Immobilization of Ascorbic Acid on Ni-Zn Layered Hydroxide Salts and its Application as [AuCl<sub>4</sub>]<sup>-</sup> Adsorbent

Abstract

Immobilization of ascorbic acid on Ni-Zn LHS (Nickel-Zink Layered Hydroxide Salt) was done through sample preparations and immobilization studies. Ni-Zn LHS was synthesized using coprecipitation method by mixing Ni (NO3)2 and Zn (NO3)2 with molar ratio 2:1, respectively. The green solid material was characterized using XRD, FTIR and SEM-EDX. Diffraction pattern of Ni-Zn LHS shows the peaks from (001), (003), (020) and (220) reflections at 9.30, 18.99, 33.36 and 59.50o, respectively. Ni-Zn LHS has zero charge or netral at pH 6.7. There is no significant shift of 2θ shown after immobilization process. It indicated that ascorbic acid was present on the outer material’s surface. The successful of immobilization was confirmed by the presence of ascorbic groups in FTIR spectra. The 2924 and 1465 cm-1 were the bands of C-H sp3 and C-H sp2, respectively. The immobilized material shown the decreasing of wide range particle size. The Ni, Zn, N and O atoms were detected in Ni-Zn LHS, Ni and Zn were the metal and N and O were the nitrate ion. Immobilization were confirmed by the presence of C atom on material’s surface, C was indicated the ascorbic acid. The immobilization process was followed the Langmuir model due to the highest value of correlation coefficient. Langmuir model assumed that there’s one major interaction in adsorption. The Ni-Zn-AA LHS has stability at pH 5-6 due to its lowest amount of ascorbic acid that released from the structure. The adsorption of [AuCl4]- was successfully done at pH 6 following pseudo second order kinetic model and Freundlich adsorption isotherm model with correlation coefficient 0.9791 and 0.9381, respectively.