Abbreviations

increases; finally, the CO2 diffusion rate will slow down. As for CC-LDHs, it has the lowest effective surface area, which finally influences its CO2 adsorption ability.

For practical applications, the stability of adsorbents during the adsorptiondesorption process should be considered. Hence, it is badly needed to test its cycle operation. Figure 9 shows six successive runs of adsorption-desorption isotherms of LDHs at 80°C. TUC-LDHs shows an initial cyclic adsorption capacity

). However, it decreased to CO2 adsorption capacity of 0.21 mmol g<sup>1</sup> at second cycle, which is 67% of the original capacity. At six cycles of absorption, the adsorption capacity is still 0.2 mmol g<sup>1</sup> with 60.6% of the original capacity although CO2 adsorption is fluctuated during the middle process. The decrease of adsorption capacity over several cycles has also been reported by several research groups. The main reason for the decrease of CO2 adsorption is possible that some chemical sorption sites are blocked during the subsequent adsorption/ desorption cycles. TU-LDHs and CC-LDHs show an initial CO2 adsorption capacity

and 54.7%, respectively. These results indicate that the TU process played a role not only in increasing CO2 sorption capacity, but also in improving the cyclic performance. The experimental results show that stability of hydrotalcites synthesized by both TUC and TU method are higher than the conventional prepared LDHs, which

The present studies have demonstrated that the MgAl LDHs as a CO2 adsorbent

1. It was found that the prepared TUC-LDHs had a clear layered structure and the average size was approximately 100 nm with the largest surface area, which

adsorption capacity of LDHs. The highest capture capacity was got when the

3. The CO2 adsorption stability of TU-LDHs and TUC-LDHs is higher than the

This work was financially supported by National Natural Science Foundation of

China (NSFC) (Grant No. 21576141) and Zhejiang Provincial Natural Science Foundation (Grant No. LY15B060001). This work was carried out at the Interna-

tional Doctoral Innovation Centre (IDIC). Xiani Huang would also like to

can be synthesized successfully through an ultrasonic assisted 'T-mixer' (TU-LDHs), hybrid two-step preparation method (TUC-LDHs) and conventional copreparation (CC-LDHs) method. The conclusions reached as the results of the

makes it a promising adsorbent material for CO2 capture in practical

2. Increasing the adsorption temperature is benefit to improve the CO2

CO2 adsorption took place at 200°C by TUC-LDHs.

CC-LDHs after six adsorption/desorption cycles.

, in which the retentions could achieve as high as 69.8

3.5 CO2 adsorption/desorption cycling test

seems promising adsorbents for CO2 adsorption.

(0.33 mmol g<sup>1</sup>

Sorption in 2020s

of 0.30 and 0.24 mmol g<sup>1</sup>

current study are as follows:

application.

Acknowledgements

138

4. Conclusions

