Phosphorus Adsorption and Desorption Characteristics on Micronutrient Doped Biochar

Authors

Moe Kikuchi '27, DePauw University

Files

Document Type

Poster

Publication Date

2-2026

Abstract

The increasing global demand for food necessitates efficient agricultural practices; however, the overuse of phosphorus (P) fertilizers presents a major environmental concern. Advanced materials, including biochar, offer promising strategies for mitigating these effects. Biochar, a carbonaceous material derived from biomass, can be functionalized with micronutrients such as magnesium (Mg) or iron (Fe) to enhance its P adsorption and retention characteristics so that the ion-doped biochar could serve as a sustained nutrient release fertilizer besides improving soil health. This study investigated the adsorption and desorption behavior of dissolved P (200 µM/g and 400 µM/g) in three types of biochars: raw (BC), Mg-doped (MgBC), and Fe- doped (FeBC). Adsorption was performed in near-neutral pH at low ionic strength solution and two cycles of desorption involved NaHCO 3 for anion exchange agent. The suspension was sampled at different time points and biochar was separated followed by filtration and quantification of P using the molybdenum blue method. Post-adsorption biochar samples were analyzed using XPS, ToF-SIMS, and FTIR to assess surface- bound P. UV-Vis spectroscopy data showed that at 200 µM/g concentration, amount of P still retained in biochar after two stages of desorption was 105 µM/g (from 214 µM/g) in BC, 349 µM/g (from 1490 µM/g) in MgBC, and 110 µM/g (from 220 µM/g) in FeBC. Increasing the P concentration to 400 ppm enhanced the adsorption of P on MgBC (by 18%) and FeBC (by 29%), but no change was observed in BC. Analysis of biochar through ToF-SIMS mapping revealed strong spatial correlation between POx species and dopant ions (Fe or Mg), indicating preferential adsorption mechanisms. These findings demonstrate enhanced P adsorption and higher retention during desorption in doped biochars. Since the preferential sorption occurred at dopant ion sites, there is a potential for optimizing adsorption maxima and desorption kinetics with dopants for targeted applications.

Department

Interdisciplinary Science and Engineering Laboratory, Department of Plant and Soil Sciences, University of Delaware, Newark, DE

Project Mentor

Pavlo Ivanchenko, Dr. Deb Jaisi

Funding and Acknowledgements

CANR Summer Institute Program and USDA

Recommended Citation

Kikuchi, Moe '27, "Phosphorus Adsorption and Desorption Characteristics on Micronutrient Doped Biochar" (2026). Annual Student Research Poster Session. 239.
https://scholarship.depauw.edu/srfposters/239