The originally fabricated phytase/HHFeZ bio-conjugates could appropriately enhance enzyme stabilization after heteroatomic hierarchical Fe-ZSM-5 zeolite (HHFeZ) was developed as a novel matrix for affinitive immobilization of Escherichia coli (E. coli) phytase. The immobilization strategy was primarily dependent on the affinitive coordination between heteroatomic iron atoms anchored into the HHFeZ frameworks with multiple sites of phosphorylation in phytase. In addition, the ordered multiporous structures of HHFeZ contributed to phytase immobilization and stabilization. The conditions for phytase immobilization were optimized under a solution pH of 4.5 in a batch mode, and the maximum phytase immobilization capacity was determined to be 2.01 mg mg−1. Compared to those of free phytase, the thermal and proteolytic resistance of phytase/HHFeZ bio-conjugates were effectively improved, and the enzymatic activity was maintained over a broad pH range. The phytase/HHFeZ bio-conjugates would be an innovative choice for eco-sustainable exploitation and utilization of phytate-phosphorus, especially with respect to eutrophication control.

•Naturally occurring xanthan gum (XG) for preparation of Fe3O4@SiO2–XG composites.•Magnetic switchable composites for property of convenient solid/liquid separation.•Non-toxic XG immobilized on magnetic Fe3O4 particles through TEOS sol–gel reaction.•XG adopted as active sites for adsorptive removal of Pb2+ from aqueous solution.•The composites reutilized and Pb2+ reused in battery wastewater by 0.05 mol L−1 HCl.A magnetic Fe3O4 @ silica–xanthan gum composite was easily fabricated as a hybrid adsorbent for the removal and recovery of aqueous Pb2+ heavy metal. The natural polymer xanthan gum (XG) was fixed on the surface of the magnetic Fe3O4 microspheres through a sol–gel process. The condensation of XG molecule provided active sites for the selective adsorption of Pb2+ ions from the aqueous solution, and because the composite is magnetically switchable, the process of solid–liquid separation was convenient. Scanning electronic microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectrometry, thermogravimetry, and BET surface area determination were utilized for the characterization of the composites. The factors affecting Pb2+ adsorption in a batch mode were studied including the contact time (30–150 min), the pH of the media (2–10), the adsorbent dosage (0.01–0.2 g/20 mL), and the temperature (303–320 K). The Pb2+ adsorption followed pseudo-second-order kinetics, and the maximum Pb2+ sorption capacity was 21.32 mg g−1 at 293 K, pH = 6, according to the Langmuir isotherm. The thermodynamic parameters, including the equilibrium constant (K0 = 9.848), the standard free energy change (ΔG0 = −5.774 kJ mol−1), the standard enthalpy change (ΔH0 = 6.133 kJ mol−1), and the standard entropy change (ΔS0 = 39.21 J mol−1 K−1) were discussed. The targeted Pb2+ could be recovered efficiently using 0.05 mol L−1 HCl. Finally, the Fe3O4 @ silica–XG composites were attmepted for removal of Pb2+ from battery industry wastewater.

A hierarchical Fe-ZSM-5 zeolite monolithic column was fabricated for immobilization of low abundance phosphoprotein through specific coordination between heteroatomic Fe in the framework of the zeolite with the phosphate group in the micro-environment of the protein. Compared to traditionally immobilized metal ion chromatography, this method could be directly manipulated and handily adapted for phosphoproteomics identification.