The equilibrium solubilities of the ternary system YCl3-CdCl2-H2O, the quaternary system YCl3-CdCl2-HCl(~8.8%)-H2O were determined at 25 ℃ and the phase diagrams were constructed. The results show that the ternary system was complicated with six equilibrim solid phases CdCl2·2.5H2O, CdCl2·H2O, 8CdCl2·YCl3·15H2O (8∶1 type), 4CdCl2·YCl3·13H2O(4∶1 type), 5CdCl2·2YCl3·26H2O (5∶2 type) and YCl3·6H2O. The quaternary system was also complicated with four equilibrim solid phase CdCl2·H2O, 4CdCl2·YCl3·13H2O (4∶1 type), 5CdCl2·2YCl3·26H2O(5∶2 type) and YCl3·6H2O. Among the three new compounds 8CdCl2·YCl3·15H2O, 4CdCl2·YCl3·13H2O and 5CdCl2·2YCl3·26H2O, 8CdCl2·YCl3·15H2O was a kind of metastable compound only in ternary system, and it was changed into 4CdCl2·YCl3·13H2O with time. Both 4∶1 type and 5∶2 type existed in ternary and quaternary system, but they were also congruently soluble compounds in quaternary system. They have been prepared from the system and have been characterized by XRD, TC-DTG and DSC. 相似文献
Nanosize manganese zinc ferrites were fabricated by hydrothermal precipitation route using Fe2(SO4)3, ZnSO4·7H2O, MnSO4·H2O as material, then some calcinated at 500 ℃ and studied by XRD, TEM, IR and VSM. The results showed that the products were spinel crystal structure and uniformly sized nanoparticles (15~25 nm) with little aggregation. The analysis of IR showed that the superficial water can be eliminated, but that was embedded in crystal lattice can not be removed by calcinating. The effect Zn content x on the lattice (a) of nanosize Mn1-xZnxFe2O4 was also discussed. The lattice of nanosize Mn1-xZnxFe2O4 decreases with x increasing; and its value deviated the standard lattice (a0) of normal size manganese zinc ferrites. A lot of water was absorbed during the hydrothermal process owing to the large surface of nanosize particles. The change of magnetic properties of MnxZn1-xFe2O4 with x increasing was studied: nanosize MnxZn1-xFe2O4 particles synthesized by us exhibited peculiar magnetic properties curve with Zn content (x) increasing, Superparamagnetic behaviors of the synthesized ZnFe2O4 samples were confirmed by magnetic characterization, which can be explained by the difference between the distribution of the metal ions (Mn2+, Zn2+ and Fe3+) among the tetrahedral (A) and the octahedral (B) sites of nanosize ferrite and that of bulk ferrite. 相似文献
The luminescent properties of Pr3+-doped LaB3O6, SrAl12O19, SrB4O7 and NaYF4 in the vaccum ultraviol-et (VUV) range at different temperatures were investigated under the excitation of high-energetic synchrotron radiation. For Pr3+ ions in LaB3O6, SrAl12O19 and SrB4O7, only the parity-forbidden 1S0→4f2 transitions were observ-ed in the emission spectra at relatively low temperature; but the parity-allowed 4f5d→4f2 transitions appeared simultaneously when the temperature was high enough. And the intensity of broad 4f5d→4f2 emission increased relative to the intensity of 1S0→4f2 emissions with increasing temperature. Then the thermal equilibrium model of energy levels was employed to the lowest 4f5d state and 1S0 state of Pr3+ in the three hosts. The calculated curves were in good agreement with the experimental values, indicating the occurrence of the thermal excitation from 1S0 state to 4f5d states at high temperatures when the lowest 4f5d state lies higher than 1S0 state and the photon energy is high enough. 相似文献
Brown cotton fibers (SA-1 and MC-BL) studied were inferior to a white cotton fiber (Sure-Grow 747) in fiber quality, i.e., a shorter length, fewer twists, and lower crystallinity, but showed superior thermal resistance in thermogravimetric, differential thermogravimetric, and microscale combustion calorimetric (MCC) analyses. Brown cotton fibers yielded 11–23 % smaller total heat release and 20–40 % greater char. Washing fibers in water and a 1 % NaOH solution showed that rich natural inorganic components and the condensed tannins present in brown cotton are responsible for the unusual thermal property. The loss of inorganics from white cotton during a water wash increased the thermal decomposition temperature of cellulose, resulting in no char yield. However, the stronger binding of metal ions for brown cotton as well as its dominant adsorption of sodium ions after a 1 % NaOH wash facilitated the low-temperature thermal-reaction route; the sodium content showed a significant negative correlation with the heat release capacity of the fiber. Condensed tannins greatly enhanced the adsorption of sodium ions to the fiber and exhibited inherent thermal stability. The limiting oxygen indices (LOI) calculated from the MCC parameters indicated the slower burning characteristic of brown cotton, and its LOI was further increased upon adsorption of sodium ions. 相似文献
