Y. Deligiannakis

A water-dispersible, carboxylate-rich carbonaceous solid: synthesis, heavy metal uptake and EPR study

Thermal oxidation of Na-cholate hydrate at 300xa0°C in air results in a carbonaceous solid (SC-30) nanomaterial bearing a steroid interior and a significant fraction of carboxylate sites. Electron Paramagnetic Resonance spectroscopy reveals that SC-30 bears a significant concentration of stable C-based radicals located at the interior of the steroid carbonaceous matrix. H-binding, determined by potentiometric acid–base titrations show that the SC-30 contains three types of H-binding sites. One type with pKaxa0=xa04.2 corresponds to surfacial metal-binding COOH groups. A second type of sites with pKaxa0=xa06.2 corresponds to COOH buried at the interior of the SC-30 carbon matrix, which are inactive in metal binding. A third type with pKaxa0=xa08.5—is also inactive in metal binding—originates from aggregated stacked-states like those observed for cholate in solution. The surfacial COO− carboxylate groups, confer the solid hydrophilic character, therefore it can be easily dispersed in water at high concentrations providing clear aqueous colloids. pH-edge metal uptake experiments and Surface Complexation Modelling show that SC-30 is an efficient heavy metal adsorbent in aqueous solution for Pb2+ and Cu2+ ions at pH 5–8. A structural/functional model is discussed based on the heterogeneous character of the SC-30 material.

Recycled-tire pyrolytic carbon made functional: A high-arsenite [As(III)] uptake material PyrC350(®).

A novel material, PyrC350®, has been developed from pyrolytic-tire char (PyrC), as an efficient low-cost Arsenite [As(III)] adsorbent from water. PyrC350® achieves 31mgg-1 As(III) uptake, that remains unaltered at pH=4-8.5. A theoretical Surface Complexation Model has been developed that explains the adsorption mechanism, showing that in situ formed Fe3C, ZnS particles act cooperatively with the carbon matrix for As(III) adsorption. Addressing the key-issue of cost-effectiveness, we provide a comparison of As(III)-uptake effectiveness in conjunction with a cost analysis, showing that PyrC350® stands in the top of [effectiveness/cost] vs. existing carbon-based, low-cost materials.