Abstract
A new adsorbent biopolymer, piperazine bipolymer (PBP), was successfully modified with a piperazine derivative for CO2 adsorption. The biopolymer was purified by an alkali treatment to obtain 96.43 % degree of deacetylation and used as the reactive adsorbent for amine functionalization. For modification, the purified biopolymer was functionalized with the piperazine-2-carboxylic acid in a mixture solution of glacial acetic acid, isopropyl alcohol, and water. The structure of the modified biopolymer was characterized by Fourier transform infrared spectroscopy. The formation of amide linkages between the amine group of the biopolymer and the carboxyl group of the piperazine derivative were evident. When the mole ratio of biopolymer to piperazine-2-carboxylic acid was varied (1:1, 1:2 and 1:5), the degree of substitution was determined by high performance liquid chromatography. The ratios of 1:2 and 1:5 showed the highest degree of substitution at 72 %. The suitable biopolymer to piperazine-2-carboxylic acid of 1:2 was accepted. The modified biopolymer contained highly reactive amine groups (piperazine) in the structure for CO2 adsorption. Thermogravimetric analysis showed that the modified biopolymer was thermally stable up to 190 °C making it suitable for CO2 adsorption. For CO2 adsorption at room temperature and atmospheric pressure, the 4 % CO2 feed gas concentration in N2 balance with a flow rate of 5 mL/min was determined by gas chromatography. The adsorption capacities were 2.56 mg/g and 1.99 mg/g, respectively, for dry and moisturized conditions.
