Rice husk waste-derived super-biochar with the max surface area and Philic-CO2 textural structure: Boosting effect and mechanism of post-desilication.

[Display omitted] • A philic-CO 2 supercarbon was derived from rice husk waste by a new process. • It possessed the max specific surface area in reported biochars (4230 m2 g−1) • It possessed the max CO 2 uptake capacity in the reported biochars (341.5 mg g−1) • This study gave a new way to generate rich ultra-micropores and C-F groups in char. A super-carbon material as adsorbents of CO 2 were prepared with rice husk waste by a new two-step process, pyrolysis-activation and HF post-desilication process. This paper was focused on investigating the boosting effect and mechanism of post-desilication. It was found that the function of the post-desilication was considerably different from that of the reported pre-desilication. It could not only effectively remove Si element from rice husk biochar (RHC) but also significantly improve its performance, producing a super-biocarbon with a well-developed pore structure, rich C-F groups, and a 4230-m2 g−1 surface area, which is the max surface area of known biocarbon. It could adsorb 341.5 mg g−1 CO 2 , a max CO 2 adsorption capacity of reported biocarbon, and its CO 2 /N 2 and CO 2 /H 2 O adsorption selectivity index reached as high as 22.2 and 2.1, respectively. The large surface area was mainly originated from the expansion effect of SiF 4 gas from the post-desilication, generating numerous ultra-microspores, while these C-F groups were generated by the co-reactions of the post-desilication. The ultra-high adsorption capacity was mainly from the fill-adsorption driven by the size effect of these ultra-micropores and the strong CO 2 -affinity of C-F groups, and the adsorption selectivity was confirmed to depend on water-resistant and CO 2 -philic characteristics of its C-F groups by theoretical calculations and experimental observations. These findings presented not only an advanced CO 2 -capture material but also a facile way to tailor textural structure of other biochars. [ABSTRACT FROM AUTHOR]