Amino modified magnetic halloysite nanotube supporting chloroperoxidase immobilization: enhanced stability, reusability, and efficient degradation of pesticide residue in wastewater

Halloysite nanotube (HNT) is a natural bio-compatible and stable nanomaterial available in abundance at low-cost. In this work, HNT was modified by two strategies to make it suitable for supporting immobilization of chloroperoxidase (CPO). Firstly, Fe 3 O 4 nanoparticles were deposited on HNT, so magnetic separation can be used instead of centrifugation. Then, the magnetic HNT was modified by 3-aminopropyltriethoxysilane (APTES), which can provide amine group on surface of HNT and meanwhile inhibit the agglomeration of magnetic HNT. Then, HNT-Fe 3 O 4 -APTES was linked with branched polyethyleneimine (PEI) to provide more amino for binding with enzyme. The so-prepared CPO@HNT-Fe 3 O 4 -APTES-PEI showed enhanced enzyme loading, reusability, improved thermal stability and tolerance to organic solvents than free CPO. For example, after 10 repeated uses, CPO@HNT- Fe 3 O 4 -APTES-PEI can maintain 92.20% of its original activity compared with 65.12% of activity of CPO@HNT-APTES-PEI and 45.69% of activity of CPO@HNT. The kinetic parameters indicated the affinity and specificity of immobilized enzyme to substrate was increased. CPO@HNT-Fe 3 O 4 -APTES-PEI was very efficient when it was applied in the degradation of pesticides mesotrione in wastewater. The degradation efficiency can reach 90% within 20 min at range of 5–40 μmol·L −1 . These results ensure the potential practical application of this bio-materials in wastewater treatment. Graphic Abstract