Adsorption of norfloxacin onto titanium oxide: effect of drug carrier and dissolved humic acid.

Titanium dioxide is widely used as an effective catalyst in wastewater treatment. The effects of drug carriers (cyclodextrins, 100μM) or dissolved humic acids (0-50mg/L) or pH (3.0-11.0) on adsorption of norfloxacin to two TiO(2) (Hombikat UV-100 and Anatase TiO(2)) surfaces were systematically studied. Norfloxacin shows high adsorption affinity to TiO(2) surface. Specific surface area of TiO(2) shows great influence on norfloxacin adsorption especially in acidic solutions. The effect of pH on norfloxacin adsorption originates from the changes of TiO(2)'s surface charge and speciation of norfloxacin. The presence of humic acids (50mg/L) suppresses the adsorption of norfloxacin onto Hombikat UV-100 and Anatase TiO(2) prominently. The co-effect of heptakis(2,6-di-O-methyl)-β-cyclodextrin (methyl-β-CD) and humic acid is similar to the solo effect of humic acid on the adsorption of norfloxacin onto Hombikat UV-100, while the co-effect shows a more retardation effect on the adsorption of norfloxacin onto Anatase TiO(2). Humic acid and β-CD show a synergetic depressed effect on the adsorption of norfloxacin onto both TiO(2) surfaces. These results show that both aquatic solution chemistry and drug carrier are important to norfloxacin adsorption on TiO(2), which could alter the environmental fate and transport of norfloxacin.