Physicochemical studies toward the removal of Zn(ii) and Pb(ii) ions through adsorption on montmorillonite-supported zero-valent iron nanoparticles

Abstract

This study reports the adsorption of Zn(II) and Pb(II) on montmorillonite-supported zero-valent iron nanoparticles (nZVI-Mont). The kinetics of Zn(II) and Pb(II) adsorption were evaluated for various contact times. The adsorption of Zn(II) and Pb(II) at different initial concentrations was examined by injecting 0.5 g of adsorbents to achieve equilibrium. The adsorption of Zn(II) and Pb(II) was an exothermic process.The pseudo-second-order kinetic model fits well with the adsorption of Zn(II) and Pb(II) (r 2 > 0.99 at all temperatures tested). The Zn(II) adsorption process was a simultaneously physical and chemical process, fitting the Freundlich (r 2 ¼ 0.981), Temkin (r 2 ¼ 0.983) and the D-R isotherm models (r 2 ¼ 0.988) well.However, the Pb(II) adsorption only fits the Freundlich isotherm model. The activation energies of the Zn(II) adsorption onto nZVI-Mont were in a range from 11.71 kJ mol À1 to 46.37 kJ mol À1 and the activation energies of the Pb(II) adsorption onto nZVI-Mont were in a range from 0.26 kJ mol À1 to 17.67 kJ mol À1 . The negative values for the Gibbs free energy (DG o ) and enthalpy of adsorption (DH o ) revealed that the adsorption process was spontaneous and exothermic, respectively. In addition, the adsorption mechanisms for Zn(II) and Pb(II) are significantly different.

Enhanced removal of hexavalent chromium from aqueous media using a highly stable and magnetically separable rosin-biochar-coated TiO2@C nanocomposite

“…The adsorbent was magnetically separated and the supernatant was collected by using a high density polyethylene syringe and ltered by 0.22 mm disposable syringe lters and then analyzed by ICP-MS. A test experiment was conducted by analyzing the supernatant before and aer ltration to conrm that there was no sorption loss during ltration. The adsorption capacity and adsorption efficiency were determined by the difference method 11,34,48 using the following formulae:…”

“…† Both these pseudo-rst-order and pseudo-second-order kinetics models were employed to determine the kinetics mechanism and adsorption capacity (q e ) of Cr(VI) on the surface of the RBC-TiO 2 @C nanocomposites at equilibrium. 48,49 In addition, the modeling of experimental adsorption isotherm data was performed using four adsorption isotherm models [Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R)] to provide in depth information about the adsorption behavior of the RBC-TiO 2 @C nanocomposites. Detailed information of the kinetics and equilibrium models (ESI †) and their equations (general or non- linear form and linear form), x and y values, and their slopes and intercepts are presented in Table S1.…”

Bentonite-supported nanoscale zero-valent iron granulated electrodes for industrial wastewater remediation

“…13,14 Unfortunately, nZVI granules are inclined to aggregate and oxidate, thus decreased their performance in application. Therefore, various immobilization strategies have been developed to solve this problem, such as chitosan-stabilized nZVI, 15 montmorillonite-supported nZVI, 16 and carboxymethyl cellulose (CMC) stabilized nZVI. 17 Bentonite is one of the abundant and low-cost clay minerals that possesses high adsorption, conductivity and stability.…”

Photocatalytic Degradation of Methyl Orange by Fe2O3−Fe3O4 Nanoparticles and Fe2O3−Fe3O4−Montmorillonite Nanocomposites

“…The electrons produced in Eqs. (1) and (2) were annihilated through the two transfer processes in Eqs. (5) or (6) and were directly obtained by H 2 O 2 or trapped by Fe 3þ on the surface of the photocatalyst.…”