Challenges and recent advances in biochar as low-cost biosorbent: From batch assays to continuous-flow systems

[Display omitted] •It is proved that biochar can be considered as low-cost adsorbent.•Advances on biochar’ synthesis to enhance their adsorptive capacity have been examined.•Recent findings on organic and inorganic pollutants by biochars are summarized.•Identification of knowledge gaps before scale-up in continuous-flow system. Over the past few years, the increasing amount of pollutants and their diversity demand to develop versatile low-cost adsorption systems. The use of biomass feedstock such as agricultural residues, wood chips, manure or municipal solid wastes as source to produce low-cost biosorbent, and the new advances in their synthesis have encouraged remarkable efforts towards the development of biochar “on demand” in which their characteristics can be improved. This new trend opens the potential of biochar application in the removal of pollutants from wastewater, however, its use in environmental management requires the development of full-scale biosorption in engineered systems. Thus, this paper provides a brief review of recent progress in the research and practical application of biochar with a special emphasis on its potential to reduce the pollutants present in wastewater or to render them harmless. Furthermore, research gaps and uncertainties detected in their scale-up in continuous-flow systems are highlighted.