International Journal of Chemistry

International Journal of Chemistry | Vol. 14, No. 6, June 2023 | pp. 41–48

DOI: 10.46882/2023/IJC/000176

Article Type: Original Research Paper

Title: Mechanochemical Properties and Microstructural Performance of Fly Ash Geopolymer Grout Reinforced with Functionalized 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 class F fly ash integrated with carboxyl-functionalized 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 fly ash controls. SEM characterization revealed a highly dense matrix featuring bridging networks across micro-cracks, which significantly reduces internal cracking.

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

Manuscript Timeline: Received: January 14, 2022; Revised: February 18, 2022; Accepted: March 12, 2022; Published: June 03, 2023.

Citation: Ani, T. S., & de Oliveira, M. F. (2023). Mechanochemical Properties and Microstructural Performance of Fly Ash Geopolymer Grout Reinforced with Functionalized Carbon Nanotubes. International Journal of Chemistry, 14(6), 41–48.

International Journal of Chemistry | Vol. 14, No. 9, September 2023 | pp. 65–72

DOI: 10.46882/2023/IJC/000179

Article Type: Original Research Paper

Title: Synthesis, Microcharacterization, and Antifungal Profiles of Novel Ethambutol-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 drug structures 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 ethambutol 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(ETH)Cl₂], where ETH represents the neutral ethambutol molecule. Molar conductance tests in DMSO indicated a non-electrolytic nature. FT-IR spectra confirmed that ethambutol acts as a bidentate ligand, binding to the metal centers via the hydroxyl oxygen and the secondary amino nitrogen atoms. In vitro antifungal evaluation was conducted against Candida albicans and Aspergillus niger isolates via the disk diffusion test. The copper(II)-ethambutol complex demonstrated a two-fold increase in mycelial growth inhibition compared to standalone uncoordinated ethambutol, which is explained via cell permeability and chelation principles.

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

Manuscript Timeline: Received: February 12, 2022; Revised: March 20, 2022; Accepted: April 15, 2022; Published: September 09, 2023.

Citation: Yusuf, A. A., & Ghosh, P. K. (2023). Synthesis, Microcharacterization, and Antifungal Profiles of Novel Ethambutol-Based Transition Metal Complexes. International Journal of Chemistry, 14(9), 65–72.

International Journal of Chemistry | Vol. 14, No. 2, February 2023 | pp. 9–16

DOI: 10.46882/2023/IJC/000172

Article Type: Original Research Paper

Title: Isolation, Kinetic Modeling, and Structural Properties of Thermophilic Xylanolytic Complexes Sourced from Agricultural Silage Soils

Names of Authors: C. N. Nwosu¹, T. H. Sato²*

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

Abstract: The industrial hydrolysis of plant biomass into fermentable sugars requires robust xylanolytic enzymes that can resist thermal denaturation during high-temperature operations. This study details the isolation, microstructural profiling, and kinetic optimization of high-yielding endo-xylanase complexes produced by a thermophilic fungal strain sourced from agricultural compost and silage dumpsites. Enrichment culturing was executed in xylan-infused Mandels' media at 50°C, isolating a dominant strain identified via internal transcribed spacer (ITS) rRNA gene sequencing as Aspergillus tubingensis strain SIL-X2. Response surface methodology optimized solid-state fermentation yields using wheat bran matrices. Maximum xylanase activity (48.5 U/mL) was achieved at an incubation temperature of 50°C, an initial substrate pH of 6.5, and a fermentation period of 96 hours. Biochemical characterization showed that the crude enzyme complex retained over 85% of its initial catalytic activity across a temperature range of 45 to 65°C and a pH stability window of 5.5 to 7.5 for 24 hours. The high thermal stability of this enzyme system, along with its independence from calcium ions, makes it a viable candidate for bio-refinery industrial operations.

