Production and optimization of bamboo hydrochars for adsorption of Congo red and 2-naphthol

Twelve hydrochars were produced from bamboo sawdust for adsorption of Congo red and 2-naphthol. The bamboo hydrochars have Brunauer-Emmett-Teller (BET) surface areas ranging from 2.63 m(2)/g to 43.07 m(2)/g, average pore diameters from 3.05 nm to 3.83 nm, pore volumes between 0.02 cm(3)/g and 0.53 cm(3)/g, and the surfaces of the hydrochars have diverse functional groups. The physico-chemical properties of the hydrochars critically depend on the hydrothermal conditions. All the hydrochars can adsorb Congo red and 2-naphthol from aqueous solutions, the largest adsorption capacity for Congo red is 33.7 mg/g at the equilibrium concentration of 0.1 mg/mL at 25 degrees C, and the highest adsorption amount for 2-naphthol is 12.2 mg/g at 25 degrees C and 0.1 mg/mL. Freundlich model can describe the adsorption isotherms of the both adsorbates slightly better than Langmuir model. These results provide a reference to the production and use of hydrochars as potential adsorbents in wastewater treatment.