International Journal of Chemistry

International Journal of Chemistry | Vol. 9, No. 7, July 2018 | pp. 49–56

DOI: 10.46882/2018/IJC/000118

Article Type: Original Research Paper

Title: Electrochemical Properties and Charge Storage Profiles of Polypyrrole-Graphene Hydrogel Composites for Supercapacitors

Names of Authors: U. B. Aliyu¹, K. 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 polypyrrole-graphene hydrogel (PPy-GH) self-assembling nanocomposites prepared via in situ chemical oxidative polymerization pathways. The surface topology and morphological features of the hybrid gels were analyzed using field emission scanning electron microscopy (FESEM), FT-IR, and Raman spectroscopy. FESEM imaging confirmed that a highly porous three-dimensional polypyrrole layer was uniformly deposited across the conductive graphene skeletal network. Electrochemical performance was investigated via cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) loops in a 1.0 M H₂SO₄ electrolyte system. The optimized PPy-GH hybrid electrode delivered a maximum specific capacitance of 492 F/g at a current density of 1.0 A/g, which was substantially higher than standalone pure polypyrrole films (215 F/g). Electrochemical impedance spectroscopy (EIS) data showed a very low charge-transfer resistance of 0.25 ohms, confirming accelerated ionic transport across the polymeric interface. Cyclic stability evaluations proved that the composite material retained 92.4% of its capacitive profile after 2000 continuous cycles.

Keywords: Polypyrrole; Graphene hydrogel; Energy storage; Supercapacitors; Cyclic voltammetry; Specific capacitance

Manuscript Timeline: Received: January 22, 2017; Revised: February 25, 2017; Accepted: March 18, 2017; Published: July 08, 2018.

Citation: Aliyu, U. B., & Lee, K. Y. (2018). Electrochemical Properties and Charge Storage Profiles of Polypyrrole-Graphene Hydrogel Composites for Supercapacitors. International Journal of Chemistry, 9(7), 49–56.

International Journal of Chemistry | Vol. 9, No. 12, December 2018 | pp. 81–88

DOI: 10.46882/2018/IJC/000122

Article Type: Original Research Paper

Title: Adsorptive Sequestration of Zinc(II) Ions from Industrial Effluents Using Phosphorylated Cocoa Pod Husk Biomass

Names of Authors: E. N. Chidi¹, J. A. M. Ahmed²*

Authors’ Affiliations:
¹Department of Pure and Industrial Chemistry, Nnamdi Azikiwe University, Awka, Nigeria.
²Department of Chemical Engineering, Cairo University, Giza, Egypt.

Abstract: Heavy metal contamination of surface waters from metallurgical and electroplating industries requires the development of low-cost, chemically stable, and efficient agricultural waste remediation matrices. This study explores the adsorptive performance of a modified cocoa pod husk prepared via chemical functionalization with phosphoric acid (phosphorylated biomass). The surface chemistry and porosity of the adsorbent were studied using scanning electron microscopy (SEM) and FT-IR spectroscopy. The analytical data confirmed that phosphorylation successfully integrated phosphorus-rich phosphate functional groups onto the lignocellulosic biomass network. Batch extraction experiments evaluated parameters of solution pH, contact time, adsorbent dosage, and initial Zn(II) concentrations. Maximum Zn(II) removal occurred at an optimum pH of 6.0, using an equilibrium contact period of 90 minutes. Equilibrium data matched the Langmuir model closely, showing a maximum monolayer adsorption capacity of 48.55 mg/g at 298 K. Sorption kinetics followed a pseudo-second-order model with a high correlation coefficient (R² > 0.998), proving that chemical surface complexation reactions controlled the mass transfer rates. Thermodynamic constants showed that the adsorption process was spontaneous (delta G° = -4.18 kJ/mol) and endothermic, establishing phosphorylated biomass as an affordable choice for wastewater treatment plant designs.

Keywords: Cocoa pod husk; Chemical modification; Phosphorylation; Zinc removal; Adsorption kinetics; Chemisorption

Manuscript Timeline: Received: March 20, 2018; Revised: May 02, 2018; Accepted: June 15, 2018; Published: December 05, 2018.

