An investigation into the prospective applications of bio-catalyst metal frameworks: a novel catalyst for improved removal of Congo red from aqueous solutions

Abstract

The global textile industry poses significant challenges to public health, safety, and environmental sustainability through its discharge of wastewater. This study explores the potential of orange peel (OP) as a raw material in synthesizing a novel bio catalyst metal framework (BCM_F) for the efficient removal of Congo red dye from aqueous solutions. The adsorption capacities of both OP and BCM_F were systematically investigated, with OP undergoing inorganic salt treatment to enhance its adsorption capacity and intensify attractive forces at the nanoparticle level. The surface characteristics of the bio catalyst were thoroughly examined using FTIR, SEM, BET analysis, and EDX spectroscopy, revealing the development of a semi-crystalline structure following treatment with aluminum nitrate Al(NO₃)₃·9H₂O, accompanied by observable changes in surface morphology and elemental composition. Under standard conditions, BCM_F exhibited a remarkable increase in removal efficiency, reaching 99.61% for 300 mg L⁻¹ Congo red compared to 66.80% for OP alone at 50 mg L⁻¹. Kinetic analysis revealed a shift from pseudo-first-order to pseudo-second-order reaction kinetics after treatment with Al(NO₃)₃·9H₂O, indicating a transition from physical to chemical adsorption, with a significant reduction in equilibrium time and a substantial increase in maximum adsorption capacity from 29.27 mg g⁻¹ to 443 mg g⁻¹. Additionally, the mean pore diameter increased from 493.73 to 1874.7 nm. The interaction mechanism between the adsorbent and dye involved electrostatic interactions, hydrogen bonding, and π–π interactions. Furthermore, BCM_F demonstrated excellent stability over multiple cycles, with only a 5% reduction in efficiency after five cycles. This research underscores the potential of utilizing agricultural waste for the development of efficient and sustainable wastewater treatment solutions in the textile industry, contributing to both environmental protection and resource conservation.