Fundamental properties and phosphorus transformation mechanism of soybean straw during microwave hydrothermal conversion process

Yan Shi, Gang Luo, Jiajun Fan, James H. Clark, Shicheng Zhang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Microwave hydrothermal (MHT) conversion is emerging as a promising technology for the disposal and reutilization of biowastes. This study investigated the fundamental properties and phosphorus transformation mechanism of soybean straw during the MHT conversion process. The oxygen-containing functional groups in soybean straw were stripped, and a trend of dehydration was observed as the temperature increased during the MHT process. Cellulose was identified as the major component of the MHT solid products at high temperature. Glucose and glucuronic acid in the MHT liquid products were gradually converted to formic acid and acetic acid with increasing temperature and holding time. The characteristics of the MHT products directly affected the changes in P speciation and transformation. Most of the P was distributed in liquid products and the impact of holding time was not significant on P distribution at low MHT temperature. With the increase in temperature and holding time, P gradually transferred into the solid products. The proportion of organic phosphorus and soluble inorganic phosphorus in soybean straw was high, and it decreased noticeably after the MHT process. The increase in MHT temperature promoted the conversion of OP and AP into IP and NAIP respectively. P K-edge X-ray absorption near edge structure analysis reveals that Ca5(PO4)3(OH) was the major component of soybean straw and more Ca5(PO4)3(OH) was formed at lower MHT temperature. This study provides fundamental knowledge on the property changes of soybean straw and the transformation of phosphorus during MHT conversion process, which is essential for its disposal and further utilization.

Original languageEnglish
Pages (from-to)265-275
Number of pages11
JournalWaste Management
Early online date16 Jan 2024
Publication statusPublished - 1 Mar 2024

Bibliographical note

Funding Information:
We acknowledge the financial support provided by: China Scholarship Council ( 201906100126 ) and Shanghai Sailing Program ( 21YF1401700 ). We are thankful to the staffs of 4B7A beamline at Beijing Synchrotron Radiation Facility for the data collection of P K-edge XANES.

Publisher Copyright:
© 2024 Elsevier Ltd


  • Microwave hydrothermal conversion
  • Phosphorus
  • Soybean straw
  • Transformation
  • X-ray absorption near edge structure

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