International Journal of Chemistry

International Journal of Chemistry | Vol. 6, No. 3, March 2015 | pp. 17–24

DOI: 10.46882/2015/IJC/000078

Article Type: Original Research Paper

Title: Electrochemical Properties and Capacitive Performance of Polypyrrole-Manganese Dioxide Composite Electrodes for Supercapacitors

Names of Authors: U. B. Aliyu¹, K. N. S. Tan²*

Authors’ Affiliations:
¹Department of Chemistry, Ahmadu Bello University, Zaria, Nigeria.
²Department of Chemistry, National University of Singapore, Singapore.

Abstract: The fabrication of hybrid electrochemical capacitors requires electrode configurations that successfully merge high pseudocapacitive charge transfer with structural network longevity. This research outlines the synthesis and supercapacitive performance of polypyrrole-manganese dioxide (PPy-MnO₂) nanocomposites prepared via the in situ chemical oxidative polymerization of pyrrole monomers in the presence of hydrothermally prepared MnO₂ nanorods. The microstructural morphology and chemical networks of the composite films were analyzed using field emission scanning electron microscopy (FESEM), FT-IR, and Raman spectroscopy. FESEM images confirmed the uniform encapsulation of a thin amorphous PPy layer around the highly crystalline MnO₂ nanorods. Electrochemical characterization was carried out in a three-electrode system using a 1.0 M Na₂SO₄ electrolyte via cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) cycles. The optimized PPy-MnO₂ composite electrode delivered a maximum specific capacitance of 435 F/g at a current density of 1.0 A/g, outperforming standalone pure polypyrrole (210 F/g). Electrochemical impedance spectroscopy (EIS) data showed a low internal charge-transfer resistance of 0.42 ohms, and cyclic evaluations proved that the electrode retained 88.4% of its capacitance after 2000 continuous cycles.

Keywords: Polypyrrole; Manganese dioxide; Nanocomposites; Supercapacitors; Cyclic voltammetry; Specific capacitance

Manuscript Timeline: Received: May 02, 2014; Revised: June 15, 2014; Accepted: July 12, 2014; Published: March 04, 2015.

Citation: Aliyu, U. B., & Tan, K. N. S. (2015). Electrochemical Properties and Capacitive Performance of Polypyrrole-Manganese Dioxide Composite Electrodes for Supercapacitors. International Journal of Chemistry, 6(3), 17–24.

International Journal of Chemistry | Vol. 7, No. 5, May 2016 | pp. 33–40

DOI: 10.46882/2016/IJC/000092

Article Type: Original Research Paper

Title: Biochemical Assessment, Functional Properties, and Mineral Fingerprinting of Underutilized Cereal Grains from West Africa

Names of Authors: A. E. Ogunkoya¹, A. M. O. R. de Sousa²*

Authors’ Affiliations:
¹Department of Chemistry, Ekiti State University, Ado-Ekiti, Nigeria.
²Department of Food Science, National Institute of Health Dr. Ricardo Jorge, Lisbon, Portugal.

Abstract: Underutilized indigenous cereal grains serve as resilient agricultural reservoirs in arid zones, yet detailed mapping of their dietary matrices is required to expand their commercial adoption. This research evaluates the proximate nutritional composition, functional properties, and mineral mineral profile of three underutilized West African grains (Digitaria exilis, Pennisetum glaucum, and Eragrostis tef) gathered during the dry season harvest. Proximate analysis established high total carbohydrate contents ranging from 68.4% to 74.2% on a dry weight basis, alongside significant crude protein profiles (9.2% to 12.8%) and very low crude lipid levels (1.5% to 2.4%). Mineral profiling using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) revealed that iron and zinc were highly concentrated within D. exilis fractions (5.4 mg/100g and 3.8 mg/100g respectively), while toxic heavy metals remained well below international safety benchmarks. Quantified antinutritional matrices showed exceptionally low baseline concentrations of tannins (0.12 to 0.24 mg/g) and phytic acid (1.15 to 1.84 mg/g). Functional parameter tracking confirmed high water absorption capacities and stable gel formation limits, proving that these grains are excellent dietary matrices for developing gluten-free infant weaning formulations.

Keywords: Underutilized cereals; Proximate composition; Mineral profile; Antinutrients; Digitaria exilis; Gluten-free matrices

Manuscript Timeline: Received: October 18, 2015; Revised: November 28, 2015; Accepted: January 05, 2016; Published: May 04, 2016.

Citation: Ogunkoya, A. E., & de Sousa, A. M. O. R. (2016). Biochemical Assessment, Functional Properties, and Mineral Fingerprinting of Underutilized Cereal Grains from West Africa. International Journal of Chemistry, 7(5), 33–40.

