Congo Red Decolorization Using Textile Filters and Laccase-Based Nanocomposites in Continuous Flow Bioreactors

Abstract

Removal of azo and diazo dye content from textile industry wastewaters is crucial due to their environmental impact. Here, we report on the use of the fungal laccase from Pycnoporus sanguineus CS43 immobilized on silica nanoparticles and entrapped in textile-based filters for the degradation of Congo Red. Laccase immobilization and synthesis of the nanocomposites were carried out by two different methods, one in the presence of acetone and the second using water as solvent. This led to a change in the hydrophobicity of the obtained biofilters. Successful preparation of the nanocomposites was confirmed via FTIR spectroscopy. Changes in the secondary structure of the enzyme were inspected through the second derivative of the FTIR spectra. Six different types of filter were fabricated and tested in a continuous flow bioreactor in terms of their decolorization capabilities of Congo Red. The results indicate removal efficiencies that approached 40% for enzymes immobilized on the more hydrophobic supports. Backscattered electron (BSE) images of the different filters were obtained before and after the decolorization process. Percentage of decolorization and activity loss were determined as a function of time until a plateau in decolorization activity was reached. Experimental data was used to recreate the decolorization process in COMSOL Multiphysics® (Stockholm, Sweden). These simulations were used to determine the proper combination of parameters to maximize decolorization. Our findings suggest that the treatment of textile-based filters with immobilized laccase in conjunction with hydrophobic nanocomposites provides a suitable avenue to achieve more efficient laccase dye decolorization (39%) than that obtained with similar filters treated only with free laccase (8%). Filters treated with silica-based nanocomposites and immobilized laccases showed an increase in their decolorization capability, probably due to changes in their wetting phenomena.

Novel Magnetic Polymeric Filters with Laccase-Based Nanoparticles for Improving Congo Red Decolorization in Bioreactors

“…Afterward, the synthesized magnetite nanoparticles displayed an average hydrodynamic diameter of 88.59 nm with a polydispersity index of 0.182 as determined by DLS analysis with the aid of a Zetasizer Nano ZS, (Malvern, PA, USA). The morphology of those nanoparticles was analyzed as previously described by Lopez-Barbosa et al, (2020) [9].…”

“…About 70% of the dyes present in textile effluents contain azo (N = N) chromophores, which are thought to be responsible for fluctuations in the chemical oxygen demand, color, salinity and pH [9]; thus, numerous research efforts have focused on the development of advanced oxidation processes (AOPs) to treat these effluents. AOPs are oxidative methods based on the generation of intermediate radicals, mainly hydroxyl radicals (OH), that have been successfully applied in wastewater treatment to degrade many organic compounds [10].…”

“…In this sense, oxidoreductase enzymes, such as laccases, capable of carrying out these oxidation processes without the need for harsh chemical compounds have become an attractive alternative [12]. Nevertheless, enzyme-based wastewater treatment methods tend to be expensive due to the lack of reusability and purification processes [9,12]. Therefore, enzyme-immobilization has gained attention to overcome the reusability and stability issues, by generating strategies to recover the immobilization substrate and thus, recovering the enzyme for further use.…”

Functionalized Materials as a Versatile Platform for Enzyme Immobilization in Wastewater Treatment

“…The immobilization of these enzymes mainly focuses on silica and its composites [38,39]. Lopez-Barbosa et al [40] performed experiments with laccase immobilized on functionalized silica for decolorizing Congo Red. The silica was modified with APTES (γ-aminopropyltriethoxysilane), and the NH 2 groups were subsequently activated by adding glutaraldehyde (GA).…”

Comparison of Acetaminophen Degradation by Laccases Immobilized by Two Different Methods via a Continuous Flow Microreactor Process Scheme

“…Immobilization or encapsulation can be achieved either by physical adsorption or by covalent bonding. Nanostructured materials such as titania, alumina, silica and magnetite offer rather simplified immobilization routes, high chemical and physical stability, ease of handling, low costs, and relatively high yields [ 10 , 11 , 25 , 26 , 27 ]. In contrast, microencapsulation has been employed extensively as an efficient route to protect or isolate substances from harmful environments [ 28 ], hence, serving as a viable solution for oxidative degradation.…”