Synergistic Polyaniline-Biochar Hybrid Adsorbent for Efficient Detoxification of Organic Dyes and Hexavalent Chromium From Aqueous Solutions

Abstract

A polyaniline-coated banana biochar composite (PB-10) was synthesized as a high-performance, sustainable adsorbent for simultaneous removal of cationic (methylene blue), anionic (Congo red), and heavy metal [Cr(VI)] pollutants from water. PB-10 features a spongy porous structure with a surface area of 37.8 m2 g-1 and a pore diameter of 19.9 nm, offering abundant active sites for pollutant adsorption. Maximum capacities of 82 mg g-1 (Congo red), 58 mg g-1 (methylene blue), and 75 mg g-1 (Cr(VI)) were achieved under optimized conditions. Adsorption followed pseudo-second-order kinetics and fitted with Langmuir-Freundlich isotherms, indicating chemisorption and multilayer adsorption, respectively. Thermodynamic analysis confirmed a spontaneous, endothermic process (Delta H = 25.084 kJ mol- 1) was obtained. PB-10 also exhibited excellent reusability over five cycles, highlighting its potential as a good adsorbent and versatile material for practical wastewater treatment.