Hydrothermal synthesis and microwave-assisted activation of starch-derived carbons as an effective adsorbent for naphthalene removal

Abstract

In this work, starch-derived spherical carbon (HC) was prepared by hydrothermal carbonization and further activated with microwave assistance to obtain the target activated carbon (HMAC). The samples were characterized by methods of N₂ adsorption–desorption, Brunauer–Emmett–Teller analysis, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, elemental analysis and scanning electron microscopy. Moreover, HMAC has a high BET surface area of 616.8 m² g⁻¹. The effects of initial naphthalene concentration, contact time, temperature, and pH of the naphthalene adsorbed on HC and HMAC were investigated systematically. The HMAC exhibits higher capability for naphthalene removal than HC, and the equilibrium adsorption quantity of HMAC was 223.03 mg g⁻¹ at 303 K. The kinetic data revealed that the equilibrium time for naphthalene adsorption on samples was achieved at 40 min. The adsorption process of HC and HMAC for naphthalene both followed the pseudo-second-order kinetic and Freundlich isotherm models. Additionally, H-bond and π–π interactions were proposed to be involved in the adsorption process. An increasing adsorption amount of naphthalene onto HC and HMAC was observed when the pH value varied from 2 to 10. The HMAC can be successfully regenerated and maintained sorption performance after three cycles. This study revealed that HMAC obtained by hydrothermal synthesis combined with microwave-assisted activation has a promising application in the field of naphthalene removal.