International Journal of Chemistry | Vol. 6, No. 10, October 2015 | pp. 73–80

DOI: 10.46882/2015/IJC/000085

Article Type: Original Research Paper

Title: Kinetic Studies and Isotope Effects of the Permanganate Oxidation of L-Phenylalanine in Acidic Medium

Names of Authors: T. M. Usman¹, F. M. Al-Rasheed²*

Authors’ Affiliations:
¹Department of Chemistry, Bayero University, Kano, Nigeria.
²Department of Chemistry, King Saud University, Riyadh, Saudi Arabia.

Abstract: The kinetics of transition metal electron transfer processes involving amino acids yield essential data required to map biochemical oxidation paths and intermediate radical formations. The oxidation of L-phenylalanine by permanganate ions (MnO₄⁻) was investigated spectrophotometrically in an aqueous sulfuric acid medium at a constant ionic strength of 0.20 M (Na₂SO₄). The reaction progress was monitored under pseudo-first-order conditions by following the absorbance decay of MnO₄⁻ at its wavelength maximum of 525 nm. The empirical rate law showed a first-order dependence on [MnO₄⁻] and a fractional-first-order dependence on [L-phenylalanine]. The reaction rate increased with rising hydronium ion concentration, revealing an acid-catalyzed pathway driven by the active protonated permanganate species, HMnO₄. Variations in ionic strength produced negligible kinetic shifts, indicating a rate-determining step involving a neutral molecule and an ionic species. Stoichiometric determinations confirmed that 5 moles of L-phenylalanine consumed 2 moles of permanganate, producing phenylacetaldehyde and Mn(II) ions as the primary end products. Thermodynamic activation constants calculated from temperature-dependence datasets using the Eyring equation yielded an enthalpy of activation (delta H*) of 45.8 kJ/mol and an entropy of activation (delta S*) of -112.4 J/mol K, supporting an inner-sphere mechanism.

Keywords: Reaction kinetics; Spectrophotometry; Permanganate oxidation; L-phenylalanine; Activation parameters; Reaction mechanisms

Manuscript Timeline: Received: March 15, 2015; Revised: May 20, 2015; Accepted: July 02, 2015; Published: October 05, 2015.

Citation: Usman, T. M., & Al-Rasheed, F. M. (2015). Kinetic Studies and Isotope Effects of the Permanganate Oxidation of L-Phenylalanine in Acidic Medium. International Journal of Chemistry, 6(10), 73–80.

International Journal of Chemistry | Vol. 6, No. 11, November 2015 | pp. 81–88

DOI: 10.46882/2015/IJC/000086

Article Type: Original Research Paper

Title: Geochemical Fractions, Spatial Distribution, and Bioavailability of Copper and Zinc in Coastal Lagoon Sediments

Names of Authors: C. I. Obi¹, S. H. Kim²*

Authors’ Affiliations:
¹Department of Pure and Industrial Chemistry, University of Port Harcourt, Port Harcourt, Nigeria.
²Department of Chemistry, Seoul National University, Seoul, South Korea.

Abstract: Total concentrations of heavy metals are insufficient to assess ecological risk in coastal bodies because environmental mobility and bioavailability depend heavily on specific chemical binding forms. This study evaluates the total concentration and geochemical speciation fractions of copper (Cu) and zinc (Zn) in surface sediments collected from an urban coastal lagoon exposed to municipal and industrial waste discharges. Quantitative analysis was performed using Atomic Absorption Spectrophotometry (AAS) following the modified BCR three-step sequential extraction procedure. The total metal concentrations followed the sequence: Zn > Cu across all sampling locations. Spatial mapping revealed significant pollutant accumulation near storm-water discharge channels. Speciation patterns demonstrated that a high proportion of zinc (42.5%) was associated with the acid-soluble and exchangeable fractions, suggesting high structural instability and bioavailable risks to benthic organisms. Conversely, copper was primarily bound within the organic and reducible matrices, indicating low immediate mobility under baseline pH conditions. The Risk Assessment Code (RAC) calculated for zinc indicated a high environmental hazard rating, highlighting a strong need for local effluent regulatory frameworks.

Keywords: Coastal lagoon; Sediments; Trace metals; BCR protocol; Geochemical speciation; Bioavailability

Manuscript Timeline: Received: April 02, 2015; Revised: May 22, 2015; Accepted: June 15, 2015; Published: November 02, 2015.

Citation: Obi, C. I., & Kim, S. H. (2015). Geochemical Fractions, Spatial Distribution, and Bioavailability of Copper and Zinc in Coastal Lagoon Sediments. International Journal of Chemistry, 6(11), 81–88.

