Explicit Solutions for Real-time Reversible Inhibition Kinetics using Lambert W Function: Towards Progress Curve Analysis

Accurate estimation of kinetic parameters is challenging due to the dynamics and mathematical nature of the chemical systems. This paper presents simple, yet efficient closed-form solutions for the enzymatic conversion of the substrate to the product in real-time derived using the Lambert W function. The real values of the Lambert W function were calculated from the Lambert package as implemented in MATLAB. The expressions exhibit remarkable robustness in estimating the parameters for randomized data at 1% to 4% variation in noise levels. Furthermore, unlike the initial rates method, the expressions estimate chemical kinetic parameters utilizing a full range of experimental data, thus minimizing the risk of missing information that would be detected at an extended time-span. Thus, the implementation of closed-form solutions presented in this paper for the estimation of kinetic parameters eliminates common pitfalls imposed by the initial rates and double reciprocal methods. Keywords:          Enzyme, Lambert W function, Reversible inhibition, Closed-form solution

The role of organic acid metabolites in geo-energy pipeline corrosion in a sulfate reducing bacteria environment

The dominant factors in Microbial Influenced Corrosion (MIC) are hard to determine because normally several individual species and their metabolites are involved, and, moreover, different metabolites may cause opposing effects. To address this problem, the effects of individual metabolites from different species should be elucidated when at the same time other metabolites are held constant. In this study, the role is investigated of simulated organic acid metabolites, namely, acetic and L–ascorbic acids, on corrosion of geo-energy pipelines (carbon steel) in a simulated Sulfate Reducing Bacteria (SRB) environment. The SRB environment is simulated using a calcium alginate biofilm, abiotic sulfide, CO(2), and NaCl brine. The electrochemical results show that both simulated organic acid metabolites accelerate corrosion in a simulated SRB environment. The results are further supported by electrochemical weight losses, kinetic corrosion activation parameters, multiple linear regression, ICP-OES, pH, and XRD. However, a comparison of electrochemical results with those published in the literature for a simulated SRB environment without acetic or L-ascorbic acid under similar experimental conditions shows that the presence of acetic in this study results in lower corrosion current densities while in presence of L-ascorbic acid results into higher corrosion current densities. This implies that acetic and L-ascorbic acids inhibit and accelerate corrosion, respectively. In addition, the results highlight that H(2)S is a key role of corrosion in the presence of organic acid. The results of this study are important new and novel information on the role of acetic and L-ascorbic acids in corrosion of geo-energy pipelines in the SRB environment

Bio-waste Crude Extracts as Alternatives to Synthetic Antioxidants in Petroleum Lubricants

The increasing environmental concerns and the need for enhanced lubricant stability in petroleum industry necessitate sustainable solutions. This paper reports the use of crude extracts from bio-wastes of lemongrass and pepper fruits, as eco-friendly antioxidants to improve thermal and oxidation stability in petroleum lubricants. The bio-wastes samples were collected from Buguruni market in Ilala district of Dar es Salaam, Tanzania. The samples were dried, ground into powder, methanol-extracted, and concentrated to yield crude extracts. The crude extracts were then analyzed via phytochemical tests, Fourier Transform Infrared (FTIR) and gas Chromatography Mass Spectrometry (GC-MS) to identify antioxidant compounds. The extracts were blended with petroleum base oils and tested for oxidation and thermal stability using a Seta oxidation stability bath and Thermogravimetric Analysis, respectively. Kinematic viscosity and volatility analyses were also conducted. The phytochemical, FTIR, and GC-MS analyses confirmed that the extracts were rich in radical scavengers. The oxidation tests showed that base oils added with crude extracts had an induction time of 400 min, compared to the 320 min for those without, demonstrating that the extracts suppress oxidation. Thermal stability tests indicated that the oils blended extracts exhibited higher temperatures at maximum weight loss (>250 °C) and had fewer insoluble residues, suggesting improved stability. Moreover, kinematic viscosity increased and volatility reduced, implying enhanced lubrication and high-temperature stability. Both lemongrass and pepper fruits extracts had similar antioxidant effectiveness, validating their potential in petroleum lubricants. This research underlines bio-waste's viability as an antioxidant source, contributing to a circular economy in the energy sector

Simulated microbial corrosion in oil, gas and non-volcanic geothermal energy installations: The role of biofilm on pipeline corrosion

The role of biofilm in the Microbiologically Influenced Corrosion (MIC) of carbon steel by Sulfate Reducing Bacteria (SRB) in oil and gas exploitation, and geothermal installations is investigated. Simulated biofilm made of calcium alginate, abiotic sulfide (to mimic SRB metabolic end product HS), CO2 (to mimic CO2 from SRB dissimilatory sulfate reduction) and simulated brine (3.0 wt% NaCl) are used to simulate the SRB environment. For reference experiments, distilled water is used instead of simulated brine. The electrochemical results show that the simulated biofilm in the reference at 120 min exposure time and in brine experiments neither inhibits nor accelerates corrosion. These results are strongly supported by corrosion kinetic adsorption parameters, statistical T-test, ICP-OES, pH, SEM-EDS and XRD. The results contradict with the existing literature on the role of biofilm and this is likely due to the presence of both HS and CO2 as simulated SRB metabolites. Despite of this discrepancy, the obtained corrosion rates (0.25 to 1.6 mm/year) in the simulated SRB environment are comparable to published corrosion rates obtained in SRB experiments (0.20 to 1.2 mm/year). The results highlight the novelty of this research and have a direct impact on the role of other microbial metabolites on the corrosion of carbon steel