Experimental, theoretical explorations and MD simulation of the inhibition efficiency of tyrosine on carbon steel in hydrochloric acid

Research on the inhibitory properties and mechanism of carboxymethyl cellulose-modified sulfur quantum dots towards calcium sulfate and calcium carbonate

An eco-friendly antimicrobial sulfur quantum dot scale inhibitor (CMC-SQDs) synthesized using carboxymethyl cellulose (CMC) showed strong inhibition of calcium sulfate (CaSO4) at a concentration just below 1 mg/L, with an inhibition efficiency exceeding 99 %. However, the precise interaction process between CMC-SQDs and CaSO4 remains unclear. This article investigates the effectiveness of SQDs in inhibiting the formation of CaSO4 and calcium carbonate (CaCO3) scales. Through static scale inhibition tests, molecular dynamics simulations, and quantum chemical calculations, the study aims to elucidate the different impacts of CMC-SQDs on CaSO4 and CaCO3 scale formation. The research focuses on understanding the relationship between the structural activity of CMC-SQDs and their scale-inhibiting performance and delving into the underlying mechanisms of scale inhibition. The findings describe the role of SQDs in a water-based solution, acting as persistent "nanodusts" that interact with calcium (Ca2+) ions and sulfate ions. CMC forms complexes with Ca2+ ions, and the presence of SQDs enhances the van der Waals force, indirectly increasing the resistance of associated ions and the binding energy on the surface of precipitated gypsum. Conversely, SQDs exhibit weak surface stability and have minimal binding energy when interacting with calcite, leading to limited occupation of available adsorption sites.

Synthesis, DFT, molecular dynamics, and Monte Carlo simulation of a novel thiourea derivative with extraordinary inhibitive properties for mild steel in 0.5 M sulphuric acid

A novel thiourea derivative has been successfully synthesized via green routes and fully characterized by FT-IR, ¹H, ¹³C-NMR, and elemental analysis. The synthetic inhibitor 2-amino-N-(phenylcarbamothioyl) benzamide (APCB) was assessed as a corrosion inhibitor for mild steel (MS) in 0.5 M H₂SO₄. Various electrochemical techniques, such as electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP), have been used to evaluate inhibition efficiency. As a result, EIS and PDP agreed with each other, indicating that APCB exhibits an inhibition performance that exceeds 96% at a concentration of 2 × 10^-4 M and increases with an increase in temperature up to 98% at 333 K. However, PDP measurements showed that APCB is a mixed type of inhibitor. In addition, SEM, EDX, AFM, and contact angle measurements were used as a topological surface characterization technique that confirmed the formation of a protective layer over the MS surface. Additionally, the complex formation was thoroughly confirmed by UV-Vis measurements. The adsorption of APCB proved the highest compliance with the Langmuir adsorption isotherm. Furthermore, density functional theory (DFT) calculations were conducted to establish the correlation between the electronic structure and excellent inhibition efficiency. Moreover, molecular dynamics (MD) simulations were used to find interaction energy in different media. Finally, the adsorption affinity of the MS surface for different concentrations of APCB was verified via Monte Carlo (MC) simulations. Owing to the outcomes of this study, it is remarkable that APCB, with its low cost and simple synthesis, might be an exceptionally prominent option for mild steel protection.