Xiaodan Gao

Xiaodan Gao

Aggregation of humic acid-montmorillonite in Mg2+, Ca2+ and Cu2+ electrolytes: Effects of humic acid content and ionic concentration

Xiaodan Gao, assistant professor, Shenyang Agricultural University (China)
Rattan Lal, faculty mentor


  • Hometown: Liaoning, China
  • Degrees received: PhD in soil science, Southwest University, China

What is the issue or problem addresses in your research?

Organic coating of the clay surface by sorbed humic substances plays a key role in colloid stability and aggregate structure in soils. Some research demonstrated that humic acid inhibits the aggregation potential of colloids, while others claimed that humic acid acts as a binding substance promoting the aggregation. In response to this issue, this study carried out research on organic-inorganic composite mechanism.

What methodology did you use in your research?

Dynamic light scattering and infrared spectroscopy.

What are the purpose/rationale and implications of your research?

Clay's humic substance complexes play a major role in controlling the mobility of element and colloid in natural soils. In the present study, the interactions of HA-Mt composite nanoparticles in Ca(NO3)2, Mg(NO3)2 and Cu(NO3)2 solutions were detected by dynamic light scattering. The aggregation process was sensitive for the humic acid addition, however, more amount of humic acid does not significantly affect this process. Higher cation concentration and higher HA content are two requirements.