Effects of calcium hydroxide and calcium chloride addition to bentonite in iron ore pelletization.

Pyrite ash is created as waste from the roasting of pyrite ores during the production of sulphuric acid. These processes generate great amounts of pyrite ash waste that is generally land filled. This creates serious environmental pollution due to the release of acids and toxic substances. Pyrite ash waste can be utilized in the iron production industry as a blast furnace feed to process this waste and prevent environmental pollution. The essential parameters affecting the pelletization process of pyrite ash were studied using bentonite as a binder. Experiments were then carried out using bentonite and a mixture of bentonite with calcium hydroxide and calcium chloride in order to make the bentonite more effective. The metallurgical properties of pyrite ash, bentonite, calcium hydroxide, calcium chloride, a mixture of these and sintered pellets were studied using X-ray analysis. The crushing strength tests were carried out to investigate the strength of pyrite ash waste pellets. The results of these analyses showed that pyrite ash can be agglomerated to pellets and used in the iron production industry as a blast furnace feed. The crushing strength of the pellets containing calcium hydroxide and calcium chloride in addition to bentonite was better than the strength of pellets prepared using only bentonite binder.     

Leaching Characteristics of Fly Ash from Thermal Power Plants of Soma and Tunçbilek, Turkey

Use of lignite in power generation has led to increasing environmental problems associated not only with gaseous emissions but also with the disposal of ash residues. In particular, use of low quality coal with high ash content results in huge quantities of fly ash to be disposed of. The main problem related to fly ash disposal is the heavy metal content of the residue. In this regard, experimental results of numerous studies indicate that toxic trace metals may leach when fly ash contacts water. In this study, fly ash samples obtained from thermal power plants, namely Soma and Tunçbilek, located at the west part of Turkey, were subjected to toxicity tests such as European Committee for standardization (CEN) and toxicity characteristic leaching (TCLP) procedures of the U.S. Environmental Protection Agency (U.S. EPA). The geochemical composition of the tested ash samples from the power plant show variations depending on the coal burned in the plants. Furthermore, the CEN and TCLP extraction results showed variations such that the ash samples were classified as `toxic waste' based on TCLP result whereas they were classified as `non-toxic' wastes based on CEN results, indicating test results are pH dependent.     

Degradation of PVC Containing Mixtures in the Presence of HCl Fixators

Degradation of a model polymer mixture (PVC/PS/PE) and a waste polymer mixture in the presence of HCl fixators (Red Mud, precipitated CaCO₃ and dolamite) was studied using thermal gravimetric analysis (TGA) and a cycled-spheres-reactor. The experiments in cycled-spheres reactor model were performed by stepwise pyrolysis. Liquid products and HCl from each step were collected separately. For the model polymer mixture, the precipitated CaCO₃ showed the best effect on the fixation of evolved HCl and the reduction of chlorine content in the liquid products whereas RM yielded the best result for the waste polymer mixture. In addition, using HCl fixator also affected the degradation of both types of polymer mixture, leading to the formation of more gaseous and less residue.     

Degradation of azo dyes in water by Electro-Fenton process

The degradation of the azo dyes azobenzene, p-methyl red and methyl orange in aqueous solution at room temperature has been studied by an advanced electrochemical oxidation process (AEOPs) under potential-controlled electrolysis conditions, using a Pt anode and a carbon felt cathode. The electrochemical production of Fenton's reagent (H₂O₂, Fe²⁺) allows a controlled in situ generation of hydroxyl radicals (^·OH) by simultaneous reduction of dioxygen and ferrous ions on the carbon felt electrode. In turn, hydroxyl radicals react with azo dyes, thus leading to their mineralization into CO₂ and H₂O. The chemical composition of the azo dyes and their degradation products during electrolysis were monitored by high performance liquid chromatography (HPLC). The following degradation products were identified: hydroquinone, 1,4-benzoquinone, pyrocatechol, 4-nitrocatechol, 1,3,5-trihydroxynitrobenzene and p-nitrophenol. Degradation of the initial azo dyes was assessed by the measurement of the chemical oxygen demand (COD). Kinetic analysis of these data showed a pseudo-first order degradation reaction for all azo dyes. A pathway of degradation of azo dyes is proposed. Specifically, the degradation of dyes and intermediates proceeds by oxidation of azo bonds and aromatic ring by hydroxyl radicals. The results display the efficiency of the Electro-Fenton process to degrade organic matter. Electronic Publication     

Enhanced degradation of the antibiotic tetracycline by heterogeneous electro-Fenton with pyrite catalysis

