Pyrolytic formation of a carbonaceous solid for heavy metal adsorption

The solid-state pyrolysis of acetylenedicarboxylic acid, monopotassium salt at 300 °C in air results in bulk quantities of a micron-sized yet macroporous oxidized carbon, which inherently possesses high content of metal-binding sites, such as carboxylate groups, free radicals, and ether/hydroxyl units. Besides its high oxygen content, the solid is stable in water and does not leach or disorient, while it also exhibits an appreciable thermal stability, at temperature exceeding 200 °C in air. Several techniques including TEM/SEM, TGA, Raman/FT-IR, XPS, EPR, and potentiometric titrations were employed for the characterization of the solid. Furthermore, liquid phase adsorption experiments revealed that the material is an efficient heavy metal adsorbent due to the presence of diverse surface-accessible binding sites, showing unusually high metal uptake capacities for Pb²⁺ and Cu²⁺ ions (ca. 4.5 mmol g⁻¹).