Sustainable N-containing biochars obtained at low temperatures as sorbing materials for environmental application: Municipal biowaste-derived substances and nanosponges case studies

Bio-based substances (BBS) obtained from composted urban biowaste and nanosponges obtained from beta-cyclodextrins (beta CD) were used as green source to produce biochar via pyrolysis performed under mild conditions. Pyrolysis conditions were optimized by means of TGA analysis, and different temperatures of pyrolysis were investigated. The resulting carbonaceous materials were characterized with several physicochemical techniques (elemental analysis, FTIR spectroscopy, XRD, SEM, surface area analysis, and zeta potential measurements). Additionally, the adsorption capacity of such materials was tested toward the removal of charged dyes from aqueous environment. Isothermal experiments carried out at circumneutral pH indicated an important charge-selectivity, which encourages their use as sustainable alternative materials in wastewater purification treatments. Moreover, the analysis of the adsorption capacity as a function of specific surface area of materials suggests the strategy to obtain carbonaceous solids with enhanced capacity in capture of polar molecules.