Fabrication and ambient temperature flash O-functionalization of chlorocardium rodiei-based carbon for toxic metal adsorption

Activated carbons with their typically diverse array of heteroatom surface functionality are well-known adsorbent materials. Adsorbent functionalization by increasing oxygen heteroatom content is an important modification technique. Wet oxidation with concentrated nitric acid is among the most ubiquitous and productive strategies but current oxidation regimes utilize extended residence times and cause undesirable losses in specific surface area. Here, we fabricated activated carbons from Chlorocardium rodiei waste wood and evaluated the changes in physicochemical properties of this adsorbent when subjected to a little explored, ambient temperature, low-residence time oxidation procedure. We evaluated the types of oxygen speciation generated under various regimes and studied their impact on the removal efficiencies of Pb²⁺, Al³⁺ and Mn²⁺ in model solutions at pH 3. Flash oxidation with 10 M nitric acid for 60 min resulted in only a 12 % loss in specific surface area and increased the total carbon-bound oxygen content by 8 atomic %. This enhanced adsorption of Al³⁺ and Pb²⁺by 22 % and 5 % respectively. Al³⁺ and Pb²⁺removal efficiencies were strongly correlated with the presence of carbonyl and alcohol functional groups while Mn²⁺ was poorly adsorbed and had a negative correlation with acidic groups. The adsorption of each metal was therefore predominantly mediated by different oxygen moieties on the material surface. These results demonstrate that flash oxidation can yield strong increases in oxygen while preserving surface area and is a viable addition to existing oxygen heteroatom functionalization strategies.