International Journal of Chemistry

International Journal of Chemistry | Vol. 5, No. 2, February 2014 | pp. 9–16

DOI: 10.46882/2014/IJC/000065

Article Type: Original Research Paper

Title: Kinetic and Salt Effect Studies of the Mechanistic Oxidation of D-Glucose by Cerium(IV) in Acidic Medium

Names of Authors: T. M. Usman¹, A. M. Al-Ghoul²*

Authors’ Affiliations:
¹Department of Chemistry, Bayero University, Kano, Nigeria.
²Department of Chemistry, American University of Beirut, Beirut, Lebanon.

Abstract: Transition metal oxidants like Cerium(IV) provide vital kinetic benchmarks required to map carbohydrate oxidation mechanisms and electron transfer pathways in aqueous systems. The kinetics of the oxidation of D-glucose by Cerium(IV) was investigated spectrophotometrically in an aqueous perchloric acid medium at a constant ionic strength of 0.50 M (NaClO₄). The reaction progress was monitored under pseudo-first-order conditions by following the absorbance decay of Cerium(IV) at its absorption maximum of 320 nm. The reaction exhibited a first-order dependence on [Cerium(IV)] and a fractional-first-order dependence on [D-glucose]. The reaction rate increased with rising hydronium ion concentration, revealing an acid-catalyzed pathway governed by the reactive protonated oxidant species, [Ce(OH)³⁺]. The introduction of sodium sulfate produced a significant retarding salt effect on the reaction velocity due to the formation of less reactive sulfato-complexes of Cerium(IV). Stoichiometric determinations confirmed that 1 mole of D-glucose consumed 2 moles of Cerium(IV), producing gluconic acid as the primary end product. Thermodynamic activation constants were calculated from temperature-dependence datasets using the Eyring equation, yielding an activation enthalpy (delta H*) of 52.4 kJ/mol and an activation entropy (delta S*) of -85.6 J/mol K, supporting an inner-sphere mechanism.

Keywords: Reaction kinetics; Spectrophotometry; Cerium oxidation; D-glucose; Activation parameters; Retarding salt effect

Manuscript Timeline: Received: March 20, 2013; Revised: May 15, 2013; Accepted: June 28, 2013; Published: February 07, 2014.

Citation: Usman, T. M., & Al-Ghoul., A. M. (2014). Kinetic and Salt Effect Studies of the Mechanistic Oxidation of D-Glucose by Cerium(IV) in Acidic Medium. International Journal of Chemistry, 5(2), 9–16.

International Journal of Chemistry | Vol. 5, No. 4, April 2014 | pp. 25–32

DOI: 10.46882/2014/IJC/000067

Article Type: Original Research Paper

Title: Electrochemical Corrosion Inhibition of Carbon Steel in Hydrochloric Acid Using Seed Extract of Piper guineense

Names of Authors: M. A. Haruna¹, S. Rajagopal²*

Authors’ Affiliations:
¹Department of Chemistry, Federal University of Technology, Minna, Nigeria.
²Department of Chemistry, Indian Institute of Technology, Madras, India.

Abstract: The utilization of toxic synthetic chemical corrosion inhibitors in industrial acid descaling operations poses significant environmental risks, driving research into sustainable green alternatives. The corrosion mitigation performance of the methanolic seed extract of Piper guineense (PG-Extract) on carbon steel in 1.0 M HCl solutions was monitored via gravimetric weight loss and electrochemical measurement protocols. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) curves were recorded across varying inhibitor dosages (0.2 to 2.0 g/L) and temperatures (303 to 333 K). Weight loss metrics revealed that protection efficiency increased with extract concentration, peaking at 93.5% at a dose of 2.0 g/L. Polarization diagrams established that PG-Extract functions as a mixed-type inhibitor, suppressing both anodic iron dissolution and cathodic hydrogen gas evolution. EIS scans confirmed that charge-transfer resistance (Rct) increased with higher extract amounts, indicating the formation of a robust organic protective film on the metal face. The adsorption behavior of the bioactive compounds conformed to the Langmuir isotherm model, yielding a negative standard free energy of adsorption (delta G°ads = -22.4 kJ/mol), denoting a spontaneous chemisorption mechanism driven by the presence of piperine alkaloids.

Keywords: Carbon steel; Corrosion inhibition; Piper guineense; Electrochemical impedance spectroscopy; Polarization; Adsorption isotherm

Manuscript Timeline: Received: April 18, 2013; Revised: June 05, 2013; Accepted: July 12, 2013; Published: April 04, 2014.

