LAUSR

In the present study, Acacia leucophloea wood sawdust is utilized to prepare biochar by direct pyrolysis. This biochar is applied as an alternative adsorbent for the adsorption of Basic Red 29 (BR29) cationic dye and Reactive Red 2 (RR2) anionic dye. The adsorption performance of biochar on both the dyes is evaluated by varying the solution pH (2–10), agitation speed (30–170 rpm), initial dye concentration (40–100 mg L–1), contact time (100 min), temperature (300, 310 and 320 K) and adsorbent dose (25–200 mg). The maximum removal of 98% is achieved for RR2 using biochar under the optimum conditions of 50 mg dosage, the temperature of 300 K, 170 rpm of agitation speed, 60 mg L–1 of initial dye concentration and pH of 2. For BR29, the same removal efficiency is achieved at pH 10 under the same operating conditions. The adsorption kinetics of both the dyes follows the pseudo-second-order model and the adsorption isotherms are best suited by the Freundlich model. Thermodynamic studies suggest that the adsorption process is spontaneous and exothermic for anionic dye and endothermic for cationic dye. These findings reveal that the biochar can be used as an alternative adsorbent to remove dyes from aqueous solutions.