Adsorption of methylene blue on biochar microparticles derived from different waste materials

Biochar microparticles were prepared from three different types of biochar, derived from waste materials, such as pine wood (BC-PW), pig manure (BC-PM) and cardboard (BC-PD) under various pyrolysis conditions. The microparticles were prepared by dry grinding and sequential sieving through various ASTM sieves. Particle size and specific surface area were analyzed using laser particle size analyzer. The particles were further characterized using scanning electron microscope (SEM). The adsorption capacity of each class of adsorbent was determined by methylene blue adsorption tests in comparison with commercially available activated carbon. Experimental results showed that dye adsorption increased with initial concentration of the adsorbate and biochar dosage. Biochar microparticles prepared from different sources exhibited improvement in adsorption capacity (7.8 ± 0.5 mg g−1 to 25 ± 1.3 mg g−1) in comparison with raw biochar and commercially available activated carbon. The adsorption capacity varied with source material and method of production of biochar. The maximum adsorption capacity was 25 mg g−1 for BC-PM microparticles at 25 °C for an adsorbate concentration of 500 mg L−1 in comparison with 48.30 ± 3.6 mg g−1 for activated carbon. The equilibrium adsorption data were best described by Langmuir model for BC-PM and BC-PD and Freundlich model for BC-PW.