| dc.description.abstract | This study involved adsorption of captafol on red soil obtained from Kwale county and the
sediments collected from Ngong river, by varying the initial concentration of the
adsorbate, shaking time and weight of adsorbent. The sediment collected from Ngong river
and the red soil obtained from Kwale county used were analysed for pH, texture, cation
exchange capacity and organic carbon content. The adsorption was determined by
measuring concentration of the pesticide using UV-Vis-NIR spectrophotometer before and
after the attainment of equilibrium..Freundlich and Langmuir adsorption isotherms were
used to study adsorption behaviour of the pesticide at equilibrium conditions. The
relationship between sediments and soil characteristics and thermodynamic properties was
explored following Gibbs free energy expressions.
Captafol was found to absorb at 442 nm. A calibration for captafol showed a linear
relationship for concentration range from 0.2 to 40 ppm, and slight deviation as the
concentration increased to 100 ppm. This was in accordance with the Beer’s law.
Freundlich isotherm fitted well for most of the data. Adsorption rate for captafol for red
soil was found to be 0.035 g mg/min and 0.0245 m mg/min for sediment. Thermodynamics
parameters showed that adsorption process was exothermic and spontaneous. Gibbs energy
(ΔG), apparent equilibrium constant (K’) and number of adsorption sites (n) were some
thermodynamic properties investigated. The calculated values for K’ were 57.34±4.6 and
58.16±4.7, ΔG: -9.98±0.19 (kj/mol) and -10.05±0.21 (kj/mol), n: 1.08±0.03 and 1.10±0.01
for the sediment and red soil, respectively. | en_US |
