Tuned synthesis and characterizational insight into β-cyclodextrin amended hydrous iron-zirconium hybrid oxide: a promising scavenger of fluoride in aqueous solution

Abstract

Fluoride adsorption on CHIZO takes place with H-bonding inside the core, thus forming an encapsulated moiety.

Synthesis and characterisation of cerium(iv)-incorporated hydrous iron(iii) oxide as an adsorbent for fluoride removal from water

“…The mean free energy change is basically the change of free energy required to transform the adsorbate molecule from innity to the adsorbent surface. 40 The values of E DR were calculated from eqn (10) and are incorporated in Table 2.…”

“…It can be seen that the values of Q m decreased with increasing temperature, which supports the previous results obtained from equilibrium modelling. From the D-R equation and according to the value of E DR , an adsorption process may be one of three types: [38][39][40] (i) physisorption if E DR ¼ 8.0 kJ mol À1 , (ii) ion-exchange if E DR ¼ 8.0 to 16.0 kJ mol À1 and (iii) chemisorption if E DR > 16.0 kJ mol À1 . The gradual increase of the E DR value with increasing temperature from 12.61 to 20.32 kJ mol À1 indicates that the adsorption of uoride proceeds from ion-exchange to chemisorption.…”

“…Changes in thermodynamic parameters such as standard free energy (DG 0 ), standard enthalpy (DH 0 ) and standard entropy (DS 0 ) for this adsorption process were estimated using the following thermodynamic relations (eqn (11) and (12)), 40 assuming the activity coefficient to be unity at low solute concentrations.…”