Effect of acid concentration and reaction time on structural and surface properties of waste mica

A facile process to prepare copper oxide thin films as solar selective absorbers

Effect of gasification reaction on pore structure, microstructure, and macroscopic properties of blast furnace coke

Sulfur is one of the most significant impurities in coal, which reduces the quality of coal and also results in environmental pollution. This work was aimed to investigate the removal of sulfur from coal by the leaching method employing parameters expected to affect the removal rate such as acid concentration (10-30%), temperature (40-80 °C), and reaction time (40-100 min). A response surface methodology using Box-Behnken design was employed to maximize, model, and evaluate the factors affecting the desulfurization process. The results obtained indicated that the desulfurization value increased with increase in the acid concentration, temperature, and reaction time. A quadratic model with a high correlation coefficient (R2=0.98) is proposed and developed for the relationship between the removal value and the influential factors. The modeling results demonstrated that the significance degree of factors was in the order of acid concentration>temperature>reaction time. It was also found that the maximum desulfurization (about 87%) could be obtained under the optimal conditions of acid concentration=25%, temperature=80 °C, and leaching time=84 minutes.

Neste trabalho foi produzido bioquerosene pela reação de esterificação (utilizando o Amberlyst® 15 como catalisador heterogêneo) dos ácidos graxos livres de C6 a C16 átomos de carbono provenientes do óleo de babaçu (Orbignya speciosa) utilizando um planejamento de experimento fatorial 23 com composto central. A análise termogravimétria foi utilizada para indicar a faixa de trabalho do catalisador e a microscopia eletrônica de varredura, a morfologia. Os parâmetros de processo estudados foram a temperatura de reação entre 70 °C e 100 °C, a concentração em massa de catalisador entre 5 % e 10 % e o tempo de reação entre 240 minutos e 480 minutos. Como parâmetro de resposta do planejamento experimental foi avaliado o teor em massa de metil ésteres. A otimização do processo foi realizada através da metodologia de superfície de resposta (MSR) e o modelo polinomial de segunda ordem. Foi observado que a variável de processo de maior influência foi a temperatura de reação, sendo que a maior conversão de ésteres foi obtida com 7,5 % de catalisador; temperatura de reação de 85 °C e com um tempo de 360 minutos de reação. Com esses parâmetros a conversão alcançada foi de 94,7 % em biocombustível. Utilizando a MRS, com modelo polinomial de segunda ordem, as condições otimizadas obtidas para a reação de esterificação com Amberlyst® 15 foram: temperatura de 90,0 °C, quantidade de catalisador de 7,3 % e tempo reacional de 338,2 minutos. O rendimento teórico da conversão previsto para os ácidos graxos livres de C6 a C16 átomos de carbono em bioquerosene foi de 95,7 %. Esta pesquisa foi apoiada pela Universidade Federal do Ceará (UFC), Laboratório de Imagem Central Analítica da UFC, Fundação Núcleo de Tecnologia Industrial do Ceará (NUTEC) e financiada pelo Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) e pela Fundação Cearense de Apoio ao Desenvolvimento Científico e Tecnológico (FUNCAP).

Effect of reaction time on structural and magnetic properties of green-synthesized magnetic nanoparticles

Introduction: In this study, NaYF4:Tm,Yb upconversion microparticles were prepared by a hydrothermal method. Methods: The effects of fabrication parameters such as rare earth concentration, reaction temperature and reaction time on the structure and luminescence properties of the materials were studied by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and photoluminescence spectroscopy (PL). Depending on the reaction temperature and time, the morphology of NaYF4:Tm,Yb is either a nanoparticle or a branched structure. Results: The crystallite size is approximately 70 nm and remains almost unchanged with increasing reaction temperature and time. These NaYF4:Tm,Yb powders strongly emit at 450 nm and 798 nm. In addition, the surface of the UCMPs was also modified with maleic anhydride to improve their dispersibility in solvents and binding to biological molecules. Conclusion: Printing ink based on UCMPs modified with maleic anhydride and polyamide for screen printing was prepared. The printed patterns on paper and polymer substrates glow blue light under LED excitation at 980 nm, and they are completely transparent in daylight.

Dilute sulfuric acid pretreatment was conducted to extract hemicellulose from rice straw at reduced temperatures (<100 °C), and the process was optimized using experimental design analysis with the response surface methodology. Fourier Transform Infrared Spectroscopy analysis was performed to verify the purity of recovered hemicellulose. Central composite design of experiments (DOE) was applied to develop a statistical model to identify the main effects and interaction effects of process parameters: acid concentration, reaction temperature, and reaction time. The proposed quadratic model showed a high adjusted determination coefficient (0.91) and Fischer's test value (22.4), indicating that the model is adequate to characterize the relationships among the process parameters and explain the variation observed in response. Acid concentration and reaction temperature have significant first order and quadratic effects on hemicellulose recovery. However, reaction time exhibited only a significant quadratic effect on hemicellulose recovery. The maximum hemicellulose yield (15.78%) was obtained at optimal conditions of 0.26 moldm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> acid concentration, 98.1°C reaction temperature, and 30.48 min reaction time. In addition, residual analysis was carried out to check the adequacy of the proposed model.

