Characteristics of Wastewater from Different Pretreatments of Flax/Cotton Fabrics

To be properly used in the textile industry, the natural materials are subject to different pretreatments. During the scouring, the non-cellulosic attendants (wax, pectin, pigments) are removed. The enzymes have proved their efficiency in this regard but also in terms of being friendly with the environment. The textile industry is a water large consumer, comprising many wet processes: bioscouring, bleaching, mercerizing, and dyeing. The water quantity needed for each step is very high. The resulted wastewater comprises different types of chemicals, most of them non-biodegradable: acids, sodium hydroxide, hypochlorites, peroxides, etc. The actual trends and legislation require the change of classical methods used with ecological ones. One particular reason for this tendency is also related to the economic issue, the use of eco-friendly treatments leading to significant economical savings. The present study was focused on enzymatic treatments with the use of two chelating agents (sodium citrate and EDTA) to remove the flax/cotton fabric impurities. The new proposed scouring treatment, with sodium citrate as a chelating agent, presents less aggressivity to the environment compared with the classical one. The temperature used was lower (55 °C), the pH close to the neutral point, and biodegradable chemicals were used. The chosen technology included a series of independent steps which they assumed: washing of flax/cotton fabric at 100 °C for dust and physically linked impurities removing, dried at room temperature, and conditioning at 105 °C in the oven for 2h. Afterward, the samples were immersed in the reaction bath which contained a mixture of pectinolytic products, the chelating agents (sodium citrate or EDTA), and the surfactant. The hydrolytic reaction was optimised following the influence of a pair of parameters: enzyme concentration/exposure time. Water samples from each reaction bath were collected and different physicochemical parameters were analysed: pH, salinity, TDS, conductivity, DO, CCOMn, turbidity and dry residue. The results obtained were following the legislation. In the case of the classical treatment, the data was up to 100 % higher compared with the new proposed treatment were complexing agent sodium citrate was used. Analysing from different points of view the results obtained, we can say that the considered treatment could be a promising alternative to the current one. It might contribute to less wastewater pollution and technological economical improvement.

Влияние структурно-морфологических характеристик на сенсорные свойства пленок Cd-=SUB=-x-=/SUB=-Pb-=SUB=-1-x-=/SUB=-S

Polycrystalline films of CdxPb1−x S (0.021 ≤ x ≤ 0.090) supersaturated substitutional solid solutions with a cubic structure B1 (Fm3¯m space group) have been obtained with varying cadmium acetate salt Cd(CH3COO)2 in the reaction mixture within 0.01−0.1 mol/l on the sitall substrates. Their thickness changed from ∼ 0.4 to ∼ 1.0 microns. A correlation has been established between the structural-morphological and functional properties of CdxPb1−x S thin-film layers. The extreme character of the voltage sensitivity dependence on the cadmium salt concentration in the reaction bath is associated with the nonmonotonic introduction of cadmium into the PbS crystal lattice. It is shown that the maximum photocurrent is possessed by CdxPb1−x S thin-film layers formed from crystallites with pronounced faceting. We have found the surface sensitivity of the CdxPb1−xS films to the presence of ∼ 0.02 mg/m3 NO2 in the air, which is significantly lower than the maximum allowable concentration.

Структурные и электрофизические свойства пленок PbS, легированных Cr-=SUP=-3+-=/SUP=- в процессе химического осаждения

The evolution of the morphology, composition, structural characteristics (lattice constant, microstrains, texturing), optical and photoelectric properties of the PbS films obtained by chemical bath deposition in the presence of ammonium iodide and chromium (III) chloride at a concentration of up to 0.02 M has been studied. According to the elemental analysis by an energy dispersive X-ray spectroscopy, the chromium content in the PbS films has a nonmonotonic dependence on the CrCl3 concentration, and the largest amount is 1.08 at%. The particle size distribution is monomodal, and the average size of the particles forming the films varies from ~ 100 to ~ 225 nm with a content of 2–6% of nanoparticles. The introduction of NH4I and CrCl3 into the reactor preserves the cubic B1 structure of lead sulfide and results in an increase in the band gap Eg by 0.16–0.20 eV, a decrease in the dark resistance Rd, and an increase in the voltage sensitivity Us. The dependences of Eg and Us on the concentration of the chromium salt in the reaction bath have an extreme character with a maximum at 0.016 M, which is associated with the nonmonotonic incorporation of chromium into the PbS lattice. The results of studying the current-voltage characteristics of thin-film PbS(I) and PbS(I, Cr) layers are in good agreement with the results of the structural, optical, and photosensitive properties.

Morphology and Composition of Lead-Cadmium Sulfide Photo-Sensitive Films

CdxPb1-xS films with a thickness of 620 and 680 nm were prepared by chemical precipitation from a reaction mixture containing lead salt, thiourea, alkali and cadmium acetate. The concentration of cadmium acetate was 0.01 and 0.1 mol/l. Electron-microscopic studies showed a fundamental difference in the morphology of the CdxPb1-xS thin films with a 10-fold difference in the concentration of cadmium acetate in the reaction bath. The results of energy dispersive analysis indicate the nonstoichiometry of the synthesized films on sulfur. Auger spectrometry revealed a high content of oxygen in the surface layer of the thin film coating CdxPb1-xS (up to 10 and 40 at. %). In the sample obtained from the reaction bath containing 0.01 mol / l of cadmium acetate, after ion etching at a depth of more than 30 nm, no oxygen was detected. In a sample prepared with a cadmium acetate content of up to 0.1 mol/l, the oxygen content does not exceed 3 at. %

Nitrobenzene degradation by micro-sized iron and electron efficiency evaluation

The effect of pH, temperature, zero-valent iron (ZVI) dosage and reaction duration on nitrobenzene (NB) degradation by micro-sized ZVI was investigated in batch experiments and the electron efficiency (EE) was evaluated at constant pH. The experimental results showed that the reaction rate constant attained 0.616 min−1, which was far higher than reported in previous studies. The decrease in pH and increase in temperature of the reaction bath promoted the reaction kinetics. ZVI dosage and reaction duration were two key factors affecting NB reduction and EE. A lower ZVI dosage and a slightly longer reaction duration could afford an optimised EE and optimum NB removal. A prolonged reaction or too high a ZVI dosage resulted in increased ZVI waste.

BATH PARAMETER DEPENDENCE OF CHEMICALLY-DEPOSITED COPPER SELENIDE THIN FILM

In this article, a low cost chemical bath deposition (CBD) technique has been used for the preparation of Cu 2-x Se thin films on to glass substrate. Different thin films (0.2–0.6 μm) were prepared by adjusting the bath parameter like concentration of ammonia, deposition time, temperature of the solution, and the ratios of the mixing composition between copper and selenium in the reaction bath. From these studies, it reveals that at low concentration of ammonia or TEA, the terminal thicknesses of the films are less, which gradually increases with the increase of concentrations and then drop down at still higher concentrations. It has been found that complexing the Cu 2+ ions with TEA first, and then addition of ammonia yields better results than the reverse process. The film thickness increases with the decrease of value x of Cu 2-x Se .