Corrosion inhibition of Pichia sp. biofilm against mild steel corrosion in 1 M H2SO4

Investigation of Corrosion Inhibition of Mild Steel in 0.5 M H2SO4 with Lachancea fermentati Inhibitor Extracted from Rotten Grapefruits (Vitis vinifera): Adsorption, Thermodynamic, Electrochemical, and Quantum Chemical Studies

Corrosion inhibition of mild steel (MS) was studied using Lachancea fermentati isolate in 0.5 M H2SO4, which was isolated from rotten grapes (Vitis vinifera) via biofilm formation. Biofilm over the MS surface was asserted by employing FT-IR and FE-SEM with EDXS, electrochemical impedance spectroscopy (EIS), AFM, and DFT-ESP techniques. The weight loss experiments and temperature studies supported the physical adsorption behavior of the corrosion inhibitors. The maximum inhibition efficiency (IE) value (90%) was observed at 293 K for 9 × 106 cfu/mL of Lachancea fermentati isolate. The adsorption of Lachancea fermentati isolate on the surface of MS confirms Langmuir's adsorption isotherm model, and the -ΔG values indicate the spontaneous adsorption of inhibitor over the MS surface. Electrochemical studies, such as potentiodynamic polarization (PDP) and EIS were carried out to investigate the charge transfer (CT) reaction of the Lachancea fermentati isolate. Tafel polarization curves reveal that the Lachancea fermentati isolate acts as a mixed type of inhibitor. The Nyquist plots (EIS) indicate the increase in charge transfer resistance (Rct) and decrease of double-layer capacitance (Cdl) values when increasing the concentration of Lachancea fermentati isolate. The spectral studies, such as UV-vis and FT-IR, confirm the formation of a complex between MS and the Lachancea fermentati isolate inhibitor. The formation of biofilm on the MS surface was confirmed by FE-SEM, EDXS, and XPS analysis. The proposed bioinhibitor shows great potential for the corrosion inhibition of mild steel in acid media.

A Combined Experimental and Computational (DFT, RDF, MC and MD) Investigation of Epoxy Resin as a Potential Corrosion Inhibitor for Mild Steel in a 0.5 M H2SO4 Environment

In this work, a tetrafunctional epoxy resin entitled 2,3,4,5-tetraglycidyloxy pentanal (TGP) was tested and investigated as a potential corrosion inhibitor for mild steel (MS) in 0.5 M H₂SO₄ solution. The corrosion inhibition process for mild steel was employed alongside various techniques, such as potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), temperature effect (TE), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and theoretical approaches (DFT, MC, RDF and MD). Further, the corrosion efficacies obtained at the optimum concentration (10^-3 M of the TGP) were 85.5% (EIS) and 88.6% (PDP), respectively. The PDP results indicated that the TGP tetrafunctional epoxy resin acted the same as an anodic inhibitor type in 0.5 M H₂SO₄ solution. SEM and EDS analyses found that the protective layer formed on the MS electrode surface in the presence of TGP could prevent the attack of the sulfur ions. The DFT calculation provided more information regarding the reactivity, geometric properties and the active centers of the corrosion inhibitory efficiency of the tested epoxy resin. RDF, MC and MD simulations showed that the investigated inhibitory resin have a maximum inhibition efficiency in 0.5 M H₂SO₄ solution.

Performance of simultaneous nitrification-denitrification and denitrifying phosphorus and manganese removal by driving a single-stage moving bed biofilm reactor based on manganese redox cycling

Simultaneous removal of NH₄⁺-N, NO₃^--N, COD, and P by manganese redox cycling in nutrient wastewater was established with a single-stage moving bed biofilm reactor (MBBR) under low C/N ratio. When sodium succinate replaced the conventional denitrifying carbon source, removal efficiencies of TN, NO₃^--N, NH₄⁺-N, TP, and Mn²⁺ were 65.13 %, 79.63 %, 92.79 %, 51.57 %, and 68.10 %, respectively. Based on modified Stover-Kincannon model, 11.03 and 10.05 mg TN·L^-1·h^-1 of U_max values were obtained with sodium acetate and sodium succinate as substrates. Extracellular polymeric substances were used to evaluate the characteristics of biofilm, and microbial community of biofilm was identified. Transformation processes of NO₃^--N, NH₄⁺-N, Mn²⁺, and P were investigated, suggesting that the main functional groups (e.g., CO, Mn-O, and CN bonds) participated in N, P, and Mn²⁺ removal, and MnO₂ was the main component of biogenic manganese oxides. This study provides a new strategy for nutrients removal by Mn²⁺ driven MBBR.