Sulfuric acid modified bentonite as the support of tetraethylenepentamine for CO₂ capture

In this work, an inexpensive and commercially available bentonite was modified by sulfuric acid and explored as the new type of support to immobilize tetraethylenepentamine (TEPA) for CO₂ capture from flue gas. By applying sulfuric acid treatment, the textural properties, in particular, pore volume and surface area of bentonite, were significantly improved. Bentonite treated with 6 M sulfuric acid (Ben-H₂SO₄-6M) can reach a pore volume of 0.77 cc/g from that of the parent bentonite of 0.15 cc/g. With the maximum TEPA loading of 50 wt % onto the Ben-H₂SO₄-6M sorbent, the maximum CO₂ breakthrough sorption capacity reached 130 mg of CO₂/g of sorbent at 75 C under a dry condition. With an addition of moisture to the simulated flue gas, the CO₂ sorption capacity can be further improved to 190 mg of CO₂ at 18 vol% of moisture addition sorbent due to the bicarbonate formation under a wet condition. The TEPA/Ben-H₂SO₄-6M sorbents show a good regenerability and thermal stability below 130 C. The high CO₂ sorption capacity, positive effect of moisture addition, and low capital cost of the raw bentonite materials imply that TEPA/Ben-H₂SO₄-6M could be a promising sorbent for cost-efficient CO₂ capture from flue gas. The sulfuric acid treatment was demonstrated as an effective method for bentonite modification to immobilize TEPA for CO₂ capture.