Synthesis, Characterization, and Application of Co-Al-Zn Layered Double Hydroxide/Hydrochar Composite for Simultaneous Removal of Cationic and Anionic Dyes

Najma Memon,Safia Sanam Memon,Abdullah Memon,Urooj Kanwal,Saima Qayoom Memon,Doina Humelnicu

doi:10.1155/2021/1138493

Najma Memon, Safia Sanam Memon + Show 4 more

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https://doi.org/10.1155/2021/1138493

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Abstract

Decontamination of organic dyes from wastewater requires efficient and compatible materials that must be able to remove dyes with different charges at the same time. In this study, composites of layered double hydroxide (LDH) and hydrochar (HC) were prepared and tested for use as general-purpose sorbents for the simultaneous removal of cationic and anionic dyes (i.e., methylene blue (MB), methyl orange (MO), and reactive yellow (RY)). Characterization studies reveal that the surface functional groups on composites are –OH, NO3, M–O bonds. It was observed that crystallinity of LDH decreased with an increasing amount of HC. Preliminary experiments showed that the dyes (i.e., MB, MO, and RY) were well removed simultaneously onto the composite with HC (2.0 g HC/prepared composite). This composite was selected for more experiments, and the adsorption efficiency was optimized by the multivariate technique using the response surface methodology (RSM). Removal efficiency of 100% was obtained for all three dyes with an adsorption capacity of 243, 5.3, and 16.3 µmol g−1 for MB, MO, and RY, respectively. Elovich’s initial intake rates (α) were 4,272, 441, and 99.5 mg g−1 min−1 for RY, MB, and MO, respectively. Data fitted in various models suggested second-order multiplex kinetics, where the surface heterogeneity response was sorbate dependent.

Highlights

Due to the fast growth of urbanization and industrialization, the issue of water contamination has been worsening [1]
KNO3 was obtained from LabChem, while HCl and HNO3 was from DAEJUNG Co. e cationic and anionic dyes were selected for sorption experiments (i.e., methylene blue (MB), methyl orange (MO), and reactive yellow-II (RY-II)), and all the solutions were prepared in deionized water. e MB dye was obtained from Fluka Co. and MO and RY from Merck Co., and used without further purification
E disappearance of peak intensities with an increasing amount of biochar to layered double hydroxide (LDH) was shown that suggests that the addition of hydrothermal condition (HC) exfoliates the layers of LDHs and incorporates some of the HC into interlayers, which resulted in the improved adsorptive properties of LDHs

Summary

Introduction

Due to the fast growth of urbanization and industrialization, the issue of water contamination has been worsening [1] Many industries such as textile, tanning, printing and cosmetic, paper, and pulp are accountable for contamination of water reservoirs with various organic and inorganic pollutants [2]. Many dyes are imperfectly biodegradable or unmanageable to environmental conditions due to their complex large molecular structure, which leads to unidentified degradation products [6] Physical removal technologies such as adsorption are feasible as the whole molecule is taken up from an aqueous solution onto an adsorbate that can be desorbed or treated in a detached environment leaving the water stream free from any degradation product. LDH possesses excessive anion exchange capacity and high layer charge densities. Both characteristics support strong interaction with anion pollutants. HC is similar to activated carbon but possesses more negative charges, capable of interacting with cationic molecules [12]

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