Hierarchical porous biochar fabricated by Aspergillus tubingensis pretreatment coupling with chemical activation for Pb (II) removal

Abstract

Biochar with hierarchical pores is one of candidates for Pb(II) removal. In this study, we proposed the Aspergillus tubingensis pretreatment coupling with NaOH activation method to prepare the biochar with micro-mesoporous structure, and the corresponding characteristics and mechanism of Pb(II) adsorption were explored in detail. The result revealed that A. tubingensis mainly decomposed the cellulose in biomass to enhance the activation effect of precursor, which was conducive to create the hierarchical pores and improved the specific surface area (S BET ) of biochar. The microbial pretreatment time was a key factor in the preparation of the ideal biochar, the ACEA-14 sample prepared by A. tubingensis pretreatment of 14 days had the highest S BET of 2786 m 2 g −1 and the obvious hierarchical pores, and it also included the order crystal structure and the abundant functional groups. The Pb(II) adsorption experiment indicated that the ACEA-14 sample had prominent the adsorption performance (122.7 mg g −1 ) under the certain conditions (initial pH of 6.0, adsorbent dosage of 0.4 g L −1 and contact time of 8.0 h). This adsorption process was well fitted with pseudo-second order model and Freundlich isotherm model, showing a typical multilayer adsorption The Pb(II) adsorption mechanism of the ACEA-14 sample included the ion exchange, surface complexation, cation-π bond interactions and physical diffusion, and such hierarchical pores were conducive to the Pb(II) transportation, which guaranteed the continuous adsorption. In addition, the regeneration experiment and ternary heavy metal adsorption proved that the ACEA-14 sample had the good application value. • Templateless hierarchical biochars with high specific surface area were prepared. • Synergy of A. tubingensis pretreatment and NaOH etching were investigated. • Regulating pretreatment time and cellulose content was the key to enhancement. • Superior Pb(II) adsorption of the biochar was achieved by A. tubingensis pretreatment. • Characteristics and mechanism of Pb(II) adsorption of hierarchical biochar were clarified.