The impact of surface chemistry of carbon xerogels on their performance in phenol removal from wastewaters via combined adsorption-catalytic process

Abstract

The present work explores the influence of the surface chemistry of carbon xerogels (CXs) on their ability to remove phenol from aqueous solutions under mild reaction conditions. The surface of the CXs was functionalized introducing acidic, basic or a combination of weak acid/basic active centers via: (A) hydrothermal method with diluted nitric acid, (B) gas treatments with diluted ammonia and then oxygen, and (C) thermal modification. Obtained CXs with varied acidic-basic surface properties were used for removal of phenol via adsorption or adsorption combined with catalytic wet peroxide oxidation reaction. It was found that both sorption and catalytic properties of CXs depended strongly on the chemical structure of their surfaces. The adsorption of phenol was clearly favored on the basic surfaces (mainly in the presence of quaternary nitrogen) and hindered in the presence of carboxylic groups. Similarly, the activity of these materials in CWPO was affected not only by the total acidity/basicity of the surface of these carbocatalysts, but also by the type of N- and O-type groups present in these samples. Overall, the removal of over 60% of phenol was achieved in the first hour of the process with CX containing quaternary nitrogen and neutral O-groups on the surface.