Boron adsorption removal by commercial and modified activated carbons

Although being an essential element for plants, animals, and people, due to its many industrial applications boron content in the environment exceeds its safe levels. In this paper, the results of the studies on the effectiveness of various commercial activated carbons (CACs) in the purification of water from dissolved boron compounds are presented. To further improve boron adsorptive capacity, the CAC was modified with polyhydric chelates and the as-formed adsorbents were characterized by SEM and BET analysis. The influence of various operating factors on the adsorption of boron was investigated, including a contact time, pH of solution, initial boron concentration and temperature. Batch studies revealed that the pH of solution is a key factor affecting boron removal, and the most efficient adsorption is observed at the pH of 8.5. The adsorption was found out to follow the pseudo-second-order kinetic model, with the equilibrium state achieved within 4h. The results indicated the exothermic and non-spontaneous nature of adsorption, the reduction of the entropy of the system, as well as the presence of a mixed, physical and chemical adsorption mechanism. Consequently, CAC modified by mannitol or xylitol is shown to serve as an efficient adsorbent for boron removal from polluted water. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.