Kinetic and equilibrium study of the photocatalytic degradation of tartrazine using biochar using Microwave assisted pyrolysis from Theobroma cacao L. husk doped with iron.

In the microwave-assisted pyrolysis (MAP) process, acid-pretreated cocoa pod husk (CPH) was placed in a microwave at 600 W for 15 minutes, resulting in biochar production (BCCPH). This was followed by a doping process with iron salts (+2, +3) to obtain BCCPH-Fe. Characterization of BCCPH-Fe was carried out using surface analysis (BET), thermogravimetric analysis (TGA), particle size distribution, and Fourier Transform Infrared Spectroscopy (FTIR). Subsequently, the photodegradation process was performed using three different light sources, with tartrazine as the adsorbate. The effect of pH on photodegradation was studied, and the percentage of degradation was evaluated through equilibrium and kinetic studies. The amount of BCCPH-Fe, tartrazine concentration, and exposure time to the light source were also evaluated. The best conditions for the photodegradation process were: 254 nm light source, pH of 5, 1 g/100 mL BCCPH-Fe, 25 ppm tartrazine concentration, and 40 h exposure time. Under these conditions, a 93.45% removal of tartrazine was achieved. The experimental data of the adsorption equilibrium best fit the Langmuir-Hinshelwood model, while the adsorption kinetics best fit the pseudo-first-order model. The apparent kinetic constant was 0.04053 [h-1], and the correlation coefficient was 0.98667. In conclusion, photodegradation using BCCPH-Fe can be an effective method for the removal of tartrazine from wastewater, offering a sustainable alternative to traditional methods.