Novel synthesis of Ni/Fe layered double hydroxides using urea and glycerol and their enhanced adsorption behavior for Cr(VI) removal

Abstract

Novel modified Ni/Fe layered double hydroxides with different morphology of spherical-like shape were fabricated via using urea as a ligand and glycerol (Ni/Fe LDH/GL) with Ni:Fe molar ratios of 2:1 by the simplest co-precipitation method. Also, for comparison purposes, Ni/Fe LDH was synthesized to be used as a control one. A suggested interpretation for the morphology change was also given. The materials were characterized by X-ray diffraction (XRD), The Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), EDX for elemental analysis, high resolution transmission electron microscopy (HRTEM), Brunauer, Emmett, and Teller (BET) equation, particle size distributions and Zeta potential measurements. In addition, the synthesized materials were used as adsorbents for removal of potassium dichromate from aqueous solutions under various experimental conditions. The adsorption of Cr (VI) was strongly pH dependant and the pH PZC was studied. Kinetic studies were evaluated through different models including, pseudo first and second orders, mixed 1, 2 orders, intra particle diffusion and Avrami models. For adsorption isotherms, twoparameter models (Langmuir, Freundlich and Temkin) and three parameter models (Sips, Langmuir-Freundlich and Tooth) were investigated showing maximum adsorption capacity of 50.43 mg/g and 136.05 mg/g for Ni/Fe LDH and Ni/Fe LDH/GL, respectively. Also, the effect of temperature was investigated at (23, 35, 45, 55 °C) and the thermodynamic parameters (∆H°, ∆S° and ∆G°) were calculated showing exothermic and spontaneous adsorption process. The effect of coexisting anions (cl − , So 4 2− and HPO 4 2−) and humic acid at different concentrations on the removal efficiency of dichromate ions was investigated. Chemical stability and recyclability of these adsorbents were also studied. The intermolecular hydrogen bonds formation between dichromate ion, urea, glycerol, LDH was explored by Monte Carlo simulation This study suggested that the modified Ni/Fe LDH/GL materials were promising nanoadsorbents for efficient potassium dichromate removal. Water is the most precious natural source important for human beings, agriculture, and industrial activities. Recently, water bodies are potentially contaminated and polluted by many hazardous materials such as nuclear and industrial wastes, pharmaceuticals, organic contaminants and heavy metals. Heavy metals like cadmium, zinc, copper, lead, arsenic, mercury and chromium have significant threat to human health due to its potentially toxic effects 1,2. Chromium is one of heavy metals widely used in many industrial processes such as electroplating, dyes, mining, photography, textile and leather 3. Chromium present in water in a trivalent and hexavalent oxidation state, it is established that hexavalent chromium exhibits high toxicity toward living organisms than trivalent chromium which in contrast is a micronutrient 4. Hexavalent chromium is reported as a cause of respiratory cancers 5,6 and mutations and chromosomal dam...

Selective nitrate removal from aqueous solutions by a hydrotalcite-like absorbent FeMgMn-LDH

“…S2 (Support information). As for the FeMgMn-LDH, the spectrum shows a broad at around 3400 cm -1 is assigned to -OH stretching vibration of the interlayer water or structural -OH groups 31 . The band at around 1620 cm −1 is in accord with -OH bending vibration of water molecules.…”

Sustainable waste management and recycling of Zn–Al layered double hydroxide after adsorption of levofloxacin as a safe anti-inflammatory nanomaterial

“…54 Through FTIR investigations, some levo bands were observed in the Zn-Al LDH/levo nanocomposite spectrum, which conrmed the successful loading of levo onto the Zn-Al LDH surface, as observed in the appearance of peaks at 2037, 1497 and 1087-1036 cm À1 , which are related to C-O-C, C-O and C-F, respectively. 28,47,50,[54][55][56][57][58] Besides this, some peaks were shied to a lower wavenumber, as shown in Table 2. 3.1.3.…”

“…The spectrum of Zn-Al LDH shows an intense broad band at 3460.67 cm À1 , which might be due to the O-H stretching vibrations of the physically adsorbed water molecules and the hydrogen bonding of the -OH interlayer groups. A bending vibration appeared at 1630 cm À1 , 34,50 and peaks at 723.14, 614 and 416 cm À1 can be ascribed to the stretching vibrations of M-O and M-O-H. 51 Moreover, an intense peak was observed at 1355.96 cm À1 , which might be due to the symmetric and asymmetric stretching vibrations of the carbonate group (CO 3 ) 2À that may be formed during the sample preparation. Fig.…”

“…desorption according to Le Chatelier's principle. 50 Therefore, the physisorption decreases with an increase in temperature. Also, it may be related to the weakness of the attraction forces and the hydrogen bonding between the pollutant and the synthesized LDH.…”

Development of Mesopore Structure of Mixed Metal Oxide through Albumin-Templated Coprecipitation and Reconstruction of Layered Double Hydroxide

“…Both hysteresis types are often reported in LDHs and LDOs, which were especially designed to have high specific surface area and controlled pore [ 61 , 62 ]. Hysteresis types H4 and H2 indicate slit-like pore and ink-bottle pore, respectively [ 63 , 64 , 65 ]. AH-1 and AO-1, in which we expect strong aggregation of albumin, did not show certain types of hysteresis due to the following reason.…”