Bentonite and carbon nanotube adsorbents for the removal of bisphenol A from water

The present study investigates the adsorption of bisphenol A (BPA), a well-known endocrine dis-ruptor and widespread pollutant in the aquatic environment, using bentonite clay (Ben) and ben-tonite-carbon nanotubes composite (Ben-CNT) as adsorbents. In the study of adsorption iso-therms, the initial concentrations of BPA in water were 1 and 2 mg/L, while for the kinetic study it was 1 mg/L. The kinetics data correlated well to a pseudo-second-order reaction, with Ben and Ben-CNT reaching equilibrium in around 60 and 180 min, respectively. Isothermal data fitted well to Freundlich and Dubinin–Radushkevich models, while the Langmuir model did not provide suitable fitting. The resulting adsorption capacity was about 1.56 and 29.61 mg/g for bentonite and bentonite-carbon nanotubes composite, respectively. The removal percentage of BPA was improved from about 24% for bentonite clay to 87% for bentonite-carbon nanotubes composite for adsorbents dose of 0.25 g/100 mL. This improvement was due to the large specific surface area of carbon nanotubes and the availability of large number of active groups for binding pollutants.