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The advanced oxidation process (AOPs) has caused great concern in recent years. Among them, biochar has been widely studied as a catalyst for advanced oxidation process because of its low price and low environmental risk. In this study, a novel ball milling assisted KOH activation biochar (MKBC) was prepared and applied in peroxydisulfate (PDS) activation to degrade tetracycline hydrochloride (TC-H). In comparison with the oxidation (3.48%) by PDS alone and adsorption (36.19%) by MKBC alone, the removal rate of TC-H was increased to 84.15% in the MKBC/PDS system, indicating that MKBC can successfully activate PDS. Besides, the catalytic activity of the MKBC to activate PDS for the degradation of TC-H is 58.33% higher than that of pristine biochar (PBC). In addition, MKBC has outstanding stability that after three repeated experiments, the removal rate of TC-H by the MKBC/PDS system still remains 77.35%. Meanwhile, the mechanism was investigated that the singlet oxygen ( 1 O 2 ) seized the principal position in the degradation of TC-H in the PDS/MKBC system. This study explored a novel, solvent-free and economic method to propose this extraordinary biochar, which provided a new strategy for the future research of biochar., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021. Published by Elsevier Inc.)

The adsorbability on the carbonaceous cathode plays an important role in electro-Fenton systems but does not obtain enough attention. In this work, various carbon felts were obtained with different adsorption property by using the method of KOH activation at different temperatures to explore the influence of adsorption on the degradation efficiency of tetracycline (TC). The results of morphology characterization, nitrogen adsorption-desorption tests, XPS and FTIR analysis revealed that the surface area of carbon felt was improved, and the oxygen-containing functional groups on the surface were increased via KOH method with significantly enhanced adsorption capacity. In the batch experiment of TC electro-Fenton degradation, the carbon felt with better adsorption capacity tended to get higher degradation and mineralization efficiency. With the KOH activation process, CF-900 (carbon felt at 900 °C for 1 h) exhibited the best TC adsorption property for the removal of TC within 30 min (initial concentration: 80 mg/L). Meanwhile, the constant of reaction rate for TC degradation at the CF-900 is 0.0648 min -1 . It is higher than that (0.012 min -1 ) obtained at the raw carbon felt (∼5 times of enhancement). There are also synergistic effects between adsorption and degradation performance on some other organic pollutants. In addition, the degradation pathway was also studied by the methods of solid-phase extraction and high performance liquid chromatography-mass spectrometry (HPLC). From the obtained results, it is shown that good adsorbability is favorable for degradation in the homogeneous electro-Fenton system., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Municipal sewage sludge (MS)-derived biochar shows low-cost superiority as a potential adsorbent in organic contaminants removal, but limited by its poor adsorption capacity and heavy metal leaking risk. Herein, a novel and effective alkali-acid combined method was proposed for its modification and applied to tetracycline adsorption. The associative facilitation between the alkali and acid modifications was explored, and the influences of pyrolysis temperatures on MS-biochar’s properties were investigated. The successfully preserved γ-Fe 2 O 3 vested SNMS-800 with magnetism. It turned out that SNMS-800 exhibited optimum performance for tetracycline removal with adsorption capacity up to 286.913 mg/g, where all goodness-of-fit indexes of isothermal models were measured by MPSD model. The strong adsorption mechanisms were dominated by two considerable interactions, including strong π-π stacking interaction and pore-filling effect due to the significantly enhanced porosity which was proved by density functional theory model calculations. It manifested that appropriate multiple relation (1.7–6 times) between adsorbent’s pore size and adsorbate size closely related to the adsorption strength. The remarkably improved and stable adsorption capacity, extremely low-cost, easy magnetic preparation, and good reusability in natural water samples entrusted SNMS-800 with good potential for actual aqueous contaminant removal on a large scale. Meanwhile, it provides a clue for materials modification starting with its specific components, and supplies a cost-effective way for municipal sewage sludge’s resource disposal. [ABSTRACT FROM AUTHOR]

[Display omitted] • Floating porous g-C 3 N 4 composite (FPCN) was successfully fabricated by a facile one-pot method. • FPCN exhibited a good photocatalytic performance under visible light without any stirring. • FPCN showed a good stability and reusability. • Possible degradation pathway of tetracycline and mechanism of the photocatalytic process were proposed. Powder catalysts are difficult to recycle, which may induce secondary pollution and may limit their practical application. Herein, we successfully synthesized floating porous g-C 3 N 4 (FPCN) using a melamine sponge and urea via a facile one-pot method, which can solve the recycling problem of powder catalysts. The highest elimination efficiency of 5 mg/L tetracycline (TC) reached 70% by 2 g/L FPCN without any stirring under visible light after 4 h. However, the elimination efficiency of 5 mg/L TC by 2 g/L powder g-C 3 N 4 was only 36.9% under the same conditions. The good photocatalytic performance of FPCN is attributed to its 3D interconnected network and enhanced light absorption. The effects of inorganic ions and organic matters on the photocatalytic performance of FPCN were studied. Finally, we proposed a possible mechanism and pathway for degradation of TC. [ABSTRACT FROM AUTHOR]