Carbon foams derived from biomass with ultra-high adsorption capacity for the removal of tetracycline

Abstract

This study focusses on the development of carbon foams (CFs) derived from carbohydrates evaluated for their adsorptive removal of model pollutants. The influence of different metal nitrates (cobalt, zinc, iron, magnesium, and chromium) and carbon precursors (cellulose, agar, sucrose, and starch) on the CF preparation and their effects on the adsorptive removal of tetracycline is extensively studied. CF derived from zinc nitrate catalyzed agar was studied extensively. Batch adsorption experiments were conducted to assess the effectiveness of CF under varying initial feed concentrations (25–500 mg L⁻¹), adsorbent loadings (0.25–1.00 g L⁻¹), pH range (4.5–9.8), and temperature range (20–35 °C). A maximum adsorption capacity of 1822 mg g⁻¹ was achieved at 500 mg L⁻¹ of feed and with an adsorbent loading of 0.25 g L⁻¹. The adsorption data were well-described by the Freundlich isotherm, indicating the heterogeneous nature of the CF surface, with multiple adsorption sites resulting in a non-uniform distribution of adsorbate molecules. The adsorption kinetics followed a pseudo-second-order model, suggesting that chemisorption was the predominant mechanism in the process. Thermodynamic analysis indicated that the adsorption process was endothermic and spontaneous, with a positive entropy change. Additionally, CF demonstrated excellent reusability, maintaining adsorption efficiency over three consecutive cycles.