Engineering Chemistry Vol. 7

Abstract: Carbonate hydroxyapatite is the common derivative of hydroxyapatite found in living systems. It is the building block of most hard tissues, including the teeth and bones. A vast majority of the applications of this versatile material focus on its biomedical applications, which is attributable to its closeness to biological apatites. Hydroxyapatite is a strong precursor to carbonate apatite in nature, and many experiments show that both are similar in a few respects. A significant divergence point is carbonate's obvious impact on its physicochemical properties and concomitant applications. The inclusion of carbonate ions into the lattice of hydroxyapatite results in morphological and physicochemical changes that vary with the method of synthesis and extent of substitution. The unique crystal structure, improved surface area, and porous morphology of carbonate hydroxyapatites also make it useful for catalysis and environmental remediation as adsorbents for heavy metals. This review briefly examines carbonate hydroxyapatite, its synthesis, its modification, and its characterization. It also highlights its biomedical applications while drawing attention to its non-medical potential.

Abstract: In this study, the CCD response surface methodology was used to model and optimise the performance of Lasienthera africanum leaves extract (LALE) as a corrosion inhibitor on mild steel. The experimental parameters were assessed at different immersion time and inhibitor concentration to determine the optimum conditions for corrosion mitigation. Using experimental results of the corrosion characteristics such as the weight loss, corrosion rate, and inhibition efficiency of LALE, new models were developed, the significance of which was tested using variance analysis. The developed RSM models of WL, CR, and IE were accurate and reliable, and their P-values were 0.0001, which is less than 0.05. Likewise, the R²-statistics (R², adjusted-R², and predicted-R²), adequate precision, and diagnostic plots were also used as a means to ascertain the degree of accuracy and adequacy of the WL, CR, and IE models. In addition, optimization of the corrosion inhibition process for LALE revealed that the optimum conditions for maximum IE, minimum WL, and CR were achieved at a concentration of 93.93 ppm and an immersion time of 228 hrs. Under these settings, the inhibition efficiency, weight loss, and corrosion rate were 93.85%, 0.294g and 3.267 mm/y, respectively. Therefore, the models are considered ideal for prediction with a confidence level of 95%, and the optimal combination is suitable for the corrosion inhibition process design. Hence these models can be recommended for applications such as oil well acidizing and pickling pipelines.

Abstract: The effect of sulfonic agents on the performance of solid acid catalysts in esterification reactions of long-chain fatty acids has been studied. Herein, sulfonated activated carbon with sulfanilic acid (SAC-SA) and sulfuric acid (SAC-SO4) as a sulfonic agent were prepared and used for esterification reaction to convert long-chain fatty acids into methyl esters within 5 h at 65°C. The obtained SAC-SA has a higher surface area than SAC-SO4 of 1301.981 and 1182.096 m²/g, respectively. When SAC-SO4 and SAC-SA catalysts were applied to the esterification reaction, the FAME product conversion results were 74.47 and 46.98 %, respectively. The physical property of SAC-SO4 has more macropores size distribution than mesopores size based on the BJH method. Large pore size on the catalyst will support the diffusion of large organic molecules to improve catalytic ability. The pore size determines the performance of solid acid catalysts, especially in long-chain fatty acid reactants for biodiesel production.

Abstract: Industrial wastes such as lead metal can cause serious problems because of their toxic nature and can pollute the environment. To reduce levels of lead metal, you can use a natural adsorbent from activated charcoal on the outer shell of ketapang seeds. The ketapang tree is a type of plant that is often found in the surrounding environment because it is used as a shade for the many falling ketapang seeds making waste in the environment to reduce environmental pollution from the falling ketapang can be used as an adsorbent because it contains cellulose and carbon elements. One alternative to reduce lead levels using adsorbents is through the adsorption process which is the process of adsorption of a solid or liquid that involves physical, chemical and electrostatic interactions between the adsorbate and the adsorbent on the surface of the adsorbent. The adsorption process using activated charcoal adsorbent is one of the most frequently used non-polar adsorbents because it has better adsorption power and surface area than other types of adsorbents. This study aims to determine the influencing variables and the optimum condition of the natural adsorbent from the activated charcoal of the outer shell of ketapang seeds on decreasing levels of metal Pb (NO3)2. The research method used is an experimental method with a two-level factorial design. The results showed that the adsorption temperature was the most influential variable in this study with an optimum yield presentation of 66.77%. The activated charcoal produced has a water content of 8%, ash content of 5.2% and an absorption capacity of methylene blue of 698 mg/g.

