Synthesis of porous functional biochar through template method and plasma modification for Pb2+ removal: Performance and mechanism

Rich pore structures and functional groups are crucial for adsorbents used for heavy metal removal. In this study, porous functional biochar from corn straw was synthesized using a zinc template method and plasma modification. The impact of synthesis and adsorption conditions on Pb 2+ removal by porous biochar was investigated, and the mechanism was elucidated. The results demonstrated that porous biochar prepared at 600 °C, with a biomass-to-template ratio of 3:1, heating rate of 10  o C/min and further modification by steam plasma (60 kV, water vapor content of 1 %, 5 min) achieved a remarkable Pb 2+ removal efficiency of 90.94 % in aqueous solutions, with an adsorption capacity of 87.2 mg/g. During adsorption, some Pb 2+ was reacted with C-OH groups on the biochar to form Pb(OH) 2 , while the remaining Pb 2+ was transferred to PbCO 3 through reactions with ZnO in the biochar and soluble CO 2 in water. This indicated that ZnO particles and C-OH functional groups generated through plasma modification and the template method on the surface of biochar were primarily responsible for Pb 2+ removal. Both methods effectively enhanced the adsorption and removal performance of the biochar.