Ultrasound assisted adsorption of reactive dye-145 by biochars from marine Chlorella sp. extracted solid waste pyrolyzed at various temperatures

Algal biomass extraction for biodiesel production generates a considerable amount of solid waste known as extracted residue, which requires proper handling. This work aimed to produce biochar from the extracted marine Chlorella sp. solid waste (EMCSW) at 450, 550 and 650 degrees C. The biochar yield, physiochemical characterization and potential application in ultrasound assisted adsorption of reactive yellow dye-145 (RYD-145) were investigated. The biochar mass yield decreased from 45 to 34 % with temperature increase from 450 to 650 degrees C. Reduction of C, H, N, S and O and increased ash were observed with the temperature increase. The biochars were alkaline in nature having negative surface charges and porous structure with O-H surface functional groups and Mg, Al, K and P minerals, making them suitable candidate adsorbents. The largest 351 m2/g specific surface was observed for the biochar produced at 550 degrees C. Ultrasound assisted adsorption of RYD-145 by BC-550 was highly efficient (99 %) in 1 min. The adsorption experimental data matched well the Freundlich and the pseudo-second order models. The EMCSW was demonstrated to be a valuable feedstock for biochar production, to be used as a cost-effective and highly efficient adsorbent.