Noorazlenawati Borhan

The increasing demand for sustainable aquafeed ingredients has driven the exploration of alternative protein sources to replace conventional fishmeal and soybean meal. Defatted algae cake (DAC), a by-product of microalgae-based biofuel production, presents a promising and eco-friendly protein source for aquaculture. This review examines the potential of DAC as a sustainable alternative feed ingredient by assessing its nutritional composition, inclusion levels, digestibility, economic feasibility, and environmental benefits. Rich in proteins, essential amino acids, bioactive compounds, and functional lipids, DAC has demonstrated positive effects on fish growth, feed efficiency, and immune responses when incorporated at optimal levels. However, high production cost, variability in nutrient composition, the presence of anti-nutritional factors, and species-specific dietary requirements pose challenges to its widespread application. Comparative analyses indicate that DAC inclusion levels at optimal levels, generally under 10% in fish feed, can maintain growth performance across various species, while higher levels may impact digestibility, feed efficiency, and nutrient bioavailability. The economic viability of DAC is influenced by its cost relative to traditional feed ingredients, advancements in processing, improved digestibility for fish, and integration within circular bioeconomy models. Additionally, its use in aquaculture contributes to sustainability by reducing reliance on overexploited marine resources and mitigating environmental impacts associated with fishmeal and soybean meal production. This review highlights the need for further optimization in DAC processing and formulation to enhance its utilization as a cost-effective and sustainable aquafeed ingredient, supporting the long-term growth of the aquaculture industry.

This work reports the synthesis and catalytic evaluation of mono- and bimetallic Zr/Sn/Al-SBA-15 catalysts for the chemo-catalytic conversion of glucose to lactic acid. SBA-15 was modified via alumination to enhance Brønsted acidity and subsequently impregnated with varying loadings of zirconium and tin to introduce Lewis acid sites. Comprehensive characterization using BET, XRD, and NH₃-TPD confirmed that metal loading significantly influenced the textural and acidic properties of the catalysts. Among the monometallic variants, 2% Sn/Al-SBA-15 exhibited the highest lactic acid yield (4.1%) and glucose conversion (47.5%) under the screening conditions (200 °C, 5 bar N₂, and 3 h). Bimetallic catalysts achieved higher glucose conversions (up to 72.5%) but slightly lower lactic acid yields, likely due to side reactions and catalyst deactivation. Optimization studies identified 210 °C and 50 bar N₂ as the optimal conditions, achieving a lactic acid yield of 25.2% with 99.6% glucose conversion. The results highlight the synergistic role of Lewis and Brønsted acid sites in enhancing catalytic performance and demonstrate the potential of Zr/Sn/Al-SBA-15 catalysts for sustainable lactic acid production from biomass-derived glucose.

Density functional theory (DFT) and molecular dynamics (MD) simulations were employed to investigate the inhibition mechanism of cationic quaternary ammonium surfactant corrosion inhibitors (CIs) with varying chain lengths in 1.0 M HCl and 500 ppm acetic acid on Fe (110) surfaces. DFT calculations demonstrated that all surfactant CI molecules possess favorable inhibition properties, with the cationic quaternary ammonium groups (N⁺) and alpha carbon serving as electron-donating reactive centers, characterized by a low band-gap energy of 1.26 eV. MD simulations highlighted C12, with a 12-alkyl chain length, as the most promising CI molecule, exhibiting high adsorption and binding energies, a low diffusion coefficient, and a random distribution at low concentrations, thereby facilitating optimal adsorption onto the Fe (110) metal surface. The insights gained from computational modeling regarding the influence of alkyl chain length on inhibition efficiency, coupled with the comprehensive theoretical understanding of cationic quaternary ammonium surfactant CI molecules in acidic corrosion systems, can serve as a foundation for the future development of innovative surfactant CI molecules incorporating ammonium-based functional groups.

Density functional theory (DFT) calculation and molecular dynamics (MD) simulation were performed to do an in-depth study on the inhibition mechanism of quaternary ammonium surfactant CI molecules with a different chain length in the presence of 1.0 M HCl and 500 ppm acetic acid on the Fe (110) metal surface. Results from DFT calculation showed that all surfactant CI molecules have good inhibition properties where the cationic quaternary ammonium groups (N⁺) and the alpha carbon act as a reactive centre to donate electrons to the metal surface with low band-gap energy of 1.26 eV. In the MD simulation, C12 with a 12-alkyl chain length showed the most promising CI molecules with high adsorption energy and binding energy values, low diffusion coefficient towards the corrosion particles and randomly scattered at low concentration that give better adsorption towards the Fe (110) metal surface. The finding on the effect of the alkyl chain length on the inhibition efficiency of all quaternary ammonium CI molecules based on computer modelling data and the success of an in-depth study on the theoretical understanding of quaternary ammonium surfactant CI molecules in the acidic medium corrosion system towards metal surface could be used as the future development of new surfactant CI molecules with ammonium-based functional groups.

