Resource utilization of organic spent adsorbent to prepare three-dimensional sulfate-functionalized layered double oxide for superior removal of azo dye.

Lingjie Zhang,Siyin Zheng,Peng Li,Youqin Zou,Ping Zhang,Zhongbang Zhu

doi:10.1007/s11356-021-14327-1

Abstract

Developing superior, rapid, cost-effective adsorbents derived from organic spent adsorbent is an economically sustainable way for purifying azo dye wastewater. Herein, we report a precursor-calcination strategy for the recycle of the organic spent adsorbent to a high value-added three-dimensional sulfate-functionalized MgAl-layered double oxide (3S-LDO). Thanks to the unique property of the sulfate group and LDO, 3S-LDO exhibited a superior (4340.71 mg/g) and ultrafast (<1 h) adsorption toward methyl orange (MO, as the representative of azo dye). A thermodynamic study revealed that the reaction process was spontaneous and exothermic. FT-IR, XPS, and XRD results confirmed that the sulfate from 3S-LDO played a vital role in MO removal wherein the S=O bond (with the electrophilic character) from SO42- interacted with the N=N double bond (with rich electron) in MO through the electron donor-acceptor mechanism. And the "memory effect" and surface complexation of 3S-LDO further strengthened the MO adsorption. More importantly, 3S-LDO could work efficiently in a wide pH range and even in the presence of competitive anions (e.g., Cl-, NO3-, and CO32-). Multiple cyclic runs and selective tests demonstrated the excellent reusability and explicit selectivity of 3S-LDO. This work not only provides a prospective sulfate-functionalized adsorbent from organic waste for rapid azo dye removal from wastewater but also achieves the high value-added utilization of organic waste.

Highlights

Excessive discharge of organic dyes has already caused severe risk to the ecological system and human health (Ji et al 2021)
NO. 39-1996) can be observed for the 3S-Layered double hydroxides (LDHs) sample. This affirmed that the as-prepared precursor was the organic MgAl LDH loaded with SDS, in good agreement with previous literatures (Li et al 2008; Zhang et al 2019b)
The corresponding removal efficiency was ~91%. These results suggested that the prepared 3S-layered double oxides (LDOs) exhibited good stability and reusability for the removal of methyl orange (MO)

Summary

Introduction

Excessive discharge of organic dyes has already caused severe risk to the ecological system and human health (Ji et al 2021). Over the past few decades, a vast of strategies, such as catalytic (Fu et al 2019), photocatalytic degradations (Riaz et al 2020), adsorption (Khaled et al 2020), membrane (Yang et al 2020), filtration (Mohtor et al 2017), have been conducted on the elimination of azo dye from wastewater. Challenges inherent to azo dye removal still include expensive cost, low-efficiency, poor regeneration, or membrane fouling, hindering their largescale applications. It is still an urgent requirement to develop a technique with preeminent ability, rapid kinetic, cost-efficiency, and outstanding reusability for azo dye wastewater treatment. Layered double hydroxides (LDHs), known as a class of 2:1 type anionic clay minerals, are gaining widespread attention in water purification due to their flexible layered crystal structure, ion-exchange ability, and “memory effect” (Chen et al 2021; Hu et al 2020; Li et al.2020). It is worth mentioning that the “memory effect” is primarily responsible for endowing

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Discussion

Conclusion