Investigation of shipyard wastewater treatment using electrocoagulation process with Al electrodes

In this study, shipyard oily wastewater treatment was investigated by electrocoagulation (EC) using aluminum electrodes in a batch reactor by evaluating different operation conditions. The maximum chemical oxygen demand (COD) removal efficiency of 88.83% was obtained at current density of 3 mA/cm². The removal efficiency was gradually improved with increasing current density and decreased with increasing COD concentration. However, initial pH value was not determinant factor for this process. Total energy and electrode cost were calculated as $0.88 per m³ treated wastewater. The result of this research shows that EC process seems to be an efficient method for the oily wastewater treatment.     

Critical current density and mechanical performance of MgB2 superconductors prepared with different magnesium sources

In this study, the critical current density and mechanical performance of MgB₂ superconductors prepared using different magnesium sources (Mg and MgH₂ with 99.9% and 96.5% purities, respectively) were analyzed. When the samples were characterized structurally and electrically, we found that the grain sizes were about 40?nm and transition temperature was around 30?K being lower than the literature. Critical current densities of all samples were calculated using Bean's model and our calculations yielded critical current density values higher than 10⁶?A?cm^?2 in self-field. The highest critical transition temperature value belongs to M800 (Mg with 99.9% purity) sample and when the critical current density and transition temperature values of this sample are considered, this sample appears to have the potential for practical use. Vicker's microhardness measurements were performed and yield stress (Y), elastic modulus (E), brittleness (B_i), ductility (D) and fracture toughness (K_IC) were calculated. All samples exhibited Indentation Size Effect (ISE) and microhardness measurements were compared with some microhardness models with were compatible with ISE behavior.     

Graphene oxide-containing isocyanate-based polyimide foams: Enhanced thermal stability and flame retardancy

Isocyanate-based graphene oxide-containing polyimide foams were synthesized by a semi-prepolymer method. In this method, while the first solution containing pre-polymer was derived from pyromellitic dianhydride and excess polymethylene polyphenylene isocyanate (PM200), the second solution contains dianhydride derivatives, water, catalysts, surfactants, and graphene oxide. PIFs were prepared with 0%, 0.25%, 0.50%, 0.75%, and 1% graphene oxide by weight, respectively. PIFs exhibited a minimum side reaction and urea generation was not seen for all PIFs instead of imide bonding. The addition of graphene oxide (GO) leads to a more close-packed structure. Therefore, crosslinking density and thermal stability of graphene oxide-containing polyimide foams increased. Upon the addition of 1% GO, almost seven times higher compression strength was obtained compared to neat PIFs. Also, LOI values supported the theory that thermally stable and flame retardant PIFs can be synthesized via the isocyanate-based process with GO.     

Gas absorption into a wavy two‐layer falling film

Absorption of a weakly soluble gas into a two‐layer film flowing down a vertical wall is studied in the framework of an approximate long‐wave model. It is shown that wavy regimes in the film strongly affect the absorption rate. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2058–2069, 2015     

What Role Does Ozone Play in Preventing Dental Caries? An Evidence-Based Review

Ozone, which is also referred to as triatomic oxygen or trioxygen, is a naturally occurring inorganic molecule that consists of three oxygen atoms. Ozone has proven microbiological properties and, for this reason, it is extensively used in modern medical practices. Ozone is a powerful oxidant that demonstrates bactericide, virucide, and fungicide effects. The strong oxidation effect it produces results in the formation of highly reactive free radicals that have the capability to destroy microorganisms. Ozone has been proposed as a means of preventing caries, and existing research confirms that this form of therapy does have promising potential. However, very few clinical studies have examined the impact that ozone treatment can have on the management of caries lesions. This article presents a detailed literature review of existing peer-reviewed sources that have examined the role ozone plays in preventing and treating caries.     

Ring Opening of Epoxidized Soybean Oil with Compounds Containing Two Different Functional Groups

Epoxidized vegetable oils are desirable chemicals due to their eco‐friendly characteristics and their being a major source of many green products. Ring opening is one of the ways to convert these epoxidized oils to some new intermediates. The use of mono‐functional amines, alcohols, acid anhydrides and thioethers for epoxy ring opening has been reported in the literature. In this study, thioglycolic acid (TGA) bearing thiol and carboxylic acid as two different functional groups and methyl ester of thioglycolic acid (TGAME) were used. Currently, there is no reported literature describing epoxy ring opening using chemicals bearing two different functional groups simultaneously. In this way, two new polyols were synthesized, one with TGA (polyol 1) and one with TGAME (polyol 2). FTIR and ¹H‐ and ¹³C‐NMR spectroscopy confirmed that the ring was opened by the carboxylic acid group of TGA, and the thiol group was not involved in the ring opening whereas the ring was opened by the thiol group in the case of TGAME.     

Synthesis and film properties of epoxy esters modified with amino resins from glycolysis products of postconsumer PET bottles

Glycolysis of waste polyethylene terephthalate (PET) flakes obtained from grinding postconsumer bottles was carried out at 225–250°C and molar ratios of PET/ethylene glycol were taken as 1/1, 1/1.5, 1/5, and 1/10. Reaction product was extracted by hot water for three times and water‐soluble crystallizable fraction and water‐insoluble fraction were obtained. These fractions were characterized by acid and hydroxyl value determinations, differential scanning calorimeter analysis, and ¹H‐NMR analysis. Glycolysis product was used for synthesis of PET‐based epoxy resin. This epoxy resin was used to prepare epoxy ester resins having 40% and 50% oil content. Epoxy ester resin having 40% oil content was modified with urea‐formaldehyde and melamine‐formaldehyde resins for synthesis of epoxy ester–amino resin. Physical and chemical film properties of epoxy ester and modified epoxy ester resins were investigated. All the epoxy ester and modified epoxy ester films were having excellent adhesion, water, and salt water resistance properties. Modification of PET‐based epoxy ester resins with amino resin has significantly improved hardness, impact resistance, and alkaline and acid resistance of resin films. As a result, PET oligomers obtained from glycolysis of postconsumer PET bottles are suitable for manufacturing of amino‐resin‐modified epoxy ester resins that have improved physical and chemical surface coating properties. POLYM. ENG. SCI., 55:2519–2525, 2015. © 2015 Society of Plastics Engineers     

Synthesis of Quaternary,Long-Chain N-Alkyl Amides and Their Corrosion Inhibition in Acidic Media

New cationic surfactants were synthesized by the quaternization of a number of straight-chain amide derivatives with triethylamine or pyridine. The corrosion inhibition tests of the surface-active compounds were performed at room temperature for 24 h on carbon steel coupons in acidic media using the gravimetric method. The acidic media used were 1.5 M HCl and 1.5 M H₂SO₄. Almost all of the synthesized cationic surfactants showed efficient inhibition of corrosion in the test. To establish the inhibition efficiencies of the inhibitors, surface characterization studies (contact angle measurements, SEM analysis and optical profilometer images) of the metal coupons used were performed.