Ce(III) and La(III) ions adsorption using Amberlite XAD-7 resin impregnated with DEHPA extractant: response surface methodology, isotherm and kinetic study

Abstract

In this paper, the removal efficiency of Cerium (Ce(ΙΙΙ)) and lanthanum (La(ΙΙΙ)) ions from aqueous solution using Amberlite XAD-7 resin impregnated with DEHPA(XAD7-DEHPA) was studied in the batch system. The adsorbent ( XAD7-DEHPA) was characterized by SEM-EDX, FTIR and BET analysis Techniques. The response surface methodology based on the central composite design was applied to model and optimize the removal process and evaluate operating parameters like adsorbent dose (0.05-0.065), initial pH (2-6) and temperature (15-55). Variance analysis showed that the adsorbent dose, pH and temperature were the most effective parameters in the adsorption of Ce(ΙIΙ)and La(IΙI) respectively. The results showed that the optimum adsorption condition was achieved at pH = 6, the optimum amount of absorbent and the equilibrium time equal to 0.6 gr and 180 min, respectively. According to the results, the adsorption percentage of Ce(ΙIΙ) and La(ΙΙΙ) ions onto the aforementioned resin were 99.99% and 78.76% respectively. Langmuir, Freundlich, Temkin and sips isotherm models were applied to describe the equilibrium data. From the results, Langmuir isotherm (R² (Ce) = 0.999, R² (La) = 0.998) was found to better correlate the experimental rate data. The maximum adsorption capacity of the adsorbent ( XAD7-DEHPA) for both Ce(IΙI) and La(III) was found to be 8.28 and 5.52 mg g^-1 respectively. The kinetic data were fitted to pseudo-first-order, pseudo-second-order and Intra particle diffusion models. Based on the results, the pseudo-first-order model and Intra particle diffusion model described the experimental data as well. In general, the results showed that ( XAD7-DEHPA) resin is an effective adsorbent for the removal of Ce(IΙI) and La(III) ions from aqueous solutions due to its high ability to selectively remove these metals as well as its reusability.

Figure 1

The schematic of the impregnation process of Amberlite XAD-7 resin with a solvent.

Figure 2

FTIR spectra of the Amberlite XAD-7.

Figure 3

FTIR spectra of the Amberlite XAD-7 resin impregnated with DEHPA (XAD-DEHPA).

Figure 4

FTIR spectra of the Amberlite XAD-7 resin impregnated with DEHPA (XAD-DEHPA) after adsorption of Ce(III) and La(III).

Figure 5

SEM image of Amberlite XAD-7 resin surface washed with distilled water.

Figure 6

SEM image of Amberlite XAD-7 resin surface after impregnation with DEHP.

Figure 7

SEM micrographs of the XAD-7-DEHPA after adsorption Ce(IΙI) and La(IΙI).

Figure 8

(a–e) Elemental mapping of O, C, P, Ce(ΙIΙ) and La(IΙI) elements in the XAD7-DEHPA after adsorption of Ce(ΙIΙ) and La(IΙI).

Figure 9

EDX spectrum of XAD7–DEHPA after adsorption of Ce(ΙIΙ) and La(IΙI).

Figure 10

Plots of correlation between actual and predicted values for the percentage of adsorption of Ce(III) and La(ΙIΙ) ions using XAD7-DEHPA.

Figure 11

3D response surface plots for the interactive effect of Dosage of resin (g) and pH on the percentage adsorption of (a) Ce(III) and (b) La(III) by XAD7–DEHPA (initial metal ions concentration 200 mg L^–1, temperature = 35 °C and time 180 min).

Figure 12

3D response surface plots for the interactive effect of Dosage of resin (g) and temperature (°C) on the percentage adsorption of Ce(III) and La(III) by XAD7–DEHPA (initial metal ions concentration 200 mg L^–1, pH = 4 and time 180 min).

Figure 13

3D response surface plots for the interactive effect of pH and temperature (°C) on the percentage adsorption of Ce(III) and La(III) by XAD7–DEHPA (initial metal ions concentration 200 mg L^–1, dosage of resin = 0.35 g and time 180 min).

Figure 14

Molecular structure of DEHPA extractant.

Figure 15

Adsorption–desorption efficiency of XAD7–DEHPA resin in 3 consecutive cycles using HCL 0.1 mol L⁻¹.

Figure 16

Adsorption–desorption efficiency of XAD7–DEHPA resin in 3 consecutive cycles using HCl 2 mol L⁻¹.