The Effect Of Humic Acid On The Aggregation Of Nano-TiO₂ In Aquatic Environments And The Adsorption For Cd???

Nano-Ti O₂ is one of the most widely used nanomaterials,which is widely used in various fields because of their excellent dielectric and chemical properties.A large amount of nano-TiO₂ particles are inevitable to release into the water environment directly or indirectly,producing potentially harmful to aquatic ecosystems and human health.Nano-Ti O₂ is easily interact with the widespread of macromolecular organic matter in water,such as humic acid?HA?,by anion exchange,ligand exchange,hydrophobic function and cationic interaction bridge due to its strong surface activity,thereby affect its surface properties,the settlement behavior and the transformation of pollutants migration behavior on the nano-TiO₂.To study the aggregation behavior of nano-TiO₂ in different environmental factors?pH,ionic strength and Cd?II?concentration?,humic acids were extracted from peat,and then prepared the HA-TiO₂ complexes.Humic acid was graded to investigate the influence of structure and properties of humic acid on the adsorption of nano-TiO₂ for heavy metals,providing scientific basis for understanding environmental behavior of nanomaterials.Our main research results are as follows: 1.Humic acid made a significant impact on the aggregation behavior of nano-TiO₂ particles.Humic acids could enhance the stability of particles under the different pH and ionic strength.In the presence of Cd?II?,HA could form the TiO₂-HA-Cd and/ or TiO₂-Cd-HA ternary complex to promote the aggregation of.nano-TiO₂.2.The adsorption kinetics of humic acid on the nano-TiO₂ was closely related to the heterogeneity of HA.The adsorption of humic acid on the nano-TiO₂ was could be fitted with Lagrange pseudo-second-order model.The lower molecular weight HA was fist loaded on the polar nano-TiO₂ because of its more acid and aromatic group.The lower molecular weight of HA adsorpted on the nano-TiO₂ providing new hydrophobic adsorption sites for higher molecular weight HA,the higher molecular weight HA coverd on its surface.3.Humic acid could promote the Cd?II?adsorption on the nano-TiO₂,and the lower molecular weight humic acids could promote the Cd?II?adsorption more obviously.The Cd?II?adsorption was affected by the solution pH and ionic strength,it increased with the increasing pH,and increased and then decreased with the increasing ionic strengths.