Water constitutes an indispensable resource for global life but remains susceptible to pollution from diverse human activities. To mitigate this issue, researchers are committed to purifying water using a variety of materials to remove harmful chemicals, such as heavy metals. Layered double hydroxides (LDHs), with their intriguing, layered structure and chemical behavior, have attained substantial attention for their effectiveness in removing heavy metal cations and various inorganic oxoanions from water. To enhance the efficiency, considerable endeavors have focused on functionalizing LDHs with different chemical species. Intercalation with metal sulfides has proven to be particularly effective, facilitating heavy metal absorption through multiple mechanisms, including ion-exchange, reductive precipitation, and surface sorption. This review concentrates on the synthesis and performance of polysulfide (S_x, x = 2–5), Mo–S, and Sn–S anion intercalated LDHs for heavy metal cations and inorganic oxoanion sorption, along with their mechanisms. Furthermore, the discussion includes prospects for expanding the chemistry of metal sulfide intercalated LDHs, with existing challenges and future outlooks.

Water pollution by hexavalent chromium, Cr(VI), poses serious concerns due to its detrimental public health effects. In this work, we report the synthesis, characterization, and sorption properties for Cr(VI) by MoS₄^2- intercalated layered double hydroxide, CoAl-MoS₄-LDH (CoAl-MoS₄). Our results show that CoAl-MoS₄ can effectively remove Cr(VI) ions from acidic, neutral, and basic media. At neutral medium, it exhibits a very strong affinity, K_d ∼ 1.91 × 10⁵ mL/g, toward Cr(VI) ions. Under such conditions, this material can remove over 99% of Cr(VI) from a ∼10⁴ ppb of Cr(VI) contaminated solutions, leaving behind residual concentration below the World Health Organization (WHO) defined limit for drinking water. Moreover, our study shows that CoAl-MoS₄ is a highly-competent Cr(VI) adsorbent exhibiting a removal capacity (q_m) as high as ∼231 mg/g. The CoAl-MoS₄ follows pseudo-second order rate kinetics for the sorption of chromate, and the concentration dependent sorption data can be fitted well with the Langmuir sorption isotherm. Furthermore, CoAl-MoS₄ is highly selective to Cr(VI) ions in the presence of various competitive ions in contaminated water systems. All these results suggest that CoAl-MoS₄ is a very efficient sorbent for decontamination of hexavalent chromate from wastewater systems. Graphical Abstract

The phytochemicals (total phenolic, tannin, flavonoid, alkaloid, and saponin) contents in the Aloe vera gel derived from the leaf of Aloe vera (L.) Burm. f. (Synonym Aloe barbadensismiller) were extracted and their antioxidant capacity was studied by Ferric reducing antioxidant power assay (FRAP), by free radical-scavenging capability using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). Three different solvents with three different polarities CH3OH, CH3OH: HCl, CH3CH3OH: H2O were used at v/v ratio of 100, 98:2, 70:30, respectively. The acidified methanol solvent extracted the highest amounts of phytochemicals including total phenolic (4.64 mg gallic acid equivalent/g), tannin (3.84 mg tannic acid equivalent/g), alkaloid (662 mg piperine equivalent/g), and saponin (353 mg diosgenin equivalents/g) compared to the other two solvents. Similarly, in the extract with acidified methanol solvent, high level of total antioxidant activity (about 12 mg gallic acid equivalent/g) and scavenging effects expressed as 50% inhibition concentrations (IC50) for DPPH and ABTS assay were determined to be about 61 μg/mL and 371 μg/mL, respectively, which are higher than those with the other two solvents. The gel extract could be used as a potent antioxidant in medicine and food industries. Journal of Bangladesh Academy of Sciences, Vol. 44, No. 1, 33-41, 2020

Disordered aggregated porous nanoparticles of KCMS are highly efficient and have exceptionally high sorption capacity in removing Ag⁺ and Pb²⁺ following the exchange of K⁺ and Co²⁺ ions bonded electrostatically and covalently in KCMS, respectively.

This study reports an amorphous Zn _x Mo ₃ S ₁₃ chalcogel, reveals its local structure, and shows outstanding Li/Zn _x Mo ₃ S ₁₃ electrochemical performance enabled by its amorphous structure, Zn-mediated polysulfide anchoring, and a stable SEI layer.