International Journal of Chemistry

International Journal of Chemistry | Vol. 12, No. 11, November 2021 | pp. 81–88

DOI: 10.46882/2021/IJC/000157

Article Type: Original Research Paper

Title: Electrochemical Properties and Supercapacitive Characterization of Polyaniline-Graphene Oxide Micro-Electrode Arrays

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 polyaniline-graphene oxide (PANI-GO) thin-film micro-electrode arrays 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 polyaniline layer was uniformly deposited across the conductive graphene oxide 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 PANI-GO 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 polyaniline 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: Polyaniline; Graphene oxide; Energy storage; Supercapacitors; Cyclic voltammetry; Specific capacitance

Manuscript Timeline: Received: January 22, 2021; Revised: February 25, 2021; Accepted: March 18, 2021; Published: November 09, 2021.

Citation: Aliyu, U. B., & Lee, K. Y. (2021). Electrochemical Properties and Supercapacitive Characterization of Polyaniline-Graphene Oxide Micro-Electrode Arrays. International Journal of Chemistry, 12(11), 81–88.

International Journal of Chemistry | Vol. 12, No. 3, March 2021 | pp. 17–24

DOI: 10.46882/2021/IJC/000147

Article Type: Original Research Paper

Title: Thermodynamic Modeling, Kinetic Runs, and Multilayer Adsorption of Acid Blue 92 Dye onto Modified Bentonite Clay

Names of Authors: A. D. Yusuf¹, M. A. Al-Ghamdi²*

Authors’ Affiliations:
¹Department of Industrial Chemistry, Federal University of Technology, Yola, Nigeria.
²Department of Chemistry, Qatar University, Doha, Qatar.

Abstract: The release of highly stable anionic azo dyes like Acid Blue 92 from textile processing factories causes significant environmental and toxicity hazards in surface water channels. This study examines the adsorptive uptake performance of a surfactant-modified bentonite clay (SMB) prepared via chemical functionalization with hexadecyltrimethylammonium bromide (HDTMA-Br). The structural parameters of raw and modified clays were characterized using X-ray diffraction (XRD) and FT-IR spectroscopy. Adsorption operations were conducted via batch runs, monitoring changes in contact time, solution pH, initial dye loading concentrations, and system temperatures. The equilibrium datasets fit closely with the Freundlich isotherm model, demonstrating successful multilayer dye attachment onto the hydrophobic surfactant bilayers. Kinetic parameters matched the intra-particle diffusion expressions alongside a pseudo-second-order mechanism, showing that chemisorption reactions controlled the mass transfer rates. Thermodynamic constants showed that the adsorption process was endothermic (delta H° = 22.4 kJ/mol) and caused an increase in system randomness at the solid-solution interface (delta S° = 74.2 J/mol K). Negative values of Gibbs free energy (delta G°) spanning from -2.4 to -5.8 kJ/mol across the 298 to 328 K range confirmed process spontaneity, positioning SMB as an affordable material for industrial dye wastewater treatment.

Keywords: Bentonite clay; Surfactant modification; Acid blue 92; Adsorption isotherm; Chemisorption; Thermodynamic parameters

Manuscript Timeline: Received: July 20, 2020; Revised: August 28, 2020; Accepted: September 15, 2020; Published: March 04, 2021.

Citation: Yusuf, A. D., & Al-Ghamdi, M. A. (2021). Thermodynamic Modeling, Kinetic Runs, and Multilayer Adsorption of Acid Blue 92 Dye onto Modified Bentonite Clay. International Journal of Chemistry, 12(3), 17–24.

International Journal of Chemistry | Vol. 12, No. 10, October 2021 | pp. 73–80

DOI: 10.46882/2021/IJC/000156

Article Type: Original Research Paper

Title: Mechanochemical Optimization and Structural Framework of Slag-Based Geopolymer Binders Reinforced with Alumina Nanoparticles

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 wastes decreases production carbon footprints, though enhancing mechanical integrity requires structural optimization via reactive nanomaterial additives. This research tracks the structural development and mechanical profiles of geopolymer cements synthesized from ground granulated blast furnace slag (GGBS) integrated with nano-alumina (nano-Al₂O₃) particles at dosages from 0% to 3.0% 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 1012 cm⁻¹. Compressive strength experiments showed that grout cubes prepared with 2.0% nano-alumina substitution reached a maximum compressive value of 58.4 MPa after 28 days of curing at room temperature, outperforming pure slag controls. SEM characterization revealed a highly dense matrix featuring intense structural crosslinking of calcium silicate hydrate (C-S-H) gel structures, which significantly reduces internal cracking.

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

Manuscript Timeline: Received: January 14, 2021; Revised: February 18, 2021; Accepted: March 12, 2021; Published: October 05, 2021.

Citation: Ani, T. S., & de Oliveira, M. F. (2021). Mechanochemical Optimization and Structural Framework of Slag-Based Geopolymer Binders Reinforced with Alumina Nanoparticles. International Journal of Chemistry, 12(10), 73–80.

