International Journal of Chemistry

International Journal of Chemistry | Vol. 9, No. 1, January 2018 | pp. 1–8

DOI: 10.46882/2018/IJC/000112

Article Type: Original Research Paper

Title: Biochemical Characterization, Functional Attributes, and Nutritional Mineral Mapping of Underutilized Wild Dioscorea Species

Names of Authors: A. E. Ogunkoya¹, J. M. R. S. Tavares²*

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

Abstract: Non-conventional wild tuber crops serve as highly resilient food reserves in tropical zones, yet detailed chemical mapping of their dietary matrices is required to expand their domestication. This research evaluates the proximate nutritional composition, functional attributes, and mineral profile of three underutilized wild yam species (Dioscorea bulbifera, Dioscorea dumetorum, and Dioscorea praehensilis) gathered during the dry season harvest in West Africa. Proximate analysis established high total carbohydrate contents ranging from 72.4% to 78.5% on a dry weight basis, alongside moderate crude protein profiles (6.4% to 8.8%) and very low lipid concentrations (0.8% to 1.5%). Mineral profiling using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) revealed that potassium was the most abundant macro-element (640 to 820 mg/100g), followed by magnesium and phosphorus, while toxic heavy metal pollutants remained well below international safety thresholds. Quantified antinutritional matrices showed high baseline concentrations of total oxalates (3.4 to 5.2 mg/g) and alkaloid dioscorine fractions. Processing simulations proved that combined boiling and fermentation treatments effectively reduced antinutrient levels by over 82% without causing significant loss of structural proteins, establishing these wild tubers as excellent energy reservoirs.

Keywords: Wild yams; Dioscorea species; Proximate composition; Mineral profile; Antinutrients; Food chemistry

Manuscript Timeline: Received: October 18, 2016; Revised: November 28, 2016; Accepted: January 05, 2017; Published: January 03, 2018.

Citation: Ogunkoya, A. E., & Tavares, J. M. R. S. (2018). Biochemical Characterization, Functional Attributes, and Nutritional Mineral Mapping of Underutilized Wild Dioscorea Species. International Journal of Chemistry, 9(1), 1–8.

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. 6, June 2018 | pp. 41–48

DOI: 10.46882/2018/IJC/000117

Article Type: Original Research Paper

Title: Mechanochemical Properties and Microstructural Framework of Slag-Based Geopolymer Grout Reinforced with Carbon Nanotubes

Names of Authors: T. S. Ani¹, M. F. de Oliveira²*

Authors’ Affiliations:
¹Department of Electronic and Chemical Engineering, Enugu State University of Science and Technology, Enugu, Nigeria.
²Department of Chemical Engineering, Instituto Superior Técnico, Lisbon, Portugal.

Abstract: Developing high-performance geopolymer grouts from industrial materials decreases production carbon footprints, though enhancing mechanical integrity requires structural optimization via carbon nanomaterial additives. This research tracks the structural development and mechanical profiles of geopolymer cements synthesized from ground granulated blast furnace slag (GGBS) integrated with multiwalled carbon nanotubes (MWCNTs) at dosages from 0% to 1.5% by weight. Alkaline activation was executed utilizing structural mixtures of sodium silicate and 12 M sodium hydroxide solutions. Hardening kinetics and microstructural phases were analyzed using X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, and Scanning Electron Microscopy (SEM). FT-IR spectra demonstrated the formation of a rigid silicate network, indicated by the prominent framework stretching bands shifting to 1015 cm⁻¹. Compressive strength experiments showed that grout cubes prepared with 1.0% MWCNT substitution reached a maximum compressive value of 61.2 MPa after 28 days of curing at room temperature, outperforming pure slag controls. SEM characterization revealed a highly dense matrix featuring bridging networks across micro-cracks, which significantly reduces internal cracking.

Keywords: Geopolymer grout; Slag activation; Carbon nanotubes; Compressive strength; Microstructure; C-S-H gel networks

Manuscript Timeline: Received: January 14, 2017; Revised: February 18, 2017; Accepted: March 12, 2017; Published: June 03, 2018.

Citation: Ani, T. S., & de Oliveira, M. F. (2018). Mechanochemical Properties and Microstructural Framework of Slag-Based Geopolymer Grout Reinforced with Carbon Nanotubes. International Journal of Chemistry, 9(6), 41–48.

International Journal of Chemistry | Vol. 9, No. 8, August 2018 | pp. 57–64

DOI: 10.46882/2018/IJC/000119

Article Type: Original Research Paper

Title: Ultrasonic Speeds, Excess Volumetric Parameters, and Intermolecular Interactions of Binary Liquid Mixtures of Isobutanol with Aliphatic Amines

Names of Authors: E. C. Chiemeka¹, A. M. H. Al-Ghamdi²*

Authors’ Affiliations:
¹Department of Chemistry, Federal University of Technology, Owerri, Nigeria.
²Department of Chemistry, University of Khartoum, Khartoum, Sudan.

Abstract: Experimental determination of ultrasonic velocities and fluid densities across varied temperature states yields critical baseline data needed to map hydrogen bond associations and molecular packing dynamics in multi-component chemical systems. This paper presents the measurement of ultrasonic velocity (u), density (rho), and dynamic viscosity (eta) for binary liquid mixtures of isobutanol with diethylamine, triethylamine, and cyclohexylamine across the entire composition matrix at temperatures of 298.15 K, 308.15 K, and 318.15 K under atmospheric pressure. From these raw data metrics, excess molar volumes (V^E) and excess isentropic compressibilities (kappa_s^E) were calculated. The calculated excess datasets were successfully fitted to the Redlich-Kister polynomial expression to compute the binary interaction coefficients and standard deviations. All investigated binary mixtures exhibited significant negative excess molar volumes (V^E) and negative excess isentropic compressibilities (kappa_s^E) across all composition bounds. These strong negative deviations reveal dense interstitial molecular packing and strong intermolecular hydrogen bond formation between the hydroxyl protons of isobutanol and the amine nitrogen centers, which decrease in intensity as thermal motion breaks the dipole networks.

Keywords: Ultrasonic velocity; Excess molar volume; Isentropic compressibility; Aliphatic amines; Redlich-Kister equation; Hydrogen bonding

Manuscript Timeline: Received: February 05, 2017; Revised: March 12, 2017; Accepted: April 08, 2017; Published: August 03, 2018.

Citation: Chiemeka, E. C., & Al-Ghamdi, A. M. H. (2018). Ultrasonic Speeds, Excess Volumetric Parameters, and Intermolecular Interactions of Binary Liquid Mixtures of Isobutanol with Aliphatic Amines. International Journal of Chemistry, 9(8), 57–64.