The efect of microwave and ultrasound activation on the characteristics of biochar produced from tea waste in the presence of H3PO4 and KOH
Abstract
The mechanism of chemical and physical activation during biomass pyrolysis is crucial for the more efective use of biomass
and the preparation of functional porous biochemical materials. In this study, raw tea waste (RTW) was used to prepare the
biochar samples by pyrolysis at 300 and 500 °C following phosphoric acid (H3PO4) and potassium hydroxide (KOH) activation along with microwave (MW) and ultrasound irradiation (US). Textural and chemical changes of biochar samples were
designed by activation conditions and characterized in detail. SEM and N2 adsorption–desorption results showed that US and
MW activation increased dramatically the surface area of the biochar from 942 m2
/g to 1984 m2
/g in the presence of H3PO4
and from 87 m2
/g to 806 m2
/g in the presence of KOH. While homogenous cylindrical macropores biochar was produced by
acid-assisted US activation, microporous spherical nano-sized particles could be produced by acid-assisted US-MW hybrid
activation. Above an optimum US activation time, the pores and channels in the biochar were destroyed and sintering of
the particles occurred. Pyrolysis at 300 °C of the RTW activated with KOH led to the hydroxylation and reorganization
of oxygen-containing functional groups and C-H groups on the surface. Before pyrolysis, the hybrid activation of biomass
by physical and chemical methods can obtain the production of efcient engineered materials with preferable surface area
and porosity, composition, and availability of functional groups in many applications, such as catalyst, energy storage and
conversion, wastewater treatment, and soil remediation.
Source
Biomass Conversion and BiorefneryCollections
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