International Journal of Chemistry

International Journal of Chemistry | Vol. 2, No. 7, July 2011 | pp. 76–83

DOI: 10.46882/2011/IJC/000034

Article Type: Original Research Paper

Title: Extraction Optimization, Characterization, and Biodiesel Conversion Potentials of Jatropha curcas Seed Oil

Names of Authors: M. C. Okonkwo¹, G. B. Nwosu¹*

Authors’ Affiliations:
¹Department of Industrial Chemistry, Enugu State University of Science and Technology, Enugu, Nigeria.

Abstract: The production of alternative bio-fuels from non-edible crop lipids is necessary to satisfy energy demands while protecting agricultural food security reservoirs. This research optimizes the extraction parameters and transesterification conversion pathways of Jatropha curcas seed oil into fatty acid methyl esters (FAME). Soxhlet solvent extraction using n-hexane produced a base seed oil yield of 46.8%. Physicochemical evaluations showed a specific gravity of 0.915, a saponification value of 194.2 mg KOH/g, and an initial acid value of 4.12 mg KOH/g. Because of the high free fatty acid content, a two-step acid-base catalyzed transesterification route was deployed. The first step reduced the acid value below 1.0 mg KOH/g using 1% sulfuric acid in methanol, followed by base-catalyzed transesterification with potassium hydroxide (KOH). FAME yield was optimized at 94.5% using a 6:1 methanol-to-oil molar ratio, a catalyst concentration of 1.0 wt% KOH, and a process temperature of 60°C for 90 minutes. Fuel properties of the synthesized Jatropha biodiesel, including kinematic viscosity (4.2 mm²/s at 40°C), flash point (164°C), and cetane index (54), matched the international ASTM D6751 regulatory specifications.

Keywords: Jatropha curcas; Biodiesel; Transesterification; Free fatty acids; Kinematic viscosity; Renewable energy

Manuscript Timeline: Received: February 18, 2011; Revised: March 28, 2011; Accepted: April 22, 2011; Published: July 03, 2011.

Citation: Okonkwo, M. C., & Nwosu, G. B. (2011). Extraction Optimization, Characterization, and Biodiesel Conversion Potentials of Jatropha curcas Seed Oil. International Journal of Chemistry, 2(7), 76–83.

International Journal of Chemistry | Vol. 2, No. 3, March 2011 | pp. 35–43

DOI: 10.46882/2011/IJC/000029

Article Type: Original Research Paper

Title: Adsorption Dynamics and Kinetic Modeling of Malachite Green Dye Removal Sourced from Clay Deposits

Names of Authors: B. U. Osuji¹, C. N. Ibeto¹*

Authors’ Affiliations:
¹Department of Pure and Industrial Chemistry, University of Nigeria, Nsukka, Nigeria.

Abstract: Industrial wastewater from paper and leather tanning plants contains toxic cationic dyes that cause mutations in aquatic fauna if left untreated. This paper details the adsorptive removal of Malachite Green (MG) dye from aqueous systems utilizing local acid-activated bentonite clay deposits as an affordable adsorbent matrix. The raw clay was treated with 2.0 M H₂SO₄ to increase porosity and surface area parameters, which were verified using nitrogen adsorption isotherms and FT-IR spectroscopy. Batch experiments tracked changes in initial dye concentration, solution pH, contact time, and adsorbent dose. Maximum MG adsorption occurred at a solution pH of 8.0, using an adsorbent load of 0.5 g/L within 60 minutes. The equilibrium extraction profiles matched the Langmuir isotherm equations, yielding a high monolayer adsorption capacity of 82.64 mg/g at 303 K. Kinetic modeling parameters showed that the adsorption path conformed to a pseudo-second-order model with a high correlation coefficient (R² = 0.997), proving that chemical ion exchange reactions governed the transfer process. Thermodynamic metrics confirmed process spontaneity and endothermic characteristics, highlighting this modified local clay as a viable material for treatment of commercial industrial effluents.

Keywords: Bentonite clay; Acid activation; Malachite green; Adsorption kinetics; Chemisorption; Wastewater treatment

Manuscript Timeline: Received: December 02, 2010; Revised: January 15, 2011; Accepted: February 04, 2011; Published: March 03, 2011.

Citation: Osuji, B. U., & Ibeto, C. N. (2011). Adsorption Dynamics and Kinetic Modeling of Malachite Green Dye Removal Sourced from Clay Deposits. International Journal of Chemistry, 2(3), 35–43.

