Residual Lignocellulosic Biomass Based Activated Biochar: Comparison Between Single and Two Step Thermochemical and Activation Processes

Abstract

Lignocellulosic biochar has become a research hotspot recently due to its versatility in several applications for environmental remediation. It is a sustainable material, which has been proven to offer high performance in applications such as effluent treatment (through the adsorption of organic and inorganic compounds), CO2 capture, air cleaning or silage agent. Typically, a chemical activation is applied to biochars after the thermochemical process, to increase the porosity of this solid in terms of active surface area as well as pore size and distribution, to improve its performance as adsorbent. Activation with KOH has been proved to achieve well developed pore structure and active functional groups on the biochar surface. Excellent adsorption results for the removal of different pollutants have been reported with biochars produced by the mentioned method. Focusing on a potential scale and industrialization of the lignocellulosic biochar production process, the combination of the thermochemical and chemical activation processes in one step could be interesting in terms of simplicity and time saving. In this work, activated biochars were prepared using a lignocellulosic agricultural waste (apple pruning) as precursor and KOH as a chemical activator, by two different processes: a single and a two-step route, to compare the properties of the biochars generated by both processes. The obtained materials were characterized in terms of proximal analysis, active surface area, pore size and pore distribution. Furthermore, adsorption capacity ABCs was tested and compared.