Vol. 2 No. 2 (2024): July

This study aims to synthesize the NiAl-LDH/K₄[α-SiW₁₂O₄₀] composite using the coprecipitation method and evaluate its ability to adsorb Cr(VI) from aqueous solutions. The material characterization showed a significant increase in the specific surface area of the composite compared to pure NiAl-LDH, contributing to an enhanced Cr(VI) adsorption capacity. XRD and FT-IR results confirmed the successful synthesis and integration of K4[????-SiW12O40] into the NiAl-LDH structure. At the same time, BET analysis indicated that the specific surface area of the composite doubled compared to pure NiAl-LDH. The adsorption kinetics data indicated that the adsorption process followed the Pseudo-Second-Order (PSO) model with an R² value close to 1, suggesting the dominance of chemisorption in the Cr(VI) adsorption mechanism. Isotherm analysis showed that the Freundlich model was more suitable than the Langmuir model, indicating that adsorption occurred on a heterogeneous surface with multilayer formation. The Cr(VI) adsorption capacity of the NiAl-LDH/K₄[α-SiW₁₂O₄₀] composite reached 17.123 mg/g, higher than that of pure NiAl-LDH at 188.68 mg/g. The Cr(VI) adsorption process involved chemical interactions between Cr(VI) and functional groups on the adsorbent surface, complex formation, and precipitation.

The removal of hazardous anionic dyes from wastewater is a critical environmental challenge due to their toxic effects and persistence in aquatic systems. This study investigates the adsorption performance of a new composite material, consisting of MgAl layered double hydroxide (LDH) and Lignin (MgAl LDH/Lignin), to remove three different anionic dyes: congo red, direct yellow, and procion red. The composite material was synthesized and thoroughly examined using various techniques, including X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller, and Barrett-Joyner-Halenda. The adsorption isotherm studies indicate that the adsorption of congo red and procion red onto the MgAl LDH/Lignin composite follows the Langmuir isotherm model, suggesting a monolayer adsorption on a uniform surface. On the other hand, the adsorption of direct yellow conforms to the Freundlich isotherm model, indicating the possibility of multiple layers being adsorbed on a surface with varying properties. The maximum adsorption capacities for congo red, direct yellow, and procion red were found to be 75.76 mg/g, 51.55 mg/g, and 74.63 mg/g, respectively. The results of this study demonstrate the promising capabilities of MgAl LDH/Lignin composites as highly efficient adsorbents for the treatment of wastewater contaminated with anionic dyes. This research provides valuable insights into the potential of these composites to address the pressing issue of water pollution in a sustainable manner.

Pollution from dyes is well-known for its harmful effects on human health and the environment. Eliminating pollutants such as dyes is a crucial task that can be achieved through various methods, one of which is adsorption. The synthesis of graphene oxide material is achieved from graphite using the Hummers method. The obtained material was then characterised using XRD and FT-IR techniques and tested as an adsorbent for selective adsorption of anionic dyes. The obtained results indicate that the congo red dye was absorbed the most in the selective dyes process, followed by the methyl orange dye, and finally the direct yellow dye.

The intercalation of of Ca/Al layered double hydroxide (LDH) has been successfully conducted into using several intercalants with different size compounds after termal treatment process to reconstruct structure of Ca/Al LDH. Ca/Al LDH was synthesized by co-precipitation at pH 11 then calcination at various temperatures following with intercalation using water, sodium hydroxide, sodium carbonate and Keggin type of polyoxometalate K₄[α-SiW₁₂O₄₀]. Characterization of Ca/Al LDH was carried out by XRD and FTIR analyses. XRD analysis showed that unique diffraction peak of Ca/Al LDH at 10^o with interlayer space 4.67 Å. Gradual thermal treatment of Ca/Al LDH was achieved until loss unique diffraction peak at temperature 700 ^oC to form shrinking layer. Intercalation of water, sodium hydroxide, sodium carbonate, and polyoxometalate to shrink layer of Ca/Al LDH can create formation of well crystalline LDH to reconstruct layer structure with formation of unique diffraction at 10◦. The interlayer distance of Ca/Al LDH was increased after intercalation process. Thus reconstruction structure of LDH was successfully conducted with flexibility of layer.

Heavy metals in the environment can have a detrimental impact on human health. This study successfully used a new adsorbent material, specifically layered double hydroxide pillared with keggin polyoxometalate H4[α-PW₁₂O₄₀]•nH₂O (Ca-Al/POM), to effectively remove cadmium (II) from aqueous solution. The Ca-Al/POM adsorbent has been thoroughly analyzed using X-ray diffraction and FT-IR. The findings showed an increase in the maximum adsorption capacity for cadmium (II) when using Ca-Al LDH intercalated with POM. The study of equilibrium adsorption isotherms showed that the Ca-Al/POM adsorbent effectively removed cadmium (II) and fit the Freundlich isotherm model. In addition, the adsorption kinetics study showed that the adsorption of cadmium (II) on Ca-Al/POM followed a pseudo second-order kinetics model.