International Journal of Chemistry

International Journal of Chemistry | Vol. 9, No. 2, February 2018 | pp. 9–16

DOI: 10.46882/2018/IJC/000113

Article Type: Original Research Paper

Title: Isolation, Kinetic Modeling, and Structural Characterization of Thermophilic Amylases Sourced from Oil Mill Effluent 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 starch into fermentable sugars requires robust amylolytic enzymes that can resist thermal denaturation during high-temperature operations. This study details the isolation, microstructural profiling, and kinetic optimization of high-yielding alpha-amylase complexes produced by a thermophilic fungal strain sourced from palm oil mill effluent dumpsites. enrichment culturing was executed in starch-infused Mandels' media at 50°C, isolating a dominant strain identified via internal transcribed spacer (ITS) rRNA gene sequencing as Aspergillus nidulans strain POME-A2. Response surface methodology optimized solid-state fermentation yields using wheat bran matrices. Maximum alpha-amylase 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: Alpha-amylase; Aspergillus nidulans; Solid-state fermentation; Thermal stability; Kinetic optimization; Starch saccharification

Manuscript Timeline: Received: November 10, 2016; Revised: December 18, 2016; Accepted: January 14, 2017; Published: February 06, 2018.

Citation: Nwosu, C. N., & Sato, T. H. (2018). Isolation, Kinetic Modeling, and Structural Characterization of Thermophilic Amylases Sourced from Oil Mill Effluent Soils. International Journal of Chemistry, 9(2), 9–16.

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. 4, April 2018 | pp. 25–32

DOI: 10.46882/2018/IJC/000115

Article Type: Original Research Paper

Title: Spatial Analysis, Speciation, and Carcinogenic Risk Profiling of Nickel Formulations in Well Water Networks near Steel Mills

Names of Authors: T. H. Awotunde¹, R. M. Silva²*

Authors’ Affiliations:
¹Department of Chemistry, Federal University of Agriculture, Abeokuta, Nigeria.
²Department of Environmental Chemistry, University of São Paulo, São Paulo, Brazil.

Abstract: Metallurgical industrial smelting operations discharge significant amounts of nickel-rich waste into surrounding environments, causing heavy metal leaching into shallow drinking water aquifers. This study monitors the spatial variations, chemical speciation, and carcinogenic health risk profiles of nickel compounds across twenty household wells positioned around an active steel mill. Water monitoring was carried out over consecutive wet and dry cycles. Total nickel levels and specific nickel fractions were quantified utilizing ion chromatography coupled with inductively coupled plasma mass spectrometry (IC-ICP-MS). Total nickel concentrations ranged from 10.5 to 138.4 μg/L, with 38% of monitored groundwater sites surpassing the strict WHO drinkable contaminant threshold of 70.0 μg/L. Speciation analysis showed that soluble nickel ions were the dominant species, accounting for up to 64.2% of the total metal burden profiles at down-gradient coordinates. Seasonal mapping confirmed elevated nickel mobilization during the rainy period, indicating rain-induced plume leaching. Chronic Daily Intake (CDI) projections and Lifetime Cancer Risk (LCR) indices for child consumption cohorts surpassed 1.8 in 10,000 near industrial boundaries, emphasizing an immediate public healthcare concern and a need for local membrane filtration arrays.

Keywords: Groundwater pollution; Nickel speciation; Ion chromatography; Metallurgical effluents; Cancer risk assessment; Heavy metals

Manuscript Timeline: Received: December 02, 2016; Revised: January 14, 2017; Accepted: February 10, 2017; Published: April 02, 2018.

Citation: Awotunde, T. H., & Silva, R. M. (2018). Spatial Analysis, Speciation, and Carcinogenic Risk Profiling of Nickel Formulations in Well Water Networks near Steel Mills. International Journal of Chemistry, 9(4), 25–32.

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.

International Journal of Chemistry | Vol. 8, No. 6, June 2017 | pp. 41–48

DOI: 10.46882/2017/IJC/000105

Article Type: Original Research Paper

Title: Kinetic Studies and Mechanistic Pathway of the Chromic Acid Oxidation of L-Methionine in Aqueous Acidic Medium

Names of Authors: T. M. Usman¹, F. A. Al-Otaibi²*

Authors’ Affiliations:
¹Department of Chemistry, Bayero University, Kano, Nigeria.
²Department of Chemistry, King Abdulaziz University, Jeddah, Saudi Arabia.

Abstract: Investigating the kinetics of transition metal electron transfer processes involving sulfur-containing amino acids provides vital structural indicators required to map metabolic oxidation pathways. The oxidation of L-methionine by chromic acid (H₂CrO₄) was investigated spectrophotometrically in an aqueous perchloric acid medium at a constant ionic strength of 0.40 M (NaClO₄). The reaction progress was monitored under pseudo-first-order conditions by following the absorbance decay of Cr(VI) at its wavelength maximum of 350 nm. The empirical rate law showed a first-order dependence on [chromic acid] and a fractional-first-order dependence on [L-methionine]. The reaction rate increased with rising hydronium ion concentration, revealing an acid-catalyzed pathway governed by the active protonated oxidant species, [HCrO₃⁺]. Variations in the dielectric constant of the solvent medium produced significant kinetic shifts, confirming a rate-determining step involving two polar molecular species. Stoichiometric determinations confirmed that 3 moles of L-methionine consumed 2 moles of chromic acid, producing methionine sulfoxide and Cr(III) ions as the primary end products. Thermodynamic activation constants calculated from temperature-dependence datasets using the Eyring equation yielded an enthalpy of activation (delta H*) of 48.5 kJ/mol and an entropy of activation (delta S*) of -104.2 J/mol K, supporting an inner-sphere mechanism.

Keywords: Reaction kinetics; Spectrophotometry; Chromic acid oxidation; L-methionine; Activation parameters; Inner-sphere mechanism

Manuscript Timeline: Received: July 10, 2016; Revised: August 20, 2016; Accepted: September 15, 2016; Published: June 03, 2017.

Citation: Usman, T. M., & Al-Otaibi, F. A. (2017). Kinetic Studies and Mechanistic Pathway of the Chromic Acid Oxidation of L-Methionine in Aqueous Acidic Medium. International Journal of Chemistry, 8(6), 41–48.