Abstract
This study focuses on the development of a nanosupport based on halloysite nanotubes (HNTs), Fe3O4 nanoparticles (NPs), and thiolated chitosan (CTs) for laccase immobilization. First, HNTs were modified with Fe3O4 NPs (HNTs-Fe3O4) by the coprecipitation method. Then, the HNTs-Fe3O4 surface was tuned with the CTs (HNTs-Fe3O4-CTs) by a simple refluxing method. Finally, the HNTs- Fe3O4-CTs surface was thiolated (-SH) (denoted as; HNTs- Fe3O4-CTs-SH) by using the reactive NHS-ester reaction. The thiol-modified HNTs (HNTs- Fe3O4-CTs-SH) were characterized by FE-SEM, HR-TEM, XPS, XRD, FT-IR, and VSM analyses. The HNTs-Fe3O4-CTs-SH was applied for the laccase immobilization. It gave excellent immobilization of laccase with 100% activity recovery and 144 mg/g laccase loading capacity. The immobilized laccase on HNTs-Fe3O4-CTs-SH (HNTs-Fe3O4-CTs-S-S-Laccase) exhibited enhanced biocatalytic performance with improved thermal, storage, and pH stabilities. HNTs-Fe3O4-CTs-S-S-Laccase gave outstanding repeated cycle capability, at the end of the 15th cycle, it kept 61% of the laccase activity. Furthermore, HNTs-Fe3O4-CTs-S-S-Laccase was applied for redox-mediated removal of textile dye DR80 and pharmaceutical compound ampicillin. The obtained result marked the potential of the HNTs-Fe3O4-CTs-S-S-Laccase for the removal of hazardous pollutants. This nanosupport is based on clay mineral HNTs, made from low-cost biopolymer CTs, super-magnetic in nature, and can be applied in laccase-based decontamination of environmental pollutants. This study also gave excellent material HNTs-Fe3O4-CTs-SH for other enzyme immobilization processes.
Highlights
Environmental pollution is a daunting challenge to face in the modern world [1]
In summary, this study attempts the synthesis of nanocomposites mainly containing halloysite nanotubes (HNTs), Fe3O4 NPs, and thiolated CTs for laccase immobilization and application of the newly synthesized immobilization system for the biocatalytic degradation of the environmental pollutants Direct Red 80 (DR80) and the pharmaceutical compound ampicillin
The HNTs-Fe3O4 was modified with the CTs (Figure 1A) in a simple reaction process
Summary
Environmental pollution is a daunting challenge to face in the modern world [1]. Pollutants from land and water are foremost in reducing the quality of life and human health [2]. There is a huge scope to adopt new immobilization strategies One such important strategy is thiolation (-SH) of the amino (-NH2) group of CTs loaded on magnetic-HNTs [19,20,21]. This study mainly emphasized the thiolation of the amino (-NH2) group present of CTs-modified magnetic HNTs. Thiolation of chitosan has attracted significant attention in recent years for many desirable applications such as enzyme immobilization, drug delivery, cosmetics, and tissue engineering [19,20]. In summary, this study attempts the synthesis of nanocomposites mainly containing HNTs, Fe3O4 NPs, and thiolated CTs for laccase immobilization and application of the newly synthesized immobilization system for the biocatalytic degradation of the environmental pollutants Direct Red 80 (DR80) and the pharmaceutical compound ampicillin. The degradation of DR80 and ampicillin were checked by the developed immobilized system
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