Adsorbents that exhibit a high adsorption capacity and facile recyclability are considered promising materials for dye wastewater remediation. In this work, a novel sulfonate-decorated cotton fiber was fabricated as a recyclable adsorbent for the highly efficient removal of cationic dyes. Herein, poly(sodium p-styrene sulfonate-co–N-methylol acrylamide) (P(SSNa-co-NMAM)) with SSNa units as adsorption sites and NMAM units as thermal-crosslinking points was synthesized for the modification of cotton fibers. As expected, the as-obtained P(SSNa-co-NMAM)-coated cotton fibers (PCFs) presented outstanding adsorption capacities toward cationic dyes, even in the simulated effluents. The processes of cationic dye absorbing onto the PCFs were well fitted by the Langmuir isotherm model and pseudo-second-order kinetics. The thermodynamic study revealed that the adsorption reaction of the cationic dyes onto PCF was spontaneous, and the efficiency of adsorption was more desirable at higher temperatures. The maximum adsorption capacities of PCF toward methylene blue (MEB), rhodamine B (RhB), and malachite green (MG) were 3976.10, 2879.80, and 3071.55 mg/g, respectively. The dye removal mechanism was ascribed predominantly to electrostatic interactions. Moreover, the adsorption capacity of the PCFs toward cationic dyes was slightly influenced by the pH of the solutions because of the sulfonate moieties, which exhibit stability under acidic and alkaline conditions. Furthermore, the recyclability and reusability of the as-prepared PCFs were satisfactory and good mechanical properties and thermal stability were observed compared to those of pristine cotton fibers. Given the aforementioned results, the as-obtained PCFs are highly promising as ideal adsorbents for the remediation of dye-contaminated wastewater.
Comparative investigations of adsorption properties of chlorhexidine (CHX) on two cellulose fibers, bleached cotton and viscose,
were studied in order to obtain dry gauzes covered with known amount of this antiseptic. Adsorption isotherm results carried
out at 293 and 323 K can be described by Langmuir isotherm model, nevertheless, at high concentration correlation is better
to Freundlich isotherm. Electrokinetic potential evolution with CHX concentration, shows that initial negative zeta potential
of cotton and viscose diminish its absolute value as the concentration of the treatment increases; both fibers present an
isoelectric point at high concentration of CHX that is 0.3 mM for viscose and 0.8 mM for cotton. Electrostatic interactions
between cationic groups of CHX and carboxylic acid groups of the fibers could explain adsorption at low concentration, but
when it is higher than these values, possible hydrogen bonding between the amine groups of CHX and hydroxyl groups of cellulose
could explain increasing adsorption when it is hindered by electrostatic repulsion as it is predicted by Freundlich model,
that describes heterogeneous surface and multilayer adsorption. Adsorption kinetics isotherms reveal that the process is quick
with t1/2 values of 5.4 min for cotton and 2.8 min for viscose. Differences in adsorption behaviour between the two fibers could be
attributed to structural differences as we have observed from estimation of CI index based on FTIR spectra. Values obtained
1.6 for viscose and 2.2 for cotton could explain that the amount of CHX adsorbed on viscose is higher than it is on cotton.
Finally desorption experiments performed with 0.01 M of NaCl solution at room temperature and pH 6 reveals the possibility
of therapeutical application of these fibers although further investigations must be done to optimize the process. 相似文献
Adsorption thermodynamic and kinetic study of disperse dye on cotton fiber modified with tolylene diisocyanate derivative
was carried out under the condition of pH value 6.0 ± 0.2, initial dye concentration 0.01–3.0 g/L and liquor ratio 2,000:1.
