International Journal of Chemistry

International Journal of Chemistry | Vol. 5, No. 11, November 2014 | pp. 81–88

DOI: 10.46882/2014/IJC/000074

Article Type: Original Research Paper

Title: Synthesis, Rheological Profiling, and Adsorptive Features of Sodium Alginate Grafted Polyacrylamide Composite Hydrogels

Names of Authors: J. K. Mensah¹, R. P. Sharma²*

Authors’ Affiliations:
¹Department of Chemistry, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.
²Department of Chemistry, Indian Institute of Technology, Bombay, India.

Abstract: The development of durable biopolymeric hydrogel networks is essential for industrial wastewater treatment 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 sodium alginate backbone. The grafting reaction was initiated using potassium persulfate (KPS) and crosslinked via N,N'-methylenebisacrylamide (MBA) under optimized gas environments. 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 380 g/g at pH 8.0 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 75°C. Batch adsorption tests showed high affinity for divalent nickel and zinc ions, matching the Langmuir isotherm with monolayer capacities of 64.2 mg/g and 78.4 mg/g at 298 K, confirming high remediation potential.

Keywords: Sodium alginate; Acrylamide; Graft copolymerization; Hydrogel; Rheological profiling; Heavy metal adsorption

Manuscript Timeline: Received: March 04, 2014; Revised: April 15, 2014; Accepted: May 20, 2014; Published: November 02, 2014.

Citation: Mensah, J. K., & Sharma, R. P. (2014). Synthesis, Rheological Profiling, and Adsorptive Features of Sodium Alginate Grafted Polyacrylamide Composite Hydrogels. International Journal of Chemistry, 5(11), 81–88.

International Journal of Chemistry | Vol. 5, No. 8, August 2014 | pp. 57–64

DOI: 10.46882/2014/IJC/000071

Article Type: Original Research Paper

Title: Green Synthesis of Bimetallic Cu-Ag Nanoparticles Using Aqueous Leaf Extract of Azadirachta indica and Catalytic Reduction of 4-Nitrophenol

Names of Authors: S. I. Musa¹, T. A. Al-Shehri²*

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

Abstract: The fabrication of bimetallic nanoparticles using plant extracts represents an active frontier in sustainable heterogeneous catalysis due to synergistic electronic interactions at the nano-interface. This study details the green synthesis of stable copper-silver (Cu-Ag) core-shell nanoparticles utilizing the aqueous leaf extract of Azadirachta indica as a co-reducing and capping agent. The bioreduction process was monitored via UV-Vis spectrophotometry, which revealed a broad surface plasmon resonance peak at 495 nm, indicating alloyed structure formations. Transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX) showed spherical particles with an average diameter of 22 nm and uniform copper-silver atomic distributions. X-ray diffraction (XRD) confirmed the highly crystalline nature of the bimetallic system. Fourier-transform infrared (FT-IR) spectroscopy showed that plant polyphenols and flavonoids actively capped the metallic surfaces, preventing structural agglomeration. The catalytic efficiency of the synthesized Cu-Ag nanoparticles was evaluated by tracking the reduction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride (NaBH₄). The bimetallic nanocatalyst accelerated the reaction, achieving 98.6% conversion within 6 minutes, outperforming monometallic equivalents. Kinetic modeling conformed to the pseudo-first-order model with a rate constant of 0.384 min⁻¹, confirming high efficacy for nitro-aromatic wastewater remediation.

Keywords: Bimetallic nanoparticles; Green synthesis; Azadirachta indica; Core-shell structure; Heterogeneous catalysis; 4-Nitrophenol

Manuscript Timeline: Received: January 12, 2014; Revised: February 20, 2014; Accepted: March 15, 2014; Published: August 03, 2014.

Citation: Musa, S. I., & Al-Shehri, T. A. (2014). Green Synthesis of Bimetallic Cu-Ag Nanoparticles Using Aqueous Leaf Extract of Azadirachta indica and Catalytic Reduction of 4-Nitrophenol. International Journal of Chemistry, 5(8), 57–64.

International Journal of Chemistry | Vol. 5, No. 6, June 2014 | pp. 41–48

DOI: 10.46882/2014/IJC/000069

Article Type: Original Research Paper

Title: Synthesis, Molecular Docking, and In Vitro Evaluation of Novel Isatin Derivatives as Potential Acetylcholinesterase Inhibitors

Names of Authors: O. M. Kolawole¹, E. J. Cook²*

Authors’ Affiliations:
¹Department of Chemistry, Obafemi Awolowo University, Ile-Ife, Nigeria.
²Department of Chemistry, University of Cambridge, Cambridge, United Kingdom.

