This paper comparatively investigated the removal efficiency and mechanisms of rice straw biochars prepared under three pyrolytic temperatures for two kinds of tetracycline and quinolone antibiotics (doxycycline and ciprofloxacin). The influencing factors of antibiotic adsorption (including biochar dosage, pH, background electrolytes, humic acid, initial antibiotics concentration, contact time, and temperature) were comprehensively studied. The results suggest that biochars produced at high-temperature [i.e., 700°C (BC700)], have higher adsorption capacity for the two antibiotics than low-temperature (i.e., 300–500°C) biochars (BC300 and BC500). Higher surface area gives rise to greater volume of micropores and mesopores, and higher graphitic surfaces of the BC700 contributed to its higher functionality. The maximum adsorption capacity was found to be in the following order: DOX > CIP. The π-π EDA interaction and hydrogen bonding might be the predominant adsorption mechanisms. Findings in this study highlight the important roles of high-temperature biochars in controlling the contamination of tetracycline and quinolone antibiotics in the environment.

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BACKGROUND Antibiotics are widely used for the treatment of bacterial infections in humans and animals, but it can be released into water sources due to incomplete metabolism in humans or via discharge from drug manufacturers. RESULTS The efficiency of removal of three antibiotics was enhanced with increasing biochar dosage. The adsorption of three antibiotics by RH700 was much higher than by RH300 and RH500, which might be due to the larger surface area and adsorption pore volume of RH700 (211.76 m2 g‐1 and 6.25 nm, respectively). In addition, the adsorption capacity was greatly affected by the solution pH, background electrolyte and humic acid. The kinetics experiment data were well fitted by the pseudo‐second‐order kinetic model. The maximum adsorption capacities of tetracycline hydrochloride (TC), doxycycline hydrochloride (DC) and ciprofloxacin (CF) based on the Langmuir model by RH700 at 318 K were 80.9, 85.2 and 36.1 mg g‐1, respectively. RH700 exhibited high affinity for antibiotics, mainly ascribed to the chemical interaction between oxygen‐containing functional groups (phenolic hydroxyl group, carboxyl and alkoxy groups) of the biochar surface and TC, DC and CF. CONCLUSION The rice husk biochar produced at high temperature could be applied as a potential adsorbent for removal of antibiotics from water. © 2017 Society of Chemical Industry

abWith a view to reducing estrogens pollution in aqueous environments, montmorillonite/hydrochar (MMT/ HC) with or without modification by KOH via hydrothermal carbonization process (HTC) were applied to remove 17b-estradiol (E2) and 17a-ethynylestradiol (EE2). The characterizations of MMT/HC indicated that MMT had been successfully attached onto HC surface, which could cause an improvement in the stability of the clay nanoparticles. MMT/HC with 1% KOH (MMT/HC-K1) exhibited excellent adsorption) compared to those of other adsorbents; approximately 2-fold higher than that of HC. Moreover, the adsorption capacity maintained a high level over a wide pH range (2-8). The pseudo-second-order model and Freundlich model exhibited prior fitting performance for adsorption of E2 and EE2. The regenerated MMT/HC-K1 retained over 80% of its initial capacity after four cycles. The adsorption mechanism on MMT/HC-K1 could be explained by hydrophobicity, p-p bond, electrostatic interaction and H-bonding interaction. Overall, MMT/HC-K1 synthesis from two low-cost materials, could be considered as a competitive adsorbent for estrogens removal from aqueous environment, considering its high adsorption capacity and regeneration ability.