The law of the hydrogen ion diffusion coefficient in acid rock reaction

Confined Ir single sites with triggered lattice oxygen redox: Toward boosted and sustained water oxidation catalysis

Antimicrobial activity of copper chalcogenides nanoparticles was investigated by synthesizing copper selenide, copper sulfide, and copper oxide via the hot-injection method. Since reaction time has a profound effect on the nanocrystals size and shapes, the effect of reaction time was also investigated during the synthesis of the copper chalcogenides to obtain nanocrystals with desired properties. The reaction time showed no effect on the phase composition of the synthesized copper sulfide, copper oxide, and copper selenide nanoparticles. However, the size variation of nanoparticles with different reaction time was observed. Reaction time of 30 minutes gave the best optical (the shape of the absorption band edge and emission maxima values) and structural (size distribution of particles) properties for CuSe and CuS compared to other reaction times (15, 45, and 60 min). Their band edges were located at 506 (2.45 eV) and 538 nm (2.30 eV), respectively. For this reaction time, copper selenide produced nanoparticles with a size range of 1–27 nm and copper sulfide nanoparticles ranged 1–18 nm. The morphologies of both chalcogenides at 30 min reaction time were spherical. Reaction time of 15 minutes gave the best optical and structural properties for copper oxide nanoparticles with a band edge of 454 nm (2.73 eV) and particle size ranging 0.8–3.2 nm, but nonetheless, 30 min was used as the optimum reaction time for all three chalcogenides. The optimum parameter (220°C, 30 min, and 1 : 1 ratio) was used to synthesize the three copper chalcogenides which were then tested against Gram-negative (E. coli and P. aeruginosa), Gram-positive (S. aureus and E. faecalis), and fungi (C. albicans) employing both agar disk diffusion and minimum inhibitory concentration (MICs) methods. Copper oxide nanoparticles showed more sensitivity towards four bacterial microorganisms than the other two chalcogenides followed by copper sulfide nanoparticles with copper selenide nanoparticles being the least sensitive. The sensitivity of copper oxide nanoparticles is attributed to the smaller size of oxygen atom which strongly affects its reactivity and stability and hence very stable and highly reactive compared to sulfur and selenium.

Microwave-assisted acid hydrolysis to produce xylooligosaccharides from sugarcane bagasse hemicelluloses

The potential of dilute-acid hydrolysis as a treatment for improving the nutritional quality of industrial lignocellulosic by-products

Sulphonates that work as emulsifiers in asphalt emulsification are generated in-situ by partial sulphonation of asphalt. More stable emulsions can be made by using sulphonated asphalt with a conventional emulsifier. To demonstrate, the sodium oleate was used as co-emulsifier. Effect of sulphonation time, temperature, acid concentration and amount of sulphonated asphalt on emulsion properties is studied. Use of 2 factorial design revealed that acid concentration, reaction time and temperature are significantly important parameters. The stability of emulsion increases with increased severity of reaction, that is, higher acid concentration, reaction time and temperature. In the most severe conditions, the asphalt forms coke-like polymerized matter that is not emulsifiable. The most stable emulsion was prepared with asphalt that was sulphonated at slightly milder conditions, namely, 69 °C, 60 minutes and 98 % acid. Storage stability, demulsibility and viscosity improved by 41.7 %, 46.8 % and 45.7 % respectively, with 40% of sulphonated asphalt.

The Taguchi method is an engineering design optimization methodology that improves the quality of existing products and processes and simultaneously reduces their costs very rapidly, with minimum engineering resources and development man hours. In this study, this method was utilized to investigate the effect of various parameters for determining the optimum dissolution conditions of colemanite (Ca2B6O11·5H2O) in phosphoric acid solutions. The parameters investigated were the acid concentration, particle size, stirring speed, and reaction time. The most significant parameters affecting the solubility were the reaction time and particle size, whereas the acid concentration and stirring speed had a lesser effect. The optimum dissolution conditions were determined as follows: reaction time, 12 min; particle size, 2.4 mm; acid concentration, 2.7 M; stirring speed, 450 rpm; reaction temperature, 94 °C; solid-to-liquid ratio, 0.25. Under these conditions, it was found that boron extraction from colemanite ore was 100%.

In this study used clay as raw material for making aluminum oxide using sulfuric acid as pelarut.Penelitian also aims to obtain sulfuric acid concentration and reaction time is best, where the variable used is the concentration of sulfuric acid ( 60 % , 70 % and 80 % ) and reaction time ( 40 minutes , 50 minutes and 60 minutes). The results showed that the greater the concentration of sulfuric acid , the levels of aluminum oxide obtained will be greater and greater the heating period , the levels of aluminum oxide obtained will also be greater . Optimum results obtained in 80% sulfuric acid concentration and reaction time 60 minutes.