SLIP MELTING POINT ESTIMATION OF FAT BLENDS BEFORE AND AFTER INTERESTERIFICATION BASED ON THEIR FATTY ACID COMPOSITIONS

In this study the relationship between slip melting point (SMP) and fatty acid composition of blends before and after interesterification were investigated. Forty-four blends were prepared using sunflower, canola and cottonseed oils as well as palm stearin and/or fully hydrogenated palm stearin in different proportions. Fatty acid compositions and SMP of samples were determined and then SMP of the blends before and after interesterification were defined as a function of five fatty acids. Specific constants of C_16:0, C_18:0, C_18:1, C_18:2 and C_18:3 fatty acids were determined as 0.455, 0.821, 0.622, 0.215 and -1.653, respectively, for the blends before interesterification and 0.532, 0.614, 0.399, 0.055 and -2.471, respectively, for the blends after interesterification by using least squares method. Slip melting point of blends were calculated using these constants and fatty acid compositions and then compared with the experimental values. No linear relationship existed between the calculated and experimental results of the blends before interesterification, but SMP of the blends after interesterification could be estimated with high (r=0.956) accuracy.     

Leaching of blended copper slag in microwave oven

Leaching of blended slag (BS) was investigated in a microwave oven using hydrogen peroxide and acetic acid. The BS was a mixture of converter and flash furnace slag containing 51% Fe₂O₃, 3.8% CuO, and 3.2% ZnO. The important variables that influence the metal extraction yield were leaching time, liquid-solid ratio, H₂O₂ and CH₃COOH concentrations. The preferred leaching conditions were as follows: CH₃COOH concentration 4 mol/L; H₂O₂ concentration 4 mol/L; microwave power 900 W; leaching time 30 min; liquid-solid ratio 25 mL/g BS; leaching temperature 100 °C. Under these conditions, the metal extractions of 95% Cu, 1.6% Fe, and 30% Zn were obtained. The results were compared with the traditional leaching results. It is evident that microwave heating causes a reduction in the leaching time. Also, the extraction yield results indicate that selective leaching of BS can be achieved under the preferred conditions. The dissolution kinetic of BS in hydrogen peroxide with acetic acid is controlled by a shrinking unreacted core model equation. The apparent activation energy and reaction order were found to be 16.64 kJ/mol and 1.09, respectively.     

A comparison of the microstructure of silicon nitride-silicon carbide composites made with and without deoxidized starting material

Two different types of silicon carbide (SiC) matrix composites, with either 10 wt% or 20 wt% silicon nitride (Si₃N₄) reinforcement, were fabricated to investigate the effect of pretreatment on the resulting composite micro-structure. The first type of composite was prepared from as-received α-SiC and α-Si₃N₄ powders, while the second type was prepared from powder compacts that had been deoxidized to eliminate surface silica on the powder particles. The composites were hot isostatically pressed in tantalum cans at 2373 K for 1h under a pressure of 200 MPa. Density measurements showed that full theoretical density was achieved for the composites prepared from the as-received powders, while much lower densities were obtained for the composites prepared from the deoxidized green compacts. Almost all of the α-SiC transformed into β-SiC, and almost all the α-Si₃N₄ transformed into α-Si₃N₄ in the composites made from the as-received powders, while in the composites made from the deoxidized material the α-SiC remained untransformed and both α-Si₃N₄ and β-Si₃N₄ phases were present in significant quantities. High-resolution transmission electron microscopy and Fresnel fringe imaging were used to identify the grain boundary and interphase boundary structure. Most interfaces were found to be covered with ? 1 nm thick amorphous intergranular films in the composites prepared from as-received powders, whereas most interfaces were found to be free of such amorphous intergranular films in the composites prepared from the deoxidized material. Taken together, the presence of intergranular films at the interfaces and the results from density measurements are consistent with the densification and reverse α → β-SiC transformation taking place in the composites made from as-received powders by a liquid-phase sintering route. An incomplete liquid-phase sintering mechanism is also able to explain the microstructure observed in the composites made from the deoxidized material.     

A study on Cr（VI） reduction from aqueous solutions by bauxite

The reduction of Cr（Ⅵ） in aqueous solution by using bauxite ore was investigated.Experimental results for Cr（Ⅵ）reduction in aqueous solution depending on some factors such as time,sulfuric acid amount,bauxite dosage,initial Cr（Ⅵ）concentration,formic acid concentration,daylight and temperature were presented.The obtained results show that sulfuric acid amount,bauxite dosage and initial Cr（Ⅵ） concentration of solution are most effective parameters on the reduction process.Also,it has been found that the 60 g/L of bauxite dosage is sufficient to reduce up to 100% of Cr（Ⅵ） from acidic solution under the condition of low initial Cr（Ⅵ） mass concentrations such as 10 mg/L.The reduction reaction is completed within 30 min at 25 ℃ under the experimental conditions：bauxite dosage of 60 g/L,amount of sulfuric acid 40-60 stoichiometric and initial mass concentration of Cr（Ⅵ）,10 mg/L.It was determined that reduction percentage is decreasing with increasing initial Cr（Ⅵ） concentration.The chemical oxygen demand of bauxite ore was found to be 26 mg COD/g.     

CHEMICAL AND MICROBIOLOGICAL QUALITIES OF DRY-SALTED (LAKERDA) BONITO (SARDA SARDA, BLOCH 1793)

In this study, changes in the chemical and microbiological properties of bonito (Sarda sarda, Bloch 1793) salted by dry salting (lakerda) and stored for 6 months at 4 ± 1C were investigated. The fresh gutted and sliced bonitos were used as raw material for salting by using the ratio of fish to salt as 5:1 by weight. Salted fish remained in the liquid pickle formed by salt and the liquid extracted from the fish. This solution was not drained during the storage period. The product is described as “lakerda” in Turkey. In the fresh fish, total volatile basic nitrogen (TVB‐N) and trimethylamine nitrogen (TMA‐N) values were 11.21 mg/100 g and 1.19 mg/100 g, respectively. During the storage period, TVB‐N and TMA values increased slowly to 27.67 mg/100 g and 4.99 mg/100 g, respectively, at the end of the storage period. In the first month after salt processing, the total mesophilic bacteria count was 4.6 × 10² cfu/g. In the later months, mesophilic, psychotropic, coliform bacteria and yeast‐mold did not reproduce. According to the results, bonito salted by dry salting and stored at 4 ± 1C was in good quality in terms of chemical and microbiological properties during the storage period of 6 months.