There is actually increasing concern about the accumulation of antibiotics, such as tetracycline, in soil and water bodies. There is therefore a need for efficient methods to degrade antibiotics and thus clean waters. Here we tested the degradation of tetracycline using the heterogeneous electro-Fenton-pyrite method and compared the results with the conventional electro-Fenton method. The reaction was performed with a boron-doped diamond or Pt anode and carbon-felt cathode allowing electrogeneration of H₂O₂ from O₂ reduction. Results show an increasing tetracycline mineralization using the following methods: anodic oxidation with electrogenerated H₂O₂, electro-Fenton and then electro-Fenton-pyrite using boron-doped diamond. Ion-exclusion HPLC revealed the complete removal of malic malonic, succinic, acetic, oxalic and oxamic acids. Nitrogen present in tetracycline was mainly mineralized in NH₄ ⁺. The higher efficiency of electro-Fenton-pyrite is explained by self-regulation of soluble Fe²⁺ and pH to 3.0 from pyrite catalyst favoring larger ^·OH generation from Fenton’s reaction.     

Preparation, Thermal Properties and Thermal Reliability of Form-Stable Paraffin/Polypropylene Composite for Thermal Energy Storage

This study is focused on the preparation, characterization, and determination of thermal properties and thermal reliability of paraffin/polypropylene (PP) composite as a novel form-stable phase change material (PCM) for thermal energy storage applications. In the composite, paraffin acts as a PCM when PP is operated as supporting material. The composites prepared at different mass fractions of paraffin (50, 60, 70, 80, and 90 w/w%) by solution casting method were subjected to leakage test by heating the composites over the melting temperature of the PCM. The paraffin/PP composite (70/30 w/w%) is found as the maximum paraffin containing composite and was characterized using Fourier transform infrared spectroscopy, optic microscopy, differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA) techniques. DSC analysis indicated that the form-stable paraffin/PP composite melts at 44.77–45.52 °C and crystallizes at 53.55–54.80 °C. It has latent heats of 136.16 and −136.59 J/g for melting and crystallization, respectively. These thermal properties make it potential PCM for latent heat thermal energy storage (LHTES) purposes such as solar space heating applications. Accelerated thermal cycling tests indicated that the form-stable PCM had good thermal reliability. TGA also showed that the form-stable PCM degrades in two distinguishable steps and had good chemical stability.     

Mineral contents and proximate composition of Pistacia vera kernels

The mineral contents of Pistacia vera kernels were determined by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The minimum and maximum values of K, P, Ca, Mg, and S elements ranged from 6,333 to 8,064 mg/kg, 3,630 to 5,228 mg/kg, 1,614 to 3,226 mg/kg, 1,716 to 2,402 mg/kg, and 1,417 to 1,825 mg/kg, respectively. In addition, the mean values of Fe, Zn, Cu, Mn, B, Mo, Cr and Ni elements were determined as 42.48, 20.52, 12.81, 7.48, 11.31, 0.106, 0.511 and 1.67 mg/kg, respectively. Ash levels of kernels were found between 2.28 % (Urfa) and 2.79 % (Halebi). In addition, crude oil and protein contents were determined between 48.8 % (Halebi) to 55.3 % (Siirt) and 23.33 % (Uzun) to 27.16 % (Halebi), respectively.     

Some phenolic compounds of extracts obtained from Origanum species growing in Turkey

Caffeic acid, rosmarinic acid, rutin, apigenin 7-O-glucoside, apigenin, and acesetin were the main phenolic compounds of Origanum onites extracts in all applications. While acesetin contents ranged from 133.59 mg/100 g (U1) to 437.25 mg/100 g (S3), rosmarinic acid changed between 215.94 mg/100 g (U4) and 1120.56 mg/100 g (S2) in Origanum vulgare L. subsp. hirtum (Link) Ietsw. Both rosmarinic acid and acesetin were not found in U5 application. Only caffeic acid (19.39 mg/100 g) was found in U5 application. Rosmarinic acid contents of O. onites extract changed between 158.62 mg/100 g (U5) and 799.87 mg/100 g (S2). Generally, dominant phenolic compound of Origanum extracts was rosmarinic acid compared with other extracts. In addition, methanol:water:acetic acid mixture (S2) (95:4.5:0.5) was found as the best application. Phenolic contents of extracts obtained with U series mixtures were found low.     

Correction to: Where is the gray side of green growth? Theoretical insights,policy directions,and evidence from a multidimensional approach

Environmental Science and Pollution Research - A Correction to this paper has been published: https://doi.org/10.1007/s11356-021-13479-4     

Renewables as a pathway to environmental sustainability targets in the era of trade liberalization: empirical evidence from Turkey and the Caspian countries

Environmental Science and Pollution Research - The quest for improved environmental quality through low-carbon emission has been explored in this study in the wake of the growing call for a...