Asian Journal of Physical and Chemical Sciences

Environmental Pollution Caused by Laboratory Gold Processing: A Study of Soil and Water Contamination by Heavy Metals

Chaibou Yacouba Abdoul Rachid — 2025-08-30

Waste generated during gold ore processing often contains toxic substances such as heavy metals like lead and chemicals (cyanide, acids). If not properly controlled, these components can contaminate/pollute soil and ecosystems.

The objective of this study is to assess the degree of soil and groundwater contamination around a mining laboratory where chemical and metallurgical analyses are carried out. The main sources of contamination identified come from lead smelting (“Fire Assay”) and aqua regia digestion activities, which generate solid waste and liquid effluents rich in heavy metals and acidic substances.

To carry out this assessment, soil, wastewater, and groundwater samples were collected inside the laboratory. The samples were analyzed to determine the presence of heavy metals such as lead, as well as physical and chemical parameters such as pH and conductivity.

The results of the physical and chemical parameters of wastewater from basins A and B indicate high acidity ranging from 1.87 to 2.57, an average temperature of 26 °C, and high mineralization due to high electrical conductivities exceeding 2000 μS/cm. RFX analysis shows a high presence of heavy metals, lead (3435.49 ppm), chromium (439.21 ppm), arsenic (155.59 ppm), and strontium (1066.13 ppm), illustrating significant soil contamination, particularly in areas where solid residues (cups, crucibles, slag) are stored in the open air. Chemical analysis of groundwater reveals that it is of good quality and meets WHO standards.

This study highlights the environmental impact of current waste management practices in laboratories and emphasizes the urgent need to implement pollutant treatment solutions to limit the spread of contaminants in the environment.

Evaluation of the Thermal Performance of a Locally Designed and Manufactured Optimized Roasting Oven

David NAMOANO — 2025-09-22

The present work concerns an experimental study of the energy performance of a prototype optimized oven developed by local craftsmen. The Water Boiling Technique (WBT) is the method used to evaluate the energy efficiency of the oven. The temperatures of the oven’s walls and the ambient temperature were measured to evaluate energy losses by convection into the environment. The oven's heat balance was used to determine the amount of energy lost through the smoke. The results showed that a large amount of thermal energy is lost through the smoke (50% of the energy generated by gas combustion). Losses through the walls were reduced to 8%. The oven's efficiency reached 42%. This is in line with the standard efficiency of optimized gas ovens (between 40 and 50%). Future improvements should focus on reducing smoke-related heat losses to enhance overall efficiency.

Performance of Some Selected Natural Dye and Their Mixture as Photosensitizers in the Fabrication of DSSCs

Chukwuenye Janefrances Chinyere — 2025-09-27

Performance of some selected natural dye and their mixture as photosensitizer in the fabrication of dye sensitize solar cell (DSSC) was examined. Six different cells of DSSC was fabricated using natural dye extracts from; Bush or Wild mango leaf (WM), Mucuna pruriens (MS) leaf, Sand cherry (SC) leaf and African velvet tamarinds (AV) leaf. The dyes of Mucuna pruriens and sand cherry (Co-MS) were co-sensitized and also four of the sample dyes were co-sensitized, (AV, SC, MP and WP) (Co-All) as photosensitizers. These natural dyes were extracted using ethanol and Doctor Blade’s technique was used for the deposition of the TiO₂ on a transparent Fluorine-doped Tin Oxide (FTO) coated glass substrates. The deposited TiO₂thin film were subjected to XRD, UV-Vis spectroscopy and I-V characterization to determine their structural, optical and solar cell parameter. Films structural analysis from XRD pattern of the samples showed prominent polycrystalline films with sharp and narrow diffraction peak intensities observed at (200), (210) and (310), (511) respectively corresponding to 2θ value of 25.61^o-65.68^ofor AV,WM and Co-All, 25.56^o-38.02^ofor SC, MP and Co-MS with an oriented growth of hexagonal structures, respectively. AV dye has the highest absorbance and reflectance value of 0.99 a.u and 0.21 a.u while Co-All has the peak transmittance value of 0.85a.u in the UV-Vis region of the electromagnetic spectrum. AV dye has the least band gap value of 2.32eV. The I-V characteristics of the fabricated films were analyzed under light illumination intensity of 100W/cm² and dark illumination. The result showed that the efficiency of DSSC under light illumination is higher than that under dark illumination.MP single dye produced the highest efficiency value of 0.14%. The efficiency of the single dye MP was found to be higher than that of the co-sensitized dyes. Co-All has a slight higher conversion efficiency value of 0.029% under standard light illumination when compared to the Co-MS with value of 0.025%. Though the conversion efficiency of the dyes were not improved by co-sensitization, the dyes showed a promising applications in solar cells as light havesting material.

