Effect of pre-treatment on humic acid adsorption by granular activated carbon

Abstract

The surface chemistry of granular activated carbon (GAC) has been a subject of much debate for long time. Heterogeneity in production and raw material has been the main reason for this uncertainty. Although acidity of activated carbon (AC) has been well understood but basicity causing functional groups have not been identified with much certainty. Least of the study is done on using this pre-treated granular activated carbon to primarily remove humic fractions of dissolved organic carbon (DOC). This is because both GAC and Humic acid are least understood due to the heterogeneity in properties and sources. The effect of various chemical oxidation treatments on surface functionality of GAC has been studied .The removal of Aldrich Humic acid has been checked using chemically tailored GACs. The surface reactivity and functional groups of a series of chemically modified GACs has been accessed using various dry (FTIR) and wet (Boehm titration) methods. Six types of oxidation treatments were used: Nitric acid, ammonium persulphate, thermal, amine, hydrogen peroxide and sodium hydroxide treatment .Hydrogen peroxide treated GAC was found to be the best in removing humic acid. Although acid functional groups were evaluated but presence of basic functional groups could not be detected.