International Journal of Chemistry | Vol. 6, No. 9, September 2015 | pp. 65–72

DOI: 10.46882/2015/IJC/000084

Article Type: Original Research Paper

Title: Transesterification Kinetics, Thermodynamic Modeling, and Emission Profiles of Biodiesel from Hevea brasiliensis Seed Oil

Names of Authors: M. C. Okonkwo¹, L. H. Nguyen²*

Authors’ Affiliations:
¹Department of Industrial Chemistry, Enugu State University of Science and Technology, Enugu, Nigeria.
²Department of Chemical Engineering, Ho Chi Minh City University of Technology, Ho Chi Minh City, Vietnam.

Abstract: Utilizing non-edible agricultural waste seeds as chemical feedstocks for alternative fuel synthesis promotes green energy targets without competing with food supplies. This study investigates the transesterification kinetics and chemical properties of biodiesel synthesized from rubber (Hevea brasiliensis) seed oil. Because of an elevated initial free fatty acid content (6.12 mg KOH/g), a two-step acid-base catalyzed transesterification route was deployed. The first step reduced the acid value below 1.0 mg KOH/g using 1.5% v/v sulfuric acid in methanol, followed by standard base-catalyzed transesterification with potassium methoxide. Fatty acid methyl ester (FAME) yield was optimized at 94.2% 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. Kinetic analysis confirmed that the transesterification process followed pseudo-first-order reaction mechanics with an activation energy of 42.6 kJ/mol. Fuel properties of the prepared biodiesel, including kinematic viscosity (4.25 mm²/s at 40°C), flash point (162°C), and cetane number (51), matched international ASTM D6751 regulatory specifications. Diesel engine tests using a B20 blend showed a 14.5% reduction in particulate emissions compared to conventional diesel.

Keywords: Hevea brasiliensis; Biodiesel; Transesterification; Reaction kinetics; Activation energy; Kinematic viscosity

Manuscript Timeline: Received: March 04, 2015; Revised: May 11, 2015; Accepted: June 20, 2015; Published: September 09, 2015.

Citation: Okonkwo, M. C., & Nguyen, L. H. (2015). Transesterification Kinetics, Thermodynamic Modeling, and Emission Profiles of Biodiesel from Hevea brasiliensis Seed Oil. International Journal of Chemistry, 6(9), 65–72.

International Journal of Chemistry | Vol. 6, No. 8, August 2015 | pp. 57–64

DOI: 10.46882/2015/IJC/000083

Article Type: Original Research Paper

Title: Phytochemical Profiling, Volatile Oil Characterization, and Radical Scavenging Traits of Cymbopogon citratus Essential Oils

Names of Authors: S. A. Abdulrahman¹, E. C. Dumont²*

Authors’ Affiliations:
¹Department of Chemistry, Federal University of Technology, Minna, Nigeria.
²Department of Pharmacy, University of Paris-Sud, Châtenay-Malabry, France.

Abstract: Cymbopogon citratus (Lemongrass) is extensively utilized in traditional medicine due to its sedative and antimicrobial activities, yet geographical soil variations heavily alter its essential oil yield. This research maps the qualitative chemical constituents, determines volatile bioactives via Gas Chromatography-Mass Spectrometry (GC-MS), and evaluates the antioxidant profiles of essential oils extracted from lemongrass leaves cultivated in Central Nigeria. Essential oils gathered via hydro-distillation in a Clevenger apparatus were separated into 16 distinct peaks via GC-MS, with citral (composed of geranial, 38.4% and neral, 28.2%), myrcene (12.4%), and geraniol (6.5%) emerging as the dominant active constituents. The antioxidant capacity was evaluated in vitro utilizing the DPPH radical scavenging assay and the Ferric Reducing Antioxidant Power (FRAP) test, using standard ascorbic acid as a control benchmark. The essential oil displayed significant free radical scavenging traits, yielding an IC50 value of 45.8 μg/mL, compared to 10.2 μg/mL achieved by standard reference antioxidants. A linear correlation was observed between the high citral content and radical neutralization indices, confirming that monoterpene aldehydes are the driving contributors to cellular protective performance.

Keywords: Cymbopogon citratus; Essential oils; GC-MS profiling; Monoterpenes; DPPH assay; Antioxidant activity

Manuscript Timeline: Received: February 15, 2015; Revised: April 02, 2015; Accepted: May 12, 2015; Published: August 03, 2015.

Citation: Abdulrahman, S. A., & Dumont, E. C. (2015). Phytochemical Profiling, Volatile Oil Characterization, and Radical Scavenging Traits of Cymbopogon citratus Essential Oils. International Journal of Chemistry, 6(8), 57–64.