Design and preparation magnetic bio-surfactant rhamnolipid-layered double hydroxide nanocomposite as an efficient and recyclable adsorbent for the removal of Rifampin from aqueous solution

In this study, a magnetic core–shell rhamnolipid (MCSR) intercalated cobalt/aluminum layered double hydroxide (LDH) has been used for water remediation and rifampin (RIF) removal. Biosurfactants, including rhamnolipid (RL), exhibit advantages such as low toxicity and environmental compatibility. Moreover, rhamnolipid can promote the removal efficiency of the adsorbent. The effect of major factors on the adsorption process, including pH of the solution, initial RIF concentration, contact time, and adsorbent dosage were examined and optimized in detail. Accordingly, in acidic pH the adsorption efficiency was the highest because in this condition, OH functional groups of RIF molecules may be protonated leading to interacting with positively charged LDH layers. The results showed that the RIF removal efficiency is 96 %. According to the Langmuir model, the maximum adsorption capacity obtained for 0.67 g/L of adsorbent (20 mg of adsorbent in 30 mL of RIF solution) was 221.30 mg/g. In accordance with the modeling results, the Temkin isotherm better expresses the adsorption mechanism at the surface of MCSR-LDH. Furthermore, the kinetic data was better suited to the pseudo-first-order model, indicating that the solution reaches equilibrium between 20 and 30 min. Evaluation of thermodynamic parameters indicated the exothermic nature of adsorption process (ΔH° = −68362.70 J/mol). The magnetic property of MCSR-LDH leads to the easy recovery of the adsorbent by an external magnet at the end of the adsorption process, so that it can be regenerated for repeated cycles of at least four cycles without a significant decrease in efficiency.