MOF-Heterostructure-Mediated pH-Responsive Adsorptive Removal of Ciprofloxacin: A Step towards Pharmaceutical Wastewater Treatment

One of the biggest challenges of the modern world is the antibiotic pollution in the water resources owing to the lack of effective removal techniques in the conventional wastewater treatment processes. Importantly, very few commercially available adsorbents are at the same time porous, magnetic, and have the capacity to bind and remove particular antibiotic classes from the slurries in a selective manner. Herein we report CNS@ZIF67 heterostructure derived adsorbent for the pH-dependent removal of ciprofloxacin (CIP). The materials can be synthesized via a simple two-step wet chemical method followed by annealing in a controlled atmosphere. The material demonstrates an attractive surface-to-mass ratio of 203.02 m(2) g(-1). We have performed a detailed time dependent adsorption study indicating a high removal efficiency of 96% within 2 h. Experimental adsorption data matches the Langmuir isotherm model and the kinetics follows pseudo-second-order reaction kinetics suggesting a chemisorption pathway of adsorption kinetics. The adsorbent has an interesting pH dependent adsorption behavior towards CIP. The adsorbent has also demonstrated its value in being reusable for four cycles of adsorption and desorption without significantly changing the removal efficiency.

Automated summary

One of the biggest challenges of the modern world is the antibiotic pollution in water resources due to the lack of effective removal techniques in conventional wastewater treatment processes. However, commercially available adsorbents with the desired properties for selective removal of specific antibiotic classes are rare. In this study, a CNS@ZIF67 heterostructure derived adsorbent was developed for the pH-dependent removal of ciprofloxacin (CIP). The adsorbent demonstrated a high removal efficiency of 96% within 2 hours and showed interesting pH dependent adsorption behavior. It also proved to be reusable for four cycles without significant loss of removal efficiency.