Recovery of palladium by silica/polymer-based 2,6-bis(5,6,7,8-tetrahydro-5,8,9,9-tetramethyl-5,8-methano-1,2,4-benzotriazin-3-yl)pyridine adsorbents from high level liquid waste

Figures & data

Figure 1. Chemical structure of R-BTP and Me₂-CA-BTP (a) and SEM image of Me₂-CA-BTP/SiO₂-P (b).

Figure 2. Effect of initial nitric acid concentration on Me₂-CA-BTP/SiO₂-P adsorption abilities towards Pd(II) (adsorbent: 0.1 g, solution: 5 cm³, metal: 20 mmol/dm³, temperature: 298 K, contact time: 24 h, shaking speed: 120 rpm).

Figure 3. Adsorption kinetics and pseudo-first-order and pseudo-second-order models of Pd(II) on Me₂-CA-BTP/SiO₂-P in 3.0 mol/dm³ HNO₃ solution (adsorbent: 0.1 g, solution: 5 cm³, [Pd]: 20 mmol/dm³, temperature: 298 K, shaking speed: 120 rpm).

Table 1. Fitted parameters of pseudo-first-order model and pseudo-second-order model for Pd(II) adsorption.

Pseudo-first-order model			Pseudo-second-order
k1 (h^−1)	Qe (mmol/g)	R^2	k2 (g/(mmol h))	Qe (mmol/g)	R^2	Experimental Qe (mmol/g)
0.74	0.72	0.89	1.38	0.78	0.96	0.76

Figure 4. Adsorption isotherm of Pd(II) on Me₂-CA-BTP/SiO₂-P in 3.0 mol/dm³ HNO₃ solution (adsorbent: 0.1 g, solution: 5 cm³, contact time: 24 h, temperature: 298 K, shaking speed: 120 rpm).

Figure 5. Fitted isotherm curve based on the Langmuir model.

Table 2. Fitted parameters of Langmuir and Freundlich models for Pd (II) adsorption.

Langmuir model			Freundlich model
Qmax (mmol/g)	KL (dm/mmol)	R^2	n	KF (mmol/g)	R^2
0.80	4.31	0.99	3.64	0.62	0.66

Figure 6. Effect of TU concentration on desorption of Pd(II) from Me₂-CA-BTP/SiO₂-P adsorbent (adsorption conditions: adsorbent: 0.1 g, solution: 5 cm³, [Pd]: 20 mmol/dm³, nitric acid: 3.0 mol/dm³ HNO₃, temperature: 298 K, contact time: 24 h, shaking speed: 120 rpm; desorption conditions: adsorbent: 0.1 g, solution: 5 cm³, temperature: 298 K, contact time: 24 h, shaking speed: 120 rpm).

Figure 7. Distribution ratios of typical HLLW elements at different concentrations of HNO₃ (adsorption conditions: adsorbent: 0.1 g, solution: 5 cm³, ²⁴¹Am(III): 800 Bq/L, metal: 1 mmol/dm³, temperature: 298 K, contact time: 24 h, shaking speed: 120 rpm).

Table 3. Separation factor (SF) between Pd(II) and some typical FP ions.

HNO3 (mol/dm^3)	SFPd/Cs	SFPd/Y	SFPd/Zr	SFPd/Ru	SFPd/Eu	SFPd/Gd	SFPd/Ce
0.5	>10^3	16	2	0.3	1	1	>10^3
1	>10^3	7	3	0.4	0.5	0.4	>10^3
2	>10^3	26	9	14	3	2	>10^3
3	>10^3	>10^3	19	18	212	46	>10^3
4	>10^3	>10^3	41	32	>10^3	>10^3	>10^3

Figure 8. Effect of contact time with nitric acid solution on the adsorption of Pd(II) onto Me₂-CA-BTP/SiO₂-P. (adsorption conditions: adsorbent: 0.1 g, solution: 5 cm³, [Pd]: 20 mmol/dm³, temperature: 298 K, contact time: 24 h, shaking speed: 120 rpm).

Figure 9. Effect of absorbed dose on Me2-CA-BTP/SiO2-P(dry state) adsorption towards Pd(II) (adsorption conditions: adsorbent: 0.1 g, solution: 5 cm³, [Pd]: 20 mmol/dm³, nitric acid: 3.0 mol/dm³ HNO₃, temperature: 298 K, contact time: 24 h, shaking speed: 120 rpm).

Figure 10. Effect of absorbed dose on Me₂-CA-BTP/SiO₂-P (in nitric acid) adsorption towards Pd(II) (adsorption conditions: adsorbent: 0.1 g, solution: 5 cm³, [Pd]: 20 mmol/dm³, temperature: 298 K, contact time: 24 h, shaking speed: 120 rpm).