Abstract
Sustainable and green synthesis of nanocomposites for degradation of pharmaceuticals was developed via immobilization and stabilization of the biological strong oxidizing agents, peroxidase enzymes, on a solid support. Sol–gel encapsulated enzyme composites were characterized using electron microscopy (TEM, SEM), atomic force microscopy, FTIR spectroscopy, and thermogravimetric analysis. Horseradish peroxidase (HRP) and lignin peroxidase (LiP) were adsorbed onto magnetite nanoparticles and sol–gel encapsulated in a surface silica layer. Encapsulation enhanced the stability of the biocatalysts over time and thermal stability. The biocatalysts showed appreciable selectivity in oxidation of the organic drinking water pollutants diclofenac, carbamazepine, and paracetamol with improved activity being pharmaceutical specific for each enzyme. In particular, sol–gel encapsulated LiP- and HRP-based nanocomposites were active over 20 consecutive cycles for 20 days at 55 °C (24 h/cycle). The stability of the sol–gel encapsulated catalysts in acidic medium was also improved compared to native enzymes. Carbamazepine and diclofenac were degraded to 68% and 64% by sol–gel LiP composites respectively at pH 5 under elevated temperature. Total destruction of carbamazepine and diclofenac was achieved at pH 3 (55 °C) within 3 days, in the case of both immobilized HRP and LiP. Using NMR spectroscopy, characterization of the drug decomposition products, and decomposition pathways by the peroxidase enzymes suggested.
Highlights
Worldwide urbanization and population increase and associated expansion in the use of pharmaceuticals is driving the search for new materials to insure efficient and rapid purification of both drinking water and wastewaters
Total degradation of diclofenac in the case of Horseradish peroxidase (HRP) is due to a higher number of enzyme units (10-fold number of enzyme units compared to lignin peroxidase (LiP))
NMR spectra for diclofenac and its metabolites after interaction with sol–gel encapsulated HRP and LiP enzyme composites at pH 5 are shown in Figure 5a–c respectively
Summary
Worldwide urbanization and population increase and associated expansion in the use of pharmaceuticals is driving the search for new materials to insure efficient and rapid purification of both drinking water and wastewaters. Apart from the widespread problem of heavy metal pollution aggravated by warmer weather and increased acidity [1], there is a growing worldwide problem of water pollution by pharmaceuticals. It is well-known that the content of persistent organic pollutants such as pharmaceuticals [2], personal care products [3], and their metabolites are increasing due to human activity. In wastewater treatment plant (WWTP) effluents, the concentration of carbamazepine (CBZ) has been reported as reaching 0.95 μg/L, and 0.99 μg/L for diclofenac [4]. Sweden); ABTS (2,2 -azino-bis(3-ethylbenzothiazoline-6-sulphonic acid), Sigma-Aldrich Sweden AB, Stockholm, Sweden)
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