Heterojunction material BiYO3/g-C3N4 modified with cellulose nanofibers for photocatalytic degradation of tetracycline.

Cellulose nanofibers (CNFs) with large specific surface area and superb adsorption capacity are excellent photocatalyst carriers. In this study, heterojunction powder material BiYO3/g-C3N4 was successfully synthesized for the photocatalytic degradation of tetracycline (TC). The photocatalytic material BiYO3/g-C3N4/CNFs was obtained by loading BiYO3/g-C3N4 on CNFs using electrostatic self-assembly method. BiYO3/g-C3N4/CNFs exhibit a fluffy porous structure and large specific surface area, strong absorption in the visible light range, and the rapid transfer of photogenerated electron-hole pairs. Polymer-modified photocatalytic materials overcome the disadvantages of powder materials that are easy to reunite and difficult to recover. With synergistic effects of adsorption and photocatalysis, the catalyst demonstrated excellent TC removal efficiency, and the composite maintained nearly 90 % of its initial photocatalytic degradation activity after five cycles of use. The superior photocatalytic activity of the catalysts is also attributable to the formation of heterojunctions, and the heterojunction electron transfer pathway was confirmed by experimental studies and theoretical calculations. This work demonstrates that there is great research potential in using polymer modified photocatalysts to improve photocatalyst performance.

Visible-UVC upconversion polymer films for prevention of microbial infection.

Bacterial infections caused by the growth and reproduction of pathogenic bacteria on wounds are one of the main reasons that hinder wound healing. Antibacterial wound dressings protect wounds from bacterial infections. Herein, we developed a polymeric antibacterial composite film using polyvinyl alcohol (PVA) and sodium alginate (SA) as the substrate. The film used praseodymium-doped yttrium orthosilicate (Y2SiO5: Pr3+, YSO-Pr) to convert visible light into short-wavelength ultraviolet light (UVC) to kill bacteria. The YSO-Pr/PVA/SA showed upconversion luminescence in photoluminescence spectrometry tests, and the emitted UVC inhibited Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria in antibacterial tests. In vivo animal tests showed that YSO-Pr/PVA/SA is effective and safe for inhibiting bacteria in real wounds. The in vitro cytotoxicity test further confirmed the good biocompatibility of the antibacterial film. In addition, YSO-Pr/PVA/SA exhibited sufficient tensile strength. Overall, this study demonstrates the potential of upconversion materials for use in medical dressings.

Photocatalytic degradation of dye wastewater by stepwise assembling PVA aerogel/TiO2/MoS2/Au composites in visible light.

A PVA aerogel/TiO2/MoS2/Au catalyst formed gradually using a hydrothermal method is used to degrade Rhodamine B. SEM and TEM results show that the composite presents a uniform and well-structured porous network structure, high specific surface area and large pore diameter were proved by the results of nitrogen adsorption measurement. UV-vis DRS and PL results indicate that the composite has a high absorption rate in the visible light range, and the recombination of photogenerated electron-hole pairs can be effectively inhibited because the composite material forms a heterojunction. In the photocatalytic degradation experiment of Rhodamine B, the composite material shows high photocatalytic performance, which can reach 86% in two hours of light. The photocatalysts supported by PVA are easy to recover and have high catalytic performance even after five recycles. The study shows that PVA/TiO2/MoS2/Au composite material has great potential to be used for the degradation of dye wastewater.

Bacteriostatic activity and cytotoxicity of bacterial cellulose-chitosan film loaded with in-situ synthesized silver nanoparticles.

Bacterial infections on open wounds have always been a threat to human health. Herein, we prepared a silver (Ag)-polydopamine (PDA)/bacterial cellulose (BC)-chitosan (CTS) film using biological self-generation and in situ reduction. CTS was added to culture medium to allow BC to intertwine with CTS during film formation. Silver nitrate was reduced in situ to Ag nanoparticles under ultraviolet irradiation, and the nanoparticles were well dispersed in the BC-CTS film with the help of PDA, which worked synergistically with the CTS. The Ag-PDA/BC-CTS film was enriched in functional groups, and it had good tensile and swelling properties. The inhibition film demonstrated broad-spectrum inhibition of Gram-positive and Gram-negative bacteria, and this inhibition was maintained at more than 80% after 48 h of continuous use. The good biocompatibility of the film was verified using NIH3T3 fibroblasts. The results suggested that the Ag-PDA/BC-CTS film inhibited the growth of harmful bacteria while having little effect on healthy cells.

A RGO aerogel/TiO2/MoS2 composite photocatalyst for the removal of organic dyes by the cooperative action of adsorption and photocatalysis.

