Synergistic mechanism in H3PO4/Fe2O3 co-assisted bamboo slow pyrolysis for enhanced biochar carbon retention and applications on green low-carbon cement

Abstract

Additives-assisted bamboo pyrolysis is an efficient method for enhancing carbon retention of biochar. Herein, we propose the utilization of synergistic H₃PO₄/Fe₂O₃ co-assisted bamboo pyrolysis, which strengthens biochar yield and carbon retention. The results indicated that the synergistic effect of H₃PO₄ and Fe₂O₃ increased biochar yield and carbon retention, compared with biochar doped with H₃PO₄ or Fe₂O₃ alone (with an increase of 6.95 % and 7.78 %, respectively). In the H₃PO₄/Fe₂O₃ co-assisted pyrolysis process, P-O-C and Fe-OH structures were formed in the biochar, which generated a physical barrier on the surface of biochar and promoted its resistance to oxidation and biomineralization, leading to more carbon retention and a high yield. Meanwhile, phosphorus/iron synergistic doping of biochar in cement modification enhances the compressive properties of cement, which provides a non-returned field biochar disposal method to avoid environmental pollution. The results of cement compressive properties showed that the addition of the prepared biochar improved the mechanical properties of cement by 17.7 %-27.7 %. This study provides a synergistic H₃PO₄/Fe₂O₃ co-assisted bamboo slow pyrolysis in terms of product distribution, biochar formation mechanism, so that synergistic enhancement of biochar yield and carbon retention can be achieved, and successfully applied to cement modification, creating a green low-carbon cement carbon sink.