Efficient removal of chromium(VI) ions by hexagonal nanosheets of CoAl-MoS₄layered double hydroxide

Unveiling the Potential of [Sn2S6]4– Functionalized Layered Double Hydroxides for the Sorption of ReO4– as a Surrogate for 99TcO4–

“…This observation further suggests the necessity of the functionalization of LDH structure with Sn 2 S 6 anions for the efficient removal of perrhenate. This finding relevant to LDH functionalization by sulfides or metal sulfides has already been well established earlier for the separation of other metal ions. ,, …”

“…This should be because of the intercalation of the smaller ReO 4 anion by the exchange of the larger Sn 2 S 6 ions. Hence, this kind of shrinkage of the crystallographic c axis of the LDH was observed for the ion exchange of the MoS 4 anion of the LDH-MoS 4 with CrO 4 2– and SeO 4 2– /SeO 3 2– . ,,,− …”

“…This finding relevant to LDH functionalization by sulfides or metal sulfides has already been well established earlier for the separation of other metal ions. 17,46,47 To understand the effects of competitive anions, we analyzed the , NO 3 − , and CH 3 COO − with a concentration of 1000 ppb of each, at neutral pH. This analysis revealed that ReO 4 − removal is ∼35.2% in 24 h, which is lower than the experiments conducted in deionized water for the same concentration and time scale.…”

“…In recent years, metal–organic frameworks (MOFs), specifically cationic MOFs, have appealed to attention because of their efficient uptake of TcO 4 – from defense legacy nuclear waste, but their complex synthetic procedures, scalability, reusability, and high cost hinder their practical application. − On the other hand, layered double hydroxides (LDHs), a hydrotalcite type clay, are attractive because of their low cost, scalability, and efficient sorption properties for TcO 4 – . LDH can be defined by the general formula [M II (1– x ) M III x (OH) 2 ] x + [(A n – ) x / n · m H 2 O] x − , where M II and M III correspond to divalent and trivalent cations and A n – is an anion. − In LDH, the positively charged metal hydroxide layers are counterbalanced with exchangeable anions that inhabit the interlayer spacings. , Because of such distinct structural features, LDHs adopt diverse sorption mechanisms for TcO 4 – and its oxoanionic surrogates, such as adsorption on the outer surface via M 2+ /M 3+ –O–H···O 4 –Tc interactions, ion-exchange-driven trapping in between the positively charged host LDH layers, and reconstruction of the LDH structures . Furthermore, metal sulfides/polysulfides are known to remove TcO 4 – from the solution by reductive precipitation (Tc 7+ (sol) → Tc 4+ (s) ) and surface sorption through S···TcO 4 covalent interactions. − These features, along with the LDH’s intrinsic sorption properties toward TcO 4 – , appealed to us to design and fabricate an LDH with metal sulfide anions to produce LDH-Mo 3 S 13 .…”

“…This finding relevant to LDH functionalization by sulfides or metal sulfides has already been well established earlier for the separation of other metal ions. 17,46,47 To understand the effects of competitive anions, we analyzed the ReO − from complex solutions, as described above. Wang and Gao 48 developed a correlation between the basal spacing d 003 of the LDH and the ionic radius and ratio of the M II and M III layered cations.…”