Current Issue : July-September Volume : 2022 Issue Number : 3 Articles : 5 Articles
Mechanochemistry initiated the reaction of hydrogen-terminated porous silicon (H/por- Si) powder with arginine. Samples were analyzed using Fourier-transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), zeta potential, scanning electron microscopy (SEM), and photoluminescence (PL) spectroscopy. Arginine, which was physisorbed onto the surface of por-Si, blue-shifted the peak PL intensity from ~630 nm for the H/por-Si to ~565 nm for arginine-coated por-Si. Grinding for 4 h reduced >80% of the initially 2–45 μm particles to <500 nm, but was observed to quench the PL. With appropriate rinsing and centrifugation, particles in the 100 nm range were isolated. Rinsing ground powder with water was required to remove the unreacted arginine. Without rinsing, excess arginine induced the aggregation of passivated particles. However, water reacted with the freshly ground por-Si powder producing H2. A zeta potential of +42 mV was measured for arginine-terminated por-Si particles dispersed in deionized water. This positive value was consistent with termination such that NH2 groups extended away from the surface. Furthermore, this result was confirmed by FTIR spectra, which suggested that arginine was bound to silicon through the formation of a covalent Si–O bond....
Sewage sludge is here studied as a valuable source for processing or energy conversation thanks to its high nutrition and energy content. However, various origins of the wastewater, different water cleaning technologies, and seasonal and regional dependencies lead to the high variability of the sewage sludge properties. In thermal treatment units, that is, incineration, gasification and pyrolysis, sewage sludge serves as feedstock or fuel, hence a proper characterization and a mathematical description of the sewage sludge are required to estimate product streams and to formulate numerical simulations and optimization methods. The presented work introduces a surrogate concept that allows replication of sewage sludge’s ultimate composition, moisture, and ash content. The surrogate approach aims to model the decomposition of any sewage sludge sample, opposite to the established determination of kinetic rates for individual samples. Based on chemical solid surrogate species and corresponding reaction mechanisms, the thermal decomposition path is described. Sewage sludge is represented by a combination of lignocellulosic species, proteins, sugars, lipids, and representative inorganic species. The devolatilization and heterogeneous reactions are formulated such that they can be used together with a detailed gas-phase model, including tar oxidation and emission models for nitrogen and sulfur oxides, recently proposed by the authors. The developed chemical model is applied using a zero-dimensional gasification reactor in order to model weight loss within the thermogravimetric analysis, pyrolysis, gasification and combustion conditions. Weight loss, the composition of product gases, and emission release (nitrogen and sulfur oxides) are captured well by the model. The flexible surrogate approach allows us to represent various sewage sludge samples....
Standard gases are often prepared using high-pressure gas cylinders. However, it is difficult to accurately prepare a known concentration of hydrogen chloride (HCl) gas using this method because HCl is highly corrosive and adsorptive. In this study, a simple method for the continuous generation of HCl gas was developed using a diffusion tube containing hydrochloric acid and a nitrogen carrier gas. The concentration of HCl produced from this system was almost unstable, but constant gas generation was realized for several hours when azeotropic hydrochloric acid (20.6% HCl in water) and a temperature near the azeotropic point (108.5 ◦C) were used, resulting in the generation of 103.6 ppm (mean, n = 5) of HCl gas with a relative standard deviation (RSD) of 2.34%. In this case, the percentage of HCl present in the entire gas mixture of HCl and water vapor was 22.5%, which is almost equivalent to the HCl content in the azeotropic hydrochloric acid (20.6%). The HCl concentration could also be controlled by changing the flow rate of the carrier gas. This work demonstrates a simple technique based on the diffusion theory that allows for the constant, controllable generation of a known concentration of HCl gas using an azeotropic hydrochloric acid system....
Nonionic surfactants are reported as being able to enhance enzyme stability and increase the conversion of enzymatic reactions. Surfactant‐assisted enzymatic hydrolysis conversion is affected by surfactant HLB values. This work investigated the influence of nonionic surfactants with different HLB values on chitosan enzymatic hydrolysis using cellulase enzyme by measuring the reducing sugars formation, viscosity, and molecular weight of hydrolyzed chitosan. A characterization analysis of hydrolyzed products was also carried out. A higher HLB value exhibits a better enzymatic chitosan hydrolysis performance, shown by the decrease in a solution’s viscosity and the increase in reducing sugar formation. Increasing the surfactant concentration will also increase the hydrolysis rate. Nonionic surfactants can protect cellulase enzyme from the denaturation of temperature and stirring influence. The higher the HLB value, the lower the molecular weight of the hydrolyzed chitosan. The result of UV–Vis demonstrated aldehyde groups formation during hydrolysis. The SEM analysis showed that the chitosan, hydrolyzed using different HLB values of surfactants, had different surface morphologies. However, it did not change the chemical structure of the hydrolysis product seen by the FTIR analysis. The XRD patterns showed that the relative crystallinity of raw chitosan decreased when hydrolyzed with surfactants....
Bio-degradable cassava starch-based adhesives were produced from chemically gelatinized starch formulations. The varying combinations of process parameters applied include: concentration of gelatinization modifier, mass % borax/starch, and temperature of reaction mixture. The physico-chemical parameters for characterizing the adhesive samples were viscosity, density, pH and bonding strength. The effects of the variation of process parameters on the quality of the adhesives were assessed using response surface (central composite) designs with 2 factors, to relate the highest adhesive quality with the optimal combination of process factors. The adhesives produced using HCl as the gelatinization modifier were of a higher quality than those produced using NaOH with one of the most important quality assessment parameters which is the bond strength being 22.31 kPa at 0.01 M and 20% mass borax/starch and 11.60 kPa at 0.01 M and 8% mass borax/starch for HCl and NaOH respectively. The experimental results demonstrated that the optimal temperature for the production of the adhesive was 85˚C....
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