International Journal of Chemistry | Vol. 2, No. 12, December 2011 | pp. 116–123

DOI: 10.46882/2011/IJC/000039

Article Type: Original Research Paper

Title: Synthesis, Computational Docking, and Enzyme Inhibition Profiles of Novel Thiazolidine-2,4-dione Derivatives

Names of Authors: O. M. Kolawole¹, L. C. Nwosu¹*

Authors’ Affiliations:
¹Department of Chemistry, Obafemi Awolowo University, Ile-Ife, Nigeria.

Abstract: Thiazolidine-2,4-dione (TZD) rings are important pharmacophores used to manage type 2 diabetes mellitus due to their ability to activate peroxisome proliferator-activated receptor gamma (PPAR-gamma). In this work, five novel 5-benzylidene-thiazolidine-2,4-dione derivatives were synthesized via Knoevenagel condensation of TZD with various substituted benzaldehydes in the presence of piperidine catalysts. The chemical frameworks of the synthesized molecules were confirmed using elemental analysis, FT-IR, and ¹H-NMR spectroscopy. In vitro alpha-glucosidase enzyme inhibition assays revealed that compound 4c, bearing a p-nitro substituent, possessed the highest inhibitory potency, showing an IC50 value of 14.5 μM, compared to the acarbose clinical standard (IC50 = 38.2 μM). To investigate the binding orientations, in silico molecular docking simulations were run inside the catalytic site of alpha-glucosidase using AutoDock Vina. The docking models showed that the TZD carbonyl oxygen forms stable hydrogen bonds with Arg315 and Asp214 residues. The aromatic ring extensions fit well into the hydrophobic pocket, forming pi-pi stacking interactions with Phe178. These structural contacts stabilize the ligand-protein framework, supporting the low inhibition constants and highlighting these derivatives as promising antidiabetic drug candidates.

Keywords: Thiazolidine-2,4-dione; Knoevenagel condensation; Alpha-glucosidase; Enzyme inhibition; Molecular docking; Antidiabetic candidates

Manuscript Timeline: Received: May 05, 2011; Revised: June 18, 2011; Accepted: July 10, 2011; Published: December 04, 2011.

Citation: Kolawole, O. M., & Nwosu, L. C. (2011). Synthesis, Computational Docking, and Enzyme Inhibition Profiles of Novel Thiazolidine-2,4-dione Derivatives. International Journal of Chemistry, 2(12), 116–123.

International Journal of Chemistry | Vol. 2, No. 5, May 2011 | pp. 60–67

DOI: 10.46882/2011/IJC/000032

Article Type: Original Research Paper

Title: Sorption Kinetic Profiles and Equilibrium Thermodynamics of Chromium(VI) Ion Sequestration Using Modified Rice Husk

Names of Authors: E. N. Chidi¹, O. P. Ejike¹*

Authors’ Affiliations:
¹Department of Pure and Industrial Chemistry, Nnamdi Azikiwe University, Awka, Nigeria.

Abstract: Industrial electroplating and leather processing release toxic hexavalent chromium [Cr(VI)] into aquatic channels, presenting heavy mutational and carcinogenic hazards. This investigation explores the utilization of chemically modified rice husk (CMRH) prepared via nitric acid oxidation for the adsorptive removal of Cr(VI) ions from simulated effluents. The surface chemistry and porosity of the adsorbent were studied using scanning electron microscopy (SEM) and FT-IR spectroscopy. Batch extraction experiments evaluated parameters of solution pH, contact time, adsorbent dosage, and initial metal ions concentration. Maximum Cr(VI) sorption occurred at an acidic pH of 2.0, with an equilibrium contact period of 120 minutes. Equilibrium data matched the Langmuir isotherm expressions, indicating a maximum monolayer adsorption capacity of 38.46 mg/g at 298 K. Sorption kinetics followed the pseudo-second-order kinetic model with a correlation coefficient (R²) greater than 0.99, indicating a chemisorption process. Thermodynamic constants, including enthalpy (delta H° = 14.2 kJ/mol) and entropy (delta S° = 56.4 J/mol K), confirmed that the phase transformation was endothermic and spontaneous. Desorption trials using 0.1 M NaOH showed high recovery metrics, presenting CMRH as a cost-effective choice for industrial water treatment.

Keywords: Rice husk; Acid modification; Hexavalent chromium; Adsorption kinetics; Chemisorption; Wastewater treatment

Manuscript Timeline: Received: January 15, 2011; Revised: February 22, 2011; Accepted: March 12, 2011; Published: May 04, 2011.

