Adsorption and Recovery Studies of Cadmium and Lead Ions Using Biowaste Adsorbents from Aqueous Solution

The use of low-cost biowaste adsorbents for the removal of toxic metal ions from aqueous solutions offers significant environmental benefits and demonstrates strong potential. This research studied the adsorption and recovery of Cd2+ and Pb2+ ions in batch and column modes with luffa peels and chamomile flowers. Metal ion concentrations were determined with ICP-OES. The biosorbents were treated with either acid or base. FTIR characterization indicated that surface carboxylic acid groups played a role in the adsorption process. L-type isotherms were obtained for Pb2+, fitting both the Langmuir and Freundlich models, with maximum adsorption capacities of 34.0 mg/g for luffa peels and 49.5 mg/g for chamomile flowers. Adsorption isotherm for Cd2+fitted better with the Freundlich model with smaller adsorption capacity than Pb2+. Base treated sorbents have higher adsorption capacity. The adsorption kinetic for both ions followed a pseudo-second order chemosorption model. Fixed-bed column dynamic adsorption with luffa peels obtained a Thomas dynamic adsorption capacity of 32.9 mg/g for Pb2+ and 25.8 mg/g for Cd2+. The recovery efficiency remained above 87% over three adsorption-regeneration cycles.