ZIF-8 derived porous carbon/ZnO as an effective nanocomposite adsorbent for removal of acetic acid

A porous carbon/zinc oxide nanocomposite adsorbent was prepared by carbonization/oxidation of ZIF8 metal-organic framework (MOF) and then used to investigate the adsorption of acetic acid from water. Preliminary tests revealed that the adsorbent composed of 25% porous carbon/zinc oxide and 75% zeolite could result in superior acetic acid removal. Response surface methodology and central composite design algorithm (CCD) were used to optimize the operating variables affecting the acid removal. The optimal conditions were obtained at the initial acid concentration of 257.5 mg/L, the adsorbent amount of 152.5 mg, the contact time of 32.5 min and the sample volume of 28.75 mL. In the optimal conditions, an adsorption capacity equal to 106 mg/g was obtained. The experimental equilibrium adsorption was well-described by the Langmuir isotherm model, reflecting the monolayer chemisorption of the acid on the active sites. In addition, adsorption on the developed adsorbent followed the pseudo-second-order kinetics, and according to the thermodynamic study results, the adsorption was exothermic and spontaneous. In conclusion, the adsorption capacity of the porous carbon/zinc oxide-zeolite composite was fair, while its removal rate was extremely higher compared to that of the similar adsorbents.