Keywords: Xylanase; Aspergillus tubingensis; Solid-state fermentation; Thermal stability; Kinetic optimization; Biomass conversion

Manuscript Timeline: Received: November 10, 2022; Revised: December 18, 2022; Accepted: January 14, 2023; Published: February 06, 2023.

Citation: Nwosu, C. N., & Sato, T. H. (2023). Isolation, Kinetic Modeling, and Structural Properties of Thermophilic Xylanolytic Complexes Sourced from Agricultural Silage Soils. International Journal of Chemistry, 14(2), 9–16.

International Journal of Chemistry | Vol. 14, No. 11, November 2023 | pp. 81–88

DOI: 10.46882/2023/IJC/000181

Article Type: Original Research Paper

Title: Adsorptive Remediation of Hexavalent Chromium Using Chemically Functionalized Banana Pseudo-Stem Biomass

Names of Authors: E. N. Chidi¹, L. M. van der Westhuizen²*

Authors’ Affiliations:
¹Department of Pure and Industrial Chemistry, Nnamdi Azikiwe University, Awka, Nigeria.
²Department of Chemical Engineering, Stellenbosch University, Stellenbosch, South Africa.

Abstract: Heavy metal contamination of surface water resources by metallurgical effluents 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 banana pseudo-stem wastes prepared via surface functionalization with succinic anhydride. 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 modification process successfully integrated carboxylic acid functional ligand networks across the cellulosic biomass strands. Batch extraction experiments evaluated parameters of solution pH, equilibrium contact time, adsorbent dosage, and initial Cr(VI) concentrations. Maximum chromium adsorption occurred at an acidic pH of 2.0, 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 industrial water treatment plant design.

Keywords: Banana pseudo-stem; Surface functionalization; Hexavalent chromium; Adsorption kinetics; Chemisorption; Wastewater remediation

Manuscript Timeline: Received: June 02, 2022; Revised: July 15, 2022; Accepted: August 10, 2022; Published: November 09, 2023.

Citation: Chidi, E. N., & van der Westhuizen, L. M. (2023). Adsorptive Remediation of Hexavalent Chromium Using Chemically Functionalized Banana Pseudo-Stem Biomass. International Journal of Chemistry, 14(11), 81–88.

International Journal of Chemistry | Vol. 14, No. 3, March 2023 | pp. 17–24

DOI: 10.46882/2023/IJC/000173

Article Type: Original Research Paper

Title: Synthesis, Microstructural Framework, and Swelling Kinetics of Alginate-Graft-Poly(Acrylic Acid) Superabsorbent Biopolymer 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 sodium alginate 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: Sodium alginate; Acrylic acid; Graft copolymerization; Hydrogel; Swelling kinetics; Heavy metal adsorption

Manuscript Timeline: Received: November 15, 2022; Revised: December 22, 2022; Accepted: January 20, 2023; Published: March 04, 2023.

Citation: Mensah, J. K., & Mukherjee, S. K. (2023). Synthesis, Microstructural Framework, and Swelling Kinetics of Alginate-Graft-Poly(Acrylic Acid) Superabsorbent Biopolymer Hydrogels. International Journal of Chemistry, 14(3), 17–24.

International Journal of Chemistry | Vol. 14, No. 8, August 2023 | pp. 57–64

DOI: 10.46882/2023/IJC/000178

Article Type: Original Research Paper

Title: Ultrasonic Speeds, Excess Thermodynamic Parameters, and Intermolecular Transport Features of Binary Liquid Systems of Hexanol with 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 n-hexanol 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 n-hexanol 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, 2022; Revised: March 12, 2022; Accepted: April 08, 2022; Published: August 03, 2023.

Citation: Chiemeka, E. C., & Al-Ghamdi, A. M. H. (2023). Ultrasonic Speeds, Excess Thermodynamic Parameters, and Intermolecular Transport Features of Binary Liquid Systems of Hexanol with Amines. International Journal of Chemistry, 14(8), 57–64.