International Journal of Chemistry | Vol. 12, No. 7, July 2021 | pp. 49–56

DOI: 10.46882/2021/IJC/000153

Article Type: Original Research Paper

Title: Synthesis, Microstructural Framework, and Swelling Kinetics of Xanthan Gum-Graft-Polyacrylamide Hydrogels

Names of Authors: J. K. Mensah¹, S. K. Roy²*

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 agricultural soil water retention and controlled agrochemical delivery 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 acrylamide onto a high-viscosity xanthan gum 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 410 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 zinc and copper ions, matching the Langmuir isotherm with monolayer capacities of 72.4 mg/g and 85.6 mg/g at 298 K, confirming high remediation potential.

Keywords: Xanthan gum; Acrylamide; Graft copolymerization; Hydrogel; Swelling kinetics; Heavy metal adsorption

Manuscript Timeline: Received: November 15, 2020; Revised: December 22, 2020; Accepted: January 20, 2021; Published: July 08, 2021.

Citation: Mensah, J. K., & Roy, S. K. (2021). Synthesis, Microstructural Framework, and Swelling Kinetics of Xanthan Gum-Graft-Polyacrylamide Hydrogels. International Journal of Chemistry, 12(7), 49–56.

International Journal of Chemistry | Vol. 11, No. 12, December 2020 | pp. 89–96

DOI: 10.46882/2020/IJC/000144

Article Type: Original Research Paper

Title: Geochemical Speciation, Spatial Distribution, and Environmental Hazard Index of Mercury and Lead in Estuarine Mudflats

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 mercury (Hg) and lead (Pb) in surface sediments collected from an urban coastal estuary exposed to municipal and industrial waste discharges. Quantitative analysis was performed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) following the modified BCR three-step sequential extraction procedure. The total metal concentrations followed the sequence: Pb > Hg across all sampling locations. Spatial mapping revealed significant pollutant accumulation near storm-water discharge channels. Speciation patterns demonstrated that a high proportion of mercury (42.5%) was associated with the acid-soluble and exchangeable fractions, suggesting high structural instability and bioavailable risks to benthic organisms. Conversely, lead was primarily bound within the residual and organic matrices, indicating low immediate mobility under baseline pH conditions. The Risk Assessment Code (RAC) calculated for mercury indicated a high environmental hazard rating, highlighting a strong need for local effluent regulatory frameworks.

Keywords: Coastal estuary; Sediments; Mercury; Lead pollution; Geochemical speciation; Bioavailability

Manuscript Timeline: Received: April 18, 2020; Revised: June 05, 2020; Accepted: July 12, 2020; Published: December 04, 2020.

Citation: Obi, C. I., & Kim, S. H. (2020). Geochemical Speciation, Spatial Distribution, and Environmental Hazard Index of Mercury and Lead in Estuarine Mudflats. International Journal of Chemistry, 11(12), 89–96.

International Journal of Chemistry | Vol. 11, No. 8, August 2020 | pp. 57–64

DOI: 10.46882/2020/IJC/000142

Article Type: Original Research Paper

Title: Adsorptive Elimination of Lead(II) Ions from Saline Effluents Using Chemically Functionalized Orange Peel Biomass

Names of Authors: E. N. Chidi¹, M. A. van der Berg²*

Authors’ Affiliations:
¹Department of Pure and Industrial Chemistry, Nnamdi Azikiwe University, Awka, Nigeria.
²Department of Chemical Engineering, Delft University of Technology, Delft, Netherlands.

Abstract: Heavy metal contamination of surface waters by battery assembly facilities demands the chemical configuration of low-cost, stable, and highly active biosorption matrices. This investigation reports the adsorptive efficiency of a modified agricultural adsorbent derived from orange (Citrus sinensis) peel wastes prepared via carboxylation with monochloroacetic acid. The chemical transformations and surface porous architectures of the matrix were examined through scanning electron microscopy (SEM) and FT-IR spectroscopy. The analytical data confirmed that the carboxylation process successfully integrated carboxyl (-COOH) functional ligand networks across the cellulosic biomass structure. Batch extraction experiments evaluated parameters of solution pH, equilibrium contact time, adsorbent dosage, and initial Pb(II) concentrations. Maximum Pb(II) adsorption occurred at an optimum pH of 5.5, using an equilibrium contact period of 90 minutes. Equilibrium data matched the Langmuir model closely, showing a maximum monolayer adsorption capacity of 62.45 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 parameters confirmed process spontaneity and endothermic characteristics, highlighting this modified biomass as an affordable material for water treatment plant design.

Keywords: Orange peel; Chemical modification; Carboxylation; Lead removal; Adsorption kinetics; Chemisorption

Manuscript Timeline: Received: February 18, 2020; Revised: April 02, 2020; Accepted: May 15, 2020; Published: August 03, 2020.

Citation: Chidi, E. N., & van der Berg, M. A. (2020). Adsorptive Elimination of Lead(II) Ions from Saline Effluents Using Chemically Functionalized Orange Peel Biomass. International Journal of Chemistry, 11(8), 57–64.