Bittern-Derived Mg/Al Layered Double Hydroxide Adsorbent for Potential Ciprofloxacin Removal in Water Treatment Application

The presence of ciprofloxacin (CIP), an antibiotic, in pharmaceutical wastewater has emerged as a significant environmental concern. This study presents the synthesis of magnesium/aluminum layered double hydroxide (MAL) through a co-precipitation method, utilizing seawater bittern as the magnesium source, with the objective of addressing CIP removal effectively. MAL was prepared at three different pH levels (5, 9, and 12), resulting in three distinct samples: MAL5, MAL9, and MAL12. Among these, MAL9 was identified as the most effective variant, exhibiting well-formed crystal structures alongside the highest adsorption capacity for CIP, achieving a removal rate of 63%. Moreover, we evaluated several factors that influence the adsorption process, including the dosage of the adsorbent, the solution’s pH, and the presence of co-ions. The findings indicated that optimal adsorption occurs at a concentration of 1 mg/mL within a pH range of 6 to 9, demonstrating significant resistance to both monovalent and divalent co-ions. The adsorption mechanism was further investigated through isothermal modeling (the Freundlich isothermal model), resulting in data that aligned with the Freundlich isothermal model, which indicated a maximum adsorption capacity of 95.15 mg/g at the concentration of CIP of 100 mg/L. Kinetic analysis showed that the sorption process follows a pseudo-second-order model, reaching equilibrium in about 100 minutes. The MAL demonstrated an impressive reusability, maintaining 90% to 50% performance over three adsorption-desorption cycles. Thus, bittern-derived MAL is an effective adsorbent for CIP removal and promotes the sustainable use of bittern waste as a magnesium precursor in functional nanomaterials synthesis.