Transforming pores of bentonite from mesoporous to microporous structure by coupling activation of bio-oil

Bentonite is a commonly used adsorbent material, but micropores in bentonite are generally deficient when compared with typical activated carbon (AC) from biomass. Herein, a facile method was proposed by impregnating bio-oil into bentonite (mixed at different mass ratios) followed by activation with K 2 C 2 O 4 at 800 °C to create additional micropores. The results showed that activation of bentonite (BT) with K 2 C 2 O 4 was difficult, forming AC-BT with S BET of 184.6 m 2 g −1 and little micropores (21.4 %). The activation of the mixture of bentonite and bio-oil with mass ratio of 1: 3 or 1: 1 generated AC-BT 1 /Bio 3 and AC-BT 1 /Bio 1 with much higher S BET (448.1 and 541.2 m 2 g −1 ) and enhanced proportion of micropores (60.2 % and 61.8 %). Further increasing mass ratio of bentonite and bio-oil to 6: 1 and 9: 1 formed the AC-BT 6 /Bio 1 (452.6 m 2 g −1 ) and AC-BT 9 /Bio 1 (339.3 m 2 g −1 ) of lower S BET and reduced proportion of micropores (42.3 % and 33.5 %). The carbon skeleton derived from bio-oil was essential for maintaining the micropores generated. The in-situ IR characterization of the activation process demonstrated importance of aliphatic organics from bio-oil in creating the micropore structures that was the key for efficient adsorption of phenol or tetracycline. Additionally, the bio-oil played the roles as a binder to form clusters-like structures in resulting ACs.