Effect of Sulfuric Acid Concentration on the Corrosion Rate of ASTM A213-T12 Steel

Even though carbon steel is susceptible to corrosion degradation, carbon steel is widely used for applications in the industry. Impurities in steel composition are known to affect the mechanical and corrosion properties. There are many studies on the corrosion of steel, but for a specific application, further research still required. The present work is conducted to determine the effect of low concentration of sulfuric acid on the corrosion rate of power plant steel ASTM A213-T12 with a solution concentration from 0.01-0.05 M H2SO4. The corrosion rate was determined by using an immersion test as well as a polarization method using a potentiostat. The result shows that increasing the concentration of sulfuric acid molarity, the corrosion rate tended to increase. Furthermore, the effect of phosphor contents significantly affects the corrosion rate in which steel with high phosphor contents has a high corrosion rate.

Optimizing Conditions for Scandium Extraction from Bauxite Residue Using Taguchi Methodology

Bauxite residue is the voluminous by-product of alumina production after Bayer process. Its high alkalinity causes disposal problems and harmful environmental impacts. However, the residue contains significant amounts of valuable elements, such as rare earth elements, including scandium. Greek bauxite residue contains a high amount of scandium close to its main resources. Taking into account scandium’s limited availability coupled with its high demand in modern technology, bauxite residue could be considered as a potential resource for scandium recovery. In this study, the optimization of scandium extraction from bauxite residue with sulfuric acid is investigated using Taguchi methodology. Based on previous studies, acid molarity, leaching time, solid/liquid ratio, and reaction temperature were selected as control parameters for the selective Sc recovery. Method optimization targeted the highest concentration of scandium combined with the lowest concentration of iron without taking into account application constraints. Maximization of scandium concentration can be achieved only by reduced selectivity. The predicted values resulted from the Taguchi methodology were affirmed by a confirmation experiment conducted at optimal conditions. Regression analysis provided the respective equations to be applied on several conditions, depending on different applications.

Optimizing Conditions for Scandium Extraction from Bauxite Residue Using Taguchi Methodology

Bauxite residue is the voluminous by-product of alumina production after Bayer process. Its high alkalinity causes disposal problems and harmful environmental impacts. However, the residue contains significant amounts of valuable elements such as rare earth elements including scandium. Greek bauxite residue contains a high amount of scandium close to its main resources. Taking into account scandium limited availability coupled with its high demand in modern technology, bauxite residue could be considered as a potential resource for scandium recovery. In this study, the optimization of scandium extraction from bauxite residue with sulfuric acid is investigated using Taguchi methodology. Based on previous studies acid molarity, leaching time, solid/liquid ratio and reaction temperature were selected as control parameters for the selective Sc recovery. Method optimization targeted the highest concentration of scandium combined with the lowest concentration of iron without taking into account applications constraints. The predicted values resulted by Taguchi methodology were affirmed by a confirmation experiment conducted at optimal conditions. Regression analysis provided the respective equations to be applied on several conditions depending on different applications.

Optimization of a spectrofluorimetric method based on a central composite design for the determination of potassium losartan in pharmaceutical products

Here, a spectrofluorimetric method for the determination of potassium losartan (PL) in pharmaceutical products is described. The effects of critical parameters, pH, acid molarity, and temperature, on the fluorescence intensity of PL were analyzed, and these parameters were optimized using a central composite design (CCD). The highest fluorescent intensity at excitation (λex) and emission (λem) wavelengths of 248 nm and 410 nm, respectively, was achieved using 0.01 M sulfurous acid (pH 2) at 21.6 °C. Under optimum conditions, the method was linear from 0.025-0.5 µg/mL, with a reasonably high correlation coefficient (0.9993). Furthermore, the method was very sensitive (LOQ, 0.006), accurate (RE, ≤7.06), and precise (%RSD, ≤6.51). After development and validation of the method, samples containing PL were analyzed with this method, and the obtained data were statistically compared with those obtained with a previously published reference method using a two one-sided equivalence test (TOST). According to the data, the results from the proposed and reference assays were equivalent.

PENGARUH KONSENTRASI ASAM ASETAT DAN WAKTU EKSTRAKSI TERHADAP MUTU KOLAGEN KULIT NILA HITAMPENGARUH KONSENTRASI ASAM ASETAT DAN WAKTU EKSTRAKSI TERHADAP MUTU KOLAGEN KULIT NILA HITAM

The objective of the research was studied the effect of acetic acid concentration and extraction time on the collagen quality of black tilapia leather. Black tilapia leather processed into collagen as an alternative to increasing value-added of fisheries industry waste. Collagen of black tilapia was extracted by the treatment of acetic acid molarity, each: 0.25 M, 0.50 M, and 0.75 M (A factor) and extraction time of 16 and 48 hours (B factor). Based on the analysis of variance, is known that the interaction of those treatments (AB) didn’t significantly effect on the yield (p>0.05). Collagen extraction of tilapia leather with 0.75 M of acetic acid at 16 hours, produces the greatest yield (5.97%), with denaturation temperature is 35.75oC, and quantitative composition of glisine, alanine, and glutamic amino acids were: 5395.82 ppm (52.99%), 2979.15 ppm (22.08%), and 1684.42 ppm (7.45%). Based on the analysis of SDS-PAGE, is known that the collagen contained were α component and β component, so that collagen of tilapia leather has type I collagen.

Spectroscopic, crystal, and halogen-exchange studies of halogenotrimolybdates(II)

Quantitative solid (potassium halide disk) and hydrochloric acid solution adsorption spectra of halogenotrimolybdates(II) indicate that the compounds are of a common structural type, both in solid and solution, but that at least two kinds of chloro- or bromo-molybdate(II) are present. Variation of absorption intensities with hydrochloric acid molarity suggests the equilibrium (Mo3Cl12)6-+Cl- ↔ (Mo3Cl13)7-, and moreover similar intensity changes occur when K6Mo3Cl12 is in KCl. X-ray diffraction powder photographs of K6Mo3Cl12 and AI7Mo3Cl13,H2O (AI = NH4 or Rb) have been indexed on a pseudo-tetragonal unit cell and indicate 15 and 18 molybdenum atoms per unit oell respectively. The values are decisive for trimers (Mo3) if it is assumed that all the compounds have similar structures. Halogen-exchange studies support the (Mo3X13)7- parental structure, having four bridging, and nine terminal and labile, halogeno groups, since (NH4)7Mo3Cl13,H2O rapidly exchanges only nine chlorine atoms in 1M hydrochloric acid.