Adsorption-enhanced photocatalytic property of Ag-doped biochar/g-C3N4/TiO2 composite by incorporating cotton-based biochar.

In this study, the biochar obtained from waste cotton fibers was introduced into the Ag-doped g-C3N4/TiO2 hybrid composite through a facile one-step hydrothermal process. The morphology, elemental composition, crystal structure, microstructure, specific surface area, chemical bonding state, energy band structure, and separation efficiency of photoinduced charge carriers of the resultant composite were examined using scanning electron microscope, energy dispersive X-ray spectrometer, X-ray diffractometer, transmission electron microscope, surface area analyzer, X-ray photoelectron spectroscope, Ultraviolet-visible spectrophotometer, ultraviolet photoelectron spectroscope, and photoluminescence spectroscope. The adsorption isotherms, kinetics and thermodynamics of the biochar, Ag-doped g-C3N4/TiO2 and Ag-doped biochar/g-C3N4/TiO2 were evaluated using the model methyl orange dye. The photoacatalytic degradation of the model pollutants including methyl orange, methylene blue, congo red, and tetracycline hydrochloride and the photocatalytic reduction of Cr(VI) ions were also assessed under visible light. Experimental results indicated that the photocatalytic property of the Ag-doped biochar/g-C3N4/TiO2 was significantly enhanced through the adsorption enhancement compared with the Ag-doped g-C3N4/TiO2. This was due to the uniform doping of multi-scale porous biochar with g-C3N4 nanosheet, Ag and TiO2 nanoparticles. The adsorptive enhancement induced by the biochar resulted in the narrowed band gap, suitable electronic energy band structure, and fast separation of photoinduced charge carriers of the Ag-doped biochar/g-C3N4/TiO2, which was probably due to the coexistence of multi-valence Ti+4/+3 and Ag0/+1 species and oxygen-containing groups of biochar. The major reactive species of the Ag-doped biochar/g-C3N4/TiO2 were 1O2 and h+. The MO dye adsorption onto the Ag-doped biochar/g-C3N4/TiO2 followed the Langmuir isotherm model, pseudo-first-order and pseudo-second-order kinetic models, and the adsorption process was an endothermic reaction with entropy reduction effects. As such, the Ag-doped biochar/g-C3N4/TiO2 exhibited a promising application for the treatment of wastewater containing multi-pollutants especially organic dyes and heavy metal ions.

Magnetically Recyclable Wool Keratin Modified Magnetite Powders for Efficient Removal of Cu2+ Ions from Aqueous Solutions.

The treatment of wastewater containing heavy metals and the utilization of wool waste are very important for the sustainable development of textile mills. In this study, the wool keratin modified magnetite (Fe3O4) powders were fabricated by using wool waste via a co-precipitation technique for removal of Cu2+ ions from aqueous solutions. The morphology, chemical compositions, crystal structure, microstructure, magnetism properties, organic content, and specific surface area of as-fabricated powders were systematically characterized by various techniques including field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), thermogravimetric (TG) analysis, and Brunauer-Emmett-Teller (BET) surface area analyzer. The effects of experimental parameters such as the volume of wool keratin hydrolysate, the dosage of powder, the initial Cu2+ ion concentration, and the pH value of solution on the adsorption capacity of Cu2+ ions by the powders were examined. The experimental results indicated that the Cu2+ ion adsorption performance of the wool keratin modified Fe3O4 powders exhibited much better than that of the chitosan modified ones with a maximum Cu2+ adsorption capacity of 27.4 mg/g under favorable conditions (0.05 g powders; 50 mL of 40 mg/L CuSO4; pH 5; temperature 293 K). The high adsorption capacity towards Cu2+ ions on the wool keratin modified Fe3O4 powders was primarily because of the strong surface complexation of -COOH and -NH2 functional groups of wool keratins with Cu2+ ions. The Cu2+ ion adsorption process on the wool keratin modified Fe3O4 powders followed the Temkin adsorption isotherm model and the intraparticle diffusion and pseudo-second-order adsorption kinetic models. After Cu2+ ion removal, the wool keratin modified Fe3O4 powders were easily separated using a magnet from aqueous solution and efficiently regenerated using 0.5 M ethylene diamine tetraacetic acid (EDTA)-H2SO4 eluting. The wool keratin modified Fe3O4 powders possessed good regenerative performance after five cycles. This study provided a feasible way to utilize waste wool textiles for preparing magnetic biomass-based adsorbents for the removal of heavy metal ions from aqueous solutions.

Photocatalytic mechanism and performance of a novel wool flake-BiFeO3nanosheet-TiO2core-shell-structured composite photocatalyst.

