Immobilization of laccase onto porous polyvinyl alcohol/halloysite hybrid beads for dye removal

Abstract

Laccase was immobilized in polyvinyl alcohol beads containing halloysite nanotubes (PVA/HNTs) to improve the stability and reusability of enzyme. The porous structure of PVA/HNTs beads facilitates the entrapment of enzyme and prevents the leaching of immobilized laccase as well. Halloysite nanotubes act as bridge to connect the adjacent pores, facilitating the electron transfer and enhancing the mechanical properties. PVA/HNTs beads have high laccase immobilization capacity (237.02 mg/g) and activity recovery yield (79.15%), indicating it can be used as potential support for laccase immobilization. Compared with free laccase, the immobilized laccase on hybrid beads exhibits enhanced pH tolerance (even at pH 8.0), good thermal stability (57.5% of the initial activity can be maintained at 75 °C), and excellent storage stability (81.17% of enzyme activity could be retained after storage at 4 °C for 5 weeks compared with that for free enzyme of 60%). Also, the removal efficiency for reactive blue can reach as high as 93.41% in the presence of redox mediator 2,2-azinobis(3-ethylbenzthiazoline-6-sulfonate), in which adsorption and degradation exist simultaneously. The remarkable pH tolerance, thermal and storage stability, and reuse ability imply potential application of porous PVA/HNTs immobilized enzyme in environmental fields.

Synergistic Degradation of Dye Wastewaters Using Binary or Ternary Oxide Systems with Immobilized Laccase

“…These results are in agreement with a study by Li et al, who immobilized laccase onto ZnO/SiO 2 material and degraded Remazol Brilliant Blue B and Acid Blue 25 from an aqueous solution at a concentration 0.1 mol/L. The researchers also suggested that the presence of SiO 2 enabled the effective immobilization of the enzyme and increased the effective degradation of selected dyes [40]. In the case of a 1 mg/L RBBR dye solution, degradation occurs at 100%, as for a 10 mg/L RBBR solution, it is about 70% for both systems obtained after immobilization.…”

“…In other study, Reda et al immobilized laccase by entrapment method onto alginate-gelatin support. After seven catalytic cycles of synthetic dyes degradation, the biocatalytic system showed 65% activity compared to the initial one [40]. On the other hand, Ma et al obtained 48% of degradation efficiency of synthetic dyes after 14 catalytic cycles for laccase immobilized on chitosan crosslinked with genipin [49].…”

Layered composite based on halloysite and natural polymers: a carrier for the pH controlled release of drugs

“…[12][13][14] Nowadays, these systems are attracting the attention of material scientists and engineers due to their wide applications including biomedical technology, catalysis, remediation, cultural heritage treatment and food packaging. [15][16][17][18][19][20][21][22][23][24] Recently, great efforts have been addressed to the design of biohybrid materials composed of organic moieties and inorganic clay minerals, which can present different features in terms of chemistry, aspect ratio, morphology and charge. 25,26 Among them, Halloysite Nanotubes (HNTs) are naturally occurring aluminosilicates composed by a layer of Si-O-Si tetrahedrons overlapped to Al-OH octahedrons that create a kaolinite-like sheet which further rolls up forming hollow tubular nanoparticles.…”

Removal of Reactive Blue 52 by Electrocoagulation and UV/Persulfate from Aqueous Solutions

“…Figure 3 illustrates that the maximum removal efficiency of dye is observed at the pH of about 7, which is a nearly neutral range. This can be explained in this way that the degree of solubility Fe (OH) 3 , beyond the pH value 7 increases as a result of soluble Fe (OH) 4 formation, which doesn't participate in the COD reduction (23). At acidic conditions, a large amount of irons in the form of Fe 2+ , that is soluble and stable in the environment, causes reduced formation of coagulant and thus, dye removal (24).…”

“…With the rapid growth of communities, greater amounts of pollutants are released into soil or water areas, which do great harm to human health as well as ecosystem (1,2). In the past decades, the release of dye effluents from industries such as textile, paper and pulp, leather, food, cosmetic, and etc., has become one of the major environmental concerns owing to their carcinogenic, genotoxic, and/or mutagenic nature (3,4). About 20% to 50% of used reactive dyes in textile mills can be released in aquatic environments (5).…”