SYNTHESIS, CHARACTERIZATION, AND APPLICATION OF Ca-MOFs IN THE REMOVAL OF METHYLENE BLUE VIA ADSORPTION

Silva Junior, Olímpio J.; Moreira, Camilla. V. C.; Monteiro, Arthur. F. F.; Melo, Victor. E. R.; Oliveira, João. B. L.; Kulesza, Joanna E.; Barros, Bráulio S.

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Artigo • Quím. Nova 45 (05) • 2022 • https://doi.org/10.21577/0100-4042.20170852 copy

SYNTHESIS, CHARACTERIZATION, AND APPLICATION OF Ca-MOFs IN THE REMOVAL OF METHYLENE BLUE VIA ADSORPTION

Authorship SCIMAGO INSTITUTIONS RANKINGS

Metal-organic frameworks (MOFs) based on Calcium-terephthalate(Ca-MOFs) were synthesized by the sonochemical method and applied to remove methylene blue (MB) from an aqueous solution via adsorption. The samples were prepared and characterized by X-ray Powder Diffraction (PXRD), Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Thermal Analysis (TGA-DTA), and Scanning Electron Microscopy (SEM). The studied of the effect of the synthesis temperature on the crystallization of MOFs indicated two different crystal structures were identified, Ca(BDC) and Ca(BDC)(H2O)3. Observed that samples with a higher proportion of the Ca(BDC) phase showed greater dye adsorption capacity. The experimental data fit the pseudo-second-order kinetic model. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms, and the isotherm constants were also determined. The adsorption equilibrium data preferably fit the Freundlich model. The samples were applied to methylene blue adsorption at pH 5.6, with maximum adsorption of 60.241 μmol.g^-1 and high reuse efficiency, reaching 97% of the initial adsorption capacity in the second reuse cycle.

Keywords:
Ca-MOF; adsorption; methylene blue; coordination polymers

Amostra	Potência (%)	Tempo (min)	Tempo total (min)
CA1	40	30	50
CA2	80	14	24
CA3	60	30	50

Variáveis	-	0	+
Potência (%)	40	60	80
Tempo (min)	15	30	45

Amostra	Potência (%)	Tempo (min)	Massa obtida (g)
CA4 (1)	-	-	0,013
CA5 (2)	-	+	0,008
CA6 (3)	+	-	0,127
CA7 (4)	+	+	0,044
CA8 (5)	0	0	0,051

Modelo		293,0 K	303,0 K	313,0 K	323,0 K
Primeira ordem	Q_e (µmol g^-1)	30,072	24,301	15,319	18,078
	K₁	1,1398	0,9721	0,9838	0,9200
	R²	0,9434	0,9285	0,9818	0,9596
Segunda ordem	Q_e (µmol g^-1)	40,323	32,051	21,930	19,646
	K₂ (L^-1 h^-1 µmol)	0,062	0,075	0,113	0,023
	R²	0,9993	0,9991	0,9995	0,9939
	h (µmol L^-1 h^-1)	101,010	76,923	54,348	8,818
	t_1/2 (h)	0,399	0,417	0,404	2,228

C₀ (µmol L^-1)	133,7	267,4	401,1	534,8
Primeira ordem	0,9792	0,9434	0,9712	0,9832
Segunda ordem	0,9975	0,9993	0,9990	0,9994

Modelo		293,0 K	303,0 K	313,0 K
Langmuir	Q_m (µmol g^-1)	83,333	140,845	98,039
	K_L (L mol^-1)	3643,540	1000,169	1041,954
	R_L	0,8039	0,9443	0,9937
	R²	0,9527	0,7612	0,8904
Freundlich	Q_m (µmol g^-1)	54,717	47,487	34,944
	K_F (µmol g^-1)	1,503	0,297	0,212
	n	1,719	1,223	1,220
	R²	0,9981	0,9928	0,9956

Isotermas		Freundlich	Langmuir
R²		0,9981	0,9527
Concentração (µmol L^-1)	Q_e,exp (µmol g^-1)	Q_e,cal (µmol g^-1)	Q_e,cal (µmol g^-1)
66,952	14,719	14,739	12,848
133,905	23,173	22,939	23,376
267,809	35,305	35,470	37,664
401,714	45,445	46,035	46,960
535,619	56,344	54,754	52,915

C₀ (µmol L^-1)	ΔH	ΔG (kJ mol^-1)			ΔS (J mol^-1 K^-1)
C₀ (µmol L^-1)	(kJ mol^-1)	293 K	303 K	313 K	293 K	303 K	313 K
66,952	-8,099	-4,188	-3,081	-3,175	-13,347	-16,561	-15,731
133,905	-4,255	-4,188	-3,081	-3,175	-14,524	-14,045	-13,596
267,809	-4,680	-4,188	-3,081	-3,175	-15,973	-15,445	-14,952
401,714	-3,246	-4,188	-3,081	-3,175	-11,080	-10,714	-10,372
535,619	-1,936	-4,188	-3,081	-3,175	-6,608	-6,390	-6,186

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[1] *e-mail: olimpio.silva@ifrn.edu.br