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

Antibacterial, antioxidant, Cr(VI) adsorption and dye adsorption effects of biochar-based silver nanoparticles‑sodium alginate-tannic acid composite gel beads

Ultrasonic extraction of Osmanthus fragrans was used for reducing Ag+ to prepare AgNPs, which were further loaded on barley distiller's grains shell biochar. By supplementary of sodium alginate and tannic acid, composite gel beads were prepared. The physical properties of biochar-based AgNPs‑sodium alginate-tannic acid composite gel beads (C-Ag/SA/TA) were characterized. SEM, FTIR, and XRD showed that biochar-based AgNPs were compatible with sodium alginate-tannic acid. CAg greatly improved the dissolution, swelling, and expansion of gel beads. Through the analysis by the agar diffusion method, C-Ag/SA/TA gel beads had high antibacterial activity (inhibition zone: 22 mm against Escherichia coli and 20 mm against Staphylococcus aureus). It was observed that C-Ag/SA/TA composite gel beads had high antioxidant capacity and the free radical scavenging rate reached 89.0 %. The dye adsorption performance of gel beads was studied by establishing a kinetic model. The maximum adsorption capacities of C-Ag/SA/TA gel beads for methylene blue and Congo red were 166.57 and 318.06 mg/g, respectively. The removal rate of Cr(VI) reached 96.4 %. These results indicated that the prepared composite gel beads had a high adsorption capacity for dyes and metal ions. Overall, C-Ag/SA/TA composite gel beads were biocompatible and had potential applications in environmental pollution treatment.

Antibacterial, antioxidant and fruit packaging ability of biochar-based silver nanoparticles-polyvinyl alcohol-chitosan composite film

Silver nanoparticles were prepared by loading Ag+ into biochar of waste barley distillers' grains shell by reduction with trisodium citrate, and this silver-loaded biochar was introduced into polyvinyl alcohol-chitosan. Various analysis with Fourier Transform Infrared spectroscopy, X-ray diffraction, Thermogravimetric analysis, and water contact angle revealed that biochar-based silver nanoparticle was incorporated into the polyvinyl alcohol-chitosan film, the biochar-based silver nanoparticles-polyvinyl alcohol-chitosan (C-Ag-loaded PVA/CS) composite film had good thermostability and hydrophobicity. Through the analysis via disk diffusion method, the composite containing 3 % of biochar-based silver nanoparticles-polyvinyl alcohol-chitosan had high antibacterial activity (inhibition zone: 18 mm against E. coli and 15 mm against S. aureus), and the bacterial membrane permeability was measured, indicating that C-Ag-loaded PVA/CS composite film could destroy the cell membrane, release intracellular substances, and have high antioxidant activity. During the storage, the weight loss rate of the biochar-based silver nanoparticles-polyvinyl alcohol-chitosan plastic wrap group was 0.14 %, and the titratable acid content only decreased by 0.061 %, which had a good effect on extending the shelf life of blueberries. The C-Ag-loaded PVA/CS composite film could also delay deterioration of blueberries and prolong storage time. Overall, this composite film had potential in food packaging and extending food shelf-life aspects.

Ultraviolet blocking ability, antioxidant and antibacterial properties of newly prepared polyvinyl alcohol-nanocellulose‑silver nanoparticles-ChunJian peel extract composite film

In this work, nanocellulose (CNC) from waste water chestnut (WCT) shell was firstly used for preparing nanocomposite films, by using ChunJian peel extract (CJPE) as a green reducing agent to synthesize silver nanoparticles (AgNPs), and then loading them into polyvinyl alcohol-nanocellulose (PVA-CNC) matrix, a multifunctional nanocomposite material that could be used in food packaging was developed. The prepared films were tested for mechanical strength, barrier properties, thermal properties, antibacterial, antioxidant and biocompatibility through various characterizations. The PVA-CNC-AgNPs-CJPE film had good thermostability, mechanical strength, barrier properties, and biocompatibility. Compared with pure PVA film and PVA-CNC film, PVA-CNC-AgNPs-CJPE could shield over 95 % of the UVB (320-275 nm) spectrum and UVC (275-200 nm) spectrum and most of the UVA (400-320 nm). By disk diffusion analysis, the inhibition zones of PVA-CNC-AgNPs-CJPE film against E. coli, P. aeruginosa, S. aureus and E. faecalis were 22.3 mm, 25.0 mm, 22.0 mm and 19.3 mm, respectively. The milk antibacterial simulation test confirmed that PVA-CNC-AgNPs-CJPE film could effectively limit bacterial reproduction and prolong the shelf life of milk. PVA-CNC-AgNPs-CJPE film had excellent UV barrier properties, good antioxidant properties and high-efficiency antibacterial activity, which is expected to be widely used in sustainable nanocomposite food packaging.

