Table 1 Foundational features of different methods for separation or utilization of CO2 (Bhatia et al. 2019; Thakur et al. 2018; Cheah et al. 2016)
Category | Method | Mechanism | Advantage | Insufficient |
|---|---|---|---|---|
Physical method | Absorption | Henry's law. Usually, in absorbents, CO2 changes with pressure and temperature | Strong absorptive capacity, high selectivity, and simple operation | High energy consumption and cost |
Adsorption | Some solid adsorbents are selective to CO2 and can be desorbed with changes in temperature and pressure | Low energy consumption, simple operation, and controllable cost | Low selectivity and poor adsorption effect | |
Membrane separation | The permeation rates of membrane materials to different gases are different | Simple operation, low energy consumption, and cost | Low durability of membrane materials | |
Low-temperature distillation | The compressed and cooled CO2 is liquefied or solidified and then separated by distillation | Easy to operate and avoid the formation of by-products | High cost and low recovery rate of CO2 | |
Chemical method | Absorption | CO2 can react with the absorbent and release CO2 again after heating | Strong absorption, good selectivity, mature and stable technology | Large loss of absorbent, high energy consumption, and cost |
Adsorption | Separation and recovery of CO2 components from a gas mixture by solid material adsorption or chemical reaction | Easy to operate and good adsorbability | Factors such as adsorption–desorption times and temperature have a too great influence on the performance | |
Membrane absorption | Selective separation of CO2 by the combination of membrane contactor and chemical absorption | High selectivity, large contact area, and simple device | Low durability of membrane materials | |
Electrochemical | CO2 was captured and separated by an electrochemical system | The technology is widely used and the separation cost is low | The electrode material is difficult to find and is highly corrosive at high temperatures | |
Hydrate | Water and CO2 form CO2 hydrate at a certain temperature and pressure | A simple process has low energy consumption, good effect, and low loss of raw materials | The device is easy to corrode, and the requirement of material selection for equipment is high | |
Biological method | Enzyme catalysis | CO2 can be captured and transformed into substances such as formic acid by enzymes such as the RuBisCo enzyme and carbonic anhydrase | High efficiency, no by-products, strong specificity, the product can be used directly | The factors such as temperature have a great influence, the cost is high, and the controllability of the multi-enzyme system is low |
Whole-cell catalysis | Use cells (cyanobacteria, etc.) to capture and convert CO2 into products, such as biodiesel | Easy to operate, high efficiency, no by-products, strong specificity, the product can be used directly | The high temperature and toxicity of flue gas limit the growth of cells, and the transformation ability of natural cells is weak |