Abstract: Inhibiting acetylcholinesterase (AChE) represents a vital clinical strategy for managing Alzheimer's disease by maintaining systemic acetylcholine neurotransmitter levels. In this work, five novel N-substituted isatin derivatives were synthesized via nucleophilic substitution reactions of isatin with various benzyl bromides in the presence of potassium carbonate. The molecular structures of the synthesized targets were verified using elemental analysis, FT-IR, and ¹H-NMR spectroscopy. In vitro AChE enzyme inhibition assays revealed that compound 5b, bearing a p-fluorobenzyl substituent, possessed the highest inhibitory potency, showing an IC50 value of 8.4 μM compared to the donepezil clinical standard (IC50 = 2.1 μM). To investigate specific binding modes, in silico molecular docking simulations were run inside the catalytic active site of human AChE using AutoDock Vina software. The computational docking models demonstrated that the isatin core forms stable hydrogen bonds with Gly121 and Ser203 residues. The aromatic ring extensions fit well into the peripheral anionic site, engaging in significant edge-to-face pi-pi stacking interactions with Trp286. These structural contacts stabilize the ligand-protein topology, explaining the sub-micromolar inhibition constants and presenting a potential scaffold for further antidementia drug design.

Keywords: Isatin derivatives; Chemical synthesis; Acetylcholinesterase; Enzyme inhibition; Molecular docking; Alzheimer's disease

Manuscript Timeline: Received: June 12, 2013; Revised: July 25, 2013; Accepted: August 18, 2013; Published: June 03, 2014.

Citation: Kolawole, O. M., & Cook., E. J. (2014). Synthesis, Molecular Docking, and In Vitro Evaluation of Novel Isatin Derivatives as Potential Acetylcholinesterase Inhibitors. International Journal of Chemistry, 5(6), 41–48.

International Journal of Chemistry | Vol. 5, No. 2, February 2014 | pp. 9–16

DOI: 10.46882/2014/IJC/000065

Article Type: Original Research Paper

Title: Kinetic and Salt Effect Studies of the Mechanistic Oxidation of D-Glucose by Cerium(IV) in Acidic Medium

Names of Authors: T. M. Usman¹, A. M. Al-Ghoul²*

Authors’ Affiliations:
¹Department of Chemistry, Bayero University, Kano, Nigeria.
²Department of Chemistry, American University of Beirut, Beirut, Lebanon.

Abstract: Transition metal oxidants like Cerium(IV) provide vital kinetic benchmarks required to map carbohydrate oxidation mechanisms and electron transfer pathways in aqueous systems. The kinetics of the oxidation of D-glucose by Cerium(IV) was investigated spectrophotometrically in an aqueous perchloric acid medium at a constant ionic strength of 0.50 M (NaClO₄). The reaction progress was monitored under pseudo-first-order conditions by following the absorbance decay of Cerium(IV) at its absorption maximum of 320 nm. The reaction exhibited a first-order dependence on [Cerium(IV)] and a fractional-first-order dependence on [D-glucose]. The reaction rate increased with rising hydronium ion concentration, revealing an acid-catalyzed pathway governed by the reactive protonated oxidant species, [Ce(OH)³⁺]. The introduction of sodium sulfate produced a significant retarding salt effect on the reaction velocity due to the formation of less reactive sulfato-complexes of Cerium(IV). Stoichiometric determinations confirmed that 1 mole of D-glucose consumed 2 moles of Cerium(IV), producing gluconic acid as the primary end product. Thermodynamic activation constants were calculated from temperature-dependence datasets using the Eyring equation, yielding an activation enthalpy (delta H*) of 52.4 kJ/mol and an activation entropy (delta S*) of -85.6 J/mol K, supporting an inner-sphere mechanism.

Keywords: Reaction kinetics; Spectrophotometry; Cerium oxidation; D-glucose; Activation parameters; Retarding salt effect

Manuscript Timeline: Received: March 20, 2013; Revised: May 15, 2013; Accepted: June 28, 2013; Published: February 07, 2014.

Citation: Usman, T. M., & Al-Ghoul., A. M. (2014). Kinetic and Salt Effect Studies of the Mechanistic Oxidation of D-Glucose by Cerium(IV) in Acidic Medium. International Journal of Chemistry, 5(2), 9–16.

