A novel magnetic intercalation Fe3O4-QDs@g-C3N4/ATP photocatalyst was first prepared by a combined eutectic method with deposition technology; it shows superior degradation efficiency for removing 2-mercaptobenzothiazole (MBT) under visible light. The improved photocatalytic performance is mainly attributed to the intercalation effect of attapulgite (ATP) in g-C3N4 together with the quantum effect of Fe3O4 quantum dots (QDs) and the better conductivity between ATP and g-C3N4 resulting in the enhanced separation efficiency of photogenerated electron–hole pairs in the light absorption range. Moreover, insight into this mechanism indicates that the holes and superoxide radicals are the major active species in the MBT removal procedure. This work provides an efficient and promising approach to construct new high-performance g-C3N4-based photocatalytic materials for wastewater treatment.Keywords: 2-Mercaptobenzothiazole; Fe3O4-QDs; g-C3N4; Intercalation effect of attapulgite; Photocatalytic degradation;

A bioinspired photocatalytic nanocomposite membrane was successfully prepared via polydopamine (pDA)-coated poly(vinylidene fluoride) (PVDF) membrane, as a secondary platform for vacuum-filtrated Au-TiO2 nanocomposites, with enhanced photocatalytic activity. The degradation efficiency of Au-TiO2/pDA/PVDF membranes reached 92% when exposed to visible light for 120 min, and the degradation efficiency of Au-TiO2/pDA/PVDF membranes increased by 26% compared to that of Au-TiO2 powder and increased by 51% compared to that of TiO2/pDA/PVDF nanocomposite membranes. The degradation efficiency remained about 90% after five cycle experiments, and the Au-TiO2/pDA/PVDF nanocomposite membranes showed good stability, regeneration performance, and easy recycling. The pDA coating not only served as a bioadhesion interface to improve the bonding force between the catalyst and the membrane substrate but also acted as a photosensitizer to broaden the wavelength response range of TiO2, and the structure of Au-TiO2/pDA/PVDF also improves the transfer rate of photogenerated electrons; the surface plasmon resonance effect of Au also played a positive role in improving the activity of the catalyst. Therefore, we believe that this study opens up a new strategy in preparing the bioinspired photocatalytic nanocomposite membrane for potential wastewater purification, catalysis, and as a membrane separation field.Keywords: Au-TiO2 nanocomposite; photocatalytic membranes; polydopamine; tetracycline; visible-light degradation;

•The Novel multi-dimensional CQDs@In2S3/SWNTs composites with S-C heterostructure had been successfully prepared for the first time.•The CQDs@In2S3/SWNTs exhibited extensively enhanced photocatalytic activity for degradation of CIP, TC and LEV under visible light irradiation.•Such excellent properties of CQD@In2S3/SWNTs are attributable to the multi-dimensional structure and superior charge transfer capability of the CQDs.•The possible mechanism of CQDs for the enhancement of visible light performance was proposed.One of current ideal thought to reduce the recombination of photogenerated electrons and holes from semiconductors is constructing Multi-dimensional semiconductor-carbon (S-C) heterostructures. As well as acting to photo-degrade the organic contaminant and decrease the toxicity, β-In2S3 is chosen as a potential semiconductors for photocatalysts. Relative good photocatalytic properties delivered on β-In2S3, however, the fast recombination of photogenerated charge carriers are often appeared, causing reduced further application. Carbon quantum dots (CQDs) involve the introduction of plasma effect into the zero-dimensional nanomaterials in order to arouse an effect: either promoting the charge carriers transfer or plasma energy conversion of the photo-excited CQDs. However, state of the two components also encompass the poor quantum yield existed in the CQDs by its serious agglomeration. Thereby, the delivery of extraordinary ballistic electrical and thermal conductivity on single-walled carbon nanotubes (SWNTs), have shown potential for use in a variety of semiconductors decorating application. Herein, we show that a novel CQDs@In2S3/SWNTs composite in the Multi-dimensional (3D) hierarchical superstructures with an enhanced photocatalytic efficiency. The ESR analysis and free radicals trapping experiments indicated that the O2•− and h+ were the main active species for the photocatalytic degradation. The potential photocatalytic mechanism of the three components is discussed and the direction in the plasma effect exhibited in CQDs is also considered, with a particular focus on photocatalytic area.Download high-res image (186KB)Download full-size image

PNIPAM@ZnO/C composite photocatalyst was prepared by cross-linking polymerization technology with N-isopropylacrylamide used as functional monomer, N,N'-methylenebis (acrylamide) used as cross-linking agent, ammonium persulfate used as initiator, and 3-(trimethoxysilyl) propyl methacrylate used as surface modification reagent. The morphology, structure, electrochemical and photocatalytic properties of as-prepared samples were characterized via the serial tests. The temperature-response performances of PNIPAM@ZnO/C were evaluated by the photocatalytic degradation of tetracycline (TC) under different temperatures. The results show that the synthesized composite photocatalysts possess the excellent and switchable photocatalytic activity. The photocatalytic degradation activity of PNIPAM@ZnO/C is suppressed above the lower critical solution temperature (LCST), and it is enhanced below the LCST.Temperature sensitive photocatalyst of PNIPAM@ZnO/C was successfully prepared by cross-linking polymerization technology and it possesses excellent and switchable photocatalytic activity.Download high-res image (187KB)Download full-size image

