Co-precipitated magnetic graphene oxide nanocomposites for methyl orange uptake: Isotherm, kinetic, and regeneration

Methyl orange (MO) synthetic dyes are one of the greatest threats to aquatic ecosystems due to their toxicity, persistence, and lack of biodegradability. Traditional treatment methods, e.g., biological, chemical, and membrane processes, are susceptible to elevated operational costs, fouling, or the formation of secondary waste. Adsorption is a comparatively sustainable process, offering advantages such as simplicity and reusability. This study investigates the development and application of magnetic graphene oxide (MGO) nanocomposites, synthesized through a modified Hummers process with the in-situ deposition of Fe₃O₄ nanoparticles, for enhanced separation and adsorption efficiency in MO removal. GO and MGO variants were studied by BET analysis, which determined surface areas of 453.6 m 2 /g for GO and 112.8–122.6 m 2 /g for MGO, with respective pore volumes of 0.945 cm 3 /g and 0.268–0.271 cm 3 /g. Batch adsorption experiments (10–35 mg/L MO, 1 g/L adsorbent) confirmed GO's superior adsorption (21.3 mg/g, 62 % removal at 10 mg/L) compared with that of MGO9 (18.2 mg/g, 32 % removal), the maximum adsorption capacity (qₘₐₓ) of MGO9 being 60.241 mg/g. Isotherm behavior of mixed monolayer and heterogeneity was exhibited; GO most closely conformed to the Redlich–Peterson model ( R 2 = 0.94), while MGO9 conformed to the Langmuir and Temkin models ( R 2 > 0.97). Kinetic investigations demonstrated pseudo-second-order behavior ( R 2 > 0.98) with predominant chemisorption. Regeneration with HCl/ethanol resulted in a significant efficiency loss, particularly for GO (73–48 %) and MGO9 (48–6 %), underscoring the need for more rigorous recovery methods.