Abstract: In this study, we utilized an adsorbent based on rice straw for reducing hexavalent chromium ions (Cr (VI)) in an aqueous solution. The rice straw as adsorbent raw material was washed, dried, and powdered. Rice straw powder was heated at 450°C for 2 hours to obtain rice straw adsorbent. The adsorbent was activated with 1M H₃PO₄ for 4 hours. Characterization of the adsorbent was done using Fourier Transform Infra-Red (FTIR) method. FTIR spectra showed the presence of hydroxy, carboxylic, aromatic, and ether groups on the surface of the rice straw and the made adsorbent. The reduction of Cr (VI) ions in aqueous solutions was carried out using the adsorption batch method. The adsorption process was conducted in various the Cr (VI) solutions pH for 1-5 and variations in contact time for 5-720 minutes. The highest percentage reduction of Cr (VI) reached 66.90%. It has occurred at pH 2 and equilibrium at 600 minutes of contact time.

Abstract: The interfacial solar steam generator presents a viable and environmentally conscious solution for generating fresh water from seawater. The interfacial solar steam generator is accomplished through the integration of a photothermal material with a supporting material, resulting in a bilayer structure. In general, the efficiency of achieving a bilayer structure by the coating of a photothermal material on the surface of a substrate is limited. This is due to the potential for separation and variations in coating thickness, which can result in a drop in the rate of evaporation. In this study, a bilayer structure was successfully obtained through the implementation of a co-gelation technique utilizing a biomass-derived substrate, aerogel cellulose, and magnetite (Fe₃O₄) as photothermal materials. Additionally, we investigate the impact of magnetic fields on the evaporation rate of photothermal materials. The bilayer solar steam generator obtained demonstrates a notable evaporation rate of 1.87 kg.m^-2h^-1, which is sufficient to meet the daily water requirements of individuals.

Abstract: Accumulation of untreated and unrecycled paper has a negative impact on the environment. Like liquid waste handling, paper waste handling is also still being developed. It is known that activated carbon (AC) is one of the promising adsorbents that can be used to solve the environmental issue. Activated carbon can be made from organic waste, such as waste paper. The objective of this study is to investigate the operation condition of the pyrolysis process to obtain the activated carbon. The furnace temperature was set at 400°C for 1 hour under N₂ stream with a flow rate of 0.5 L/min. To provide a synergistic effect in the adsorption process, ZnO was derived from ZnCl₂ as a chemical activator for making active carbon. While Zn (CH₃COO)₂.2H₂O with different concentrations of 0.01, 0.05, and 0.1 M was grown into the pores of activated carbon. The photocatalytic activity of AC/ZnO was identified in the degradation process of methylene blue as a model of organic pollutants. X-ray diffraction (XRD), scanning electron microscope (SEM), and fourier transform infrared (FTIR) were used to characterize the product. The morphology of ZnO was observed in the form of a flower-like and occupying the surface of activated carbon. The photocatalytic activity showed that the methylene blue was completely degraded.

Abstract: Hydrogen is an environmentally friendly energy source that can be extracted from water through electrolysis. However, the slow oxygen evolution reaction (OER) at the anode side is the main obstacle to the widespread use of water-splitting devices. This study used self-developed highly porous nickel structures (SMNF) and commercial nickel foam (CNF) as working electrodes in the electrolysis process. Iron (II, III) Oxide (Fe₃O₄) as a catalyst is coated with a dip coating technique on the Ni porous structure and then calcined using a laser process to produce a Ni-Fe₃O₄-based electrode. Electrochemical test results show that the presence of Fe₃O₄ significantly impacts high reaction kinetics. The SMNF-Fe₃O₄ demonstrated an overpotential of 217,3 mV at 1 M KOH electrolyte, at a current density of 10 mA, lower to SMNF electrode without Fe₃O₄ with an overpotential of 361,4 mV under the same conditions. In addition, the difference in porosity less significantly affects the electrode's effectiveness due to the slight difference in mass loading, which is only < 5 mg. However, electro-impedance spectroscopy (EIS) testing shows better performance on SMNF-Fe₃O₄ with a smaller electrical series resistance (ESR), around 0.638 Ω, compared to CNF-Fe₃O₄, which is 0.767 Ω. Overall, observations by chronoamperometry test at an overpotential of 155 mV at 5 hrs show stable performance of SMNF-Fe₃O₄ electrodes.