Investigation of water softening using ceramic adsorbents in a continuous adsorption process

Ceramic adsorbents offer a sustainable and cost-effective approach to water treatment, particularly for reducing water hardness. This study aimed to evaluate the performance of natural zeolite and activated alumina, modified with NaNO₃ and H₂SO₄ respectively, in a continuous fixed-bed column system for water softening. Adsorption experiments were conducted under varying operational conditions, including column diameters (1 and 1.5 cm), flow rates (10 and 20 mL/min), and an operation time of 600 min. The optimal setup, 1.5 cm column diameter and 10 mL/min flow rate, yielded bed saturation times of 600 min for modified zeolite and 570 min for modified alumina. NaNO₃-modified zeolite achieved removal efficiencies of 99.23% for total hardness, 99.37% for calcium, and 99.17% for magnesium. Breakthrough and saturation times indicated superior performance compared to unmodified adsorbents. Kinetic models, including Thomas, Adams–Bohart, and Yoon–Nelson, were applied, with the Thomas and Yoon–Nelson models fitting best (R² ≈ 0.98). The findings demonstrate that surface modification enhances the adsorption capacity of ceramic materials, highlighting their potential for efficient and scalable water hardness treatment in continuous systems.