Engineering Chemistry Vol. 1

Abstract: In biodiesel industries, the removal of glycerol from biodiesel is very important in the downstream process of the biodiesel production since the presence of glycerol in biodiesel causes diesel engine problems. Glycerol is commonly separated from biodiesel by extraction method using water, however, this method results in a vast amount of wastewater and requires a high energy consumption. In this work, a ceramic microfiltration membrane made of α-alumina was applied to remove glycerol from biodiesel. The microfiltration experiment was carried out using biodiesel containing various glycerol concentrations as the feed. For all investigated glycerol concentrations from 1000 ppm until 10,000 ppm in the feed, the membrane showed an excellent separation performance with rejection values of 91 to 99%. The profile of the permeate flux against the permeation time showed a flux decline because of the fouling phenomenon during the crossflow microfiltration experiment, and stable permeate fluxes were obtained after 2 h of permeation time. The result of this work showed that the separation process using the microfiltration membrane is a promising method to purify biodiesel instead of the conventional water washing method.

Abstract: Energy challenges in developing countries are more significant if they continue to use fossil materials and have an impact on air quality. Lignocellulosic biomass can be an alternative to new renewable sources to replace fossil materials. Indonesia produces various sources of lignocellulosic biomass, which can be used in multiple energy sources such as bioethanol. The hybrid pathway is one of the routes for producing bioethanol. The first stage of the hybrid process is the conversion of biomass into CO, CO₂, and H₂ (syngas) gas through the gasification process. Then the syngas is converted into bioethanol through fermentation using microorganisms as biocatalysts. The bioethanol production line is the Wood-Ljungdahlii pathway. Factors that affect syngas are the type of biomass (chemical, physical, and morphological properties) and the gasification process (type of gasifier, temperature, gasification agent, and ratio equilibrium (ER)). This paper reviews the challenges in implementing syngas fermentation. In particular, variations in the composition of syngas as a substrate for fermentation.

Abstract: Syngas fermentation is an alternative route that combines the advantages of thermochemical and biochemical processes have been proposed for biomass conversion to ethanol. One of the main obstacles to syngas fermentation is the low yield of ethanol, caused by the limited utilization of the syngas substrate due to low microbial cell concentration in the fermentation system. This research examined the modification of fermentation medium to improve microbial cell growth. The modifications were to increase the concentration of micronutrients/trace metals and macronutrients in the medium. The results showed that the maximum mass cell and maximum growth rate produced by microbial growth in the modified trace metal medium were 0.63 g/L and 0.0076 h^-1, while in a modified macronutrient medium were 0.97 g/L and 0.0298 h^-1. Modification of the macronutrient medium was able to increase the yield of biomass, but the opposite occurred in the modification of the trace metals. Meanwhile, the maximum concentration of ethanol from syngas fermentation in the modified macronutrient medium was lower than the concentration of ethanol in the standard medium.

Abstract: DME production by methanol dehydration using reactive distillation has a lot of potentials. However, the DME purity and methanol conversion is hard to be controlled and need inferential variable to be controlled. Data driven soft sensors can be utilised to select inferential variables, which can be used to control DME production by using reactive distillation. The data was collected from process simulation using ASPEN and analyzed by using PCA (Principal Component Analysis) and PLSR (Partial Least Squares Regression). The results show that based on the data driven soft sensors method, the DME purity can be controlled by using T4 as an inferential variable and ratio reflux as the manipulated variable. However, the methanol conversion is hard to be controlled because the potential inferential temperature was not significantly affected by reflux ratio and reboiler duty as the candidate manipulated variables.

Abstract: Spherical colloidal clusters have various types of particle arrangements. Interestingly, one type has an icosahedron symmetry, characterized by the existence of five-fold axes. When the colloidal particle size is comparable to the wavelength of light, icosahedral colloidal clusters exhibit a unique triangular reflection with a specific wavelength, owing to optical interference. In this paper, we report the results of a detailed optical study on the position-dependent peak wavelength within the triangular region. Based on the map of the peak wavelength and spectral shape, we propose a structural model of the icosahedral colloidal cluster and discuss its formation process.

Abstract: Manganese sulfate is an important base manganese salt; nearly 80% of the world's manganese products are produced using manganese sulfate or manganese sulfate solution. Furthermore, manganese sulfate has many applications in industry and agriculture; thus, manganese sulfate solution impurity removal technology is important. This study aims to remove impurities from manganese sulfate solution-using complex low-grade manganese ore and manganese-rich fumes after pressure acid leaching to obtain a manganese sulfate solution, which is then purified through iron removal by oxidation neutralization; finally, the purified liquid is treated using extraction-back-extraction. We investigated the effects of various extraction parameters on the extraction rate of manganese, as well as the effects of various back-extraction parameters on the manganese back-extraction rate and manganese ion concentration in the back-extraction solution, and studied the extraction-back-extraction process. We found that the extraction and back-extraction rates of manganese could reach 95% and 96.9%, respectively, under optimal conditions..

Abstract: In recent years, the frequent use of antibiotics has led to the continuous release of antibiotics into the water environment, which not only poses a potential threat to public health, but also contributes to the generation and spread of antibiotic resistance. In addition, due to the high environmental persistence and low biodegradability of antibiotics, it is difficult to be effectively degraded by traditional water treatment processes. Therefore, it is urgent to develop clean and efficient treatment technologies. Advanced oxidation processes (AOPs), which can effectively remove refractory organic pollutants from water, has become a promising water treatment technology. In this regard, persulfate (PS)-based AOPs (PS-AOPs) has attracted extensive attention of researchers. In this system, PS can be activated by energy and catalysts to produce highly oxidizing active species, and achieve efficient degradation of antibiotics. Due to its rich surface functional groups, high specific surface area and high adsorption properties, researches on the activation of PS by carbonaceous materials have been reported continuously. In this paper, the research progress of carbon nanotubes, graphene, biological carbon, active carbon and hetero-atom doped carbon materials as catalysts to activate PS and degrade antibiotics is reviewed. In addition, the structure and properties of different carbon materials and the activation mechanism of free radical and non-free radical mediated by carbon materials were introduced, and the effects of PS dosage, catalyst dosage, temperature and pH on the degradation of antibiotics were discussed. Finally, this paper points out the important development direction in the future, that is, the development of environmental protection, high efficiency, low cost carbon materials and further research on the actual wastewater treatment performance.