ZIF-8/carbon fiber for continuous adsorption of sodium dodecyl sulfate (SDS) from aqueous solutions: Kinetics and equilibrium studies

Abstract

In this research, sodium dodecyl sulfate (SDS) separation from aqueous solutions using hierarchical porous zeolitic imidazolate framework-8/carbon fiber (ZIF-8/carbon fiber) nanosorbent was assessed by batch and column process. The characterization of the ZIF-8/carbon fiber nanocomposite was conducted by X-ray diffractometer (XRD) and field emission-scanning electron microscopy (FE-SEM). In addition, the influence of pH on the adsorption batch studies was investigated. The quantity and quality of SDS uptake by ZIF-8/carbon fiber were studied based on ultraviolet–visible spectroscopy measurements and Fourier transform infrared spectroscopy (FTIR) spectra. Aside from that, a practical process involving column of the ZIF-8/carbon fiber adsorbent to remove SDS was performed, dynamically. It was found that the loading of ZIF-8 nanoparticles on carbon fiber struts increased the hydrophobicity of carbon fiber, and its contact angle with water increased from 90° to 150°. Besides, the results of FTIR confirmed successful adsorption of SDS onto ZIF-8/carbon fiber surfaces, which is believed to be governed by both electrostatic attraction and hydrophobic interactions. In addition, the results of batch experiments illustrated that adsorption of SDS onto ZIF-8/carbon fiber adsorbent is rapid with an equilibrium time of 30 min and follows a first-order kinetic model (R2 = 0.9944). Furthermore, the Langmuir isotherm model was best fitted adsorption equilibrium (R2 = 0.9899), at different pH values. The results revealed the removal quantity after five cycles was decreased by 20% for SDS removal. Moreover, the maximum adsorption capacity of SDS on the ZIF-8/carbon fiber was obtained 377 ± 7 mg/g at the optimal conditions. The column adsorption experiments showed that inline SDS removal is possible.