Citation: Chidi, E. N., & Ahmed, J. A. M. (2018). Adsorptive Sequestration of Zinc(II) Ions from Industrial Effluents Using Phosphorylated Cocoa Pod Husk Biomass. International Journal of Chemistry, 9(12), 81–88.

International Journal of Chemistry | Vol. 9, No. 3, March 2018 | pp. 17–24

DOI: 10.46882/2018/IJC/000114

Article Type: Original Research Paper

Title: Synthesis, Microstructural Framework, and Swelling Kinetics of Chitosan-Graft-Poly(Acrylic Acid) Superabsorbent Hydrogels

Names of Authors: J. K. Mensah¹, S. K. Mukherjee²*

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: The development of durable biopolymeric hydrogel networks is essential for controlled agrochemical delivery and agricultural soil water retention due to the requirement for specific structural coordination sites. This study describes the chemical synthesis and rheological optimization of a hybrid hydrogel fabricated via the free-radical graft copolymerization of acrylic acid onto a high-viscosity seafood chitosan backbone. The grafting reaction was initiated using potassium persulfate (KPS) and crosslinked via N,N'-methylenebisacrylamide (MBA) under optimized atmospheric conditions. Structural networks and morphology features were characterized using FT-IR spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Swelling kinetics were evaluated as a function of time, pH, and saline concentration. The hydrogel showed highly responsive pH-dependent swelling profiles, achieving a maximum water absorption capacity of 430 g/g at pH 7.4 due to structural carboxylate ionizations causing intermolecular chain repulsions. Rheological analysis confirmed strong non-Newtonian shear-thinning characteristics with a storage modulus (G') that remained constant up to 80°C. Batch adsorption tests showed high affinity for divalent cadmium and lead ions, matching the Langmuir isotherm with monolayer capacities of 68.4 mg/g and 82.6 mg/g at 298 K, confirming high remediation potential.

Keywords: Chitosan; Acrylic acid; Graft copolymerization; Hydrogel; Swelling kinetics; Heavy metal adsorption

Manuscript Timeline: Received: November 15, 2016; Revised: December 22, 2016; Accepted: January 20, 2017; Published: March 04, 2018.

Citation: Mensah, J. K., & Mukherjee, S. K. (2018). Synthesis, Microstructural Framework, and Swelling Kinetics of Chitosan-Graft-Poly(Acrylic Acid) Superabsorbent Hydrogels. International Journal of Chemistry, 9(3), 17–24.

International Journal of Chemistry | Vol. 9, No. 10, October 2018 | pp. 65–72

DOI: 10.46882/2018/IJC/000120

Article Type: Original Research Paper

Title: Synthesis, Characterization, and Antifungal Profile of Novel Rifampicin-Based Transition Metal Complexes

Names of Authors: A. A. Yusuf¹, P. K. Ghosh²*

Authors’ Affiliations:
¹Department of Chemistry, Ahmadu Bello University, Zaria, Nigeria.
²Department of Pharmaceutical Technology, Jadavpur University, Kolkata, India.

Abstract: The emergence of drug resistance among opportunistic fungal strains requires the structural modification of classic macrocyclic derivatives via coordination to transition metal ions to boost clinical performance. This research outlines the synthesis, structural characterization, and in vitro antifungal testing of novel copper(II), nickel(II), and cobalt(II) complexes coordinated with rifampicin ligands. The synthesized coordination compounds were profiled utilizing elemental analysis, molar conductance measurements, magnetic susceptibility, and FT-IR spectroscopy. Analytical metrics established a 1:1 metal-to-ligand stoichiometric coordination pattern for all complexes, corresponding to a general structural configuration of [M(RIF)Cl₂], where RIF represents the neutral rifampicin molecule. Molar conductance tests in DMSO indicated a non-electrolytic nature. FT-IR spectra confirmed that rifampicin acts as a bidentate ligand, binding to the metal centers via the chromophoric oxygen and the piperazinyl nitrogen atoms. In vitro antifungal evaluation was conducted against Candida albicans and Aspergillus niger isolates via the disk diffusion test. The copper(II)-rifampicin complex demonstrated a two-fold increase in mycelial growth inhibition compared to standalone uncoordinated rifampicin, which is explained via cell permeability and chelation principles.

Keywords: Rifampicin; Metal complexes; Antifungal activity; FT-IR spectroscopy; Candida albicans; Chelation theory

Manuscript Timeline: Received: February 12, 2017; Revised: March 20, 2017; Accepted: April 15, 2017; Published: October 05, 2018.

