Green Adsorption Approach: Competitive Adsorption of Cu(II), Pb(II), and Cd(II) Using Cabbage Waste

This study investigates the potential of cabbage (Brassica oleracea var. capitata f. alba) leaves as a low-cost, eco-friendly adsorbent for the removal of heavy metals—Cu(II), Pb(II), and Cd(II)—from aqueous solutions. The research aims to evaluate single, binary, and ternary metal systems under experimental conditions with initial metal concentrations (20–200 mg/L) and contact time (10–180 min). Adsorption efficiency increased with initial metal concentration, reaching saturation at 40 ppm for Cu and Pb. In competitive binary and ternary systems, Cu exhibited the highest adsorption capacity, followed by Pb and Cd (Cu > Pb > Cd), likely due to differences in ionic radius and hydration energy. The adsorption mechanism predominantly followed chemisorption, as indicated by the pseudo-second-order kinetic model. Kinetic studies revealed that the adsorption process follows the pseudo-second-order model more closely, whereas equilibrium data fitted well with the Langmuir isotherm, indicating monolayer adsorption. The maximum adsorption capacities (q_max) for Cu(II), Pb(II), and Cd(II) were found to be 42.5, 56.8, and 33.2 mg/g, respectively. The results demonstrate the effectiveness of cabbage leaves in treating heavy metal contaminated water and highlight their potential application in sustainable wastewater treatment technologies.