CEE Seminar (ZOOM): Biochar-based Composites Application for Simultaneous Nitrogen Retention and Heavy Metal Immobilization in Agricultural Soils

Abstract: Poor nitrogen fertilizer use efficiency and heavy metal pollution are common co-existing problems in agricultural soils. The discovery of excellent and inexpensive materials as soil conditioners is a promising strategy of simultaneously addressing these problems. Herein, biochar-based composite materials, including layered double hydroxide-biochar and hydrogel-biochar, were synthesized, and their potentials for simultaneous nitrogen retention and heavy metal immobilization were systematically investigated. Results suggest that these materials could efficiently co-adsorb nitrogen and heavy metals. Importantly, they showed relatively strong desorption capacity for nitrogen (> 6%) compared to all kinds of heavy metals (< 1%). The difference was primarily attributed to the strength of bonding forces of inorganic nitrogen (i.e., Van der Waals force, electrostatic attraction and hydrogen bonding) and heavy metals (i.e., ionic bonding and coordination bonding) with the composites. Both column leaching and plant experiments were successfully conducted to evaluate the practical applications of these materials in agriculture. These materials not only dramatically decreased the mobility of nitrogen and heavy metals in soils through physical adsorption, but also altered soil microbial community and their functions so as to further improve the soil nitrogen cycle and enhance heavy metal immobilization simultaneously.

Bio: Lixun Zhang is currently a George E. Hewitt postdoctoral scholar in the Department of Civil and Environmental Engineering at UC Irvine. He received his bachelor’s degree in water supply and sewerage engineering from Tongji University in 2014, and his doctoral degree in environmental science and engineering from Tsinghua University in 2019. His research interests lie in environmental nanotechnology, water chemistry, agricultural science and analytical chemistry. His Ph.D. research mainly focused on geobiochemical cycles of heavy metals, nitrogen and silicon, and functional material synthesis/application for adsorption, catalytic degradation and microbial mediation. His postdoctoral research is working on the synthesis of functional hydrogel-based materials for selective and efficient capture of trace organic pollutants (e.g., microcystin and pesticides) and the application of these materials as new medias in biofiltration systems for surface water purification.