Preparation and characterization of an algal-based magnetic biochar nanocomposite for the removal of azocarmine G2 dye from aqueous solutions

Abstract Dyes are released into bodies of water as the textile industry expands in response to the growth of the global population. These textile dyes have severe effects on the environment, including wildlife, terrestrial species, and humans. This study explores the synthesis, characterization, and application of an algal-based magnetic biochar nanocomposite for the efficient adsorption of azocarmine G2 (ACG2) dye from aqueous solutions. The magnetic biochar (Fe 3 O 4 @BC) was characterized by Raman spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectrometry (FTIR). Batch adsorption experiments were performed to assess the impact of the initial dye concentration (25 to 100 mg / L), contact time (up to 300 min), pH (1–3) and temperature (298 to 328 K). The nano-composite achieved a maximum adsorption capacity (q max ) of 71.3 mg/g at pH 1, with equilibrium reached within 240 min. Adsorption kinetics followed a pseudo-second-order model (R2 = 0.99), while isotherm analysis fit well with the Langmuir model (R2 = 0.98), indicating monolayer adsorption. However, the Freundlich model provided a better fit, indicating that the multilayer covered a heterogeneous surface with a chemisorption process. The nanocomposite demonstrated as > 90% adsorption efficiency for ACG2 under a variety of conditions, with reusability tests showing retention of over 80% adsorption capacity after five regeneration cycles. This study focusses on the synthesis of an algae-derived biochar with magnetic properties, enhancing its efficiency in post-adsorption separation. The adsorption of Azocarmine G2 (ACG2), a hazardous azo dye, is addressed herein for the first time, establishing the novelty of this research within the domain. Furthermore, this innovative Fe 3 O 4 @BC adsorbent compound effectively resolves the issue of recyclability. The results highlight that the algal-based magnetic biochar nanocomposite is a viable and sustainable adsorbent, demonstrating exceptional dye adsorption capacity, simplified separation processes, and recyclability. Therefore, it is deemed appropriate for extensive applications in wastewater treatment processes.