Abstract
The intensive use of water containing dyes by the textile industry, and consequently the contamination of soils and water, represents serious environmental concerns. Amongst the several processes applied in the treatment of textile effluents, biological-based processes, if designed to be cost-effective and ecofriendly, are promising alternatives to decolorize textile effluents. In this work we investigate and propose the novel use of ionic liquids (ILs) with surfactant characteristics to improve the degradation of the largely used and highly hydrophobic textile dye indigo carmine (IC) by laccase. An initial screening on the activity of laccase in aqueous solutions of twelve surfactant-based ILs from three different families, namely tetraalkylammonium- and imidazolium-based cationic surfactants and cholinium-based anionic surfactants, at different concentrations, was carried out. Significant improvements in the activity of laccase were observed with decyltrimethylammonium bromide, [N10111]Br, and 1-decyl-3-methylimidazolium chloride, [C10mim]Cl, at 75 mM (above the critical micellar concentration of each IL). These ILs were then investigated in aqueous solutions to simultaneously encapsulate laccase and IC for the in situ enzymatic biodegradation of the dye. The use of ILs remarkably increases the degradation rate of the dye and decolorization efficiency; a degradation efficiency of IC of 82% is attained in 0.5 h using aqueous solutions of [N10111]Br, whereas without IL only 6% of IC is degraded. Furthermore, 93% of the dye decolorization was achieved with [N10111]Br. The overall gathered results show that it is possible to significantly improve the degradation of hydrophobic dyes by enzymes using appropriate surfactant-based ILs, while foreseeing the use of the treated water by the same textile industries in new dyeing steps and thus contributing to a substantial decrease of the economic input and environmental footprint of these industries.
Highlights
Serious environmental concerns have arisen due to industrial developments, leading to significant risks to human health and to the ecosystem [1]
We investigate and propose the use of ionic liquids (ILs) with surfactant behavior to improve the degradation of the indigo carmine (IC) dye by laccase, which may allow the reuse of the discharged water by the textile industry
It is of high importance to identify appropriate IL-based surfactants able to improve the catalytic activity of 2 laccases and related bioreactions performance
Summary
Serious environmental concerns have arisen due to industrial developments, leading to significant risks to human health and to the ecosystem [1]. Bioremediation using enzymes have gained significant notoriety due to its versatility and efficiency in the degradation of persistent organic pollutants from wastewater [10, 11] Oxidative enzymes such as laccases, peroxidases and tyrosinases have high potential in the oxidation of persistent environmental pollutants [12]. Most aprotic ILs display negligible vapor pressures, low flammability, and high thermal and chemical stability [25] Due to their tunable character achieved by altering the anion or cation chemical structure, it is possible to tailor the properties of ILs and to synthesize a specific IL to a target reaction or application. We investigate and propose the use of ILs with surfactant behavior to improve the degradation of the IC dye by laccase, which may allow the reuse of the discharged water by the textile industry. [C8mim]Cl [C10mim]Cl [C12mim]Cl [C14mim]Cl [N8111]Br [N10111]Br [N12111]Br [N14111]Br [Ch][C12O2] [Ch][C14O2]
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