Persulfate assisted hydrothermal processing of spirulina for enhanced deoxidation carbonization

Abstract The influence of persulfate assisted hydrothermal carbonization (HTC) (160 °C–220 °C) of spirulina and hydrochar properties was assessed. The elementary composition and proximate analysis of hydrochar were investigated on the carbonization degree and basic fuel properties, and the surface functional groups and morphological characteristics of hydrochar were analyzed as well as thermal stability. Results suggested that persulfate assisted process enhanced the carbonization degree of hydrochar by oxygen reduction (1.53%–2.74%) and increase of C ratio, and HHVs increased 0.81–1.39 MJ/kg at temperature above 180 °C. The –OH and C O on hydrochar surface were significantly reduced, and C–(C, H) and C–(O, N) were weakened by persulfate addition and more C–H peaks was formed. Additionally, the persulfate addition enhanced the thermal stability of hydrochar by lowing the maximum mass loss rate. The result suggested that HTC can be conducted with persulfate at lower temperature for hydrochar biofuel production.