Microwave assisted hydrothermal preparation of rice straw hydrochars for adsorption of organics and heavy metals.

A series of rice straw hydrochars were produced through a microwave-assisted hydrothermal treatment method, characterized and used for the adsorption of three organics and two heavy metals from aqueous solutions. The hydrochars have carbon contents from 37.44% to 43.31%, are rich in oxygen containing functional groups, and the equilibrium of hydrothermal carbonization reactions could be reached rapidly in microwave environment. The hydrochars can effectively adsorb the model pollutants, the maximum adsorption capacities of Congo red, berberine hydrochloride and 2-naphthol at 298 K and initial concentration of 0.5 mg/mL were 222.1, 174.0 and 48.7 mg/g, respectively, and those of Zn2+ and Cu2+ were 112.8 and 144.9 mg/g, respectively. Adsorption thermodynamic parameters were calculated. These results suggest that microwave-assisted hydrothermal treatment is an effective method for the rapid production of hydrochars, and rice straw hydrochars are promising adsorbents for the removal of water pollutants such as organics and heavy metals.

Characterization, isotherm and kinetic data for adsorption of Congo red and 2-naphthol on different bamboo hydrochars.

Hydrochars were prepared using bamboo sawdust as raw material through hydrothermal carbonization with the present of acid or alkali in the medium and applied to remove Congo red and 2-naphthol from aqueous solutions. This data article provides information on FTIR and SEM profiles of the bamboo hydrochars, and the equation fitting results of the adsorption isotherms and kinetics for the two organics. The FTIR spectra show the differences of functional groups on the hydrochars with different process conditions. The SEM images show the surface morphology of selected hydrochars. Freundlich equation is slightly better than Langmuir model for the correlation of adsorption isotherms for both Congo red and 2-naphthol. Correlation coefficients from the pseudo-second order equation are greater than those of the pseudo-first order equation for both the organics on selected hydorchars.

Hydrochars from bamboo sawdust through acid assisted and two-stage hydrothermal carbonization for removal of two organics from aqueous solution.

A series of bamboo hydrochars were prepared through acid-assisted and two-stage hydrothermal carbonization, characterized and evaluated for the adsorption of Congo red and 2-naphthol in aqueous solutions. The hydrochars have rough surfaces with BET surface areas of 6.77-57.74 m2/g and oxygen-rich functional groups. The additives in feed water revealed critical influences on the physical-chemical and adsorption properties of the hydrochars. The hydrochars can adsorb the two organics effectively, the highest adsorption capacities for Congo red and 2-naphthol are 90.51 and 72.93 mg/g, respectively, at 0.1 mg/mL and 298 K. The adsorption of the two organics on the selected hydrochars is a spontaneous and mainly physical adsorption process. 95% and 92% of the adsorption equilibrium could be accomplished in one hour for Congo red and 2-naphthol on the selected hydrochars, respectively. This study provides references for the production and application of hydrochars as efficient adsorbents in wastewater treatment.