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, 100   μM) or dissolved humic acids (0–50   mg/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 (50   mg/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.