RESULT: The amount of feedstock was directly proportional to the final pyrolysis temperature. The pyrolysis reached a maximum final temperature of 760 ∘C when ≥300 g of OPS was loaded into the reactor without microwave absorbent. A heating rate of up to 105 ∘C min−1 was recorded, producing a yield of 40wt% of biochar at a short processing time of 20 min. The biochar obtained at 700 ∘C showed relatively low volatile matter (24wt%), higher fixed carbon content (66wt%), carbon (78.5 wt%), oxygen (17.7 wt%), a highly porous structure with high BET surface area of 410m2 g−1 and pore volume of 0.16 cm3 g−1, and recorded a methylene blue dye adsorption efficiency of 20mg g−1.
CONCLUSION: The SPMP approach showed exceptional promise to produce biochar with low H/C ratio (0.5) and O/C ratio (0.2), which indicated a high degree of carbonization and stability of the biochar to act as a durable agent in wastewater treatment.