Synthesis of Mg/Al Layered Double Hydroxides for Adsorptive Removal of Fluoride from Water: A Mechanistic and Kinetic Study

Abstract

Herein, we report the synthesis of Mg/Al-CO 3 layered double hydroxides (LDHs) by the urea hydrolysis method under hydrothermal conditions at different aging times. The LDHs were characterized by different microscopic, spectroscopic, diffractometric, and thermal analysis techniques. The as-prepared LDHs were then used as adsorbents for the removal of fluoride ions from water. The adsorption process was systematically studied in terms of influences of pH, interaction time, temperature, adsorbent loading, fluoride ion concentration, and the effect of coexisting anions to understand the ideal conditions for adsorption. The adsorption process primarily followed pseudo-secondorder kinetics. The Langmuir monolayer adsorption capacities of different adsorbents are in the range of 15.13−27.03 mg g −1 at 303 K. The hydrothermal aging time has a negative impact on the adsorption capacities of the LDHs. The as-prepared LDHs are reusable up to five cycles of the fluoride ion adsorption−desorption process.

A switchable sensor and scavenger: detection and removal of fluorinated chemical species by a luminescent metal–organic framework

“…An uptake capacity of 36.7 mg g −1 (original concentration 100 ppb, remaining concentration 1.2 ppb) was achieved for this scavenger, a value that is higher than those of most of the F − removal materials, such as graphene, mesoporous alumina, and hydrous ferric oxide. 50 …”

Synthesis and Characterization of Magnetic Superadsorbent Fe3O4-PEG-Mg-Al-LDH Nanocomposites for Ultrahigh Removal of Organic Dyes

“…It was close to 1.64% at a temperature range of 25 to 150 °C. The second huge weight loss is due to the dehydroxylation, interlayer water molecules, and disappearance of intercalated ions and, furthermore, the LDH-layered structure collapse by 42.38% at the temperature range of 250 to 615 °C. , …”

“…The second huge weight loss is due to the dehydroxylation, interlayer water molecules, and disappearance of intercalated ions and, furthermore, the LDH-layered structure collapse by 42.38% at the temperature range of 250 to 615 °C. 34,35 The TGA curves of 6FPL magnetic layered nanocomposites resulted in two stages of weight loss from room temperature to 800 °C. The first weight loss of 13.5% in the variation from 175 to 335 °C is associated with the removal of water molecules, decomposition of PEG, and the dehydroxylation of the interlayer water molecules and the fact of intercalated ions.…”

Adsorption Analysis of Fluoride Removal Using Graphene Oxide/Eggshell Adsorbent

“…According to pseudo-second-order theory, the adsorption of fluoride onto GO/ES adsorbent is a chemisorption process which involves sharing or exchange of electrons between the adsorbent and F - [13]. There is a possibility that Fmay diffuse across a liquid phase prior to GO/ES's active sites through intraparticle diffusion and indirectly reacts with available active sites, such Ca 2+ to produce CaF [17][18][19][20].…”