Carrageenan is a polysaccharide of a plant origin, commonly used as a thickening and gelling agent in the food, pharmaceutical, and cosmetic industries. Due to the negative charges of its sulfate ...groups, carrageenan macromolecules strongly interact with oppositely charged polyions. The ionic complexes of carrageenan with poly(diallyldimethylammonium chloride) were obtained at the molar ratios 4:1, 2;1, 1:1, 1:2, and 1:4. The structure and characteristics of the polyanion-polycation associates were studied by XRD, IR, optical microscopy, and via sedimentation and particle size measurements. It was found that the suspended particles flocculate and settle fastest when the molar ratio of the polyions is near 1:1. Turbidimetric titration experiments enabled us to measure the molar ratio of cationic to anionic groups at the onset of flocculation, and the value in question was found to be 1:1.32. In other words, a mass of 511 mg carrageenan corresponds to one millimole of ester sulfate (monobasic) groups. The measurement of the onset of flocculation has been employed for the accurate determination of carrageenan in real samples of food products. The color and turbidity of the sample do not interfere with the determination results.
In aqueous solutions, cetyltrimethylammonium cations bind to carrageenan polyanions, and the resulting ionic associates form macroscopic aggregates due to hydrophobic interaction. At certain ratios ...of cetyltrimethylammonium to carrageenan, the resulting colloidal particles auto-flocculate. According to visual observations, the ratio ranges from 1 to 3 mmol/g; otherwise the suspensions are stable. By measuring the sedimentation rate and particle size distribution, the most extensive flocculation was found to be from 1.7 to 2.3 mmol/g. The ratio corresponding to the fastest auto-flocculation was precisely determined by titrating the reagents with small increments and recording the turbidity. The turbidimetric titration plots contain distinct break points corresponding to the most extensive flocculation. These break points occur at the same ratio of carrageenan to cetyltrimethylammonium over a wide range of reagent concentrations. The precise values of the critical ratio were found to be 1.78 and 1.53 mmol/g, respectively, during the titration of cetyltrimethylammonium with carrageenan and vice versa. The number of anionic sulfate groups in carrageenan was measured by ICP OES and found to be 1.35 mmol/g. This value is consistent with the critical ratio of the auto-flocculation.
The method of colloid titration with poly(diallyldimethylammonium) chloride has been improved to detect the endpoint with an off-vessel light reflectance sensor. The digital color sensor used ...measures light reflectance by means of light guides, with no immersion into the reaction solution. In such a method, the optical signal is free of disturbances caused by sticky flocs in the solution. The improved automatic titration set was applied for the determination of sodium laureth sulfate (SLES) in industrial batches and commercial personal care products. The sample color and opacity do not disturb the SLES quantification. When the SLES content lies in the range from 5% to 9%, the optimal sample weight is from 6 g to 3 g.
Mechanically separated meat (MSM) is a by-product of the poultry industry that requires routine quality assessment. Calcium content is an indirect indicator of bone debris in MSM but is difficult to ...determine by EDTA titration due to the poor solubility of calcium phosphate. Therefore, 1,2-diaminocyclohexane-N,N,N’,N’-tetraacetic acid was used instead, which has two orders of magnitude higher affinity for calcium ions. In addition, the auxiliary complexing agents triethanolamine and Arsenazo III, an indicator that is sensitive to low calcium concentrations, were used. Automatic titration endpoint detection was performed using an immersion probe at 660 nm. It has been shown that the color change in Arsenazo III can also be read with an RGB camera. The CDTA titration procedure has been tested on commercial Bologna-type sausages and the results were in line with AAS and ICP reference data. The content of calcium in sausages turned out to be very diverse and weakly correlated with the content of MSM. The tested MSM samples had a wide range of calcium content: from 62 to 2833 ppm. Calcium-rich poultry by-products include fat and skin (115 to 412 ppm), articular cartilage (1069 to 1704 ppm), and tendons (532 to 34,539 ppm). The CDTA titration procedure is fully suitable for small meat processing plants due to its simplicity of use and low cost.
The oxidative degradation of Rhodamine B dye under ultraviolet irradiation was studied. The degradation rate was measured with using of smartphone camera. Photocatalytic degradation of the Rhodamine ...B dye over the P25-TiO2 catalyst has been found to accelerate substantially in the presence of hydrogen peroxide. The relationship between the photocatalytic degradation rate and H2O2 concentration has been studied. The optimal concentration of H2O2 has been found to in the range of 10-25 mM. The proposed mixture of P25 photocatalyst and H2O2 oxidizer can be used to remove organic pollutions from industrial waste water.
This review is devoted to the study of the adsorption behavior of uranium(VI) using titanium dioxide based sorbents. Uranium pollution of groundwater, soil and rocks is a big problem due to the ...long-term toxicity of uranium compounds. Waste uranium is a by-product of the enrichment process used in the production of atomic energy, and the danger associated with this is due to the radioactivity of uranium and its toxicity as a heavy metal. The mechanisms of uranium adsorption by titania adsorbents are presented here, depending on the various environmental conditions, as well as the kinetics of adsorption. The influence of the structural characteristics of the sorbents on the adsorption behavior of uranium is depicted. Surface chemistry and sorption activity of titanium dioxide were reviewed. Examples of new advanced sorbents with nanometer dispersion are described and the parameters of adsorption isotherms are also presented. One of the practical tasks of this analytical review is to obtain information for modeling the behavior of uranium in the water/adsorbent system due to anthropogenic pollution.
