Synthesis of clay/carbon adsorbent through hydrothermal carbonization of cellulose on palygorskite

• Palygorskite/carbon composites were prepared using cellulose as carbon source.
• Nanocarbons with CH, CH2, CHCH, and CO were loaded onto the clay surface.
• The loading of carbon improved the organophilic property of palygorskite.
• Palygorskite/carbon showed the same adsorption ability for phenol as active carbon.

Organophilic palygorskite/carbon composites were prepared through a green hydrothermal carbonization process using palygorskite clay and cheap cellulose as raw materials. The effects of reaction temperature (210 °C to 250 °C) and time (2 h to 48 h) on the product structures were investigated, and a potential reaction mechanism was proposed. Nanocarbon particles (10 nm in diameter) were loaded onto the palygorskite surface (220–250 °C, 12 h or 210 °C, 24–48 h). Results from the Fourier transform infrared and X-ray photoelectron spectroscopy showed that the resultant palygorskite/carbon composites contained organic groups, including CH, CH2, CHCH and CO. The coating mechanisms of palygorskite and nanocarbon were also discussed. The contribution of organic carbon to organophilic improvement was further confirmed by the static adsorption of phenol. The removal rate of phenol from aqueous solution increased with hydrothermal time and temperature, indicating that the loading of nanocarbon particles with organic groups made an important contribution for the organic modification of palygorskite. The palygorskite/carbon obtained at 250 °C in 48 h exhibited the highest adsorption (92 wt.%) of phenol, which was slightly higher than that of commercial active carbon (90 wt.%) and significantly higher than that of unmodified palygorskite (18 wt.%).