Single-Step Topochemical Synthesis of NiFe Layered Double Hydroxides for Superior Anion Removal from Aquatic Systems

Abstract

Layered double hydroxides (LDHs) have attracted significant attention as adsorbents for the removal of anions from wastewater. However, it is challenging to develop a simple, economical, and environmentally friendly method for fabricating efficient LDH adsorbents. In this paper, we present an alternative approach for preparing a superb NiFe LDH adsorbent via a single-step topochemical synthesis method based on density functional theory (DFT) calculation. The NiFe LDH adsorbent [Ni0.75Fe0.25(OH)2]·(CO3)0.125·0.25H2O was obtained via the topotactic transformation of an oxide precursor (NaNi0.75Fe0.25O2), which was prepared by utilizing the high-temperature flux method, in ultrapure water. When the oxide precursor was soaked in ultrapure water, the host layer valence state changed from Ni3+ and Fe3+ to Ni2+ and Fe3+, and carbonate (CO3 2–) ions were simultaneously intercalated in the interlayer. Thereafter, the CO3 2– ions were deintercalated by Cl– ions to increase the adsorption capacity. The adsorbent exhibited high crystallinity, cation state, and porosity, and unique particle shape. In addition, it showed superior adsorption capacities of approximately 194.92, 176.15, and 146.28 mg g–1 toward phosphate, fluoride, and nitrate ions, respectively. The adsorption capacity toward all the anions reached over 70% within 10 min. The adsorption behavior was investigated by performing from adsorption kinetics, isotherm, and thermodynamics studies. The results showed that the anions were endothermically and spontaneously chemisorbed through an ion exchange process onto the adsorbent in a monolayer. In addition, the as-prepared NiFe LDH adsorbent showed high stability after multicycle testing.

Charge Distribution Controls On‐Target Separation of Low Nucleophilicity Anions in Layered Double Hydroxides

“…Synthesis: All pristine NaNi 1−x Co x O 2 (NCO) compounds with x = 0.25-0.76 were synthesized following the self-flux method, as specified in a previous report. 30,31 Reagent-grade NiO, Co 3 O 4 , and NaNO 3 powders (Wako Pure Chemical Industries, Ltd.) were used as precursors. Reagent-grade NaClO and KOH (Wako Pure Chemical Industries, Ltd.) were used to oxidatively hydrolyze NCO.…”

“…Based on the topochemical route previously reported by us, [30,31] pristine NCOs with x = 0.25-0.76 were prepared by the hightemperature reaction method, and subsequently subjected to redox treatment processes to obtain the corresponding LDHs. Hereafter, NCO and NCL with x = 0.XX are referred to as NCO-XX and NCL-XX, respectively.…”

“…We previously reported that the topochemical synthesis of LDHs from layered transition-metal oxides NaMO 2 [30,31] is a promising strategy that can be used to improve the crystallinity of poorly crystalline LDHs obtained by the co-precipitation method. This reaction eliminates the necessity to employ the complicated precipitation process used to obtain LDHs.…”

One-step solvent-free synthesis of carbon dot-based layered composites exhibiting color-tunable photoluminescence

“…Layered inorganic compounds are anisotropic host materials that can incorporate organic molecules and metal ions inside their interlayer spaces. [19][20][21][22][23][24][25][26][27][28][29][30][31][32] A variety of chemical reactions utilizing the surface and nanospace of layered compounds have also been studied. [33][34][35][36][37][38][39] Among these layered compounds, clay minerals have been widely used as components for the development of functional materials because they are abundant, lowcost, biocompatible, and environmentally friendly.…”

Preparation of hydrogel based on poplar cellulose and its removal of Cd(II) from aqueous solution

“…The common chemical treatment methods include neutralization, physicochemical coagulation, physicochemical deposition and oxide reduction. The adsorption method is superior to other technologies in terms of initial cost, exibility, design di culty, operation method and toxicity [9][10][11][12][13][14].…”