Fabrication of functional biomass carbon aerogels derived from sisal fibers for application in selenium extraction

Abstract

Selenium (Se) is a rare element, usually in ionic form in aqueous media. The separation of selenium from aqueous solution has received considerable attention due to the large-batch application of selenide. In this work, the Mg–Al layered double hydroxides (LDHs)-functionalized biomass carbon aerogels (CAs) were fabricated by combining freeze-drying, carbonization with in-situ growth method. And the process for extracting selenium based on adsorption of CAs and “memory effect” of LDHs nanosheets has been developed. Firstly, CAs was prepared by alkalization, bleaching, freeze-drying and carbonization using the sisal fiber as precursor. Then, Mg–Al LDHs-functionalized CAs were fabricated by in situ growth of LDHs platelets on the CAs surfaces. The physical and chemical properties of the LDHs-functionalized CAs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET). The SEM results showed that sisal cellulose fibers used in this paper have a smooth surface with a diameter about 8μm and a length of several millimeters. Furthermore, the flowerlike nanosheets are uniform in both size and shape, with each LDHs nanoplatelet grafted to the CAs. The nitrogen sorption analysis confirmed that LDHs-functionalized CAs is mesoporous structure with the mesopores centered at about 3.5–5nm and BET surface area of 165.26m2/g. It is indicated that the maximum adsorption capacity of selenium on LDHs-functionalized CAs reached 73.6mg[Se]/g. The adsorption time profile of selenium onto LDHs-functionalized CAs ndicates that the adsorption equilibrium was achieved within 4h. After recycling 9 times, the regenerated LDHs-functionalized CAs still displayed high selenium absorption properties. Therefore, the high absorption capacity and excellent recycling capabilities of LDHs-functionalized CAs composites give the material an ideal choice for the selenium recovery in practical applications.