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 microscale, in chain-like aggregates of almost spherical primary particles with diameter in the range of 15-20 nm, while 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 mostly carboxylic acids, at the edge of the graphitic layers[5,6] of the CB particles which makes possible the exploitation of heavy metal adsorption capability. In this work we propose a characterization of acid-base properties of the functional groups on the HNPs surface by using potentiometry and infrared spectroscopy techniques.