A three-dimensional active biochar for sintering in steel industry and remove methylene blue by synergistic activation of H3PO4 and ZnCl2

In the context of treating waste with waste, the development of three-dimensional biochar that may be used for sintering in the steel sector as well as successfully removing methylene blue from waste water is effective. The biochar activated by H3PO4 alone (DCP), ZnCl2 alone (DCZ) and H3PO4 cooperated with ZnCl2 (DCM) were prepared to investigate the mechanism of the synergism of H3PO4 and ZnCl2 at pyrolysis temperature 500 °C (selecting from 300 °C to 1000 °C). The SEM analysis indicates DCM possesses a stereoscopic porous network comparing agglomeration and stacking of the others, and the SEM and BET analysis indicate that DCM possesses a stereoscopic porous network and higher effective pore volume (VM/VT = 0.951) than DCP (VM/VT = 0.584) and DCZ (VM/VT = 0.812). EDS, XPS and FTIR analysis revealed that the surface heteroatom of P and Zn enhanced on DCM compared with that of DCP (P weight%=6.39 vs 3.26) and DCZ (Zn weight% = 5.93 vs 1.85) although the activator dosage was halved for DCM. The methylene blue isotherm adsorption curve of DCM fits well with Freundlich and Dual Langmuir adsorption isotherms, the adsorption kinetics is in line with the pseudo-second-order kinetic model. The results indicate that the adsorption process is based on a heterogeneous multilayer, that physisorption-chemisorption adsorption is the primary adsorption mechanism, and that the adsorption process is regulated by the combination of intra-particle and film diffusion. The DCM demonstrates to be a promising adsorbent for methylene blue removal, performing a high removal capacity at 576 mg/g. In this study, a feasible method to synergistically activate biochar from textile wastes was proposed, to deal with the removal of methylene blue.