Coelho, Ricardo Silva; Teixeira, Mônica Cristina

doi:10.1590/S1413-41522020197400

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Artigo Técnico • Eng. Sanit. Ambient. 25 (04) • Jul-Aug 2020 • https://doi.org/10.1590/S1413-41522020197400 copy

Bioremediation of arsenic-contaminated soil through soil washing using biosurfactants

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

Gold mining is one of the main sources of Arsenic (As) contamination in Minas Gerais, particularly at the Iron quadrangle. Arsenic is a toxic element that causes damage to human health. The soil washing technique using biosurfactants (BS) containing extracts was tested to promote the mobilization of the As contained in some soil samples collected in an abandoned gold mine, to investigate an environmentally friendly but equally efficient alternative to remove As from soils. Two mixed cultures of biosurfactant-producing bacteria (MPCB and MPBR), both adapted to the cultivation at high As concentrations (8 mg.L^-1), were selected for extracts production. Surfactants were stable over a wide pH range, 3-11; temperature, 28-50ºC and salinity, 1-5% NaCl (p.v^-1), and promoted the mobilization of As. The pH and solid:liquid ratio influenced the removal efficiency of the tested extracts. The highest removals were obtained at pH 11.0 and a solid:liquid ratio of 1:40 (g.mL^-1). Under pH 11.0, the arsenic removal results obtained with MPCB (14.01 and 13.72%) and MPBR extracts (12.04 and 12.31%) were superior to those obtained by using 1% (w/v) solutions of the commercial surfactants SDS (0.87 and 0.71%), saponin (0.57 and 0.55%) and, soy lecithin (2.05 and 2.63%). The pH and the solid: liquid ratio influenced the results of the column tests. The highest As removals: 25.43% (MPCB) and 22.43% (MPBR) were obtained after 10 extraction cycles, at pH 11 and 1:40 ratio (g.mL^-1).

The extracts MPCB and MPBR removed the water-soluble arsenic as well as the carbonate associated As and the adsorbed ions. Both extracts behaved similarly to EDTA and the commercial microbial extract (GorduraKlin®).

Keywords:
arsenic; bioremediation; biosurfactant; soil

Agente extrator	Fração removida	Possíveis mecanismos de solubilização	Referência
Água destilada	As solúvel	Dissolução com água.	(JAVED; KACHANOSKI; SIDDIQUE, 2013JAVED, M.B.; KACHANOSKI, G.; SIDDIQUE, T. (2013) A modified sequential extraction method for arsenic fractionation in sediments. Analytica Chimica Acta, v. 787, p. 102-110. https://doi.org/10.1016/j.aca.2013.05.050 https://doi.org/https://doi.org/10.1016/... )
Acetato de sódio (1,0 M, pH 8,2)	As fracamente adsorvido	Troca iônica do As com o acetato.
Acetato de sódio (1M, pH 5,0)	As ligado em carbonatos	Liberação do As pela dissolução dos minerais contendo carbonatos.
CaCl₂ (1,0 M, pH 7,0)	As facilmente trocável	Troca iônica do As com os íons de cloro.
NaH₂PO₄ (1,0 M, pH 5,0)	As fortemente adsorvido	Troca iônica do As com os íons PO₄ ^-3.
Ácidos orgânicos 0,1 M (acético 0,043 M, cítrico 0,031 M, lático 0,021, oxálico 0,005)	As fortemente e fracamente adsorvido	Troca iônica das formas de As mais lábeis e provenientes de sítios de adsorção mais específicos.	(PIRES; MATTIAZZO, 2007PIRES, A.M.M.; MATTIAZZO, M.E. (2007) Cinética de solubilização de metais pesados por ácidos orgânicos em solos tratados com lodo de esgoto. Revista Brasileira de Ciências do Solo, Viçosa, v. 31, n. 1, p. 143-151. https://doi.org/10.1590/S0100-06832007000100015 https://doi.org/https://doi.org/10.1590/... )

Granulometria	(%)	Composição elementar**	(mg.kg^-1 de solo)
0,250 < φ < 0,420 mm	23,30	As/As***	4.598,541/2.760,49
0,105 < φ < 0,250 mm	25,80	Cd	15,877
0,088 < φ < 0,105 mm	5,87	Cu	63,976
0,053 < φ < 0,088 mm	28,67	Ni	105,301
0,044 < φ < 0,053 mm	11,26	Pb	25,428
0,044 < φ < 0,037 mm	3,34	Zn	61,230
φ < 0,037 mm	1,77	Fe	87.779,136
pH*	3,48	Al	3.683,127
Eh*	+ 479,9 mV	Mn	5.766,289
Minerais	Qz, Ka, Um	Mg	906,028

Extrato de biossurfactante	Condição	Equação	Coeficiente de determinação (R²)
MPBR	MPBR (28ºC; pH 4,5; 1% NaCl)	$Y = 1.842 X + 4.63 8$	0,924
	MPBR (28ºC; pH 8,5; 1% NaCl)	$Y = 15.691 X + 3.06 0$	0,961
	MPBR (28ºC; pH 11,0; 1% NaCl)	$Y = 5.079 X + 16,8 9$	0,977
MPCB	MPCB (28ºC; pH 4,5; 1% NaCl)	$Y = 4.636,2 . l n (X) + 5.108, 9$	0,953
	MPCB (28ºC; pH 8,5; 1% NaCl)	$Y = 6.735,5 . l n (X) + 7.762, 9$	0,916
	MPCB (28ºC; pH 11,0; 1% NaCl)	$Y = 16.207 . l n (X) + 22.63 8$	0,953

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[1] * Autora correspondente: teixeira@ufop.edu.br