Microwave digestion-assisted HFO/biochar adsorption to recover phosphorus from swine manure

Tao Zhang; Haoyu Xu; Huanhuan Li; Xinyue He; Yuanji Shi; Andrea Kruse

doi:10.1016/j.scitotenv.2017.10.077

Microwave digestion-assisted HFO/biochar adsorption to recover phosphorus from swine manure

Sci Total Environ. 2018 Apr 15:621:1512-1526. doi: 10.1016/j.scitotenv.2017.10.077. Epub 2017 Nov 6.

Authors

Tao Zhang¹, Haoyu Xu², Huanhuan Li², Xinyue He², Yuanji Shi², Andrea Kruse³

Affiliations

¹ Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, Key Laboratory of Plant-Soil Interactions of Ministry of Education, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China; Biomass Engineering Center, China Agricultural University, Beijing 100193, China. Electronic address: taozhang@cau.edu.cn.
² Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, Key Laboratory of Plant-Soil Interactions of Ministry of Education, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China.
³ Institue for Agricultural Engineering, University of Hohenheim, Garbenstrabe 9, 70599 Stuttgart, Germany.

PMID: 29102181
DOI: 10.1016/j.scitotenv.2017.10.077

Abstract

A sustainable management option for dealing with waste straw is to pyrolyze it to create biochar, which can then be used as a sorbent in pollution treatments, such as the recovery of phosphorus (P) from swine manure. However, the inability to directly capture soluble organic P (OP) and sparingly soluble P and the low selectivity of biochar remain key issues in this process. To overcome these, we investigated a microwave (MW) digestion pretreatment with a HFO/biochar adsorption process. The MW digestion-assisted treatment showed good performance for the solubilization of OP and sparingly soluble P. Optimized conditions (temperature=348K, time=45min, H₂O₂=3mL/30mL, HCl=0.13%) achieved an inorganic phosphorus (IP) release ratio of 83.98% and a total phosphorus (TP) release ratio of 91.83%. The P adsorption on the HFO/biochar was confirmed to follow pseudo-second-order kinetics, indicating that the P adsorption process was mainly controlled by chemical processes. The Freundlich model offered the best fit to the experimental data. The maximum amount of P adsorbed on HFO/biochar was in the range of 51.71-56.15mg/g. Thermodynamic calculations showed that the P adsorption process was exothermic, spontaneous, and increased the disorder in the system. Saturated adsorbed HFO/biochar was able to continually release P and was most suitable for use in an alkaline soil. The amount of P released from saturated adsorbed HFO/biochar reached 8.16mg/g after five interval extractions. A P mass balance indicated that 8.76% of the TP was available after the solubilization, capture, and recovery processes.

Keywords: Ferric oxide hydrate/biochar (HFO/biochar); Microwave digestion; Phosphorus; Swine manure.