HYDROPHILIC NANOPARTICLES FROM CARBON BLACK OXIDATION: ACID-BASE CHARACTERIZATION

Carbon blacks (CB) are carbonaceous materials that have a low hydrogen content, high specific surface area, and a great structural variability on the mesoscopic scale, which is strongly dependent on the synthesis conditions.1 CB are largely composed of hydrophobic material organised, at the nanoscale level, in graphene layers that have various degrees of deviation from planarity and a different amount of the less organised soot areas (i.e., amorphous and disordered carbons) that make CB particles more reactive than graphite.2 CB oxidation methods in gas-phase (i.e., air, nitrogen oxide, and ozone) and liquid-phase (i.e., nitric acid, potassium permanganate, potassium dichromate)3,4 are extensively used to improve the CB dispersibility in aqueous media. In this work we propose a study on the hydrophilic carbonaceous nanoparticles (HNPs) of uniform size with a very good degree of dispersion in water obtained through wet oxidation of CB with hot nitric acid. This process provided selective functionalization with oxygen functional groups such as carboxylics, at the edge of the graphitic layers5,6 of the CB particles which makes possible the exploitation of heavy metal adsorption capability. Acidity constants and site concentrations for the major surface functional group on the HNPs surface samples, obtained by varying the CB particle contact time with hot nitric acid, were determined by coulometric–potentiometric titrations. Zn(II) adsorption capacity tests by polarographic technique have been carried out.