Citation: Haruna, M. A., & Rajagopal., S. (2014). Electrochemical Corrosion Inhibition of Carbon Steel in Hydrochloric Acid Using Seed Extract of Piper guineense. International Journal of Chemistry, 5(4), 25–32.

International Journal of Chemistry | Vol. 5, No. 12, December 2014 | pp. 89–96

DOI: 10.46882/2014/IJC/000075

Article Type: Original Research Paper

Title: Spatial Analysis, Seasonal Partitioning, and Chemical Speciation of Arsenic Compounds in Urban Coastal Aquifers

Names of Authors: T. H. Awotunde¹, E. C. Silva²*

Authors’ Affiliations:
¹Department of Chemistry, Federal University of Agriculture, Abeokuta, Nigeria.
²Department of Earth Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.

Abstract: Arsenic leaching into shallow drinking water wells from nearby electronic wastes and industrial dumpsites poses severe public health threats due to its systemic toxicity and carcinogenicity. This study monitors the spatial variations, chemical speciation, and seasonal partitioning profiles of arsenic compounds across twenty communal wells located in a crowded coastal industrial zone. Water monitoring was executed concurrently across dry and wet seasons. Total arsenic and inorganic arsenic species [As(III) and As(V)] were resolved quantitatively using Hydride Generation Atomic Absorption Spectrophotometry (HG-AAS). Total arsenic concentrations ranged from 2.15 to 45.8 μg/L, with 40% of the sampled groundwater sites exceeding the strict WHO maximum drinkable contaminant limit of 10.0 μg/L. Speciation mapping showed that toxic As(III) was the dominant form in highly reducing, low-oxygen shallow aquifers. Seasonal evaluations confirmed elevated arsenic migration during the rainy period, driven by fluctuating water tables and aquifer leaching pathways. Chronic Hazard Index (HI) calculations for infant exposure pathways surpassed 3.2 at peripheral coordinates, emphasizing an immediate public health risk and highlighting the necessity for widespread local bone-char filtration setups.

Keywords: Groundwater quality; Arsenic speciation; Hydride generation; Seasonal variations; Bioavailability; Hazard index

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

Citation: Awotunde, T. H., & Silva, E. C. (2014). Spatial Analysis, Seasonal Partitioning, and Chemical Speciation of Arsenic Compounds in Urban Coastal Aquifers. International Journal of Chemistry, 5(12), 89–96.

International Journal of Chemistry | Vol. 5, No. 1, January 2014 | pp. 1–8

DOI: 10.46882/2014/IJC/000064

Article Type: Original Research Paper

Title: Kinetic Modeling, Transesterification Optimization, and Engine Performance of Biodiesel Sourced from Calophyllum inophyllum Oil

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

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

Abstract: The utilization of non-edible seed oils as chemical feedstocks for biodiesel synthesis mitigates the food-versus-fuel conflict while presenting a sustainable replacement for petroleum diesel. This study investigates the transesterification optimization and kinetic modeling of biodiesel production from crude Calophyllum inophyllum seed oil. Due to an elevated initial free fatty acid content (5.42 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% v/v sulfuric acid in methanol, followed by a base-catalyzed transesterification with sodium methoxide. Fatty acid methyl ester (FAME) yield was optimized at 96.5% using a 6:1 methanol-to-oil molar ratio, a catalyst concentration of 1.2 wt%, and a reaction temperature of 60°C for 60 minutes. Kinetic analysis established that the transesterification process followed pseudo-first-order kinetics with an activation energy of 38.4 kJ/mol. Fuel properties of the optimized biodiesel, including kinematic viscosity (4.15 mm²/s at 40°C), flash point (158°C), and cetane number (52), matched ASTM D6751 regulatory specifications. Diesel engine tests using a B20 blend showed a 12.5% reduction in carbon monoxide emissions compared to conventional diesel.

Keywords: Calophyllum inophyllum; Biodiesel; Transesterification; Reaction kinetics; Activation energy; Emission profiles

Manuscript Timeline: Received: March 10, 2013; Revised: May 02, 2013; Accepted: June 15, 2013; Published: January 05, 2014.

Citation: Okonkwo, M. C., & Nguyen, T. H. (2014). Kinetic Modeling, Transesterification Optimization, and Engine Performance of Biodiesel Sourced from Calophyllum inophyllum Oil. International Journal of Chemistry, 5(1), 1–8.

