Activated carbon surface modifications by adsorption of bacteria and theireffect on aqueous lead adsorption

The adsorption of Escherichia coli on different activated carbons has been studied. The activated carbon samples used have been characterized, determi ning their surface area, pore size distribution, elemental analysis, minera l matter analysis and pH of the point of zero charge. The adsorption capaci ty of these carbons increased with their hydrophobicity and macropore volum e. The number of bacteria adsorbed on the demineralized activated carbon in a solution of pH value equal to the iso-electric point of the carbon was n egligible. However, in the presence of cations the proportions of bacterial cells adsorbed were 87.8% (Fe3+), 54.7% (Ca2+) and 24.8% (Mg2+) respective ly. This increase in adsorption capacity in the presence of electrolytes ha s been explained on the basis of both the reduction in electrostatic free e nergy and the increase in cell surface hydrophobicity due to the metal boun d by some compounds of the cell membrane. When the solution pH was intermed iate between the pH values of the point of zero charge of the carbon and ba cteria the number of bacteria adsorbed increased due to the attractive inte ractions between the carbon and bacteria. The adsorption of bacteria on act ivated carbons decreased the porosity and increased the negative charge den sity of the latter. Depending on the experimental conditions used, the pres ence of bacteria can enhance the capacity of activated carbons to adsorb le ad. (C) 2001 Society of Chemical Industry.