Citation: Yusuf, A. A., & Ghosh, P. K. (2018). Synthesis, Characterization, and Antifungal Profile of Novel Rifampicin-Based Transition Metal Complexes. International Journal of Chemistry, 9(10), 65–72.

International Journal of Chemistry | Vol. 9, No. 5, May 2018 | pp. 33–40

DOI: 10.46882/2018/IJC/000116

Article Type: Original Research Paper

Title: Assessing the Hydrocarbon Tolerance and Phytoremediation Trait of Vigna unguiculata L. in Aviation Fuel Spiked Soils

Names of Authors: O. F. Olawal¹, H. de Koning²*

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

Abstract: The accidental leakage of aviation fuel from commercial storage facilities damages agricultural soil porosity and introduces toxic aromatic hydrocarbons into arable land, demanding green restoration strategies. This controlled study investigates the growth kinetics and remediation efficiency of Vigna unguiculata L. (Cowpea) cultivated in soils artificially spiked with varying concentrations of aviation fuel (1.0% to 4.0% w/w). Plant structural indices, remaining soil total petroleum hydrocarbon (TPH) concentrations, and root zone microbial populations were quantified over a 90-day developmental period. Vigna unguiculata demonstrated strong physiological tolerance, maintaining high root nodulation indices across all fuel loading levels below 3.0%. Gas Chromatography (GC-FID) profiling showed a 71.4% reduction in soil TPH content within the rhizosphere of cultivated systems, compared to minimal attenuation (24.5%) in unplanted controls. Soil microbiological testing revealed a five-fold expansion of heterotrophic degradation bacteria within the legume root matrix. This confirms that root exudates and symbiotic nitrogen-fixing bacteria actively interact to stimulate microbial proliferation, accelerating the degradation of complex petroleum structures in contaminated agricultural terrains.

Keywords: Aviation fuel; Vigna unguiculata; Total petroleum hydrocarbons; Soil phytoremediation; Rhizosphere effect; Legume symbiosis

Manuscript Timeline: Received: December 08, 2016; Revised: January 20, 2017; Accepted: February 15, 2017; Published: May 05, 2018.

Citation: Olawal, O. F., & de Koning, J. (2018). Assessing the Hydrocarbon Tolerance and Phytoremediation Trait of Vigna unguiculata L. in Aviation Fuel Spiked Soils. International Journal of Chemistry, 9(5), 33–40.

International Journal of Chemistry | Vol. 10, No. 2, February 2019 | pp. 9–16

DOI: 10.46882/2019/IJC/000124

Article Type: Original Research Paper

Title: Transesterification Optimization, Kinetic Parameters, and Engine Emission Profiles of Biodiesel from Ricinus communis Seed 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 crop lipids as chemical feedstocks for alternative bio-fuel synthesis promotes green energy targets without competing with food supplies. This study investigates the transesterification kinetics and chemical properties of biodiesel synthesized from castor (Ricinus communis) seed oil. Because of an elevated initial free fatty acid content (5.64 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 1.2% v/v sulfuric acid in methanol, followed by a base-catalyzed transesterification with sodium methoxide. Fatty acid methyl ester (FAME) yield was optimized at 94.5% using a 6:1 methanol-to-oil molar ratio, a catalyst concentration of 1.0 wt% NaOH, 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 40.5 kJ/mol. Fuel properties of the prepared biodiesel, including kinematic viscosity (4.38 mm²/s at 40°C), flash point (168°C), and cetane number (52), matched international ASTM D6751 regulatory specifications. Diesel engine tests using a B20 blend showed a 12.4% reduction in hydrocarbon emissions compared to conventional diesel.

Keywords: Ricinus communis; Biodiesel; Transesterification; Reaction kinetics; Activation energy; Kinematic viscosity

Manuscript Timeline: Received: April 10, 2018; Revised: May 22, 2018; Accepted: June 18, 2018; Published: February 06, 2019.

Citation: Okonkwo, M. C., & Nguyen, T. H. (2019). Transesterification Optimization, Kinetic Parameters, and Engine Emission Profiles of Biodiesel from Ricinus communis Seed Oil. International Journal of Chemistry, 10(2), 9–16.