Characterization of Surface Heterogeneity of Carbon-Composite Adsorbents

Abstract

Surface functionality of carbon-composite adsorbents were characterised in terms of proton affinity distribution using potentiometric titration method and numerically stable algorithm CONTIN. Surface groups beyond the experimentally measured range of pH was accounted for by constant background term. Modification of carbon with titanium and silicon oxides increases 2.5 times the total amount of ion exchange sites and creates new groups mostly with pK=5.8 and 8.3. Synthetic carbons modified with phosphorus compounds possess acidic character like oxidised carbons and shows 3 types of surface groups. In addition, such carbons possess considerable amount of super acidic groups with pK<2. Oxidation with nitric acid creates mostly acidic (pK=3.6) and phenolic (pK=10.6) groups. Due to very acidic character phosphorus-containin carbons may be regarded as prospective cation exchangers for removal of heavy metals from water solutions.