Adsorption of congo red dye from aqueous solution onto amino-functionalized silica gel

Farias, Raquel Studart de; Buarque, Hugo Leonardo de Brito; Cruz, Mabel Ribeiro da; Cardoso, Luana Meg Freitas; Gondim, Tamyris de Aquino; Paulo, Vanessa Rodrigues de

doi:10.1590/S1413-41522018172982

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Technical Article • Eng. Sanit. Ambient. 23 (6) • Nov-Dec 2018 • https://doi.org/10.1590/S1413-41522018172982 copy

Adsorption of congo red dye from aqueous solution onto amino-functionalized silica gel

Adsorção do corante vermelho congo em solução aquosa com sílica aminofuncionalizada

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

This study investigates the potential use of amino-functionalized silica gel as an adsorbent for the recovering of congo red dye from aqueous solution. The effects of pH, contact time, and temperature were determined and evaluated. Equilibrium isotherms were also studied. The adsorption kinetics was modeled by pseudo-first order and pseudo-second order. Furthermore, desorption of congo red was preliminarily studied. The pH range from 4.5 to 7.0 was favorable for the adsorption of congo red onto amine modified silica at 25ºC. Higher adsorption capacity was obtained at 50ºC. Langmuir and Freundlich models were fitted to the adsorption equilibrium data. The best fittings were obtained with the pseudo-second order and Langmuir model for kinetics and equilibrium, respectively. Desorption studies suggest that ion exchange might be the major mode of adsorption. KOH solution was the best desorbing agent for recovering the adsorbed dye.

Keywords:
3-aminopropyltriethoxysilane; anionic dye; color removal; grafted silica

Adsorbent	Temperature	Model	Parameters	Deviation (%)
CSG	25ºC	pseudo-first order	$m_{1} = 0.439 \pm 0.028 m g / g$	142.65
		pseudo-first order	$k_{1} = (8.92 \pm 2.29) \times 10^{3} {m i n}^{- 1}$	142.65
		pseudo-second order	$m_{2} = 0.497 \pm 0.031 m g / g$	176.34
		pseudo-second order	$k_{2} = (20.2 \pm 6.37) \times 10^{- 3} g {m g}^{- 1} {m i n}^{- 1}$	176.34
	40ºC	pseudo-first order	$m_{1} = 0.336 \pm 0.052 m g / g$	279.75
		pseudo-first order	$k_{1} = (21.9 \pm 14.3) \times 10^{- 3} {m i n}^{- 1}$	279.75
		pseudo-second order	$m_{2} = 0.373 \pm 0.064 m g / g$	302.06
		pseudo-second order	$k_{2} = (60.6 \pm 57.2) \times 10^{- 3} g {m g}^{- 1} {m i n}^{- 1}$	302.06
AMS	25ºC	pseudo-first order	$m_{1} = 5.545 \pm 0.252 m g / g$	18.87
		pseudo-first order	$k_{1} = (8.00 \pm 1.51) \times 10^{- 3} {m i n}^{- 1}$	18.87
		pseudo-second order	$m_{2} = 6.163 \pm 0.200 m g / g$	11.75
		pseudo-second order	$k_{2} = (1.78 \pm 0.29) \times 10^{- 3} g {m g}^{- 1} {m i n}^{- 1}$	11.75
	40ºC	pseudo-first order	$m_{1} = 9.675 \pm 0.581 m g / g$	15.71
		pseudo-first order	$k_{1} = (15.8 \pm 3.5) \times 10^{- 3} {m i n}^{- 1}$	15.71
		pseudo-second order	$m_{2} = 11.121 \pm 0.451 m g / g$	12.01
		pseudo-second order	$k_{2} = (1.01 \pm 0.30) \times 10^{- 3} g {m g}^{- 1} {m i n}^{- 1}$	12.01

Temperature	Model	Parameters	Deviation (%)
25ºC	Langmuir	$m = 5.368 \pm 0.171 m g g^{- 1}$	7.99
	Langmuir	$b = 0.337 \pm 0.056 L {m g}^{- 1}$	7.99
	Freundlich	$k = 2.258 \pm 0.228 m g g^{- 1} {(m g L^{- 1})}^{- 0,215}$	12.16
	Freundlich	$n = 4.661 \pm 0.657$	12.16
40ºC	Langmuir	$m = 53.369 \pm 4.397 m g g^{- 1}$	7.39
	Langmuir	$b = 0.020 \pm 0.002 L {m g}^{- 1}$	7.39
	Freundlich	$k = 1.510 \pm 0.108 m g g^{- 1} {(m g L^{- 1})}^{- 0,757}$	9.62
	Freundlich	$n = 1.321 \pm 0.040$	9.62
50ºC	Langmuir	$m = 66.529 \pm 21.5171 m g g^{- 1}$	12.84
	Langmuir	$b = 0.028 \pm 0.0105 L {m g}^{- 1}$	12.84
	Freundlich	$k = 1.881 \pm 0.163 m g g^{- 1} {(m g L^{- 1})}^{- 0,895}$	8.67
	Freundlich	$n = 1.117 \pm 0.060$	8.67
60ºC	Langmuir	$m = 19.103 \pm 3.148 m g g^{- 1}$	12.18
	Langmuir	$b = 0.031 \pm 0.009 L {m g}^{- 1}$	12.18
	Freundlich	$k = 1.120 \pm 0.278 m g g^{- 1} {(m g L^{- 1})}^{- 0,612}$	14.87
	Freundlich	$n = 1.634 \pm 0.207$	14.87

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[1] *Corresponding author: raquelstudartf@yahoo.com.br