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Biochar was prepared from corncob-to-xylose residue (CCXR) by KOH activation and anaerobic pyrolysis method. The effect of activation temperature on the microstructure of the biochar was studied. Results showed that the biochar prepared at 850°C (850NBC) possessed high specific surface area and exhibited excellent adsorption property. The maximum adsorption capacity of 2249 mg g −1 was obtained when 850NBC was used for treating methylene blue (MB) solution. Adsorption isotherm fittings revealed that Langmuir and Freundlich models were applicable to 850NBC adsorption process, and the adsorption process was limited by adsorption site and the biochar surface functional groups. Furthermore, 850NBC showed good adsorption property when it was used to treat the other organic dyes of Congo red (751 mg g −1 ), Orange II (735 mg g −1 ), Indigo carmine (662 mg g −1 ) and Methyl Orange (465 mg g −1 ). Biochar 850NBC also possessed an acceptable recyclability which maintained 68.7% absorption capacity after 6 cycles when it was used to treat MB solution. These results proposed that 850NBC is expected to be a promising potential adsorbent for treating organic dyes waste water.

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To remove antibiotics from waste water, an alkali active porous biochar, 850BC, was prepared from corncob xylose residue. In preparation, NaOH dipping was used for silicon removal and KOH activation was operated at 850℃. Further characterization containing BET, SEM, and FTIR were confirmed. 850BC possessed a huge specific surface area of 3043 m2·g−1, developed pore structure and abundant oxygen functional groups. The adsorption performance of sulfamethoxazole on 850BC was quick and efficient, and the adsorption capacity reached 1429 mg·g−1, which was significantly higher than other adsorbents reported previously. While pseudo-second-order kinetic model and Langmuir model could better describe the adsorption, chemisorption dominated the SMX adsorption onto 850BC. In virtue of pore-filling and π–π interaction as major mechanism, a large surface area and rich oxygen-containing functional groups led to an excellent adsorption performance. Thus, this preparation method provided a biochar-based adsorbent with enhanced specific surface for efficient removal of antibiotic pollutants. Graphical Abstract

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