Insight into the effects of biochar as adsorbent and microwave receptor from one-step microwave pyrolysis of sewage sludge

The effect of biochar, derived from one-step microwave pyrolysis of sewage sludge (OMPSS), on the removal of industrial wastewater (eosin and safranine T) was investigated in this study. Meanwhile, the multiple-reuse potential of biochar as microwave receptor to raise the pyrolysis temperature was also tested during the pyrolysis process. The results showed that OMPSS prepared adsorbents had excellent adsorption performance, achieving the highest removal efficiencies of 97.3 and 95.9% for eosin and safranine T, respectively. Further analysis indicated that this was due to its appropriate porous structure and surface chemistry characteristics, where the S_BET and pore volume of adsorbent AC-1 reached 459 m²/g and 0.23 cm³/g, respectively. The multiple reuses of biochar adsorbents after five times as microwave receptor was feasible, where the pyrolysis temperature could increase sharply from room temperature to 800 °C within 5 min. The mechanism analysis revealed that the limiting stage of adsorption was chemical sorption. This research provided an alternative way for the preparation of functional adsorbent and microwave receptor.