Selective adsorption of p-chloronitrobenzene from aqueous mixture of p-chloronitrobenzene and o-chloronitrobenzene using HZSM-5 zeolite

The selective adsorption of p-chloronitrobenzene (p-CNB) using zeolite as the adsorbent from an aqueous mixture containing p-CNB and o-chloronitrobenzene (o-CNB) was investigated. The maximum adsorption amounts of p-CNB in HZSM-5 zeolite were found to be approximately 4 molecules per unit cell (mol/uc) at all adsorption temperatures investigated. The maximum adsorption amounts of o-CNB in HZSM-5 zeolite were, however, markedly lower than those of p-CNB at different adsorption temperatures. Diffusion results revealed that the diffusivity of p-CNB at 300 K was about 100 times higher than that of o-CNB in HZSM-5 zeolite. The remarkable difference in the adsorption amounts and diffusivities between p-CNB and o-CNB resulted in separation factors of 463.6, 96.8 and 21.9 for p-CNB at 278, 300 and 323 K, respectively, indicating a selective adsorption of p-CNB in HZSM-5 zeolite from the aqueous mixture of p- and o-CNB.