Recent Innovations in Chemical Engineering (Formerly Recent Patents on Chemical Engineering) - Online First

This study investigates the potential of Laurus nobilis essential oil (LNEO) as a corrosion inhibitor for steel in a 1 M hydrochloric acid (HCl) solution.

Gas Chromatography-Mass Spectrometry (GC-MS) analysis was performed to determine the chemical composition of LNEO, revealing key constituents, including 1.8-cineole (33.47%), α-terpinyl acetate (17.39%), and sabinene (9.18%). Corrosion inhibition efficiency was evaluated through electrochemical techniques, and adsorption behavior was analyzed using the Langmuir isotherm model. Thermodynamic parameters were also assessed to elucidate the adsorption mechanism.

The inhibition efficiency reached a maximum of approximately 93.4% at an optimal concentration of 2 g/l. Langmuir adsorption isotherm studies confirmed a strong interaction between LNEO and the steel surface, with an adsorption free energy (ΔGads = -21.2 kJ/mol) and an adsorption equilibrium constant (Kads = 5.21 L/g), indicating a physisorption mechanism with partial charge transfer. Thermodynamic analyses showed an activation energy (Ea = 44.7 kJ/mol), enthalpy change (ΔHa = 42.1 kJ/mol), and entropy change (ΔSa = -69.3 J/mol.K), supporting a spontaneous and endothermic adsorption process.

Density Functional Theory (DFT) calculations and Scanning Electron Microscopy (SEM) analyses confirmed the adsorption mechanism, highlighting the protective film formation on the steel surface.

These findings demonstrate that Laurus nobilis essential oil is an effective corrosion inhibitor for steel in acidic media, with strong adsorption properties and high inhibitory efficiency.

The use of various dyes to colour products is a general practice in various industries. The occurrence of these dyes in water, even at small concentrations, is highly noticeable and aesthetically objectionable. In the present study, the applicability of inexpensive and eco-friendly bio-adsorbent has been tested as an alternative substitution of the commercially available activated carbon for the removal of reactive dye from the aqueous solution.

Bio-adsorbent prepared from pomegranate peel was successfully used to remove the reactive dye (Reactive Black 5) from the aqueous solution. The effects of major parameters such as pH, adsorbent dosage, and contact time on dye removal efficiency were studied. Statistical models were articulated based on selected variables to optimize the decolourisation efficiency of the adsorption process using a full factorial central composite design.

Dye removal efficiency of close to 100% was observed at a pH 12 using 1 g adsorbent/200 mL dye solution within a contact time of 60 min., yielding a virtually colourless solution. A fixed-bed column study with an initial dye concentration of 100 mg/L at bed depths of 4 cm, 8 cm, and 12 cm yielded a breakthrough time of 300 min, 570 min, and 780 min, respectively.

Langmuir, Freundlich, and Temkin isotherm models were applied to analyze the sorption equilibrium parameters. The experimental results of the analysis revealed that the Langmuir isotherm fits better than the other isotherms with a linear regression coefficient (R²) of 0.99. The high correlation coefficient (R² > 0.95) and low p-values (< 0.0001) indicate that the model and its terms are significant, making it effective for optimizing operational parameters and accurately predicting the response.

The breakthrough curve serves as a tool to evaluate the effectiveness of the prepared adsorbent in real-world applications. The present work not only provides an alternative to commercially available activated carbon for dye wastewater colour removal but also emphasizes the importance of repurposing fruit residues, which could otherwise become environmental pollutants if improperly disposed of.