International Journal of Chemistry | Vol. 4, No. 7, July 2013 | pp. 49–56

DOI: 10.46882/2013/IJC/000058

Article Type: Original Research Paper

Title: Electrochemical Performance and Supercapacitive Characterization of Polyrhodanine-Carbon Nanotube Thin Film Electrodes

Names of Authors: U. B. Aliyu¹, J. Y. Lee²*

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

Abstract: Fabricating highly efficient electrochemical energy storage units requires the development of hybrid polymer electrodes that exhibit high specific capacitance and fast ion diffusion kinetics. This research details the synthesis and electrochemical characterization of polyrhodanine-multiwalled carbon nanotube (PRHD-MWCNT) thin-film nanocomposites prepared via in situ chemical oxidative polymerization pathways. The surface topology and morphological features of the hybrid films were analyzed using field emission scanning electron microscopy (FESEM), FT-IR, and Raman spectroscopy. FESEM imaging confirmed that a highly continuous, ultra-thin polyrhodanine layer was uniformly deposited across the conductive multiwalled carbon nanotube skeletal network. Electrochemical performance was investigated via cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) loops in a 1.0 M HCl electrolyte system. The optimized PRHD-MWCNT hybrid electrode delivered a maximum specific capacitance of 412 F/g at a current density of 1.0 A/g, which was substantially higher than standalone pure polyrhodanine films (145 F/g). Electrochemical impedance spectroscopy (EIS) data showed a very low charge-transfer resistance of 0.38 ohms, confirming accelerated ionic transport across the polymeric interface. Cyclic stability evaluations proved that the composite material retained 89.2% of its capacitive profile after 2000 continuous cycles.

Keywords: Polyrhodanine; Carbon nanotubes; Thin films; Supercapacitors; Cyclic voltammetry; Specific capacitance

Manuscript Timeline: Received: October 02, 2012; Revised: November 15, 2012; Accepted: December 04, 2012; Published: June 15, 2013.

Citation: Aliyu, U. B., & Lee, J. Y. (2013). Electrochemical Performance and Supercapacitive Characterization of Polyrhodanine-Carbon Nanotube Thin Film Electrodes. International Journal of Chemistry, 4(7), 49–56.

International Journal of Chemistry | Vol. 4, No. 3, March 2013 | pp. 17–24

DOI: 10.46882/2013/IJC/000054

Article Type: Original Research Paper

Title: Synthesis, Structural Characterization, and Dynamic Swelling of Chitosan-Graft-Polyacrylamide Hydrogels for Heavy Metal Extraction

Names of Authors: J. K. Mensah¹, S. Chatterjee²*

Authors’ Affiliations:
¹Department of Chemistry, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.
²Department of Chemical Engineering, Indian Institute of Technology, Kharagpur, India.

Abstract: Developing high-capacity polymeric adsorbents from biopolymer backbones is essential for green remediation of heavy metals from industrial effluents. This study describes the chemical synthesis and structural optimization of a crosslinked hydrogel prepared via the free-radical graft copolymerization of acrylamide onto a highly purified chitosan backbone. The reaction was initiated using ammonium persulfate (APS) and crosslinked via N,N'-methylenebisacrylamide (MBA). The structural configuration of the chitosan-graft-polyacrylamide (Ch-g-PAM) matrix was verified through FT-IR spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). Swelling kinetics were systematically evaluated across varying solution pH (2.0 to 10.0) and ionic strengths. The hydrogel displayed sensitive pH-dependent swelling profiles, achieving a maximum water absorption capacity of 310 g/g at pH 5.5 due to the complete protonation of amine functional groups causing maximum polymer chain expansion. Batch adsorption tests showed that the Ch-g-PAM hydrogel possessed high affinity for copper(II) and lead(II) ions in aqueous solutions. The adsorption data matched the Langmuir isotherm model with maximum monolayer adsorption capacities of 54.5 mg/g for Cu(II) and 82.6 mg/g for Pb(II) at 298 K, presenting an effective bio-sorption framework.

Keywords: Chitosan; Acrylamide; Graft copolymerization; Hydrogel; pH-sensitive swelling; Heavy metal adsorption

Manuscript Timeline: Received: August 05, 2012; Revised: September 18, 2012; Accepted: October 12, 2012; Published: March 02, 2013.

Citation: Mensah, J. K., & Chatterjee, S. (2013). Synthesis, Structural Characterization, and Dynamic Swelling of Chitosan-Graft-Polyacrylamide Hydrogels for Heavy Metal Extraction. International Journal of Chemistry, 4(3), 17–24.