Citation: Chidi, E. N., & Ejike, O. P. (2011). Sorption Kinetic Profiles and Equilibrium Thermodynamics of Chromium(VI) Ion Sequestration Using Modified Rice Husk. International Journal of Chemistry, 2(5), 60–67.

International Journal of Chemistry | Vol. 2, No. 8, August 2011 | pp. 84–91

DOI: 10.46882/2011/IJC/000035

Article Type: Original Research Paper

Title: Kinetic, Mechanistic, and Thermodynamic Profiling of Alkaline Hydrolysis of Ethyl Acetate in Mixed Aqueous Solvents

Names of Authors: T. M. Usman¹, H. U. Dikko¹*

Authors’ Affiliations:
¹Department of Chemistry, Bayero University, Kano, Nigeria.

Abstract: Investigating reaction velocities in mixed binary solvents yields important insights into solute-solvent interactions, transition state solvation, and dielectric impacts on reaction kinetics. The alkaline hydrolysis of ethyl acetate by sodium hydroxide was investigated titrimetrically in water-ethanol and water-acetone binary solvent mixtures across varying compositions (10% to 50% v/v) and temperatures (298.15 K to 318.15 K). The reaction followed second-order kinetic behavior, displaying a first-order dependence on both the ester and the hydroxyl ion concentrations. The specific rate constant (k) decreased systematically with increasing concentrations of the organic co-solvent in the reaction medium. This trend is attributed to the reduction of the dielectric constant of the medium, which destabilizes the polar activated complex relative to the isolated reactants. Activation parameters were computed via the Arrhenius and Eyring expressions. In 30% ethanol, the activation energy (Ea) was 48.5 kJ/mol, the enthalpy of activation (delta H*) was 45.8 kJ/mol, and the entropy of activation (delta S*) was -94.2 J/mol K. The highly negative entropy values confirm that the transition state possesses a more structured orientation than the ground-state reactants.

Keywords: Reaction kinetics; Alkaline hydrolysis; Ethyl acetate; Dielectric constant; Activation parameters; Solvation effects

Manuscript Timeline: Received: March 12, 2011; Revised: April 25, 2011; Accepted: May 14, 2011; Published: August 06, 2011.

Citation: Usman, T. M., & Dikko, H. U. (2011). Kinetic, Mechanistic, and Thermodynamic Profiling of Alkaline Hydrolysis of Ethyl Acetate in Mixed Aqueous Solvents. International Journal of Chemistry, 2(8), 84–91.

International Journal of Chemistry | Vol. 2, No. 10, October 2011 | pp. 100–107

DOI: 10.46882/2011/IJC/000037

Article Type: Original Research Paper

Title: Eco-Friendly Corrosion Mitigation of Mild Steel in Sulphuric Acid Medium Using Leaves Extract of Khaya senegalensis

Names of Authors: M. A. Haruna¹, S. S. Bala¹*

Authors’ Affiliations:
¹Department of Chemistry, Federal University of Technology, Minna, Nigeria.

Abstract: The degradation of mild steel structures in acidic industrial pickling vats causes substantial economic losses, requiring the development of non-toxic, eco-friendly green corrosion inhibitors. The inhibition efficiency of the aqueous leaf extract of Khaya senegalensis (KS-Extract) on mild steel in 0.5 M H₂SO₄ was evaluated using weight loss and hydrogen evolution measurements at 303–323 K. Weight loss metrics showed that the protection efficiency increased with extract concentration, peaking at 92.4% at a concentration of 1.8 g/L. The hydrogen evolution data confirmed a significant decrease in gas generation rates upon adding the inhibitor. Activation parameters calculated using the Arrhenius expression revealed that the activation energy (Ea) increased from 28.4 kJ/mol in the blank acid to 58.6 kJ/mol in the inhibited system, indicating a physical adsorption process on the mild steel surface. The adsorption behavior of the phytochemical components fit the Langmuir adsorption isotherm model, with standard free energy of adsorption (delta G°ads) values around -20.4 kJ/mol. FT-IR analysis of the corrosion products confirmed that the rich pool of tannins and alkaloids within the extract formed a protective organic passivating layer.

Keywords: Mild steel; Acid corrosion; Green inhibitor; Khaya senegalensis; Hydrogen evolution; Adsorption isotherm

Manuscript Timeline: Received: April 12, 2011; Revised: May 25, 2011; Accepted: June 15, 2011; Published: October 05, 2011.

Citation: Haruna, M. A., & Bala, S. S. (2011). Eco-Friendly Corrosion Mitigation of Mild Steel in Sulphuric Acid Medium Using Leaves Extract of Khaya senegalensis. International Journal of Chemistry, 2(10), 100–107.