Biochar as an Adsorbent: A Short Overview

The change of lignocellulosic biomass into valuable products is gradually gaining research interest, not only because of their abundance, but also because of the quantity of cellulose, hemicellulose and lignin it contains. Thermochemical processes like combustion, gasification and pyrolysis are considered as an efficient approach for changing lignocellulosic biomass into valuable materials, with pyrolysis as the most efficient for biomass conversion into biochar, bio-oil and syngas. Notwithstanding, biochar is emerging as the most desirable product, due to its numerous benefits in energy generation (acting as an energy carrier), carbon sequestration, soil amendment, climate change mitigation and environmental management (reducing pollutants concentration in the atmosphere). Effectiveness of biochar in various applications is linked to its good physicochemical properties, including huge surface area, large pore size and volume, high cation and anion exchange capacity, high water-retaining capacity and presence of mineral content, with rich surface functional groups. These intrinsic properties, in turn, determine biochar’s adsorption ability through various physisorption and chemisorption mechanisms and have presented biochar as a desired adsorbent. This overview discusses the principles governing adsorption, applications of adsorption technology, the techniques being utilized in biochar production and the need for biochar as a substitute for commercial adsorbent. Lastly, areas where biochar has been successfully applied as an adsorbent are highlighted.