Gemini surfactant corrosion inhibitor (CI) is one type of CI mainly used in mitigating corrosion in the complex system of oil/gas production industries. Computer modeling methods such as density functional theory (DFT) calculation and molecular dynamic (MD) simulation are required to develop new CI molecules focusing on their application condition as a prediction or screening process before the physical empirical assessment. In this work, the adsorption inhibition efficiencies of two monomer surfactants (2B and H) and their respective Gemini structures with the addition of different spacers (alkyl, benzene, ester, ether, and ketone) are investigated using DFT calculation and MD simulation method in 3% sodium chloride (NaCl), and 1500 ppm acetic acid solutions. In DFT calculation, 2B-benzene molecules are assumed to have the most promising inhibition efficiency based on their high reactivity and electron-donating ability at their electron-rich benzene ring region based on the lowest bandgap energy (0.765 eV) and highest HOMO energy value (−2.879 eV), respectively. DFT calculation results correlate with the adsorption energy calculated from MD simulation, where 2B-benzene is also assumed to work better as a CI molecule with the most adsorption strength towards Fe (110) metal with the highest negative adsorption energy value (−1837.33 kJ/mol at temperature 323 K). Further, diffusion coefficient and molecular aggregation analysis in different CI concentrations through MD simulation reveals that only a small amount of Gemini surfactant CI is needed in the inhibition application compared to its respective monomer. Computer simulation methods successfully predict and screen the Gemini surfactant CI molecules that can work better as a corrosion inhibitor in acetic acid media. The amount of Gemini surfactant CI that needs to be used is also predicted. The future planning or way forward from this study will be the development of the most promising Gemini surfactant CI based on the results from DFT calculation and MD simulations.

More aggressive reservoir conditions, such as higher concentrations of CO2 corrosive gases, have a massive effect on corrosion. Moreover, additional aqueous species, such as organic acids, have complicated the conditions and enhanced corrosion to the maximum rate. This study investigates and screens three commercial corrosion inhibitors on their performance in mitigating corrosion at welded areas of carbon steel in high CO2 conditions with the presence of organic acids. These investigations were conducted via chemical elucidations to study the functional groups present in the compounds that affect the inhibition performance and the electrochemical measurements to evaluate the inhibition activities and efficiency of these commercial inhibitors under extreme conditions of high CO2 and organic acids. The results indicated that only CT5727 and CT17906 gave a high inhibition efficiency of 90% in the absence and presence of organic acid, with CT5727 giving the lowest corrosion rate of 0.038 mmpy in the absence of organic acid, while CT17906 gave the lowest corrosion rate of 1.00 mmpy in organic acid condition. On the other hand, D4305 gave the worst inhibition performance under both conditions. The elucidation of these inhibitors also found that specific functional groups such as hydroxy, carboxylic acid, alkyl and alkene presence in the structure were believed to affect the inhibition performance of these commercial inhibitors in mitigating corrosion. These could be used as a future reference for the new development of corrosion inhibitors in similar conditions.

In recent years, numerous research work has been conducted in order to find the most practical and cost-effective solution for corrosion issues in the oil and gas industry. Several studies have revealed that fatty hydrazide derivatives are the most suitable corrosion inhibitor for the application in the said industry. These compounds can also act as effective corrosion inhibitors in acidic medium with inhibition efficiency greater than 95%. This review summarizes and discusses the recent corrosion inhibitor development in acidic media from 2017 until 2021, focusing on fatty hydrazide derivatives. The significant findings and mechanisms of inhibition have been elucidated. In addition, intake on the computer simulation studies of fatty hydrazide inhibition properties is also included in this review. Finally, some suggestions for future research on corrosion inhibitors have been recommended.

Injection of alkaline (A), polymer (P), and surfactant (S) chemicals in enhanced oil recovery (cEOR) processes increases output by changing the properties of the injected fluid. In this work, micellar fluid interactions were studied via microemulsion rheological analysis. Crude oil and stimulated brine with ASP or SP was used for bottle testing. The results revealed that no microemulsion was produced when ASP (Alkaline, Surfactant, and Polymer) or SP (Surfactant and Polymer) was left out during the bottle testing phase. The addition of ASP and SP led to the formation of microemulsions—up to 29% for 50% water cut (WC) ASP, and 36% for 40% WC SP. This shows that the addition of ASP and SP can be applied to flooding applications. The results of the rheological analysis show that the microemulsions behaved as a shear-thinning micellar fluid by decreasing viscosity with increase in shear rate. As per the power-law equation, the ASP micellar fluid viscoelastic behavior shows better shear-thinning compared to SP, suggesting more efficiency in fluid mobility and sweep efficiency. Most of the microemulsions exhibited viscoelastic fluid behavior (G’ = G”) at angular frequency of 10 to 60 rad s⁻¹, and stable elastic fluid behavior (G’ > G’’) below 10 rad s⁻¹ angular frequency. The viscosity of microemulsion fluids decreases as temperature increases; this indicates that the crude oil (i.e., alkanes) was solubilized in core micelles, leading to radial growth in the cylindrical part of the wormlike micelles, and resulting in a drop in end-cap energy and micelle length. No significant difference was found in the analysis of viscoelasticity evaluation and viscosity analysis for both ASP and SP microemulsions. The microemulsion tendency test and rheology test show that the addition of ASP and SP in the oil-water interface yields excellent viscoelastic properties.