Diethyl ether-modified calix[4]pyrrole receptor: thermodynamics of lead cation complexation – lead extraction from water by its polymer

Figures & data

Table 1.  Elemental analysis data of meso-tetramethyltetrakis-[4 hydroxyphenyl] calix[4]-pyrrole (1) and meso-tetramethyltetrakis-[4-(2 ethoxy)ethoxyphenyl]calix[4]pyrrole (2).

		Analysis (%) found (calculated)
Comp. no.	Compound molecular formula	Carbon (C)	Hydrogen (H)	Nitrogen (N)
1	C48H44O4N4	77.60 (77.81)	5.94 (5.99)	7.15 (7.56)
2	C64H76O8N4	74.59 (74.68)	7.31 (7.44)	5.39 (5.44)

Table 2.  Fundamental IR spectral data of calix[4]pyrrole compounds (1, 2, 3 and 4).

		Selected IR peaks (KBr, cm^−1)
Comp.no.	Compound molecular formula	Stretch	Bend
1	C48H44O4N4	3400	1508.2	3251.8	2979.8	1178.4	–
2	C64H76O8N4	3420	1502.6	–	2920.0	1188.3	1120
3	(C48H44O4N4)n	3400	1508.2	3230.1	2920.0	1178.4	–
4	(C64H76O8N4)n	3400	1508.2		2979.8	1175.6	1100

Figure 1. TGA-DSC of meso-tetramethyltetrakis-[4-hydroxyphenyl]calix[4]-pyrrole (1).

Figure 2. TGA/differential thermogravimetry-DTA of meso-tetramenthyltetrakis-[4-(2-ethoxy)ethoxyphenyl] calix[4]pyrrole polymer (4).

Table 3.  Thermal analysis data, TG, DSC/DTA for the compounds (1, 3 and 4).

T (°C)	% Mass loss	Enthalpy change Δ H (J g^−1) (process)
meso-tetramethyltetrakis-[4-hydroxyphenyl]calix[4]-pyrrole (1)
83.31	9.73	141.70 (Endo)
130.58	5.89	6.75 (Endo)
181.52	9.41	54.06 (Endo)
292.34	46.25	205.37 (Endo)
485.38	15.49	182.08 (Endo)
meso-tetramenthyltetrakis-[4-hydroxyphenyl]-calix[4]pyrrole polymer (3)
59.73	9.47	82.43 (Endo)
100–700	70.00	–
472.61	–	1168.98 (Endo)
meso-tetramethyltetrakis-[4-(2-ethoxy)ethoxyphenyl]calix[4]pyrrole polymer (4)
51.48	6.03	257.79 (Endo)
385.00	43.79	–

Figure 3. Absorbance data (at 240 nm) versus mole ratio (Pb(II)/(2)) in acetonitrile at 298 K.

Figure 4. Absorbance data (at 240 nm) versus mole ratio (Cd(II)/(2)) in acetonitrile at 298 K.

Figure 5. Absorbance data (at 240 nm) versus mole ratio (Hg(II)/(2)) in acetonitrile at 298 K.

Table 4.  Values of K_f for complexation of Pb²⁺ with (2) obtained at different temperatures in acetonitrile.

T(K)		ln Kf
298	8.13	9.00±0.03
303	6.21	8.73±0.12
313	5.45	8.60±0.05
318	4.49	8.41±0.06

Table 5.  Thermodynamic parameters for complexation of Pb²⁺ with (2) in acetonitrile.

T(K)	−Δ H (kJ mol^−1)	−Δ G (kJ mol^−1)	−Δ S (J mol^−1 K^−1)
298			1.68±0.11
308			1.43±0.13
313			1.33±0.23
318			1.79±0.24

Figure 6. Plot of the variation in K_f for complexation of Pb²⁺ with (2) as a function of (1/T) in acetonitrile.

Figure 7. Optimum time for the uptake of lead (II) (200 ppm) by 4 from water.

Figure 8. Pseudo-first-order kinetics for lead (II) (200 ppm) uptake by 4 from water.

Figure 9. Pseudo-second-order kinetics for lead (II) (200 ppm) uptake by 4 from water.

Table 6.  Pseudo-first-order and second-order constants for lead (II) cation uptake at 298.15 K (cal.=calculated; exp.=experimental).

		Pseudo-first-order rate			Pseudo-second-order rate
Ci (mg L^−1)	Qe, exp. (mg g^−1)	k1 (1/min)	Qe, cal. (mg g^−1)	R^2	k2 (g min^−1 mg^−1)	Qe, cal. (mg g^−1)	R^2
200	47.00	0.017	24.43	0.97	0.001	50.00	0.99

Figure 10. Optimum temperature for the uptake of lead (II) (200 ppm) uptake by 4 from water.

Figure 11. Plot of ln K. vs. 1/T for the uptake of lead ion by 4.

Table 7.  Thermodynamic parameters for lead (II) cation uptake using 4 at different temperatures.

	Lead concentration (200 mg L^−1)
Temperature (K)	Keq	Δ H (kJ mol^−1)	Δ S (1) (J mol^−1)	Δ S (2) (J mol^−1)	Δ G (kJ mol^−1)
298	0.794	53.907	178.979	178.933	0.571
303	1.103	53.907	178.729	178.933	−0.247
308	1.652	53.907	179.197	178.933	−1.285
313	2.210	53.907	178.822	178.933	−2.064

Note: Δ S (1) obtained from equation (2) and Δ S (2) obtained from the intercept of equation (3).

Figure 12. Freundlich isotherm plot for the uptake of lead (II) by 4 at 298.15 K.

Table 8.  Langmuir, Freundlich and Temkin isotherm constants for the uptake of lead (II) cation at 298.15 K.

	Langmuir constants			Freundlich constants			Temkin constants
T (K)	Qm (mg g^−1)	b (L mg^−1)	R^2	Kf	n	R^2	KT (L mol^−1)	b (kJ mol^−1)	R^2
298.15	80.000	0.012	0.996	14.643	4.060	0.974	0.232	0.174	0.971

Figure 13. Langmuir isotherm plot for the uptake of lead (II) by 4 at 298.15 K.

Table 9.  R_L Langmuir values for the uptake of lead (II) cation at 298.15 K.

Concentration C0 (mg L^−1)	70	200	300	400	600	800
RL	0.412	0.197	0.140	0.109	0.076	0.058

Figure 14. Temkin isotherm plot for uptake of lead (II) by 4 at 298.15 K.

Table 10.  Calix[4]pyrrole uptake capacity of lead in comparison with other materials.

Materials	Capacity (mg g^−1)	Reference
Calix[4]pyrrole polymer (4)	80.00	Present work
Kaolinite	11.10	[38]
zeolite (clinoptilolite)	106.71	[39]
Local clay (bentonite)	90.34	[39]
P. granatum leaves	19.56	[40]
Algae	194.77	[40]
Fucus spiralis	204.10	[41]
Spirogyra insignis	51.50	[42]
Activated carbon	54.95	[43]

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