Aqueous phosphorous adsorption onto SnO₂ and WO₃ nanoparticles in batch mode: kinetic, isotherm and thermodynamic study

Figures & data

Figure 1. Powder X-ray diffraction of SnO2 (a) and WO3 (b) nano adsorbent.

Figure 2. Energy Dispersive X-Ray (EDX) spectrum of SnO2 (a) and WO3 (b) nano adsorbent.

Figure 3. FTIR spectrum of SnO2 (a) and WO3 (b) nano adsorbent.

Figure 4. SEM image of SnO2 (a) and WO3 (b) nano adsorbent.

Figure 5. Effect of initial pH on phosphate removal (initial concentration of phosphate, 50 mg L⁻¹;absorbent dosage, 0.025 g L⁻¹; contact time, 24 h; Temperature, 25 °C).

Figure 6. Effect of adsorbent dosage on phosphate removal (initial concentration of phosphate, 50 mg L⁻1; contact time, 24 h; Temperature, 25 °C).

Figure 7. Effect of contact time on phosphate removal (initial concentration of phosphate, 50 mg L⁻¹; absorbent dosage, 1g L⁻¹; Temperature, 25 °C).

Table 1. Kinetic parameters for the adsorption of phosphate onto nano adsorbent.

	kinetic models
	pseudo-first-order			pseudo-second-order
Nano adsorbent	R^2	qe (mg g^-1)	K1 (min^−1)	R^2	qe (mg g^−1)	K2 (g mg^−1 min)
WO3 nanoparticle	0.43	13.1	−0.02	0.99	15.3	−0.009
SnO2 nanoparticle	0.43	13.0	−0.02	0.99	15.9	−0.009

Table 2. Maximum adsorption capacities of phosphorus onto various adsorbents.

Adsorbents	Capacity (PO4^3−-P) (mg/g )	Reference
Silver nanoparticles-loaded activated	4.5	[75]
Zr/Al-pillared montmorillonite	5.7	[76]
Nanocrystalline akaganeite	19.9	[77]
Hydroxy-aluminum pillared bentonite	12.7	[78]
Iron oxide nanoparticles	5.9	[79]
Bayoxide	8.7	[80]
Hydrated ferric oxide nanoparticles	12.9	[81]
Magnetite-enriched particles (MEP)	6.4	[82]
Magnetite based nanoparticles	5.2	[83]
Sewage sludge-based biochar	4.8	[84]
Powder activated carbon	1.36	[84]
ZSFB-Composite fiber	4.18	[85]
Hollow magnetic	11.95	[86]
NaCl- zeolite	6.67	[87]
Bismuth impregnated biochar	1.48	[88]
WO3 nano particle	19.0	This study
SnO2 nano particle	21.5	This study

Figure 8. Freundlich isotherm model of phosphate adsorption (pH, 3; adsorbent dosage, 1 g L⁻¹; contact time, 40 min; Temperature, 15 °C).

Table 3. Freundlich isotherm constants for the adsorption of phosphate onto nano adsorbent.

Nano adsorbent	R^2	1/n	Kf (mg g^−1)
WO3 nanoparticle	0.95	0.73	1.35
SnO2 nanoparticle	0.91	0.75	1.55

Figure 9. SEM image after adsorption isotherm of SnO2 (a) and WO3 (b) nano adsorbent (initial concentration of phosphate, 60 mg L⁻¹).

Figure 10. Energy Dispersive X-Ray (EDX) spectrum after adsorption isotherm of SnO2 (a) and WO3 (b) nano adsorbent (initial concentration of phosphate, 60 mg L⁻¹).

Figure 11. Desorption of phosphate from nano adsorbent using CaCl2 0.01 M.

Figure 12. Effect of coexisting anions on phosphate adsorption by SnO2 nano adsorbent.

Figure 13. Effect of coexisting anions on phosphate adsorption by WO3 nano adsorbent.

Figure 14. SEM image of SnO2 (a) and WO3 (b) nano adsorbent with coexisting of Cl⁻ anion.

Figure 15. SEM image of SnO2 (a) and WO3 (b) nano adsorbent with coexisting Cl⁻, Cr₂O₇^– and NO₃⁻ anions.

Figure 16. EDX spectrum of SnO2 (a) and WO3 (b) nano adsorbent with coexisting of Cl⁻ anion.

Figure 17. EDX spectrum of SnO2 (a) and WO3 (b) nano adsorbent with coexisting Cl⁻, Cr2O7⁻ and NO₃- anions.

Figure 18. Effect of temperature on phosphorus removal (initial concentration of phosphate, 50 mg L⁻¹₁; absorbent dosage, 1g L⁻¹; pH, 3; time, 40 min).

Table 4. Thermodynamic parameters for adsorption of phosphate onto nano adsorbent.

Nano adsorbent	Temperature (°C)	Ln Kd	ΔG (KJ mol^−1)	ΔH (KJ mol^−1)	ΔS (J mol^−1 K^−1)
SnO2 nanoparticle	15	+6.7	−16.2
	20	+6.6	−16.1
	25	+6.4	−15.8	−45.5	+100.5
	30	+6.1	−15.3
	35	+5.6	−14.3
	40	+5.3	−13.9
WO3 nanoparticle	15	+6.9	−16.6
	20	+7.0	−17.1
	25	+7.0	−17.6	+11.1	−96.2
	30	+7.2	−18.2
	35	+7.3	−18.7
	40	+7.2	−18.9

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