Ultrahigh adsorption capacity of carbohydrate-derived carbon foam/ZIF-8 composite for malachite green removal: mechanistic Insights and practical applications

In this study, we developed a composite of zeolitic imidazolate framework-8 (ZIF-8) with carbohydrate-derived carbon foam (CF) as an adsorbent for efficient removal of malachite green (MG) dye and real textile wastewater. The composite was synthesized through a sustainable route: CF was produced at low temperatures (180 °C) using agar powder. Batch adsorption experiments demonstrated an exceptional maximum adsorption capacity of 3132 mg g⁻¹ at 400 mg L^-1 MG concentration and 0.125 g L^-1 adsorbent dosage. Kinetic studies revealed that the process followed the pseudo-second-order model (R² > 0.999), indicating chemisorption-driven uptake, while equilibrium data best fitted the Sips isotherm (R² = 0.966), highlighting heterogeneous surface interactions. In fixed-bed column studies, the CF/ZIF-8 composite achieved > 50 % removal efficiency for real textile effluent under optimized conditions (1 cm bed height, 0.5 mL min⁻¹ flow rate). The breakthrough curves aligned with the Thomas model, demonstrating practical scalability. Reusability tests over three cycles retained > 96 % efficiency, underscoring the composite’s stability. The composite’s ultrahigh adsorption capacity is higher than many reported materials coupled with its low-cost, energy-efficient synthesis, positioning it as a promising solution for real textile wastewater treatment.