Effects of Temperature and Carrier Gas on Phosphorus Transformation in Biosolids Biochar
2024
Shefali Aktar | Md Afzal Hossain | Gabriel Gasco | Ana Mendez | Cicero Celio de Figueiredo | Kalpit Shah | Jorge Paz-Ferreiro
Phosphorus (P) is an essential macronutrient for plants. The focus of this work is to recover P from biosolids and their derived biochar. The effect of three different pyrolysis temperatures (400 °:C, 500 °:C, and 600 °:C) and two carrier gases (CO2 and N2) on P fractionation and the speciation of P on biochars produced from two biosolids were investigated. The Hedley chemical sequential extraction method and 31P liquid NMR were used for P characterization and quantification. Higher pyrolysis temperatures increased P fixation and decreased short-term P bioavailability. Carrier gas had also significant effects on P fractionation in the biochars. Biochar produced in a CO2 environment had slightly higher water-soluble P, NaHCO3-Pi, NaOH-Pi, and residual P than in biochar prepared in a N2 environment, while HCl-P showed the opposite trend. Additionally, the predominant molecular configuration of P was present in the inorganic form identified by 31P liquid NMR spectra, while organic P transformed into inorganic P with increasing pyrolysis temperature.
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