In this article, several ideas have been proposed for CO2 separation and biogas upgrading using industrial wastewater. Synthetic gas (60% CH4, 40% CO2) has been upgrading in atmospheric pressure in a T-shaped microchannel using municipal, meat processing, water distillation, dairy, caustic, and fish pond wastewater. The municipal, fish pond, and meat processing wastewater contain ammonia, while dairy, and water distillation wastewater contains Ca2+, and Mg2+. Also, the caustic refinery wastewater contains NaOH, with higher alkalinity for CO2 separation. The effect of temperature, gas, and liquid flow rate were investigated. RSM analysis provided a function of three dependent variables of quadratic model for prediction of responses (CO2 removal efficiency and total mass transfer in gas phase) by each absorbent, and all models were meaningful. In addition, given that all R2 values were greater than 0.94, it was indicated that experimental values for removal of CO2 and mass transfer coefficient are favorably consistent with the values of the model. Maximum CO2 absorption was obtained at 30°C, liquid flow rate of 150 mL/hr, and biogas flow rate of 50 mL/min. According to the results obtained for mass transfer coefficient, these coefficients are at least 5 to 22 times greater than mass transfer coefficient in chemical absorption in normal absorption towers, such as packed towers.
