Kinetic and Thermodynamic Characteristics of Fluoride Ions Adsorption from Solution onto the Aluminum Oxide Nanolayer of a Bacterial Cellulose-Based Composite Material

Abstract

The described research examined the adsorption of fluoride ions from solution immobilized onto an aluminum oxide-coated bacterial cellulose-based composite material in which aluminum oxide had been deposited using ALD technology. The kinetic regularities of the adsorption of fluoride ions from the solution as well as the mechanism of the processes were analyzed. The established equations show that the dynamics of adsorption correspond to first-order kinetics. Based on the Langmuir adsorption isotherms, we defined the adsorption equilibrium constants, parameter maximum adsorption, and change in Gibbs free energy. It is shown that, with increasing temperature, an increase in the reaction rate is constant, both forward and reverse. This testifies to the activated character of adsorption of the first fluoride on the surface of the sorbent based on bacterial cellulose modified with an alumina nanolayer. The activation energy of the desorption process is higher than the activation energy of the adsorption process, which characterizes the adsorption as ionic. The negative value of entropy indicates that in the course of sorption, an adsorption complex “aluminum-fluorine” is formed, where the system is more ordered than the initial system in which fluorine ions are in solution. The limiting stages of the process are revealed. The high sorption capacity of the resulting bacterial cellulose-based composite material obtained by means of biosynthesis through cultivation of the bacterium Komagataeibacter sucrofermentans B-11267 was demonstrated.

Pilot-Scale Field Demonstration of Environmental Nanotechnology for Groundwater Defluoridation

“…However, AA is unstable under acidic or alkaline conditions, and thereby aluminum-containing salts like Al 2 (SO 4 ) 3 and NaAlO 2 rather than alkali are often used to regenerate the exhausted adsorbents . Also, the wide application of AA is hindered by the possible leaching of Al 3+ and the tendency to harden during long-term runs. , With respect to HAP, the adsorption toward fluoride is mainly associated with the exchange between the interlaminar hydroxide ions, yet the leaching of phosphorus and difficulty in complete regeneration of the exhausted adsorbent still retard its application in full-scale water treatment. , …”

“…18 Also, the wide application of AA is hindered by the possible leaching of Al 3+ and the tendency to harden during long-term runs. 18,19 With respect to HAP, the adsorption toward fluoride is mainly associated with the exchange between the interlaminar hydroxide ions, yet the leaching of phosphorus and difficulty in complete regeneration of the exhausted adsorbent still retard its application in fullscale water treatment. 20,21 In the past few decades, the rapid development of nanotechnology has offered a new chance for process innovation in water treatment.…”