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The classes and forms of antibiotics directly determine their ecotoxicity and environmental chemical behavior, and developing a sensor array for simultaneous and in situ detection of antibiotics is highly anticipated. In this study, different morphologies of g-C3N4with different fluorescence properties and peroxidase activity were prepared by regulating the degree of interlayer stacking and planar connectivity. Subsequently, in order to enhance its enzyme activity and amplify the differences in response signals to different antibiotics, three morphologies of g-C3N4/MIL-101(Fe) were prepared by in situ growth of equivalent amounts of MIL-101(Fe) on g-C3N4, respectively. The sensor array constructed based on the cross-response signals between g-C3N4/MIL-101(Fe) and antibiotics not only realized the simultaneous detection of quinolones, furans, tetracyclines, and lincomamides but also could efficiently identify their seven different forms. In the range of 0.2–0.8 ppm, the minimum detection limit for antibiotics was 12 ppb. In addition, the recovery experiments of multicomponent-mixed antibiotics in environmental samples show that the recovery rate remained at 91.42–107.59%, confirming the reliability and practicality of the sensor array. This study not only revealed the influence of crystal morphology regulation on the optical properties and enzyme activities of nanozymes, but also provided support for tracing, ecological remediation, and in situ environmental chemical behavior research of antibiotics.

In-situ generation of H2O2and its efficient utilization in chemical oxidation for water pollution treatment has garnered increasing attention. However, dependency on sacrificial agents and low working pH range greatly impeded its practical application. In this study, we reported an efficient and stable in-situ H2O2generation (382 μM g−1h−1) at a variable pH range from acid to alkaline (pH 3–9) via a photocatalytic process over a covalent organic polymer (COP-TT) Based on a series of probe experiments using various electron and hole sacrificial agents, the reaction mechanism especially the contribution of oxygen reduction reaction (ORR) and water oxidation reaction (WOR) to H2O2production was investigated. Importantly, the advantages of in-situ production and utilization of H2O2were evaluated by the degradation efficiency of antibiotics in the visible light-assisted Fenton reaction and UV/H2O2processes. Compared with UV/H2O2, a much higher sulfamethoxazole (SMX) degradation efficiency was obtained in the photo-Fenton process (51.2 % vs.97.3 %). Moreover, according to electron spin resonance (ESR) analysis and radical quenching results, •OH was proven to be the major reactive oxygen species (ROS) responsible for efficient SMX degradation. Hence, this study provides a promising alternative for in situ generation and utilization of H2O2for water purification.

The performance of the Fenton reaction under alkaline conditions is important to promote its application in practical water treatment. In this study, a sulfide doped mesoporous carbon (SC) and CuFeO2composite (SC@CuFeO2) was prepared and its Fenton-like activity was evaluated by the degradation of sulfamethoxazole (SMX) in an alkaline solution especially in the presence of bicarbonate. The results indicated that 93% of SMX was efficiently degraded over SC@CuFeO2at pH 8.7 with 15 mM HCO3−in water. In comparison, the SMX removal efficiency was only about 20% without HCO3−. Furthermore, the introduction of SC can indeed improve the Fenton activity of CuFeO2. For instance, the removal efficiency of SMX over CuFeO2and SC@CuFeO2was 80% and 70%, respectively, under the same conditions. Based on the characterization results, electron paramagnetic resonance spectra, probe experiments and OH radicals' quantitative measurement, more radical production especially the transformation processes involving reactive oxygen species (OH, O2−CO3−and 1O2) were responsible for the enhanced SMX degradation over SC@CuFeO2under alkaline conditions. Finally, the intermediates of SMX degradation were detected by GC-MS/MS and the degradation pathway was discussed. These findings suggest that the effect of the water matrix on the oxidation efficiency of the Fenton reaction should be considered in real water treatment.

As(iii) pollution has caused increasing concern due to its significant impact in environmental safety and human health. Carbon dots (CDs)–MnO2nanocomposites were prepared and characterized for As(iii) detection. The intense blue fluorescence of CDs can be greatly quenched by functionalization with MnO2nanosheets due to the existence of the fluorescence resonance energy transfer (FRET) effect. CDs–MnO2nanocomposites were then used as a fluorescence sensor for As(iii) detection with high detection sensitivity and selectivity. The redox reaction between As(iii) and MnO2nanosheets can induce the decomposition of MnO2and termination of the FRET process. Then the blue fluorescence originating from CDs can be recovered. The detection limit of CDs–MnO2nanocomposites toward As(iii) was calculated to be 16.8 nM (1.40 ppb) in a linear concentration range of 0–200 nM. CDs–MnO2nanocomposites were also found to possess highly selective ability toward As(iii) detection. In addition, the spiked and recovery test also confirmed the practicality and reliability of CDs–MnO2nanocomposites toward As(iii) detection in real water samples, such as groundwater etc.Our research has provided a reliable tool and strategy for visual detection of As(iii) with outstanding sensing ability.

In this study, polyethylenimine-functionalized corn bract (PEI–CB) was first used to remove aqueous Cr(VI) via the “waste control by waste” concept. The results indicated that PEI–CB had an excellent performance for Cr(VI) removal and the maximum removal capacity was 438 mg/g. The adsorption of Cr(VI) was fitted to the Langmuir model, and kinetics of uptake could be described by a pseudo-second-order rate model well. Amine was proven to be the active center for Cr(VI) adsorption and partial reduction to Cr(III), while removal efficiency was enhanced at a lower pH value and higher temperature. Besides, nanosized Cr2O3with a high purity was obtained by simple calcination of a Cr(VI)-laden adsorbent. Hence, this study provided a novel strategy for Cr(VI) wastewater remediation and pure Cr2O3recovery. Prepared PEI–CB was then a promising alternative of low cost for replacement of the current expensive absorbent of removing Cr(VI) from wastewater from the view of sustainability.