₂PO₄) solution. The reaction temperature?(T), the KH₂PO₄ concentration (C), the stirring speed (W), the solid-to-liquid ratio (S/L) and particle size (D) of the colemanite were selected as parameters affecting the rate of its dissolution. The Statistica software package was used to correlate the experimental results. The findings of the study showed that the dissolution rate of colemanite in KH₂PO₄ solution increased with increasing reaction temperature and KH₂PO₄ concentration, while an increase in particle size and solid-to-liquid ratio caused a decrease. Heterogeneous and homogeneous reaction models were tried in order to derive a proper kinetic model for colemanite dissolution. According to the results, it was determined that the colemanite dissolution process is controlled by a chemical reaction model. The activation energy value (41.88 kJ mol^?1) also verified this conclusion.     

From potential forecast to foresight of Turkey's renewable energy with Delphi approach

A Delphi Survey is a series of questionnaires that allow experts or people with specific knowledge to develop ideas about potential future developments around an issue. The Delphi questionnaires were developed throughout the foresight process in relation to the responses given by participants in bibliometric and SWOT analysis conducted prior to the Delphi survey. In this paper, Turkey's renewable energy future is evaluated using the Delphi method. A two-round Delphi research study was undertaken to determine and measure the expectations of the sector representatives regarding the foresight of renewable energies. First and second round of Delphi study were carried out by using online surveys. About 382 participants responded in the first round of the Delphi questionnaire yielding a respond rate of 20.1%, whereas 325 participants responded at the second round yielding a respond rate of 84.9%. About 50% of Turkey's energy demand was foresighted to be met by renewable energies around 2030. The results showed that all types of renewable energies would not only provide economic and environmental benefits but also improve living standards.     

A snapshot of renewable energy research in Turkey

The present study was conducted to find out the development trends of the scientific studies in the field of renewable energies in Turkey. All the publications in the ISI Web database were screened using 36 different keywords in title or topics based on the affiliation addresses including the word “Turkey”. A total of 12,197 publications were processed article by article and as a result 1555 papers were found to focus on renewable energies between the years 1980 and 2008 with the contributions of 1605 authors. The results showed that 45.2% was experimental, 34.3% informational studies whereas 20.5% was available system analysis. Number of publications in biomass and conversion system (39.1%) and solar energy systems (20.0%) were dominating. Both number of publications and citations increased in the last decade and more than half of total contributions were published last four years. Results indicated that policy development studies (3.3%) were the weakest among the whole parameters investigated.