High-performance sorbents from ionic liquid activated walnut shell carbon: an investigation of adsorption and regeneration

In this paper, walnut shells were selected to make activated charcoal using ionic activators. Based on the physical/chemical activation process and the properties of activated carbon products, the Fourier Transform Infrared reflection and Brunauer-Emmett-Teller analysis methods were adopted to comparatively analyse activation principles and pore-structure parameters. Also ciprofloxacin adsorption was compared among various activated carbon. Then, an absence of microporous structure in both walnut shells and their carbonized derivatives was found. Moreover, the specific surface area of activated carbon, prepared via KOH wet activation within physical/chemical procedures, attains a noteworthy 1787.06 m 2 g −1 , underlining its commendable adsorption performance. The specific surface areas of five distinct activated carbons, processed via ionic activation, extend from 1302.01 to 2214.06 m 2 g −1 . Concurrently, the micropore volumes span from 0.47 to 0.93 cm 3 g −1 . Obviously, the adsorption proficiency of ion-activated carbon markedly exceeds that of carbons activated physically or chemically. Of all materials investigated in this paper, ion-activated carbon D consistently exhibits superior performance, maintaining a ciprofloxacin removal rate nearing 100% at 40 °C. Remarkably, the maximum regeneration frequency of ion-activated carbons can reach up to 10 cycles. In conclusion, these five ion-activated carbons, demonstrating superior pore-structure parameters and adsorptive capacities, outperform those prepared through physical/chemical methods. They emerge as promising contenders for new, high-performing adsorbents. Ionic reagents have demonstrated a unique capacity to hydrolyze the residual cellulose found in walnut shell-based biomass char. The process leads to the creation of pores within carbon structure, which are crucial for its adsorption capabilities.