In this study, BiFeO3(BFO) nanosheets ground from BFO particles were first incorporated with wool flakes to construct sandwich-like wool-BFO composites using the vibration-assisted ball milling technique in freezing conditions. The wool-BFO composites were then loaded with a thick layer of TiO2nanoparticles to prepare the core-shell-structured wool-BFO-TiO2composites using a hydrothermal synthesis process. The microstructure of the core-shell wool-BFO-TiO2composites and its photocatalytic applications were systematically examined using a series of characterization methods. Trapping experiments and electron spin resonance spectra were also employed to judge the active radical species like superoxide radicals (·O2-), singlet oxygen (1O2), holes (h+), and hydroxyl radicals (·OH) using benzoquinone, furfuryl alcohol, ethylenediamine tetraacetic acid, and tert-butanol as the scavengers, respectively. The photodegradation performance of the wool-BFO-TiO2composites was measured using more resistant methyl orange (MO) dye as the pollutant model. In comparison with the wool-TiO2or wool-BFO composites, the superior photocatalytic properties of the wool-BFO-TiO2composites under visible light irradiation were attributed to the presence of mesopores and macropores, the large specific surface area and intimate interface between wool-BFO composites and TiO2nanoparticles, the coexistence of Fe3+, Fe2+, Bi3+, Bi(3-x)+, Ti4+, and Ti3+species, and the strong visible light harvesting, thus leading to the fast separation of photogenerated electron-hole pairs. The wool-BFO-TiO2composites could be used for the repeated photodegradation of organic pollutants and be recycled easily using a magnet. The active radical species of the wool-BFO-TiO2composites were ·O2-and1O2rather than ·OH and h+, which were involved in the photodegradation of MO dye under visible light irradiation.

TiO2 modified orthocortical and paracortical cells having enhanced photocatalytic degradation and photoreduction properties.

In this study, cortical cells resultant from wool fibers were loaded with TiO2 nanoparticles in a hydrothermal process and were then engineered as organic-nonorganic hybrid composite photocatalysts for both photodegradation of organic dyes and photoreduction of heavy metal ions. The microstructure and photocatalytic properties of TiO2 modified cortical cells (i.e. both orthocortical and paracortical cells) were systematically characterized using a series of analytical techniques including FESEM, TEM, element analysis, Mott-Schottky curve, BET specific surface area, Zeta potentials, as well as XRD, FTIR, XPS, DRS, PL, UPS, EDS and ESR spectra. Their photocatalytic performance and trapping experiments of the TiO2 modified cortical cells were measured in the photodegradation of methylene blue (MB) dye and Congo Red (CR) dye as well as the photoreduction of Cr(VI) ions under visible light irradiation. It was found that anatase TiO2 nanoparticles were chemically grafted on the surface of the two cortical cells via O-Ti4+/O-Ti3+ bonds, and that TiO2 nanoparticles were formed inside the orthocortical cells in the hydrothermal process. The TiO2 modified orthocortical and paracortical cells possessed much higher photocatalytic efficiency than the commercially available TiO2 nanoparticle powder, Degussa P25, in the photodegradation of cationic MB dye and photoreduction of Cr(VI) ions, while their photocatalytic efficiency in the photodegradation of anionic CR dye is smaller because of their greater negative Zeta potentials and photogenerated holes as the main reactive radical species. In comparison with the TiO2 modified paracortical cells, the higher photocatalytic efficiency of the TiO2 modified orthocortical cells was demonstrated in the photodegradation of MB dye solution and this might be due to both the S-doped TiO2 nanoparticles infiltrated into the naturally hydrophilic orthocortical cells and the primary reactive radical species of photogenerated holes being trapped in the cells.

Enhanced Photocatalytic Properties of PET Filaments Coated with Ag-N Co-Doped TiO2 Nanoparticles Sensitized with Disperse Blue Dyes.

In this study, the effects of disperse blue dye-sensitization on the photocatalytic properties of the Ag-N co-doped TiO2 nanoparticles loaded on polyethylene terephthalate (PET) filaments are investigated under visible light irradiation. The microstructure and photocatalytic properties of the as-synthesized TiO2 nanocomposites, as well as the as-prepared PET filaments, are systematically characterized. The photocatalytic performance of the PET filaments coated with the Ag-N co-doped TiO2 nanoparticles sensitized with disperse blue dyes is evaluated via its capacity of photo-degrading methyl orange (MO) dyes under visible light irradiation. It is found that the holes are the predominant reactive radical species and the hydroxyl and superoxide radicals play a subordinate role in the photocatalytic reaction process. The reaction rate constant of the photocatalytic composite filaments is nearly 4.0 times higher than that of the PET filaments loaded solely with TiO2 nanoparticles. The resultant photocatalytic composite filaments are evident to be capable of repeatedly photo-degrading MO dyes without losing its photocatalytic activity significantly.