Phytochemical-Assisted Synthesis of Silver Nanoparticles Using Eucalyptus Leaf Extract: Structural Characterization and Antimicrobial Evaluation

Grace K. Abere — 2025-09-30

The search for safer and environmentally friendly nanoparticle-synthesis methods is becoming more prominent in sustainable nanotechnology. In this study, phytochemical-assisted green synthesis of silver nanoparticles (AgNPs) was achieved using Eucalyptus globulus leaf extract (ELE), a rich source of phenolics, flavonoids, and tannins. The ELE concentrations ranging from 1–6% w/v provided differential phytochemical availability, directly influencing nanoparticle nucleation, growth, and stabilization. UV–Vis spectroscopy confirmed surface plasmon resonance bands at 420-422 nm responsible for AgNPs. FTIR analysis confirmed the presence of O–H, C=O, and C=C functional groups responsible for both reduction and capping of the AgNPs. TEM imaging demonstrated a concentration-dependent decrease in particle agglomeration, with 6% w/v ELE producing predominantly spherical nanoparticles averaging 12.90 nm. XRD analysis indicated crystalline face-centred cubic structures of AgNPs. Antibacterial assays showed significant inhibitory activity against Staphylococcus aureus and Klebsiella pneumoniae, with MIC values surpassing those of Neomycin. These findings established that phytochemical-assisted green synthesis of AgNPs has a promising antimicrobial potential against the pneumonia-causing pathogens with controlled morphology and bioactivity.

Forensic Authentication of Paracetamol Using FTIR and UV–Vis Spectroscopy Coupled with Similarity Metrics

Kipronoh Theophilus Korir — 2025-10-06

The global circulation of counterfeit and substandard medicines poses a serious threat to public health and challenges forensic science in generating reliable evidence. Paracetamol, a widely used analgesic and antipyretic, is among the most frequently falsified drugs in low- and middle-income countries. This study employed Ultraviolet-Visible (UV-Vis) and Fourier Transform Infrared (FTIR) spectrophotometry to authenticate paracetamol (PAR). The specific objectives were to examine active pharmaceutical ingredients, and to identify unknown components in paracetamol PAR1–PAR4 samples were analyzed against a certified reference standard. FTIR spectra were obtained using potassium bromide pelletization, while UV–Vis spectra were recorded by dissolving the sample in methanol and phosphate buffer, followed by dilution with distilled water. The data obtained were evaluated by Pearson correlation coefficients (r) and Euclidean distance (ED). Results showed that PAR1 (r ≥ 0.99, ED = 0.051) and PAR3 (r = 0.9983, ED = 0.0389) matched the standard and were classified as authentic. In contrast, PAR2 (r = 0.992, ED = 0.084) exhibited a shifted amide band with reduced absorbance, while PAR4 (r = 0.991, ED = 0.089) showed weakened O–H bands confirming suspect and counterfeit status, respectively. This work addresses a key forensic gap by introducing quantitative, pharmacopeia-compliant thresholds for paracetamol authentication. The novelty lies in combining FTIR and UV–Vis spectra with similarity metrics to deliver objective and legally defensible authentication of paracetamol. The protocol strengthens scientific reliability while offering a scalable, low-cost tool for surveillance and regulatory enforcement in regions most affected by counterfeit medicines.