The result showed the equilibrium adsorption isotherm of disperse dye on modified cotton fiber was Langmuir—Nernst mixed Model and the saturated adsorption capacity of the turning point was 7.1429 mg/g. The calculation of the thermodynamic
parameters indicated that the Van der Waals’ forces played a major role between the disperse dye and the modified cotton fiber,
and the adsorption of disperse dye on the modified cotton fiber was exothermic process. Compared with the diffusion coefficient
and the activation energy of disperse dye on various fibers, the disperse dye diffusion in modified cotton fiber was more
difficult than that in original cotton. Meanwhile, it was found that the adsorption kinetics of disperse dye on modified cotton
fiber was well agreed with a pseudo second-order kinetic model. 相似文献
The objective of this research is to produce high surface area-activated carbon derived from cotton linter fibers by fused NaOH activation and to examine the feasibility of removing oxytetracycline (OTC) from aqueous solution. The cotton linter fibers activated carbon (CLAC) was characterized by N(2) adsorption/desorption isotherms, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM). The results showed that CLAC had a predominantly microporous structure with a large surface area of 2143 m(2)/g. The adsorption system followed pseudo-second-order kinetic model, and equilibrium was achieved within 24h. The equilibrium data were described well by Langmuir isotherm. Thermodynamic study showed that the adsorption was exothermic reaction at low concentration and became endothermic nature with the concentration increasing. Competitive adsorption took place in the weakly acidic to neutral conditions. Under the strong acidity or strong alkaline condition, the adsorption of the oxytetracycline was hindered by electrostatic repulsion. The adsorption mechanism depended on the pH of the solutions as well as the pK(a) of the oxytetracycline. 相似文献
Cotton and linen fibers were ground in a ball-mill, and the effect of grinding on the microstructure and surface properties of the fibers was determined by combining a couple of simple tests with powerful techniques of surface and structure analysis. Results clearly proved that the effect of grinding on cotton fiber was much less severe than on linen. For both fibers, the degree of polymerization reduced (by 14.5% and 30.5% for cotton and linen, respectively) with a simultaneous increase in copper number. The increased water sorption capacity of the ground substrates was in good agreement with the X-ray results, which proved a less perfect crystalline structure in the ground samples. Data from XPS and SEM-EDS methods revealed that the concentration of oxygen atoms (bonded especially in acetal and/or carbonyl groups) on the ground surfaces increased significantly, resulting in an increase in oxygen/carbon atomic ratio (XPS data: from 0.11 to 0.14 and from 0.16 to 0.29 for cotton and linen, respectively). Although grinding created new surfaces rich in O atoms, the probable higher energy of the surface could not be measured by IGC, most likely due to the limited adsorption of the n-alkane probes on the less perfect crystalline surfaces. 相似文献
Cationic p(St-co-BA) nanospheres were prepared and their adsorption on cotton fibers was carried out. The effect of Gemini emulsifier ethanediyl bis(hexadecyl dimethyl ammonium bromide) (G16-2-16) on the colloidal features and adsorption properties of the cationic nanospheres was investigated. To get a clear understanding, the corresponding single-chain emulsifier hexadecyl trimethyl ammonium bromide (CTAB) was used as a comparison. Colloidal features, such as particle size and surface charge density, and adsorption properties, such as adsorption rate, were measured. G16-2-16 produced cationic p(St-co-BA) nanospheres with bigger particle size, better monodispersity, and higher surface charge density than CTAB. Compared with CTAB, G16-2-16 resulted in higher adsorption rate and more uniform arrangement of nanospheres at the cotton fiber surface. 相似文献
Adsorption is an efficient method to combat the important issues of water pollution caused by dyes and metal ions. However, due to the surface charge diversity of pollutants, there is a pressing need to develop an all-round, efficient, cheap and environmentally friendly adsorbent. To this end, this work synthesized an amphiprotic adsorbent based on cotton fibers, which were chemically modified with a cationic monomer (3-chloro-2-hydroxypropyl trimethyl ammonium chloride) and anionic monomer (2-acrylamide-2-methyl propane sulfonic acid) respectively. The resultant amphiprotic cotton (AP-cotton) can cope with both of anionic and cationic pollutants. Its adsorption behavior as influenced by the pH value, adsorption time and initial concentration of various adsorbates was investigated. The results demonstrate that the adsorption equilibrium was reached within 4 h for Congo red (CR) and methylene blue (MB), 2 h for Cu2+ and 3 h for Pb2+, respectively. Adsorption kinetics showed that the adsorption rate was well fitted with the pseudo-second-order rate model, and the best adsorption isotherms fitted the Langmuir model. The Langmuir maximum adsorption capacities were 175.1 mg/g for CR, 113.1 mg/g for MB, 88.9 mg/g for Cu2+ and 70.6 mg/g for Pb2+, respectively, and the adsorption capacities could be maintained above 90 % after six regenerations. The all-round adsorption capacity and good regeneration performance of AP-cotton benefited from its hollow, flat-banded structure and amphiprotic characteristic. Therefore, AP-cotton exhibited a much better application potential compared with many other reported adsorbents based on natural materials. 相似文献