Ultrasonication Assisted Urea Treated Biochar: An Eco-Friendly Adsorbent for CO2 Capture

Abstract

Cheap, efficient and eco-friendly adsorbents have received great attention for CO2 capture. Nowadays, biochars are promising CO2 adsorbents with the advantages of their low-cost, tunable porous structural characteristics, facile surface treatment and easy regeneration. In this work, biochar synthesized from wheat straw, an agricultural waste, by pyrolysis was used as a CO2 adsorbent. CO2 capture studies were conducted by thermogravimetric analyses (TGA) at 25 degrees C under 100 mL min(-1) CO2 for 2 h. The CO2 adsorption capacity of the biochar was determined as 23.33 mg g(-1). To enhance CO2 adsorption capacity, ultrasonication and urea treatment were applied to the biochar. With the combination of these treatment methods, CO2 adsorption capacity of the biochar increased to 73.56 mg g(-1) due to an increase in its micro-pore volume and presence of functional amine groups. Possible CO2 capture mechanisms were stated as pore filling with CO2 molecules, van der Waals forces, weak hydrogen bond, and Lewis acid-base interactions in addition to reactions of amine groups with CO2 molecules. After five CO2 adsorption-desorption cycles, ultrasonication assisted urea treated biochar was still used with over 90 % performance. The results show that the low-cost and eco-friendly physicochemical treated biochar is a favorable adsorbent for CO2 capture.