Effect of pyrolytic temperature on the adsorptive removal of p-benzoquinone, tetracycline, and polyvinyl alcohol by the biochars from sugarcane bagasse

Sugarcane bagasse was pyrolyzed under oxygen-limited conditions from 100 to 600 °C and used for the adsorptive removal of oxidation intermediate p-benzoquinone, tetracycline, and polyvinyl alcohol. The three organic pollutants have different polarities and solubilities. The carbon content increased from 57.7% of the raw bagasse to 75.3% of the biochar pyrolyzed at 600 °C, while the O content decreased from 13.2% to 6.1%. Accordingly, the biochar surface became more hydrophobic with increasing pyrolytic temperature. Interestingly, the adsorption affinity of biochars towards the three pollutants improved with an increase in the pyrolytic temperature. The adsorption of tetracycline molecules was almost unaffected by its being negatively charged with increasing solution pH. A mechanism of π-π electron-donor-acceptor interaction might contribute to the adsorption of tetracycline and p-benzoquinone, while H-bond interaction between polyvinyl alcohol and the biochar might be dominant during adsorption. The Elovich model fitted the kinetic model well, indicating that the diffusional rate-determining step was more pronounced. An isotherm study indicated that the contribution of partitioning was also dominant in the adsorption processes. Wide application of the prepared biochars is expected for the efficient adsorptive removal of organic pollutants.