Super adsorption capability of rhombic dodecahedral Ca-Al layered double oxides for Congo red removal

• Published in: Journal of alloys and compounds 2018-11, Vol.768, p.572-581
• Main Authors: Zhang, Heng, Chen, Hang, Azat, Seytkhan, Mansurov, Zulkhair A., Liu, Xueming, Wang, Jide, Su, Xintai, Wu, Ronglan
• Format: Article
• Language: English
• Subjects: Adsorption; Alloys; Ca-Al layered double oxides; Chemical bonds; Congo red; Energy dispersive X ray spectroscopy; Hydrogen bonding; Hydroxides; Infrared spectra; Ion exchange; Morphology; Quantum theory; Rhombic dodecahedral structure; Scanning electron microscopy; Solid phases; Thermodynamics; Transmission electron microscopy; Water treatment; X ray spectra; X-ray diffraction; Zinc oxides
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2018.07.241

In this work, a novel rhombic dodecahedral structure of Ca-Al-layered double hydroxides (Ca-Al-LDHs) was synthesized by a two-phase solvothermal method. Subsequently, Ca-Al layered double oxides (Ca-Al-LDOs) were obtained by calcinating Ca-Al-LDHs at 600 °C which maintained the rhombic dodecahedral structures well. The morphologies of as-obtained samples were characterized by both transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The phase structure and elemental composition were analyzed by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS), respectively. Fourier transformed infrared (FT-IR) spectra were performed to confirm the existence of LDH structures. The Ca-Al-LDOs exhibited high adsorption rates and superb adsorption capacities for removal of Congo red (CR) from aqueous solution. The maximum adsorption capacities of Ca-Al-LDOs towards CR reached to 1536.1 mg g−1, which is extremely higher than most of hydrotalcite-like materials. The adsorption process of Ca-Al-LDHs and Ca-Al-LDOs were described by the Langmuir isotherm model and pseudo-second-order model well. The adsorption mechanisms mainly dominated by electrostatic adsorption, ion exchange process, hydrogen bonding interactions and surface complexation. This general strategy afforded a wide possibility to prepare a novel and advanced LDOs adsorption material for water treatment. [Display omitted] •Ca-Al-LDHs were synthesized via a two-phase solvothermal method.•Ca-Al-LDHs and Ca-Al-LDOs with rhombic dodecahedral morphology.•The Ca-Al-LDOs has the maximum adsorption capacity of 1536.1 mg g−1.