Ball-milled biochar-vermiculite/zeolite magnetic composites for adsorption of lead and p-nitrophenol from wastewater: Synthesis, performance, and mechanisms.

Herein, ball-milled magnetic biochar-vermiculite composite (MBC@VT) and ball-milled magnetic biochar-zeolite composite (MBC@ZT) were synthesized via one-step ball-milling, and their adsorption capacities for Pb(II)/P-nitrophenol (PNP) in water were compared. The results demonstrated that the removal of Pb(II) and PNP through both materials was a complex, endothermic reaction mainly driven by chemisorption, with strong tolerance to pH changes and co-existing ions. MBC@VT showed superior adsorption for Pb(II) (reaching 367.81 mg/g after 180 min of reaction), attributed to the ion exchange facilitated by the unique interlayer cation structure of VT. Additionally, the complexation and pore-filling mechanisms contributed to the removal of Pb(II). In contrast, MBC@ZT demonstrated a higher affinity for PNP (reaching 196.14 mg/g at 45 min of reaction), likely due to the strong affinity of ZT for polar groups, which enhanced hydrogen bonding with PNP. The primary mechanisms for PNP removal included hydrogen bonding, π-π stacking, and pore filling. Additionally, circular regeneration experiments showed that after three cycles of adsorption-desorption, MBC@VT and MBC@ZT still maintained effective adsorption effects on Pb(II)/PNP, indicating that the two materials possessed certain reusability. Overall, this research provides meaningful insights into the effective remediation of Pb(II) and PNP contamination in water.