Micro-mesoporous biochars derived from the copyrolysis of agroforestry residue and eggshell for removing plasticizer from water

Porous carbonaceous materials derived from agroforestry biowaste are of great interest for environmental remediation because of not only their unique composition and structure, which provide a highly accessible surface area and consequently many exposed active sites but also their stable recycling performance. However, finding a green and low-cost way to prepare porous biochars with the desired composition and structure has been challenging. Herein, we report a green and simple carbonization method for the low-cost synthesis of micro-mesoporous biochars (MMBs) using biowaste and eggshell. Without chemical activation agents, the specific surface area and pore volume of the MMBs reached 1949 m² g⁻¹ and 1.21 cm³ g⁻¹, respectively. Graphite-like structures and abundant O-containing surface functional groups formed. A high carbonization temperature, ≥ 800 °C, was crucial for eggshell decomposition and played a role in pore opening. Pore filling led to excellent sorption removal of pollutants. The sorption amount for diethyl phthalate reached 456 mg g⁻¹. Hydrogen bonding and π–π stacking, as well as mass transfer, controlled the sorption rate. This novel synthetic method provides a simple way to prepare carbonaceous materials with advantageous properties for a variety of potential environmental and energy applications, such as wastewater treatment, gas capture, and energy storage and conversion.