Flame retardant property of flax fabrics coated by extracellular polymeric substances recovered from both activated sludge and aerobic granular sludge.

In this research, extracellular polymeric substances (EPS), such as EPSflocs and EPSgranules, were successfully extracted from activated and aerobic granular sludge, respectively, and tested as bio-based flame retardant materials. Flax fabric was coated by the biopolymeric substances and its flammability was evaluated based on a vertical burning test defined in US Federal Aviation Regulation. Both EPSflocs and EPSgranules coated flax fabrics achieved the self-extinguishment due to effective char formation. In particular, the result of the EPSgranules coated sample met the aviation requirements for the aircraft interior. Moreover, the presence of carbonated hydroxyapatite was identified in EPSgranules char residue by using FTIR and XRD analysis. It can contribute to the self-extinguishing property of the fabric by enhancing char formation. Thermogravimetric analysis also demonstrated that EPSgranules coated flax was able to produce greater amount of char residue and its decomposition rate was significantly reduced. This research indicates that there is a great potential to use this biopolymer as a resource for developing high performance bio-inspired flame retardant materials and contribute to a circular economy.

Structure/Function Analysis of Nonwoven Cotton Topsheet Fabrics: Multi-Fiber Blending Effects on Fluid Handling and Fabric Handle Mechanics.

Greige cotton (GC) has attracted interest in recent years as an eco-friendly, functional fiber for use in nonwoven topsheet materials. GC imparts favorable fluid management and sensorial properties associated with urinary liquid transport and indices related to comfort in wearable incontinence nonwovens. Nonwoven GC has material surface polarity, an ambient moisture content, and a lipid/polysaccharide matrix that imparts positive fluid mechanic properties applicable to incontinence management topsheet materials. However, a better understanding of the connection between functionality and compositional aspects of molecular, mechanical, and material property relations is still required to employ structure/function relations beyond a priori design. Thus, this study focuses on the relation of key indices of material fluid and sensorial functions to nonwoven topsheet composition. Greige cotton, polypropylene, bleached cotton, and polyester fiber blends were hydroentangled at 60, 80, and 100 bar. Greige cotton polypropylene and bleached cotton were blended at ratios to balance surface polarity, whereas low percentages of polyester were added to confer whiteness properties. Electrokinetic and contact angle measurements were obtained for the hydroentangled nonwovens to assess surface polarity in light of material composition. Notably, materials demonstrated a relation of hydrophobicity to swelling as determined electrokinetically by Δζ, ζplateau, and contact angles greater than 90°. Subsequently, three blended nonwoven fabrics were selected to assess effects on fluid management properties including topsheet performance indices of rewet, strikethrough, and fluid handling (rate and efficiency of transport to the absorbent core). These materials aligned well with commercial topsheet fluid mechanics. Using the Leeds University Fabric Handle Evaluation System (LUFHES), the nonwovens were tested for total fabric hand. The results of the LUFHES measurements are discussed in light of fiber contributions. Fiber ratios were found to correlate well with improvement in softness, flexibility, and formability. This study provides insights that improves the understanding of the multifunctional properties accessible with greige cotton toward decisions valuable to selecting greige cotton as an environmentally friendly fiber for nonwoven topsheets.

Enhanced photocatalytic activity of wool fibers having titanium dioxide nanoparticles formed inside their cortex.

A wool-TiO2 nanoparticle composite material having TiO2 nanoparticles both infiltrated in the matrix between macrofibrils inside cortical cells of wool fibers and grafted on the fiber surface is obtained in this study, and the wool-nanoparticle composite material is found to have highly photocatalytic activities with an extremely narrow band gap of 2.8 eV. The wool fibers are obtained using three successive technical steps: wool fibers are swollen by using lithium bromide, then saturated with tetrabutyl titanate ethanol solution and subsequently treated in boiling water. It was demonstrated that the chemical bonds formed between the as-synthesized TiO2 nanoparticles and the wool fibers swollen by lithium bromide include C-Ti4+(Ti3+), N-Ti4+(Ti3+), O-Ti3+, and S-Ti4+(Ti3+) bonds. The modified wool fibers have shown markedly improved photocatalytic efficiency due to their enhanced visible light absorption capability, which is much better than the (N-doped) TiO2 coated wool fibers. In contrast, TiO2 modified wool fibers swollen by using formic acid have poorer photoactivity, this might be due to the elimination of trivalent titanium between TiO2 nanoparticles and the wool fibers.