The preparation of CuAl LDH and biochar (BC) composite derived from rice husk and its application as a low-cost adsorbent for enhanced adsorptive removal of malachite green has been studied. The composite was prepared by a one-step coprecipitation method and characterized by X-ray Diffraction (XRD), Fourier Transform Infra Red (FTIR), Brunauer-Emmett-Teller (BET), and Scanning Electron Microscopy - Energy Dispersive X-ray (SEM−EDX). The result indicated that CuAl LDH was successfully incorporated with the biochar that evidenced by the broadening of XRD peak at 2θ = 24° and the appearance of a new peak at 1095 cm−1 on the FTIR spectra. The BET surface area analysis revealed that CuAl/BC composite exhibited a larger surface area (200.9 m2/g) that the original CuAl LDH (46.2 m2/g). Surface morphological changes also confirmed by SEM image, which showed more aggregated particles. The result of the adsorption study indicated the composite material was efficient in removing malachite green with Langmuir maximum adsorption capacity of CuAl/BC reaching 470.96 mg/g, which is higher than the original CuAl LDH 59.523 mg/g. The thermodynamic analysis suggested that the adsorption of malachite green occurs spontaneously (ΔG < 0 at all tested temperature) and endothermic nature. Moreover, the CuAl/BC composite showed strong potential as a low-cost adsorbent for cationic dye removal since it showed not only a high adsorption capacity but also good reusability. Copyright © 2020 BCREC Group. All rights reserved

Zn/Al and Zn/Fe layered double hydroxides has successfully synthesized by co-precipitation methods with molar ration 3:1. The samples were characterized using X-Ray Diffraction, Fourier Transform Infrared Spectroscopy and Surface Area using BET method. In this study, Zn/Al and Zn/Fe layered double hydroxides were used to remove direct yellow dye in aqueous solution. The experiments were carried out time variations with the aim of observing the kinetic studies. The results showed that the adsorption of direct yellow onto Zn/Al and Zn/Fe layered double hydroxides based on co-efficient correlation kinetic models more fit using pseudo-second-order than pseudo-first-order.

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Layered double hydroxide (LDH) of Zn/Al and citrate-Zn/Al was prepared and used as an adsorbent of Congo red from aqueous solution. LDH was characterized by X-ray, FTIR, and BET analysis. Adsorption of Congo red was studied through kinetic, isotherm, and thermodynamic analyses. Zn/Al LDH has diffraction at 10.29o (003) with interlayer distance 8.59 Å and citrate-Zn/Al LDHs have anomalous diffraction at 7.57o (003) with interlayer distance 11.68 Å. The surface area of citrate-Zn/Al (40.50 m2 g-1) has higher than pristine LDH (1.97 m2 g-1). Adsorption of Congo red was conducted at pH 6 for Zn/Al LDH and at pH 8 for citrate-Zn/Al LDH. Adsorption of Congo red on both LDHs follows the pseudo-second-order kinetic model. The isotherm parameter follows the Freundlich isotherm model with maximum adsorption capacity 166.67 mg g-1 for Zn/Al and 249.99 mg g-1 for citrate-Zn/Al LDH. Adsorption of Congo red on both LDHs was classified as physical adsorption with energy 4.085-4.148 kJ mol-1. 

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