Abstract
Hierarchical hollow Mg-Al layered double hydroxide microspheres (HHMs) are successfully prepared by hydrothermal treatment in the presence of carbon dots (CDs). Morphology and structure of the as-prepared samples are characterized using XRD, SEM, FT-IR, and TEM techniques. The growth process of HHMs has been investigated in detail, and Ostwald ripening mechanism is suggested for the hierarchical growth of HHMs. Adsorption isotherms and adsorption kinetics of HHMs for congo red (CR) are investigated. Langmuir and Temkin model are more fitted to the experimental data of CR isotherm adsorption. Adsorption kinetic data obeys the pseudo-second-order kinetic model. Moreover, thermodynamic parameters (ΔGo, ΔHo and ΔSo) show that the CR adsorption onto HHMs is an endothermic and spontaneous process. The as-prepared HHMs could be a potential adsorbent for wastewater treatment containing anion dyes.
Highlights
Dyes with high stability have been widely used in many industries
With the increasing volume of Carbon dots (CDs) solution (3mL), 2d nanosheets begin to randomly aggregate into micro-scaled cluster with irregular shape (Figure 1b)
The experimental data of Congo red (CR) adsorption can be well fitted by Langmuir and Temkin model, indicating that monolayer adsorption process occurs on the surface of Layered double hydroxides (LDHs) and binding energy uniformly distributed
Summary
Dyes with high stability have been widely used in many industries. Many dyes have detrimental influence on environmental safety and human health due to toxicity and teratogenic effect. It becomes an important issue for modern industrial society to remove dyes form wastewater. LDHs have high removal tendency for anionic dyes. Hollow LDH microspheres (HHMs) with hierarchical structure have been synthesized with the assistance of carbon dots derived from citric acid. The 2d nanosheets are self-assembled into threedimensional MgAl-LDH hollow micro/nano-structures with high anion-exchange capacity. The as-synthesized hollow hierarchical MgAl–LDH exhibits high adsorption performance for the removal of Congo red (CR) dye. Isotherm and thermodynamics of adsorption are investigated in detail
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