International Journal of Chemistry

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.

International Journal of Chemistry | Vol. 11, No. 1, January 2020 | pp. 1–8

DOI: 10.46882/2020/IJC/000135

Article Type: Original Research Paper

Title: Spatial Variation, Speciation, and Carcinogenic Hazards of Cadmium Formulations in Groundwater Networks Near Batteries

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

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

Abstract: Industrial battery processing operations discharge massive amounts of cadmium-rich effluents into surrounding topsoils, causing heavy metal leaching into shallow drinking water wells. This study monitors the spatial variations, chemical speciation, and carcinogenic health risk profiles of cadmium compounds across twenty household wells positioned around an active electronic industrial estate. Water monitoring was carried out over consecutive wet and dry cycles. Total cadmium levels and carcinogenic cadmium fractions were quantified utilizing ion chromatography coupled with inductively coupled plasma mass spectrometry (IC-ICP-MS). Total cadmium concentrations ranged from 12.5 to 145.8 μg/L, with 45% of monitored groundwater sites surpassing the strict WHO drinkable contaminant threshold of 3.0 μg/L. Speciation analysis showed that toxic free Cd²⁺ was the dominant species, accounting for up to 68.4% of the total metal burden profiles at down-gradient coordinates. Seasonal mapping confirmed elevated cadmium 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 2.4 in 10,000 near industrial boundaries, emphasizing an immediate public healthcare concern and a need for local membrane filtration arrays.

Keywords: Groundwater pollution; Cadmium speciation; Free metal ions; Ion chromatography; Battery effluents; Cancer risk assessment

Manuscript Timeline: Received: June 02, 2019; Revised: July 14, 2019; Accepted: August 10, 2019; Published: January 03, 2020.

Citation: Awotunde, T. H., & Silva, R. A. (2020). Spatial Variation, Speciation, and Carcinogenic Hazards of Cadmium Formulations in Groundwater Networks Near Batteries. International Journal of Chemistry, 11(1), 1–8.

International Journal of Chemistry | Vol. 11, No. 11, November 2020 | pp. 81–88

DOI: 10.46882/2020/IJC/000145

Article Type: Original Research Paper

Title: Kinetic Studies and Free-Radical Mechanisms of the Alkaline Ferricyanide Oxidation of L-Arginine

Names of Authors: T. M. Usman¹, F. M. Al-Rasheed²*

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

Abstract: The kinetics of transition metal electron transfer reactions involving basic amino acids yield essential data required to map biochemical oxidation paths and structural intermediate transformations. The oxidation of L-arginine by ferricyanide ions ([Fe(CN)₆]³⁻) was investigated spectrophotometrically in an aqueous sodium hydroxide medium at a constant ionic strength of 0.20 M (NaClO₄). The reaction progress was monitored under pseudo-first-order conditions by following the absorbance decay of [Fe(CN)₆]³⁻ at its absorption maximum of 420 nm. The empirical rate law showed a first-order dependence on [ferricyanide] and a fractional-first-order dependence on [L-arginine]. The reaction rate increased with rising hydroxyl ion concentration, revealing a base-catalyzed pathway driven by the active unprotonated amine species. Variations in ionic strength produced positive kinetic shifts, indicating a rate-determining step involving two similarly charged ionic species. Stoichiometric determinations confirmed that 1 mole of L-arginine consumed 2 moles of ferricyanide, producing 4-guanidinobutanal and ferrocyanide 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 45.8 kJ/mol and an entropy of activation (delta S*) of -112.4 J/mol K, supporting an outer-sphere mechanism.

Keywords: Reaction kinetics; Spectrophotometry; Ferricyanide oxidation; L-arginine; Activation parameters; Outer-sphere mechanism

Manuscript Timeline: Received: April 02, 2020; Revised: May 22, 2020; Accepted: June 15, 2020; Published: November 02, 2020.

Citation: Usman, T. M., & Al-Rasheed, F. M. (2020). Kinetic Studies and Free-Radical Mechanisms of the Alkaline Ferricyanide Oxidation of L-Arginine. International Journal of Chemistry, 11(11), 81–88.

International Journal of Chemistry | Vol. 11, No. 5, May 2020 | pp. 33–40

DOI: 10.46882/2020/IJC/000139

Article Type: Original Research Paper

Title: Ultrasonic Speeds, Excess Volumetric Parameters, and Hydrogen Bond Formations of Binary Liquid Systems of N-Butanol with Aliphatic Esters

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-butanol with methyl acetate, ethyl acetate, and propyl acetate 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 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-butanol and the ester carbonyl centers, which decrease in intensity as thermal motion breaks the dipole networks.

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

Manuscript Timeline: Received: August 05, 2019; Revised: September 12, 2019; Accepted: October 08, 2019; Published: May 04, 2020.

Citation: Chiemeka, E. C., & Al-Ghamdi, A. M. H. (2020). Ultrasonic Speeds, Excess Volumetric Parameters, and Hydrogen Bond Formations of Binary Liquid Systems of N-Butanol with Aliphatic Esters. International Journal of Chemistry, 11(5), 33–40.

International Journal of Chemistry | Vol. 11, No. 9, September 2020 | pp. 65–72

DOI: 10.46882/2020/IJC/000143

Article Type: Original Research Paper

Title: GC-MS Chemical Profiling, Quantitative Phytochemical Mapping, and Insecticidal Efficacy of Mentha longifolia Leaf Extract

Names of Authors: S. A. Abdulrahman¹, C. A. Rossi²*

Authors’ Affiliations:
¹Department of Chemistry, Federal University of Technology, Minna, Nigeria.
²Department of Pharmacy, University of Genoa, Genoa, Italy.

Abstract: The continuous emergence of chemical resistance among stored-grain insect pests requires the formulation of alternative botanical insecticides to minimize chemical pesticide hazards in agricultural facilities. This research reports the qualitative chemical characterization, volatile compound identification via Gas Chromatography-Mass Spectrometry (GC-MS), and in vitro insecticidal efficacy of Mentha longifolia leaf essential oil against Tribolium castaneum (Red flour beetle). Essential oils obtained via hydro-distillation in a Clevenger apparatus were separated into 19 distinct peaks through GC-MS profiling, with piperitone oxide (42.5%), menthone (18.2%), and pulegone (12.4%) emerging as the primary bioactive constituents. Insecticidal bioassays were conducted utilizing contact toxicity tests across a suite of oil concentrations (10 to 50 microliters/square meter) over 24-hour exposure periods. The essential oil demonstrated significant lethal potency, yielding an LC50 value of 18.4 microliters/square meter and an LC90 value of 34.2 microliters/square meter against the beetle populations. A linear correlation was observed between the concentration of oxygenated monoterpenes and insect mortality rates. This confirms that volatile monoterpenoids actively disrupt the respiratory and acetylcholinesterase enzymes of beetles, providing a sustainable botanical framework for grain storage protection.

Keywords: Mentha longifolia; Essential oils; GC-MS analysis; Piperitone oxide; Contact toxicity; Tribolium castaneum

Manuscript Timeline: Received: March 04, 2020; Revised: May 11, 2020; Accepted: June 20, 2020; Published: September 09, 2020.

Citation: Abdulrahman, S. A., & Rossi, C. A. (2020). GC-MS Chemical Profiling, Quantitative Phytochemical Mapping, and Insecticidal Efficacy of Mentha longifolia Leaf Extract. International Journal of Chemistry, 11(9), 65–72.