•The mechanisms of U(VI) adsorption by titania adsorbents are presented.•Surface chemistry and adsorption activity of titanium dioxide were reviewed.•Examples of new advanced titania adsorbents are described.
Blue-colored ceramic nanopigments with the composition of CoAl2O4 were synthesized by solution combustion method using glycine (CoAl2O4-Gly), poly(vinyl alcohol) (CoAl2O4-PVA) and urea (CoAl2O4-Urea) ...as reductants and fuels. The morphology and chemical composition of the nanopigments were studied using SEM and EDS, respectively. The composition of the crystalline phase was examined using XRD. The crystallite sizes were calculated using the modified Scherrer method, Williamson-Hall method and size-strain plot method. Particles of the CoAl2O4-PVA sample have smaller crystallite sizes, whereas particles of the CoAl2O4-Urea sample have larger crystallite sizes. Thermal gravimetric analysis showed that thermal decomposition of cobalt(II) and aluminum nitrates is accompanied by the release of gases. As a result of material loosening, finely dispersed powders with high porosity were formed. FTIR-spectra of all the nanopigments contain absorption bands related to stretching vibrations of the Me-О bonds (400-700 cm−1). Stretching and deformation vibrations of water molecules are present as well. Color characteristics of the obtained nanopigments depend on the fuel used for the combustion synthesis. The pigment CoAl2O4-PVA has saturated blue-green color. The obtained spinel-type nanomaterials possess high suspension stability and can be used as pigments in ceramic technology.
•Fuel type affects the inversion degree of cobalt aluminate spinels.•Molar ratio of Co ions in tetrahedral and octahedral sites affects pigment shade.•Pigment brightness coordinate L* is related with crystallite size of nanoparticles.•Poly(vinyl alcohol) fuel leads to reduced particle size and increased dispersion stability.
•Efficient rutile photocatalysts obtained by the reverse micelle and low temperature methods.•Monitoring of the degradation kinetics using light reflected from the TiO2 suspension.•Effect of H2O2 on ...the CR, MO and DR23 dyes photodegradation was evaluated.
The study proposes two new TiO2 photocatalysts with excellent photocatalytic properties obtained by the reverse micelle (RM-TiO2) and low temperature (LT-TiO2) methods. The crystal structure and morphology of the obtained TiO2 samples were analyzed by X-ray diffraction, scanning electron microscopy and IR-spectroscopy. The chosen synthesis conditions lead to pure rutile modification. FTIR spectra of the obtained samples contain characteristic bands, attributed to stretching vibrations of Ti–O bonds and to deformation vibrations of Ti–OH bonds. The average crystallite sizes for RM-TiO2 and LT-TiO2 samples are 5.4 and 9 nm, respectively. SEM analysis showed that the RM-TiO2 consists of TiO2 particles, assembled into spherical aggregates, while LT-TiO2 consists of smaller aggregates and is mostly mesoporous. The BET surface areas of the RM-TiO2 and LT-TiO2 samples are 39 and 63 m2/g, respectively. The photocatalytic degradation of the Congo Red (CR), Methyl Orange (MO) and Direct Red 23 (DR23) dyes in water medium has been studied under UV LED irradiation with H2O2 as an auxiliary oxidant. Both the RM-TiO2 and LT-TiO2 samples are active photocatalysts. The optimal dosages are 1.5 and 0.5 g/L respectively. The maximum photodegradation efficiency of RM-TiO2 is observed when the concentration of H2O2 is 15 mM for CR, 5 mM for MO and 10 mM for DR23. The maximum photodegradation efficiency of LT-TiO2 is observed when the concentration of H2O2 is 10 mM for CR, 2.5 mM for MO and 1.5 mM for DR23. The boosting effect of H2O2 on the degradation efficiency can be explained by an increased generation of •OH radicals. The real-time monitoring of degradation kinetics has been performed using measurements of light reflected from TiO2 suspension. The proposed technique allows the use of small volume of solution and amount of photocatalyst. The synthesized rutile photocatalysts may be used for wastewater treatment.
The cobalt ferrite Fenton catalysts were obtained by the flow co-precipitation method. FTIR, XRD, and Mössbauer spectroscopy confirmed the spinel structure. The crystallite size of the as-synthesized ...sample is 12 nm, while the samples annealed at 400 and 600 °C have crystallite sizes of 16 and 18 nm, respectively. The as-synthesized sample has a grain size of 0.1–5.0 μm in size, while the annealed samples have grain sizes of 0.5 μm–15 μm. The degree of structure inversion ranges from 0.87 to 0.97. The catalytic activity of cobalt ferrites has been tested in the decomposition of hydrogen peroxide and the oxidation of caffeine. The annealing of the CoFe2O4 increases its catalytic activity in both model reactions, with the optimal annealing temperature being 400 °C. The reaction order has been found to increase with increasing H2O2 concentration. Electromagnetic heating accelerates the catalytic reaction more than 2 times. As a result, the degree of caffeine decomposition increases from 40% to 85%. The used catalysts have insignificant changes in crystallite size and distribution of cations. Thus, the electromagnetically heated cobalt ferrite can be a controlled catalyst in water purification technology.
Display omitted
•Electromagnetic heating is used to boost the catalytic activity of cobalt ferrite.•The reaction order increases with increasing H2O2 concentration.•Induction heating accelerates the catalytic decomposition of H2O2 up to 2 times.•Induction heating accelerates the Fenton-like oxidation of caffeine more than 2 times.•Electromagnetically heated CoFe2O4 can be a controlled catalyst in water purification.
PDF
