Depollution of water contaminated by Yellow Bezacryl (YB) - Kinetic study, Isotherms modeling and Adsorption Mechanism.

Abstract Progress in industrial and agricultural activities, as well as the discharge of insufficiently treated effluents, notably dyes and heavy metals, have amplified the polluting load on the environment. These organic compounds pose considerable challenges in drinking water and wastewater treatment systems, given their toxicity, high oxygen demand, and limited biodegradability climate change poses a threat to water security by altering precipitation patterns and other weather variables, which affect river flow and freshwater availability. This study is focused on the application of adsorption and photocatalysis of the Yellow Bezacryl (YB) dye in the presence of typical TiO2 (Eg = 3.5 eV) semiconductor and suggests a likely mechanism for this process. For that the effects of contact time, initial pH, adsorbent dosage and YB initial concentration on the dye adsorption by TiO2 catalyst have been studied. The adsorption of YB onto TiO2 catalyst has been investigated at batch conditions. The adsorption mechanism of YB onto TiO2 catalyst was studied by using the First-pseudo order, Second-pseudo order models. The adsorptions kinetics were found to follow rather a pseudo-second order kinetic with a determination coefficient (0.9906 < R2 <0.9968). The adsorption isotherm is a mathematical model that relates the equilibrium amount of the adsorbate immobilized onto the adsorbent surface to those remaining in the solution. Several models Langmuir, Freundlich, Temkin and Elovich models have been documented for describing the experimental data obtained for the adsorption processes. The adsorption follows well the Langmuir equation, providing a better fit of the equilibrium adsorption data (R2 = 0.998, SSE = 0.0006). Under optimized conditions, up to 14.705 mg/g at 25 oC is removed from the solution. The experimental results showed that the efficiency of the photocatalytic process strongly depends on the pH while the initial rate of the photocatalytic reaction is proportional to the catalyst dose, but above a certain value it becomes constant and sometimes decreases. The adsorption is an important parameter controlling the apparent kinetic constant of the degradation. The photocatalytic degradation rate was favored for high concentrations of solution in agreement with Langmuir–Hinshelwood (L-H) model. The values kc and K for the photocatalytic degradation of YB were found to be 1.992 mgL/min and 0.2906 L/mg respectively. The degradation rate was found to be dependent on pH and temperature with a high degradation rate for pH 4 and a rise in temperature. The TiO2 catalyst has a better activity for the YB degradation, compared to the various commercial catalysts already available in the literature.