A composite consisting of reduced graphene oxide aerogel/titanium dioxide/molybdenum disulfide (abbreviated as RGO aerogel/TiO2/MoS2) was developed for the removal of organic dyes from solution cooperatively by adsorption and photocatalytic degradation mechanisms. The composite was successfully synthesized by stepwise layered assembly integration, including sol-gel and physical vapor deposition (PVD) methods. The resulting multi-component composite material featured a high specific surface area (255.441 m2/g) containing a myriad of negatively charged carboxylate functional groups on the surface of the composite, which enabled the composite material to demonstrate a high removal efficiency of cationic dyes, such as rhodamine B, from solution. In addition, the composite featured optimal optical and photocatalytic properties for facilitating efficient photodegradation of the dye molecules, including a large absorbance in the visible light region and a fast transfer of photogenerated electron-hole pairs. Moreover, electron paramagnetic resonance (EPR) analysis and reactive oxygen species scavenging experiments confirmed that superoxide radicals (O2•-), holes (h+), and hydroxyl radicals (•OH) were involved in photocatalytic degradation of the organic dyes.

CaCO3-coated PVA/BC-based composite for the simultaneous adsorption of Cu(II), Cd(II), Pb(II) in aqueous solution.

A polymer composite material comprising polyvinyl alcohol/bacterial cellulose/calcium carbonate (PVA/BC/CaCO3) was prepared for enabling the selective adsorption of toxic heavy metal ions, such as Cd(II), Cu(II), and Pb(II) from solution. FT-IR, SEM and XRD analyses confirmed the successful incorporation of CaCO3 into the PVA-based polymer by chemical cross-linking with epichlorohydrin. The optimal pH for adsorption of the metal ions onto PVA/BC/CaCO3 was determined to be 6.0. The pseudo-first-order kinetics model was best-suited for fitting the adsorption kinetics data, and the Langmuir model was best-suited for fitting the thermodynamic adsorption data. The maximum adsorption capacities of PVA/BC/CaCO3 for Cu(II), Pb(II), and Cd(II) were found to be 57.1, 513.6, and 238.6 mg/g, respectively, at 40 °C. In addition, the adsorbent was found to be highly recyclable. Overall, PVA/BC/CaCO3 adsorbent has the applicable potential in the removal of heavy metal ions from contaminated solution.

Preparation and bacteriostatic research of porous polyvinyl alcohol / biochar / nanosilver polymer gel for drinking water treatment.

Microbial contamination in drinking water has become an important threat to human health. There is thus an urgent need to develop antibacterial materials to treat drinking water. Here, porous silver-loaded biochar (C-Ag) was prepared using corn straw as the substrate and silver as the antibacterial agent. C-Ag was then uniformly distributed in polyvinyl alcohol gel beads of eluted calcium carbonate to prepare p-PVA/C-Ag antibacterial composite. The polymer composites were tested by FT-IR, XRD, SEM and TG-DSC. The results showed that C-Ag was more evenly distributed in the PVA gel spheres. Antibacterial experiments showed that p-PVA/C-Ag greatly inhibited Escherichia coli. Practical application tests revealed that p-PVA/C-Ag showed high and sustained bactericidal inhibition and reusability. Generally, p-PVA/C-Ag composite shows high potential to be applied to drinking water treatment.

Preparation and properties of conductive bacterial cellulose-based graphene oxide-silver nanoparticles antibacterial dressing.

It is difficult to obtain stable multifunctional silver-containing materials that are suitable for use as wound dressings. To solve this problem, we added graphene oxide (GO) to an acetobacter culture medium and used a biological blending self-growth method to fix GO onto the bacterial cellulose to form a mixed-growth film. We then used polydopamine to fix AgNPs to obtain a novel silver-based cellulose wound dressing. This composite material was characterized by infrared spectroscopy, electron microscopy, and X-ray diffractometry, and the results showed that silver nanoparticles uniformly covered the material surface, while graphene was wrapped in a layer of bacterial cellulose. This composite film was conductive and produced a weak current, and it generated heat when a voltage was applied. This allowed it to accelerate wound cell migration and promote wound healing. In addition, AgNPs immobilized on the surface released Ag+, which generated a large number of oxidizing free radicals that killed and bacteria. The in vitro cytotoxicity tests showed that the Ag-pDA/BC (rGO) composite film has excellent biocompatibility, giving it good application prospects for wound dressings.

Selective adsorption of Ag (â ) from aqueous solutions using Chitosan/polydopamine@C@magnetic fly ash adsorbent beads.

A Chitosan/polydopamine@C@magnetic fly ash (CPCMFA) adsorbent bead was prepared for adsorption of Ag (Ⅰ) in aqueous solutions and exhibited good selectivity for Ag (Ⅰ) ion. To investigate its adsorption behaviors, equilibrium, kinetic and selective studies were conducted through batch experiments. Additionally, the influence of the pH value was also evaluated. In addition, the nature, composition, morphology, and magnetic property of the prepared adsorbent beads were characterized by Fourier transform-infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) analysis, thermogravimetric-differential scanning calorimetry (TG-DSC) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating-sample magnetometry (VSM). The freeze-dry form of CPCMFA also exhibited high adsorption capacity and selectivity for Ag (Ⅰ), with a maximum adsorption capacity of 57.02 mg/g at pH 4 and 30 °C. The experimental data were well described by the Langmuir isotherm and elovich kinetic models. The thermodynamics parameters, ΔH = 10.653 kJ/mol, ΔS = 96.63 J/mol K and ΔG < 0, demonstrate that the adsorption of Ag (Ⅰ) on the freeze-dry form adsorbent is spontaneous and endothermic. Moreover, regeneration studies showed the high recyclability of the adsorbent, which after five cycles of use it was still able to adsorb 95.7% of the amount adsorbed by the fresh adsorbent.