Determination by GC/MS and ¹³C NMR of the Major Chemical Groups and Compounds in the Essential Oil from the Roots of Cyperus rotundus L. from Daloa, Côte d’Ivoire

Bamba Souleymane — 2025-10-06

Exploring local essential oils is a crucial step for valorizing Ivorian biodiversity and for developing pharmacological and industrial applications adapted to the regional context. This study aimed to characterize the chemical composition of the essential oil extracted from fresh roots of Cyperus rotundus from Daloa (Côte d’Ivoire) using GC–MS and ¹³C NMR. The extraction and analysis of the essential oil were carried out using several pieces of equipment. For the analysis of the essential oil from the roots of Cyperus rotundus, the techniques used were carbon-13 nuclear magnetic resonance (¹³C NMR) and gas chromatography coupled with mass spectrometry (GC/MS). The extraction yield was 0.36 ± 0.02%. Analyses revealed a predominance of monoterpenes, mainly β-pinene (22.8%), trans-4-thujanol (14.7%), and α-pinene (4.7%), in contrast with most profiles reported in the literature, which are often dominated by sesquiterpenes. This particular chemotype suggests a high potential for antimicrobial, antifungal, and anti-inflammatory activities and opens perspectives for innovative therapeutic and agro-food applications. This study highlights the importance of regional chemical characterization of essential oils, an essential prerequisite for their industrial valorization and the establishment of sustainable production chains in Côte d’Ivoire.

Influence of Particle Size on the Phytochemical Profile of Manihot Esculenta Leaf Extracts: An LC-MS-Based Analysis

Ouattara Logopho Hyacinthe — 2025-10-08

Introduction: Extraction is a key step in the study of organic compounds derived from plants. Over time, numerous methods and techniques have been developed to obtain extracts concentrated in bioactive compounds.

Aims: This study aims to identify and characterize, using liquid chromatography-mass spectrometry (LC-MS), the phytocompounds present in ethanol extracts obtained from the crushed and sieved leaves of Manihot esculenta, with a view to comparing the chemical composition of these two forms of preparation.

Study Design: The research adopts an experimental, analytical, and comparative design aimed at identifying and comparing the phytochemicals present in the ethanol extracts of the crushed and sieved leaves of Manihot esculenta by LC-MS.

Place and Duration of Study: Laboratory of Bio-Organic Chemistry and Natural Substances, Nangui ABROGOUA University, Abidjan, Ivory Coast, between January 2025 and July 2025.

Methodology: After drying, the plant material was ground to obtain a powder known as Broyat. This was then sieved using a 1 mm mesh to produce Tamisat. The ethanol extracts were prepared by Soxhlet extraction, using a liquid-liquid contact process. Phytochemical screening was performed using identification tests based on color reactions in test tubes. Finally, the study was completed by LC-MS analysis performed in positive mode.

Results: Qualitative phytochemical screening revealed the presence of polyphenols, flavonoids, coumarins, tannins, and sterols/terpenes in both matrices, confirming the chemical richness of the species. LC-MS analysis then revealed six bioactive compounds in the Broyat, including scopoletin, scopolin, rutin, nicotiflorin, caffeic acid, and gallic acid, while the Tamisat had a more limited composition, notably lacking hydroxycoumarins such as scopoletin and scopolin.

Conclusion: Sieving (“Tamisat”) resulted in a loss of specific classes of compounds compared to the ground powder (“Broyat”). These results highlight the influence of preparation methods on the metabolic profile obtained. Functionally, the compounds identified are known for their antioxidant, anti-inflammatory, and antidiabetic properties, thus giving M. esculenta leaves potential interest for biomedical and nutritional applications.