International Journal of Chemistry | Vol. 5, No. 4, April 2014 | pp. 25–32

DOI: 10.46882/2014/IJC/000067

Article Type: Original Research Paper

Title: Electrochemical Corrosion Inhibition of Carbon Steel in Hydrochloric Acid Using Seed Extract of Piper guineense

Names of Authors: M. A. Haruna¹, S. Rajagopal²*

Authors’ Affiliations:
¹Department of Chemistry, Federal University of Technology, Minna, Nigeria.
²Department of Chemistry, Indian Institute of Technology, Madras, India.

Abstract: The utilization of toxic synthetic chemical corrosion inhibitors in industrial acid descaling operations poses significant environmental risks, driving research into sustainable green alternatives. The corrosion mitigation performance of the methanolic seed extract of Piper guineense (PG-Extract) on carbon steel in 1.0 M HCl solutions was monitored via gravimetric weight loss and electrochemical measurement protocols. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) curves were recorded across varying inhibitor dosages (0.2 to 2.0 g/L) and temperatures (303 to 333 K). Weight loss metrics revealed that protection efficiency increased with extract concentration, peaking at 93.5% at a dose of 2.0 g/L. Polarization diagrams established that PG-Extract functions as a mixed-type inhibitor, suppressing both anodic iron dissolution and cathodic hydrogen gas evolution. EIS scans confirmed that charge-transfer resistance (Rct) increased with higher extract amounts, indicating the formation of a robust organic protective film on the metal face. The adsorption behavior of the bioactive compounds conformed to the Langmuir isotherm model, yielding a negative standard free energy of adsorption (delta G°ads = -22.4 kJ/mol), denoting a spontaneous chemisorption mechanism driven by the presence of piperine alkaloids.

Keywords: Carbon steel; Corrosion inhibition; Piper guineense; Electrochemical impedance spectroscopy; Polarization; Adsorption isotherm

Manuscript Timeline: Received: April 18, 2013; Revised: June 05, 2013; Accepted: July 12, 2013; Published: April 04, 2014.

Citation: Haruna, M. A., & Rajagopal., S. (2014). Electrochemical Corrosion Inhibition of Carbon Steel in Hydrochloric Acid Using Seed Extract of Piper guineense. International Journal of Chemistry, 5(4), 25–32.

International Journal of Chemistry | Vol. 5, No. 12, December 2014 | pp. 89–96

DOI: 10.46882/2014/IJC/000075

Article Type: Original Research Paper

Title: Spatial Analysis, Seasonal Partitioning, and Chemical Speciation of Arsenic Compounds in Urban Coastal Aquifers

Names of Authors: T. H. Awotunde¹, E. C. Silva²*

Authors’ Affiliations:
¹Department of Chemistry, Federal University of Agriculture, Abeokuta, Nigeria.
²Department of Earth Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.

Abstract: Arsenic leaching into shallow drinking water wells from nearby electronic wastes and industrial dumpsites poses severe public health threats due to its systemic toxicity and carcinogenicity. This study monitors the spatial variations, chemical speciation, and seasonal partitioning profiles of arsenic compounds across twenty communal wells located in a crowded coastal industrial zone. Water monitoring was executed concurrently across dry and wet seasons. Total arsenic and inorganic arsenic species [As(III) and As(V)] were resolved quantitatively using Hydride Generation Atomic Absorption Spectrophotometry (HG-AAS). Total arsenic concentrations ranged from 2.15 to 45.8 μg/L, with 40% of the sampled groundwater sites exceeding the strict WHO maximum drinkable contaminant limit of 10.0 μg/L. Speciation mapping showed that toxic As(III) was the dominant form in highly reducing, low-oxygen shallow aquifers. Seasonal evaluations confirmed elevated arsenic migration during the rainy period, driven by fluctuating water tables and aquifer leaching pathways. Chronic Hazard Index (HI) calculations for infant exposure pathways surpassed 3.2 at peripheral coordinates, emphasizing an immediate public health risk and highlighting the necessity for widespread local bone-char filtration setups.

Keywords: Groundwater quality; Arsenic speciation; Hydride generation; Seasonal variations; Bioavailability; Hazard index

Manuscript Timeline: Received: March 15, 2014; Revised: May 02, 2014; Accepted: June 12, 2014; Published: December 04, 2014.

Citation: Awotunde, T. H., & Silva, E. C. (2014). Spatial Analysis, Seasonal Partitioning, and Chemical Speciation of Arsenic Compounds in Urban Coastal Aquifers. International Journal of Chemistry, 5(12), 89–96.