Elaboration et caractérisation d'un composite à base biochar et ses applications à la photocatalyse et l'adsorption des polluants

Abstract

Potatoes are one of the most important crops for extensive consumption. They are cultivated in large quantities, especially in the region of Oued. This big amount results a large residues of potato plant which we have exploited as raw material for preparing activated carbon. The raw potato plant (PPT) was modified with chemical activation: ZnCl2 (PPT-ZnCl2), NaOH (PPT-NaOH) and HCl (PPT-HCl) to improve its adsorption capacity for removal of rhodamine b (RhB) in aqueous solutions. The characterization of these activated carbons (adsorbents) showed that they contain a crystalline structure with a carbon content and a porous surface due to chemical activation, followed by series of surface functions that react with pollutants during the adsorption of RhB. The results showed that the adsorption efficiency of RhB reached 98.95%, 96.1%, and 86.65% for PPT-ZnCl2, PPT-NaOH, and PPT-HCl respectively. The RhB adsorption kinetics on each adsorbent is well described by the pseudo-second order model for PPT-ZnCl2 and Elovich for PPT NaOH, PPT-HCl, and the Freundlich isotherm was best suited. The maximum Langmuir adsorption capacities obtained are in the following order: 140.34 mg/g (PPT-ZnCl2)>86.58 mg/g (PPT-NaOH)>44.48 mg/g (PPT-HCl). The PPT-ZnCl2(1-x)/Bi4Ti3O12(x) composites, abbreviated to (PPT-ZnCl2(1-x)/BTO(x)), with x= 30 wt%, 50 wt% and 70 wt%, were formed using a simple ethanol technique to create the heterojunction between pure BTO and PPT-ZnCl2. This gave a product with strong optical properties for the removal of (RhB). The composite PPT-ZnCl2(0.7)/BTO(0.3) showed a better and higher visible absorption, the role of PPT-ZnCl2 in the reduction of band gap compared to pure BTO, this showed a faster degradation compared to pure BTO. PPT-ZnCl2(0.7)/BTO(0.3) showed the best photocatalytic performance with a 99.9% degradation rate after 20 min.