Cyclohexane and benzene separation by fixed-bed adsorption on activated carbons prepared from coconut shell

Abstract

New activated carbons were prepared from coconut shell and tested to evaluate their adsorption properties to separate benzene and cyclohexane. A Taguchi experimental design was utilized to identify the best preparation conditions of the activated carbons based on their benzene adsorption capacities. Type and concentration of the chemical agent, ratio of precursor mass/chemical agent volume and physical activation time were the variables analyzed. Adsorbents were physiochemically characterized and the adsorption capacities of these adsorbents were evaluated in a dynamic system coupled to a GC-FID. Benzene and cyclohexane adsorption capacities of tested adsorbents ranged from 1.35 to 51.40 and 0.49 to 25.20 mmol/g, respectively. The statistical analysis indicated that the activating agent, impregnation ratio, and physical activation time were the most important variables to prepare an activated carbon with a high benzene adsorption during the binary mixture separation. In particular, the adsorbents obtained with ZnCl 2 showed the highest adsorption properties. The best activated carbon showed an acceptable separation of 92.64% of benzene and 7.36%: of cyclohexane and a reuse efficiency of 96% after four adsorption/desorption cycles. This study contributes with new findings on the preparation of low-cost and effective activated carbons for the separation of benzene and cyclohexane at industrial level. • Low-cost activated carbons to separate cyclohexane and benzene was synthetized. • An activated carbon (E5) separated 100% of the benzene from mixtures. • An activated carbon (E4) presented high adsorption capacity of both compounds. • Using a Taguchi design the effect of factors in adsorption capacity was evaluated. • An activated carbon (QB) showed a reuse efficiency of 96% after four adsorption/desorption cycles.