Cadmium Removal from Aqueous Solutions Using Natural Limestone from Šuplja Stijena (Montenegro)

Cadmium, a toxic element, poses significant environmental and health risks, especially when released into water systems. Mining and natural processes contribute to elevated cadmium levels in surface waters, often surpassing permissible limits set by the Water Framework Directive. This study investigates the potential of natural limestone as a cost-effective and sustainable adsorbent for cadmium removal from aqueous solutions. Cadmium concentrations were analysed using inductively coupled plasma optical emission spectrometry (ICP-OES). Adsorption isotherms and the influence of pH, particle size, adsorbent dosage, and competing metals were examined. The results showed that cadmium adsorption efficiency increased with pH and decreased with larger particle sizes or higher metal concentrations. Under optimised conditions, the maximum adsorption capacity was determined to be 8.87 mg/g, indicating limestone’s suitability for cadmium removal. Further application in acidic mining waters demonstrated lower removal efficiency due to competitive sorption, suggesting the need for process optimisation.