ChemEngineering, Volume 8, Issue 5 (October 2024) – 4 articles

In this study, we successfully fabricated a composite sheet comprising bacterial cellulose (BC) and polyaniline (PAN), integrated with activated carbon (AC), to produce electrodes in a supercapacitor. The electrical conductivity level can be adjusted by adding AC into the composite. FTIR revealed hydrogen bonding interactions between the -OH groups of the bacterial cellulose and the -NH groups of the polyaniline. The XRD pattern showed the characteristic peak of activated carbon. The SEM showed that PAN was filled into the porous network of the bacterial cellulose. The AC was randomly distributed onto the composite’s surface. The composite was thermally stable up to 200 °C. The electrical conductivity was reported to be 1.5–3.5 S/m when AC was added from 0.2 to 1 wt%. Furthermore, the specific capacitances (Cs), energy densities (Es), and power density (P) were typically reported to be 30–70 F/g, 4–11 Wh/kg, and 400–700 W/kg, respectively. Moreover, the optimization of the activated carbon ratio led to a reduction in the charge transfer resistance (R_ct), as demonstrated by a Nyquist plot analysis, thereby enhancing electrical conductivity. Overall, the bacterial cellulose and polyaniline composite sheet, incorporating activated carbon, exhibited excellent properties, making it a promising candidate for bioelectrode supercapacitor applications in the near future. Full article

Microplastic contamination in terrestrial environments has risen significantly, far exceeding levels in marine environments. This shift underscores the concerning prevalence of microplastics (MPs) in sewage sludge and soil, raising environmental apprehensions. Microplastics from various sources accumulate in sewage systems, consequently, sewage sludge and soil have transformed into primary reservoirs of microplastic pollutants, capable of infiltrating aquatic ecosystems. While using sludge to enrich soil provides nutrients, it simultaneously introduces substantial microplastic content, posing environmental hazards. These microplastics can accumulate in the soil, altering its properties and potentially polluting deeper soil layers and groundwater, compounding environmental risks. This review scrutinizes the abundance, types, and shapes of microplastics in sewage sludge and soil, evaluating their impacts and suggesting future research directions. Statistical analysis reveals higher microplastic concentrations in sludge (271 Particles/kg dry weight) than in soil (34.6 Particles/kg). Strong correlations between microplastic concentrations in soil and sludge (R² = 0.95) underscore the significant influence of sludge application on soil ecosystems. The p-value of 0.0001 indicates a significant correlation between MP amounts in soil and sludge, while the p-value of 0.47 suggests no significant association between MP concentrations in wastewater and sludge. Research confirms that microplastics influence sludge properties, microbial communities, and soil characteristics, contingent on microplastic attributes and soil conditions. Predominantly, microplastic shapes found in sludge and soil are fibers and fragments, often linked to agricultural fertilizer use. Microplastics detrimentally affect soil bulk density and aggregate stability, impairing soil structure and surface. Furthermore, their presence alters pollutant transport behavior in soil, emphasizing the imperative to investigate microplastics’ effects and transport mechanisms for mitigating environmental and health risks. Full article

The deoxygenation process in water used in well injection operations is an important matter to eliminate corrosion in the petroleum industry. This study used molecular dynamics simulations to understand the behavior of siloxane surfaces by studying the surface properties with two functional groups attached to the end of siloxane and their effect on the deoxygenation process. The simulations were performed using LAMMPS to characterize surface properties. Jmol software version 14 was used to generate siloxane chains with (8, 20, and 35) repeat units. We evaluated properties such as total energy, surface tension, and viscosity. Then, we used siloxane as a membrane to compare the efficiency of deoxygenation for both types of functional groups. The results indicated that longer chain lengths increased the total energy and viscosity while decreasing surface tension. Replacing methyl groups with trifluoromethyl (CF3) groups increased all the above mentioned properties in varying proportions. Trifluoromethyl (CF3) groups showed better removal efficiency than methyl (CH3) groups but allowed more water to pass. Furthermore, the simulations were run using the class II potential developed by Sun, Rigby, and others within an explicit-atom (EA) model. This force field is universally applicable to the atomistic simulation of polymers, inorganic small molecules, and common organic molecules. Full article

Household food waste (HFW), which is rich in organic matter, is a good candidate for producing added-value bio-based chemicals, such as volatile fatty acids (VFAs), by acidogenic fermentation processes. However, the lack of design tools, such as appropriate kinetic models, hinders the implementation of this technology because the results of these processes are affected by operational factors. In this work, VFA production by the acidogenic fermentation of HFW under uncontrolled pH levels (4–5) was studied at thermophilic (55 °C) and mesophilic (35 °C) temperature conditions. Batch reactors were used to digest HFW, and VFA production and the individual acid distributions were measured at different fermentation times from 0 to 624 h. The results showed higher individual and total VFA production at 35 °C and 120 h of fermentation time as a consequence of the competition between the VFA production and decomposition reactions. Acetic and valeric acids were VFAs mainly produced as a result of a high content of proteins in the initial substrate, and a small amount of propionic and butyric acids were present. A simplified kinetic model was successfully developed to represent the complex process of VFA formation from the acidogenic fermentation of HFW. A simple mechanism for the production–decomposition of VFAs, corresponding to a zero-order reaction for the first 48 h and a single consecutive reaction from that time on, was proposed. For both mesophilic and thermophilic conditions, the suggested kinetic model was able to predict the individual and total concentrations of VFAs along the fermentation time. Full article