Optimization using central composite design for continuous absorption of CO2 gas with green sodium silicate in a packed bed column.

ABSTRACT

If absolutely nothing is taken to reduce carbon dioxide (CO2) emissions, atmospheric concentrations of carbon dioxide will rise to 550 parts per million by 2050, which will have disastrous effects on the world's climate and food production. An apparatus has been designed and setup to convert CO2 into a useful and vital product which was silica. The effect of different experimental factors on the compositions by weight percent of SiO2 and Na2CO3 were studied including the CO2 gas flow rate (1.037, 1.648 and 2.26 L/min), initial concentration of sodium silicate (Na2SiO3) solution (5, 7.5 and 10 %wt) and the packing size (15.95, 20.175, and 24.4 mm). An optimization process was performed using the Design Expert software program to achieve the optimum experimental conditions at which the maximum weight percent of SiO2 (main product), the minimum weight percent of (Na2CO3) (side product) and the minimum reaction time were determined. From the optimization process, the maximum weight percent of SiO2 (25.63 %), the minimum weight percent of (Na2CO3) (9.62 %) and the minimum reaction time (7.59 min) were achieved at the following optimum experimental conditions of CO2 gas flow rate = 1.648 L/min, packing size = 24.4 mm and initial concentration of sodium silicate solution = 10 %wt.