Advection-Diffusion Equation with Spatially Dependent Coefficients for Instantaneous Pollutant Injection in a River

2024-12-13T10:18:08+07:00

River pollution is a major environmental concern globally, affecting ecosystems and water quality. Numerous strategies have been implemented to monitor and mitigate pollution, including mathematical modeling techniques. Among these, the advection-diffusion equation (ADE) has been widely applied to model the transport and dispersion of pollutants in rivers. Previous studies on the ADE have primarily examined pollutant concentration in rivers under scenarios where pollution enters the river continuously from the boundary or, if not continuous, is modelled with exponential decay in concentration. However, pollution in real situations can often be introduced to the river instantaneously. Furthermore, it has been demonstrated that the dispersion of the pollutant and the river velocity are not constant but varies with position (space). This research focuses on finding the analytical solution to the one-dimensional ADE with spatially dependent diffusion and velocity for the case where the pollutant is instantaneously introduced to the river. New space variables are introduced in the solution procedures to reduce the ADE to a simpler form with a single coefficient which is then solved using Laplace transform method. The findings demonstrate that velocity, diffusion coefficient, and medium inhomogeneity significantly influenced the pollutant concentration distribution in rivers. Since the pollutant is instantaneously injected, the peak concentration occurs not at the source of injection but at nearby location. While the spatially dependent effect with larger inhomogeneity demonstrates a much faster and broader pollutant distribution.

Electrosynthesis of Silver Nanoparticle Using Green Tea Leaf Extract and Photocatalytic Methylene Blue Dye Degradation

2024-12-13T11:16:11+07:00

The high toxicity of synthetic dyes poses environmental and health risks, prompting the development of catalysts that improve degradation efficiency, particularly those that support sustainable wastewater treatment. AgNPs have extraordinary catalytic capabilities, making them effective at converting methylene blue (MB) dyes into less hazardous compounds. In this study, AgNPs were synthesised utilising tea leaf extract via electrolysis, providing a sustainable green chemistry strategy with excellent AgNP properties for degrading MB for a brief time. Using two pure silver electrodes and a green tea extract solution as an electrolyte, spherical AgNPs with a surface charge of -20 mV were produced. Tea extract biomolecules serve as bioreductors and capping agents, resulting in the formation of tiny, homogenous, and stable particles maintained until 15 weeks. The small size increases the surface-to-volume ratio along with electrical conductivity, which improves catalytic activity. HPLC analysis revealed that MB degradation reached 96.99% under sunlight for 72 min. Hence, this synthesis technique offers great opportunities for utilising AgNP-based nanocatalysis in wastewater treatment and environmental protection.

Frontiers in Water and Environment

Advection-Diffusion Equation with Spatially Dependent Coefficients for Instantaneous Pollutant Injection in a River

Electrosynthesis of Silver Nanoparticle Using Green Tea Leaf Extract and Photocatalytic Methylene Blue Dye Degradation