Engineering Chemistry Vol. 12

Abstract: The changes in the mechanical and physical properties of concrete prepared by incorporating various metal oxide nanoparticles into cement products used in both the oil/gas industry and construction have been analyzed in this review. The study compares the properties exhibited by transition metal oxide and some metal nanoparticles in both isolated and complex forms with polymers in concrete. Analyses were conducted primarily in the direction of changes occurring in properties due to the addition of metal oxide nanoparticles such as magnetite Fe₃O₄, TiO₂, ZnO, Fe₂O₃, Ag, CuO, TiO₂/SiO₂, Al₂O₃, ZrO₂, core/shell Fe₃O₄/SiO₂, in dispersed form as cement powder or in water. It has been showed that appropriate changes occur in properties such as compressive and flexural strength, adhesion, initial and final setting, water absorption, porosity, electrical conductivity, degradation when metal oxide nanoparticles are added to cement. The density and size of nanoparticles affect their response to various influences, alongside the fundamental properties of the material.

Abstract: Water pollution causes about 1.4 million deaths annually, and in Nigeria, especially in rural areas and the Niger Delta, millions lack access to clean water due to crude oil contamination. This study investigates using carbonized Flamboyant (Delonix regia) pods as a sustainable, low-cost adsorbent for removing petroleum hydrocarbons from contaminated water, promoting agricultural waste valorization and pollution reduction. Water samples collected from Obiakpor in Port Harcourt, Nigeria, were found to contain 75.22 mg/L of total petroleum hydrocarbons (TPH) and were subsequently used to evaluate the efficiency of the prepared adsorbent. Activated carbon was prepared by washing, drying, carbonizing the pods at 550 °C, chemically activating with KOH, neutralizing, then drying and sieving for uniformity. Carbonization yielded 30.2%, with proximate analysis showing low moisture (1.86%), moderate ash (4.94%), and high volatile matter (77.81%), favoring thermal stability and pore formation. Scanning Electron Microscopy (SEM) and Brunauer–Emmett–Teller (BET) revealed a highly porous structure with an average pore diameter of 20 μm and a large surface area of 226.4 m²/g. X-ray Diffraction (XRD) confirmed a semi-crystalline structure dominated by graphite (36 wt.%) and silicate minerals, enhancing mechanical strength and π–π interactions. Thermogravimetric Analysis (TGA showed that thermal stability was maintained between 300–500°C. Adsorption tests showed TPH removal increased with adsorbent dosage up to 0.2 g, reaching equilibrium afterward. The Freundlich isotherm best described the adsorption (R² = 0.9104), indicating multilayer adsorption on a heterogeneous surface, supported by high constants (K_f = 166.36; n = 2.35). Kinetic studies indicated rapid adsorption within 25 minutes, fitting the pseudo second order model (R² = 0.9575). These findings confirm that carbonized Flamboyant tree pods (FTP) are effective, renewable, and thermally stable adsorbents for petroleum-contaminated water treatment.

Abstract: Biogas produced via anaerobic digestion where microorganisms break down organic matter in the absence of oxygen, is seen as a promising solution to global energy and environmental challenges. Co-digestion of two or more wastes enhances biogas yield. However, study on optimization of biogas yield using substrate combination is seldom reported. This study was conducted to determine optimum substrate combination to maximize biogas yield. Simple lattice mixture design (SLMD) of Design Expert 13 was employed for experimental design and model development. SLMD was used to systematically vary ratios of different biodegradable wastes. Cassava vinasse (CV), kitchen waste (KW), cow dung (CD) and poultry dropping (PD) were taken as independent variables, and biogas yield as response. Fifteen biodigesters were set-up for the laboratory experiment. Four of the biodigesters were single-waste setups, while the rest digesters were used for co-digestion. A Scheffé quadratic model was developed to predict biogas yield and numerical optimization technique was used for optimization. The model developed gave adequate prediction with coefficient of determination (R²) of 0.7504 and adequate precision of 7.72. The optimum substrate combination of cassava vinasse (8.6%), kitchen waste (7.1%), cow dung (41.6%) and poultry droppings (42.7%) were obtained for co-digestion process. The findings from this study made invaluable contributions to the field of waste co-digestion to enhance biogas production, offering a sustainable approach to managing organic waste and producing renewable energy.

Abstract: Refined Coconut oil (RCNO) is the most used feedstock for biodiesel production, which undergoes alkali-catalyzed transesterification to produce fatty acid alkyl esters due to its low free-fatty acids (FFA) content. This study utilized coconut oil fatty acid distillate (COFAD) as an alternative feedstock to RCNO. As it contains high amounts of FFA, it is pretreated through acid-catalyzed esterification to derive fatty acid methyl esters. The kinetics of the hydrochloric acid catalyzed esterification was investigated with the conditions of 10:1 methanol-to-COFAD molar ratio, 5wt% acid catalyst loading (0.4729N with respect to reaction mixture), reaction temperatures at 45°C, 55°C and 65°C, and 2 hours reaction time. It was found that temperature had a positive effect on the reaction. The highest FFA conversion was observed when the reaction temperature was set to 65°C, where it reached 87%, and the activation energy of the reaction was 29690.96 J^.mol^-1. The highest conversion predicted by the kinetic model is approximately equal to 89%. A good fit of the experimental and calculated data was observed with r² > 0.96. Moreover, the spontaneity of the reaction, as well as the effect of water on the reaction, were identified through the determination of thermodynamic parameters. The esterification reaction was found to be spontaneous only at high temperatures.

Abstract: The valorization of agricultural byproducts presents a viable strategy to mitigate feedstock challenges in Philippine biodiesel production. One promising feedstock for the industry is coconut oil fatty acid distillate (COFAD), which can be optimized for conventional alkali transesterification through pre-treatment by acid-catalyzed esterification. This process involves converting free fatty acids (FFAs) into fatty acid methyl esters (FAMEs) using an innovative solid acid catalyst derived from directly sulfonated cacao shell (CS-SAC). A response surface methodology (RSM) approach was employed to systematically assess the influence of two key parameters—methanol-to-COFAD molar ratio (6.4 to 16.9 mol/mol) and catalyst loading (0.07 to 0.42 mmol H+/g COFAD)—on FFA conversion, while maintaining a constant temperature of 60°C and a reaction time of two (2) hours. Catalyst reusability was evaluated over four cycles under conditions that achieved the highest FFA conversion. Results indicated that an increase in the methanol-to-COFAD ratio initially enhanced FFA conversion. However, beyond a certain point, further increases in methanol concentration led to reduced conversion due to the dilution of the reaction medium. Regarding catalyst loading, a direct positive correlation with FFA conversion was observed across the tested range. The highest FFA conversion of 0.604 was achieved at the upper limits of the evaluated parameters, suggesting that further optimization beyond these ranges may further enhance conversion efficiency. CS-SAC demonstrated excellent stability, maintaining 90.25% of its initial conversion efficiency even after three reuse cycles. These findings underscore the potential of directly sulfonated CS-SAC as a robust catalyst for industrial-scale esterification of COFAD.