Ofloxacin exclusion using novel HRP immobilized chitosan cross-link with graphene-oxide nanocomposite

Abstract

Ofloxacin (OFX) release in aquatic vicinities may execute toxicity and affect the biological hierarchy. Therefore, to save the vital beauty of our earth and water streams, it is essential to remove ofloxacin from aqueous system. In this work, green nano adsorbent was prepared by cross-linking the chitosan (Cs) to graphene oxide (GO) via electrostatic interaction. Additionally, the adsorbent was bio-catalyzed by immobilizing horseradish peroxidase (HRP) onto CsGOn (HRP-CsGOn) through covalent bonding to enhance the mechanical strength of HRP and for industrial application with high reusability and low cost. SEM and FT-IR analysis of CsGOn and HRP-CsGOn confirm cross-linking of chitosan with GO and immobilization of HRP onto CsGOn. The enzyme activity of HRP-CsGOn with the free enzyme was compared at different process conditions such as pH (6,7 and 8), temperature (303, 313 and 323 K), self-life (0–15 days) and reusability (0–5 cycles). HRP-CsGOn demonstrated that better temperature, pH stability, and self-life than free enzyme. Batch ultra-sonication assisted adsorption was performed for removal of OFX using HRP-CsGOn. Kinetic and equilibrium studies presented that the experimental data of OFX were defined by pseudo-second order kinetic with monolayer coverage (Langmuir model) and three-stage of adsorption. Maximum adsorption capacity 378 (mg/g) was obtained at an equilibrium time of 10 min and a temperature of 35 °C. The positive value of thermodynamic parameters ΔH 2939.26 (kJ/mol) and ΔS 10.10 (kJ/mol K) obtained in the present study and negative value of ΔG at temperature (328–333 K) presented that the present system is spontaneous, and endothermic. The reusability studies specified that the HRP-CsGOn can be reused for a minimum of 5 cycles. This study provides a promising HRP-CsGOn green nano adsorbent and can be used for various applications.