Soft Ion Divalent Metals toward Adsorption on Zn/Al-POM Layered Double Hydroxide

Abstract

Development of Zn/Al layered double hydroxide by intercalation using polyoxometalate (POM) K4[α-SiW12O40] to Zn/Al-POM was investigated. The success of the modification is evidenced by the XRD, FT-IR, and BET characterization data. XRD characterization showed an increase in the interlayer distance from 8.59 Å in Zn/Al LDHs to 10.26 Å in Zn/Al-POM. This success is also supported by the FT-IR data with the appearance of vibrations around 779-979 cm-1 which indicates the vibration of the polyoxometalate compound in Zn/Al-POM. Other supporting data in the form of BET also prove an increase in surface area from 1.968 m2/g in Zn/Al LDHs to 14.042 m2/g Zn/Al-POM. The ability of Zn/Al-POM as an adsorbent is proven through several parameters such as kinetics, isotherm, thermodynamics, and regeneration for Cd2+, Pb2+, Ni2+, and Co2+. Adsorption kinetics showed that Zn/Al-POM was more likely to follow the pseudo-second-order adsorption kinetics model for Cd2+, Pb2+, Ni2+, and Co2+. The results of determining the adsorption isotherm parameters of Zn/Al-POM tend to follow the Freundlich isotherm model with a maximum adsorption capacity of 74.13 mg/g on Pb2+. The regeneration process showed that Zn/Al-POM was more resistant than Zn/Al LDHs up to 3 cycles. It was proven that Zn/Al-POM was able to survive in the last cycle up to 69.19% on Ni2+.

Keywords

• soft divalent metal ions
• adsorption
• polyoxometalate
• regeneration