A stable core–shell imprinted Ag-(poly-o-phenylenediamine)/CoFe2O4 (imprinted Ag-POPD/CoFe2O4) was synthesized via the surface imprinting technique. Ag-POPD was introduced into an imprinted layer, which significantly enhanced the photocatalytic activity. Meanwhile, due to the existence of imprinted cavities in the imprinted layer, the imprinted Ag-POPD/CoFe2O4 exhibited the superior specific recognition capability for selective photodegradation of ciprofloxacin (CIP). This work puts forward a novel design idea for synthesizing imprinted photocatalysts.

Hierarchical carbon materials with ultrahigh specific surface area and high porosity were synthesized by KOH activation from sustainable α-cellulose and employed as adsorbents to study adsorption performance of tetracycline (TC) and sulfamethazine (SMZ) from aqueous solutions. The physical and chemical properties of the as-prepared materials were characterized by SEM, TEM, FT-IR, XPS, Raman and a surface area analyzer. The obtained porous carbon exhibited a hierarchical pore structure, large BET specific surface area (3187.91 m2 g−1) and pore volume (1.781 cm3 g−1) when the activation temperature reached 850 °C. The maximum adsorption capacities were 1072.86 and 786.18 mg g−1 for TC and SMZ removal at 298 K, respectively. Moreover, TC and SMZ showed similar adsorption features, kinetic results could fit well using a pseudo-second-order model, intraparticle diffusion was not the rate-controlling step and adsorption isotherm results fit well with the Langmuir model. The adsorption capacities increased with contact time and adsorption temperature and, moreover, pH and external ionic species have a significant effect on adsorption efficiency. Thermodynamic studies implied that physisorption might dominate adsorption and the adsorption process is spontaneous and thermodynamically favorable. The results are of importance to indicate that the as-prepared porous carbon could be used as a low-cost and effective adsorbent in pharmaceutical wastewater treatment.

A novel graphitic carbon nitride (g-C3N4)–ZnO/halloysite nanotube (HNT) nanocomposite photocatalyst was synthesized via a facile calcination method in order to enhance the visible-light photocatalytic activity and stability of pure ZnO photocatalysts for degradation of tetracycline. The network-layered structure of g-C3N4 was formed after compositing with previously prepared ZnO/HNTs and the g-C3N4–ZnO heterojunction has been formed during the coupling process. Furthermore, the HNTs can efficiently extend the surface area of g-C3N4, which leads to strengthening of the pathways of charge transfer and prolonging the lifetimes of photoexcited carriers. Electrochemical impedance spectroscopy (EIS) and incident-photon-to-current conversion efficiency (IPCE) measurements showed the improvement of the as-obtained g-C3N4–ZnO/HNT photocatalysts' performance which can be attributed to enhanced charge transfer as a result of more effective separation of photogenerated electron–hole pairs. Such a notable enhancement of photocatalytic performance was mainly ascribed to the improved charge transfer and separation rate of photogenerated electron–hole pairs by the heterostructure of the g-C3N4–ZnO/HNT catalyst. The mechanism of photodegradation was systematically analysed by active species trapping test and electron spin resonance (ESR) spin-trap technique with dimethyl pyridine N-oxide (DMPO), which conclude that ˙OH and ˙O2− radicals are the major reactive species during the photocatalytic reaction for g-C3N4–ZnO/HNT composite photocatalysts.

Transition metal ions have been immobilized on TiO2/fly-ash cenospheres (TiO2/FACs) with poly-o-phenylenediamine (OPD). The as-prepared ion imprinting photocatalyst (M-POPD/TiO2/FACs) has been characterized by SEM, XRD, FT-IR, UV-vis DRS and ICP-AES. The results demonstrated that the polymer and mental ions existed in the M-POPD/TiO2/FACs. The photocatalytic activity of M-POPD/TiO2/FACs was studied by the degradation of tetracycline, oxytetracycline, ciprofloxacin, tetracycline hydrochloride and chloromycetin in simulated wastewater under visible light irradiation. The results showed that the M-POPD/TiO2/FACs could effectively increase the separation rate of photoelectrons and holes in the cycling system and improve the photocatalytic activity for the degradation of antibiotics in solution. Experimental data showed that the as-prepared M-POPD/TiO2/FACs were more suitable for degradation of tetracycline (5 mg L−1), and the photodegradation rate could reach 71.7%. In addition, possible formation and photocatalytic mechanisms were proposed.