Conductometric Studies of Complexation of Benzo-15-crown-5 Ether with Some Transition Metal Ions in Pure and Binary Non-aqueous Solvent Mixtures

Kalpana H. Parmar — 2025-10-14

The complexation reaction between Benzo-15-crown-5 Ether [B15C5] with Fe³⁺, Co²⁺, Ni²⁺and Cu²⁺ cation was studied in pure acetonitrile (ACN), pure dimethyl-sulfoxide (DMSO) and in the binary solvent mixtures of ACN-DMSO at various temperatures by conductometric method. The conductance data showed that the stoichiometry of the complexes formed in pure as well as in the binary solvent mixtures was 1:1 ([Mⁿ⁺]: [B15C5]). In binary solvent mixtures, the values of log K_f decrease with increase in temperature and with increase in the percentage of ACN. The values of thermodynamic parameters (ΔG^o, ΔH^oand ΔS^o) for formation of complexes were obtained from temperature dependence of stability constant of complexes (L-Mⁿ⁺) using the Van’t Hoff plots. The negative values of ΔG^oshow the spontaneous reaction, the positive values of ΔH^o indicate that the complexation reactions are enthalpy destabilized. Besides this, the positive values of ΔS^o indicate that entropy is a driving force for the complexation reaction. The values of ΔH^oand ΔS^o for formation of the complexes were obtained from temperature dependence of the stability constants. The findings indicate that the nature and composition of the mixed solvents have an impact on both the values and the sign of these parameters.

New Analysis of the Second-class Current in the Radiative Scattering Process of Neutrinos (and Antineutrinos) by Atomic Nuclei

CHINA ADAMOU Hachimou — 2025-10-24

The study of the radiative neutrino(antineutrino)-nucleus scattering process on the lithium-6 nucleus (⁶Li) allowed us to derive the general expression of the differential cross section for this type of process and to highlight several significant results. In particular, the analysis focused on the influence of the tensor form factor FT , associated with the second-class currents (SCCs), on two key observables: the charge asymmetry coefficient and the degree of polarization of the emitted photon. The study of the charge asymmetry coefficient A_ν˜ν reveals a strong dependence on the presence of the tensor form factor. In the absence of SCCs (F_T = 0), the behavior of A_ν˜ν remains moderate and stable as a function of the neutrino energy. Conversely, when F_T \(\neq\) 0, the coefficient increases significantly and exhibits pronounced variations, including sign changes at high energy. The analysis of the relative contribution δ_Aν˜ν confirms this trend, emphasizing an enhanced sensitivity to SCCs, particularly in the high-energy domain (E_ν ≳ 200 MeV). The examination of the photon polarization degree P_Sγ also shows that it serves as a relevant indicator of the presence of SCCs. The introduction of a nonzero tensor form factor (F_T = 5 × 10⁻³ MeV⁻¹) leads to substantial modifications of the polarization degree. The analysis of the relative contribution δ_PSγ further confirms this strong sensitivity, with variations exceeding 200% at high energy.

Technical Characterization of a Pilot Cassava Processing Unit in Ouagadougou for Energy Efficient Mechanization

SAWADOGO Kalizeta — 2025-10-24

Processing operations for tubers such as cassava are traditionally carried out using knives, machetes, mortars and other tools. Mechanized processing units are sometimes used, but they are energy-intensive. Thus, it is necessary to propose processing units that are optimal in energy and meet the needs of users. The technical characterization of the equipment of the pilot mechanized cassava processing unit installed at the Institute of Research in Applied Sciences and Technologies (IRSAT) meets this objective. It was carried out on a washer, a peeler, a grater and a spin dryer. The results showed the spin dryer to be more energy-intensive with a nominal consumption of 7.5 kW. All equipment is equipped with low-voltage three-phase electric motors. The productivities of the equipment are between 100 and 2500 kg/h.