Copper-modified adsorbents based on commercial zeolites with enhanced adsorption performance for n-butanol recovery from wastewater

Abstract

Industrial production and transportation of n-butanol generate a substantial volume of wastewater, which poses significant treatment challenges because of the tendency of n-butanol to form an azeotrope with water. Adsorption, a promising method for treating n-butanol wastewater, still faces limitations such as the low adsorption capacity and desorption efficiency of conventional commercial adsorbents. This study systematically screened commercial adsorbents and identified ZSM-5-300 as a suitable candidate. The 7.5Cu-ZSM-5 adsorbent was developed to overcome the limitations of commercial adsorbents in terms of adsorption capacity, presenting an exceptional n-butanol adsorption capacity of 114 mg g⁻¹ with a 53% improvement over unmodified ZSM-5. Adsorption kinetics and isotherm studies indicated that n-butanol is adsorbed as a monolayer on 7.5Cu-ZSM-5, with physical adsorption being predominant. Thermodynamic analysis further revealed that this adsorption process is spontaneous and exothermic. Additionally, the adsorbent showed excellent adsorption–desorption cycling stability, with a low adsorption capacity loss of 17.72% after 20 cycles. This work reveals that metal-modified ZSM-5, with enhanced performance and moderate reusability, is a promising alternative to conventional commercial adsorbents for the sustainable recovery of n-butanol from wastewater.