Preparation of an antibacterial chitosan-coated biochar-nanosilver composite for drinking water purification.

Microbial contamination has evolved as a life-threatening problem afflicting people due to various diseases caused by pathogenic bacteria in drinking water. Thus developing novel antibacterial materials is an urgent need. Herein, a chitosan (CTS)/ biochar-nanosilver (C-Ag) antibacterial composite was prepared by a method of CTS-coated on C-Ag obtained through a facile high-temperature carbonization process using corn straw as the carbon substrate. The results from FT-IR, XRD, SEM and TG-DSC revealed that the biochar loading spherical silver nanoparticles was coated with CTS in the composite. The antibacterial activity of the CTS/C-Ag composite was investigated using the plate counting method with Escherichia coli (E. coli), and the results suggest that the composite exhibited excellent antibacterial activity against E. coli. In this application study, it was proven that the CTS/C-Ag composite exhibits sustainable antibacterial activity and good reusability for drinking water. Therefore, the CTS/C-Ag composite has potential application in drinking water treatment.

Recycling of Cr (VI) from weak alkaline aqueous media using a chitosan/ triethanolamine/Cu (II) composite adsorbent.

A Chitosan/triethanolamine/Cu (Ⅱ) (CTS/TEA/Cu (Ⅱ)) composite adsorbent was prepared and applied to recycle Cr (Ⅵ) from aqueous media in alkaline conditions. To investigate the adsorption behavior, the influence of pH was evaluated via batch experiments, and the prepared adsorbent was characterized by FT-IR, SEM, XRD, and Zeta potential. This adsorbent exhibited high adsorption capacity for Cr (Ⅵ) in a wide pH range (especially above 7), suggesting a possible way to separate Cr (Ⅵ) from other metal cations by adjusting the pH value prior to adsorption. Adsorption kinetic and thermodynamic experiments were conducted to explore the adsorption mechanism. Regeneration studies showed that the adsorbent can be reused for five adsorption-desorption cycles without substantial loss of adsorption capacity. Overall, the CTS/TEA/Cu (Ⅱ) adsorbent exhibits high potential for recyclingCr (Ⅵ) from wastewater.

Adsorption of molybdate on molybdate-imprinted chitosan/triethanolamine gel beads.

Mo (VI)-imprinted chitosan (CTS)/triethanolamine (TEA) gel beads (Mo (VI)-ICTGBs) (ICTGBs=imprinted chitosan triethanolamine gel beads) were prepared by using ion-imprinted technology, in which TEA and molybdate solution were used in coagulation bath. The spectrum of FT-IR implies that bonding are formed between TEA and the primary hydroxyl of CTS, and ion gel reaction happen between CTS and molybdate; XRD patterns also prove the change among CTS, TEA and molybdate. SEM images and N2 adsorption show that the surface area increases obviously after eluting Mo (VI) ions. The adsorption isotherm of Mo (VI)-ICTGBs imply that the adsorption process is according with Freundlich model. Adsorption kinetics suggests that the pseudo-second order adsorption mechanism is predominant for this adsorbent system of Mo (VI)-ICTGBs. The Mo (VI)-ICTGBs show high adsorption capacity and good selectivity for Mo (VI) anions in the coexistence system at pH=6.0. The Mo (VI)-ICTGBs have a good application prospect, because it is with a simple and rapid technique and good durance.

Synthesis of antibacterial film CTS/PVP/TiO2/Ag for drinking water system.

A CTS/PVP/TiO2/Ag functional film was prepared as an antibacterial composite used in storing drinking water. The orthogonal experiment showed that the optimal conditions for preparing membranes with best antibacterial activity and tensile strength are c(AgNO3)=0.08%, c(TiO2)=0.20%, c(CTS)=2.25%, and c(PVP)=3.00%. The FT-IR spectrum implies that hydrogen bands are formed between acetyl in PVP and hydroxyl in CTS molecule, and -NH and -OH of CTS have some interactions with sliver nano-particles (nano-Ags) which were reduced in situ. The SEM images show that the TiO2 particles are displayed on the surface and embedded in the film. And nano-Ags are further proved through XRD and SEM images. The DSC curves show that the film has a favorable compatibility and heat stability. In application study, it is proved that this film has sustainable antibacterial activity and is safe in use.