Bamboo charcoal fiber bundles loaded MOF-derived magnetic Co/CoO porous polyhedron for efficiently catalytic degradation of tetracyclines hydrochloride

The health of living things and the ecosystem of the planet have both been negatively impacted by antibiotic residue in the water environment. There has been a lot of interest in the catalyst made of metal-carbon compounds from MOFs as a potential solution for activating peroxymonosulfate (PMS) to produce reactive oxygen species to catalyze the degradation of residual antibiotics. In this study, zeolitic imidazolate frameworks (ZIF-67) on bamboo fiber bundles (BFB) were pyrolyzed to produce magnetic Co/CoO nanoparticles with porous polyhedrons mounted on bamboo charcoal fiber bundles (BCFB)(BCFB@PCo/CoO). Specific surface area of obtained BCFB@PCo/CoO with abundant active sites arrives at 302.41 m2/g. The catalytic degradation efficiency of Tetracycline hydrochloride (TCH), a target contaminant, could reach up to 99.94% within 15 minutes (PMS = 0.4g/L, Cat. = 0.2g/L). The effects of potential factors, including PMS dosage, interference ions, and temperature, on catalytic degradation efficiencies were investigated. Magnetic recovery and antimicrobial properties of the BCFB@PCo/CoO were also evaluated and the possible degradation pathways were explored. Catalytic mechanism explorations of BCFB@PCo/CoO/PMS system reveal MOF-derived magnetic Co/CoO nanoparticles embedded in BCFB promote the synergistic interaction of both radicals and non-radical pathways for catalytic degradation of TCH. The novel BCFB@PCo/CoO provides an alternative to deal with wastewater containing antibiotics.

Chitosan-modified biochar: Preparation, modifications, mechanisms and applications

The chitosan-modified biochar composite, as a carbohydrate polymer, has received increasing attention and becomes a research hotspot. It is a promising impurity adsorption material, which has potential application value in the agricultural environment fields such as soil improvement and sewage purification. The composite can combine the advantages of biochar with chitosan, and the resulting composite usually exhibits a great improvement in its surface functional groups, adsorption sites, stability, and adsorption properties. In addition, compared to other adsorbents, the composite truly achieves the concept of "waste control by waste". In this paper, the preparation method, composite classification, adsorption mechanism, and models of biochar modified by chitosan are introduced, meanwhile, we also review and summarize their effects on the decontamination of wastewater and soil. In addition to common heavy metal ions, we also review the adsorption and removal of some other organic/inorganic pollutants, including (1) drug residues; (2) dyes; (3) phosphates; (4) radionuclides; (5) perfluorochemicals, etc. Moreover, challenges and prospects for the composite are presented and further studies are called for the chitosan-biochar composite. We believe that the composite will lead to further achievements in the field of environmental remediation.

Electrical and Mechanical Properties of Sugarcane Bagasse Pyrolyzed Biochar Reinforced Polyvinyl Alcohol Biocomposite Films

Biochar obtained from the oxygen-deficient thermochemical processing of organic wastes is considered to be an effective reinforcing agent in biocomposite development. In the present research, biocomposite film was prepared using sugarcane bagasse pyrolyzed biochar and polyvinyl alcohol (PVA), and its electrical and mechanical properties were assessed. The biocomposite films were produced by varying content (5 wt.%, 8 wt.% and 12 wt.%) of the biochar produced at 400 °C, 600 °C, 800 °C and 1000 °C and characterized using X-Ray diffraction, scanning electron microscope, Fourier transform infrared spectroscopy. The experimental findings revealed that biochar produced at a higher pyrolyzing temperature could significantly improve the electrical conductance of the biocomposite film. A maximum electrical conductance of 7.67 × 10−2 S was observed for 12 wt.% addition of biochar produced at 1000 °C. A trend of improvement in the electrical properties of the biocomposite films suggested a threshold wt.% of the biochar needed to make a continuous conductive network across the biocomposite film. Rapid degradation of tensile strength was observed with an increasing level of biochar dosage. The lowest tensile strength 3.12 MPa was recorded for the film with 12 wt.% of biochar produced at 800 °C. Pyrolyzing temperature showed a minor impact on the mechanical strength of the biocomposite. The prepared biocomposites could be used as an electrically conductive layer in electronic devices.