International Journal of Chemistry

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.

International Journal of Chemistry | Vol. 4, No. 5, May 2013 | pp. 33–40

DOI: 10.46882/2013/IJC/000056

Article Type: Original Research Paper

Title: Assessing the Hydrocarbon Tolerance and Phytoremediation Trait of Ricinus communis L. in Polycyclic Aromatic Hydrocarbon Spiked Soils

Names of Authors: O. F. Olawal¹, G. de Metru²*

Authors’ Affiliations:
¹Department of Plant Biology, University of Ilorin, Ilorin, Nigeria.
²Department of Plant Sciences, Wageningen University, Wageningen, Netherlands.

Abstract: Persistent organic pollutants like polycyclic aromatic hydrocarbons (PAHs) accumulate inside industrial soil sub-surfaces, requiring cost-effective vegetative extraction strategies. This controlled study investigates the growth kinetics and remediation efficiency of Ricinus communis L. (Castor bean) cultivated in soils artificially spiked with varying concentrations of phenanthrene (100 to 500 mg/kg) and pyrene (50 to 250 mg/kg). Plant structural indices, remaining soil PAH concentrations, and root zone microbial populations were quantified over a 90-day developmental period. R. communis demonstrated strong physiological tolerance, maintaining high root-to-shoot biomass ratios across all phenanthrene loading levels. High-Performance Liquid Chromatography (HPLC) profiling showed a 78.4% reduction in soil phenanthrene and a 62.5% reduction in pyrene concentrations within the rhizosphere of cultivated systems, compared to minimal attenuation in unplanted controls. Soil microbiological testing revealed a five-fold expansion of heterotrophic degradation bacteria within the castor root matrix. This confirms that root exudates actively stimulate microbial proliferation, accelerating the degradation of complex polycyclic aromatic structures in contaminated industrial terrains.

Keywords: Ricinus communis; Phenanthrene; Pyrene; Soil phytoremediation; Rhizosphere effect; Microbial degradation

Manuscript Timeline: Received: September 02, 2012; Revised: October 12, 2012; Accepted: November 05, 2012; Published: May 02, 2013.

Citation: Olawal, O. F., & de Metru, G. (2013). Assessing the Hydrocarbon Tolerance and Phytoremediation Trait of Ricinus communis L. in Polycyclic Aromatic Hydrocarbon Spiked Soils. International Journal of Chemistry, 4(5), 33–40.

International Journal of Chemistry | Vol. 4, No. 12, December 2013 | pp. 89–96

DOI: 10.46882/2013/IJC/000063

Article Type: Original Research Paper

Title: Phytochemical Fingerprinting, Essential Oil Chemical Profiling, and In Vitro Cytotoxicity of Ocimum gratissimum Leaves

Names of Authors: S. A. Abdulrahman¹, C. A. Rossi²*

Authors’ Affiliations:
¹Department of Chemistry, Federal University of Technology, Minna, Nigeria.
²Department of Pharmacy, University of Genoa, Genoa, Italy.

Abstract: Ocimum gratissimum is heavily utilized in traditional medicine across developing countries to manage metabolic diseases, yet its volatile profile requires deep chemical mapping to clarify its therapeutic potential. This investigation reports the qualitative phytochemical screening, essential oil analysis via Gas Chromatography-Mass Spectrometry (GC-MS), and in vitro cytotoxicity profiling of hexane, ethyl acetate, and methanol leaf extracts. Qualitative tests revealed an abundance of terpenoids, flavonoids, and saponins concentrated majorly within the semi-polar ethyl acetate fraction. Essential oils gathered via hydro-distillation in a Clevenger apparatus were separated into 18 distinct peaks through GC-MS, with eugenol (42.5%), thymol (18.2%), and cis-ocimene (12.4%) emerging as the primary bioactive constituents. The cytotoxic potential was evaluated in vitro against human breast cancer (MCF-7) cell lines using the MTT assay, benchmarked against cisplatin. The ethyl acetate extract displayed significant cytotoxic activity with an IC50 value of 28.4 μg/mL, compared to 5.2 μg/mL achieved by the standard control. A linear correlation was observed between total phenolic content and cancer cell mortality, validating that eugenol and related plant phenolics drive free radical scavenging and apoptotic inductions, supporting further clinical investigation.

Keywords: Ocimum gratissimum; Essential oils; GC-MS analysis; Eugenol; Cytotoxicity; MTT assay

Manuscript Timeline: Received: February 12, 2013; Revised: March 24, 2013; Accepted: May 11, 2013; Published: December 02, 2013.

Citation: Abdulrahman, S. A., & Rossi, C. A. (2013). Phytochemical Fingerprinting, Essential Oil Chemical Profiling, and In Vitro Cytotoxicity of Ocimum gratissimum Leaves. International Journal of Chemistry, 4(12), 89–96.

International Journal of Chemistry | Vol. 4, No. 2, February 2013 | pp. 9–16

DOI: 10.46882/2013/IJC/000053

Article Type: Original Research Paper

Title: Isolation, Screening, and Kinetic Optimization of Cellulase Complexes Sourced from Thermophilic Fungal Strains

Names of Authors: C. N. Nwosu¹, H. A. Tanaka²*

Authors’ Affiliations:
¹Department of Biochemistry, Nnamdi Azikiwe University, Awka, Nigeria.
²Department of Biotechnology, Tokyo Institute of Technology, Tokyo, Japan.

Abstract: Industrial saccharification of tough lignocellulosic biomass requires robust cellulolytic enzymes that can resist thermal denaturation under operational refinery configurations. This study focuses on the selective isolation, biochemical screening, and thermal kinetic optimization of high-yielding cellulolytic fungal strains sourced from geothermal hot spring soils. Soil suspensions underwent enrichment culturing in Mandels' mineral media containing microcrystalline cellulose at elevated temperatures. Two distinct fungal strains displaying large hydrolysis zones via Gram's iodine clearing tests were isolated. The highest-yielding strain was identified morphologically and via genetic sequencing as Aspergillus fumigatus. Optimization experiments under solid-state fermentation showed that maximum endoglucanase and exoglucanase production occurred at a temperature of 45°C and a medium pH of 5.0 after 96 hours of incubation. Utilizing agricultural cotton residues as alternative substrates induced a high enzyme yield (6.2 U/mL) compared to wood sawdust (2.1 U/mL). The crude cellulase complex retained over 85% of its initial catalytic activity across a temperature stability range of 40 to 60°C for 24 hours, establishing an exceptionally stable enzyme framework for economic bioethanol manufacturing tracks.

Keywords: Thermophilic fungi; Aspergillus fumigatus; Solid-state fermentation; Cellulase; Thermal stability; Bioethanol production

Manuscript Timeline: Received: July 11, 2012; Revised: August 20, 2012; Accepted: September 15, 2012; Published: February 06, 2013.

Citation: Nwosu, C. N., & Tanaka, H. A. (2013). Isolation, Screening, and Kinetic Optimization of Cellulase Complexes Sourced from Thermophilic Fungal Strains. International Journal of Chemistry, 4(2), 9–16.