Zeolitic imidazolate framework-8 derived nanoporous carbon as an effective and recyclable adsorbent for removal of ciprofloxacin antibiotics from water

Abstract

The nanoporous carbons (NPC) derived from a one-step carbonization of zeolitic imidazolate framework-8 (ZIF-8) were synthesized and used for ciprofloxacin (CIP) removal from water. The resultant products were characterized by SEM, TEM, FT-IR, Raman, N₂ adsorption-desorption analysis, XRD, TGA and Zeta potential. The optimized NPC-700 (carbonized at 700°C for 2h) exhibited an optimal performance in CIP adsorption removal. CIP adsorption on NPC-700 as a function of contact time, initial CIP concentration, adsorbent dosage, pH, ionic strength and humic acid concentration were investigated. Kinetics of CIP removal was found to follow pseudo-second-order rate equation. Both Langmuir and Freundlich models fitted the adsorption data well and gave similar correlation coefficients (>0.96). However, Freundlich isotherm gave a better fit (r²=0.9969), suggesting a multilayer adsorption of CIP onto surface of NPC-700 adsorbent. The maximum adsorption capacity for CIP based on Langmuir model was 416.7mg/g, which was higher than those of other adsorbents. The NPC-700 material showed no apparent loss in CIP adsorption after seven cycles. These features reveal that the metal-organic framework (MOF) derived NPC may be a promising adsorbent for CIP removal from water.

Keywords: Adsorption; Ciprofloxacin; Nanoporpous carbons; Zeolitic imidazolate framework-8.