1 research outputs found
Interlayer Anions of Layered Double Hydroxides as Mobile Active Sites To Improve the Adsorptive Performance toward Cd<sup>2+</sup>
Layered double hydroxides (LDHs) have been considered
important
sinks for ionic contaminants in nature and effectively engineered
adsorbents for environmental remediation. The availability of interlayer
active sites of LDHs is critical for their adsorptive ability. However,
inorganic LDHs generally have a nano-confined interlayer space of
ca. 0.3β0.5 nm, and it is unclear how LDHs can utilize their
interlayer active sites during the adsorption process. Thus, LDHs
intercalated with SO42β, PO43β, NO3β, Clβ, or CO32β were taken as examples to
reveal this unsolved problem during Cd2+ adsorption. New
adsorption behaviors and pronounced differences in adsorption performance
were observed. Specifically, SO42β/PO43β intercalated LDHs showed a maximum Cd2+ adsorption capacity of 19.2/9.8 times higher than other
LDHs. The ligand exchange of H+ (on the surface βOH)
by Cd2+ and formation of Cd-SO42β/PO43β complexes led to the efficient
removal of Cd2+. Interestingly, interlayer SO42β was demonstrated to be able to move to the edges/outer
surfaces of LDHs, providing abundant movable adsorption sites for
Cd2+. This novel phenomenon made the SO42β intercalated LDH a superior adsorbent for Cd2+ among the tested LDHs, which also suggests that LDHs with
a nano-confined interlayer space can also highly utilize their interlayer
active sites based on the mobility of interlayer anions, offering
a new method for constructing superior LDH adsorbents