Presented study deals with the pre-treatment of cellulose fibres with the aim to activate their surface and to enlarge their pore system, leading to an enhancement of fibres’ affinity for subsequent functionalization processes. Swelling of fibres in aqueous solutions of sodium hydroxide opens their fibrillar structure, while freezing and freeze-drying retain this enlargement of the pore system, in contrast with conventional air or elevated temperature drying. Effect of different pre-treatment procedures on fibres’ supramolecular structure, enlargement of their pore system, surface topography, zeta potential and mechanical properties was investigated. Degree of enhancement of the pore system depends on the concentration of sodium hydroxide and type of freezing; higher alkali concentrations are more effective, but at the cost of extensive deterioration of mechanical properties. Swelling of fibres in lower concentrations of NaOH, in combination with freeze drying, offers an acceptable compromise between enhancement of the fibres’ pore system, changes in surface potential and tensile properties of treated fibres. Design of a suitable regime of swelling and drying of cellulose fibres results in an effective procedure for controlled tuning of their surface topography in combination with an increase of the available internal surface area and pore volume.
COBISS.SI-ID: 19514390
Fusing multiwall carbon nanotubes (MWCNTs) with TiO2 at the nano-scale level promotes the separation of the electron-hole charges generated upon UV and day light irradiation. In this study, we investigated facile sonochemical synthesis, combined with calcination process for the preparation of TiO2-MWCNT composites with different mole ratio of titanium and carbon. In order to produce stable nano dispersions, we exploited an innovative biotechnology-based approach for the covalent functionalization of TiO2-MWCNTs with in-situ synthesized soluble phenoxazine dye molecules. The none and functionalized TiO2-MWCNTs composites were analyzed by a range of analytical techniques including XRD, Raman, XPS, SEM and UV-vis diffuse reflectance spectroscopy (DRS), and dynamic light scattering (DLS). The photocatalytic activity was evaluated toward the liquid-phase degradation of methylene blue in aqueous solution under both UV and visible light irradiation. TiO2-MWCNTs with optimized mole ratio exhibit much higher photocatalytic activity and stability than bare TiO2. The as-prepared TiO2-MWCNTs photocatalyst possessed good adsorptivity of dyes, extended light absorption range and efficient charge separation properties simultaneously. The results indicated that the soluble phenoxazine dyes and amino-benzensulfonic acid monomers were covalently grafted on the surface of TiO2-MCNTs, which promoted good aquatic dispersibility and extended light absorption, issuing in increased photocatalytic efficiency.
COBISS.SI-ID: 19155734
The aim of the paper is to present a newly developed technology which can provide economic and safe use of moderate heavy metals polluted sewage sludge on agricultural lands as organic fertilizer and, therefore, returning the nutrients (nitrogen, phosphorous, potassium) back to the human food chain, instead of being incinerated or landfilled. The proposed drying technology is economically sustainable due to the low vacuum and temperature (35 °C-40 °C), that increases the efficiency of the heat pump (coefficient of performance 5-7,2) of the energy produced by the anaerobic digestion. Hence, the main emphasis is given to the development of: an efficient method for heavy metals' reduction in the sludge treatment chain by using chitosan covered magnetite nanoparticles, an efficient drying method in a vacuum with low temperature energy which can be exploited from sludge digestion to reduce organic matter, and an energy sustainable concept of sludge treatment, with the addition of fats, oil and grease (FOG) to produce enough biogas for sludge drying to produce fertilizer.
COBISS.SI-ID: 19829526
The effect of the coupling approach (chemical by using carbodiimide chemistry and grafting-to versus grafting-from synthesis routes, and enzymatic by using transglutaminase) of ɛ-poly-L-lysine (ɛPL) graft yield with wool fibers was studied and evaluated related to their antibacterial activity against gram-negative Escherichia coli and gram-positive Staphylococcus aureus bacteria, after 1–24 h of exposure. While the ɛPL applied was evaluated colorimetrically by wool staining with two acid dyes and quantitatively by evaluation of the basic groups using potentiometric titration, its orientation was determined by Fourier transform infrared spectroscopy and, for the first time, by Electron Paramagnetic Resonance spectroscopy using spin-labeled ɛPL. The highest (∼99% for E. coli versus ∼92% for S. aureus) and kinetically the fastest (in 3 h) antibacterial activity with ∼83% for E. coli versus ∼64% for S. aureus bactericidal effect was determined for the wool functionalized by the chemical grafting-to approach. Such an effect may be related to both quantitatively the highest (∼62 gɛPL/kgwool) grafting yield of ɛPL and conformationally its highly flexible “brush-like” structure. Comparably, the enzymatic coupling (∼50 gɛPL/kgwool) giving ∼95% and ∼8% reductions of E. coli and S. aureus, respectively, being additionally reduced to ∼74% and ∼78% by using the grafting-from approach (∼34 gɛPL/kgwool), was identified as the less bactericidally effective (∼63% versus ∼58%). It was also shown that a non-ionic surfactant being used in the durability testing of functionalized wool to washing adheres strongly onto the fibers, thus blocking the amino groups of ɛPL, and, as such, decreases the antibacterial efficiency of the wool, being unaffected in the case when the washing was carried out without surfactant.
COBISS.SI-ID: 19666710
In this study, we report on the fluorimetric method for the determination of biogenic amine agmatine based on hybrid SiO2 particles functionalized with thiol groups of 3-mercaptopropyltrimethoxysilane (MPTMS, SiO2–SH) and further conjugated with indicator dye o-phthaldialdehyde (OPA, SiO2–SH–OPA). Under optimal conditions, OPA reacted with agmatine and formed a fluorescent product in the alkaline media (pH 13). The fluorescence excitation and emission wavelengths were located at 340 and 430 nm. The relative fluorescence intensity was linear in the concentration range between 1.0 × 10−7 and 1.0 × 10−2 mol/L. Obtained SiO2–SH particles were characterized using infrared spectroscopy (FTIR), transmission electron microscopy, zeta potential and potentiometric titration.
COBISS.SI-ID: 19489046