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1.
Ion, precipitate and adsorbing colloid flotations of zinc(II) from dilute aqueous solutions have been investigated over a wide pH range using the anionic surfactant Aerosol OT or the cationic collector cetyl pyridinium chloride. In case of adsorbing colloid flotation (ACF) iron oxyhydroxide and aluminium hydroxide were used, either separately or together, as coprecipitants. The precipitate flotation curves were compared with the corresponding theoretical one calculated from the data published for Zn(II) hydrolysis. In addition to the effect of pH on the percent removal the effects of collector concentration, ionic strength, bubbling time and metal ion concentration were investigated and the optimum conditions were established. High removals could be achieved especially with ACF. The results obtained are discussed with respect to the chemical state of zinc, the ionization behaviour of the collectors and properties of the coprecipitants. The developed ACF process was applied to the removal of65Zn from radioactive process wastewater. 相似文献
2.
The liquid-liquid extraction, ion and precipitate flotation of Co(II) from chloride media of 1·10–4M initial Co(II) concentration and =0.1 have been investigated using decanoic acid and the results are compared. Organic solvents used were chloroform in the case of liquid-liquid extraction and ethanol (used as a solvent for the collector and a frother) in the case of flotation. From the results it appears that liquid-liquid extraction takes place through the formation of the complex: (CoR2)2(HR)2 but flotation occurs through the formation of a surface active product which has the empirical formula CoR2. The effects of pH and of decanoic acid concentration on the three separation processes were also investigated and the results discussed. Good agreement was observed between the experimental precipitate flotation curves and the theoretical curve calculated from the data published for Co(II) hydrolysis. 相似文献
3.
Hydrotalcite‐like compound (HTlc) with a Mg/Al molar ratio of 2:1 was synthesized by using a coprecipitation method and the sorption removal of Cu(II) by the Mg‐Al HTlc sample from CuSO4 solution was investigated. It was found that the Mg‐Al HTlc showed a good sorption ability for Cu(II) from CuSO4 solution, indicating that the use of hydrotalcite‐like compounds as promising inorganic sorbents for the removal of heavy metal ions from water is possible. The sorption kinetics and the sorption isotherm of Cu(II) on the HTlc obeyed the pseudo‐second order kinetic model and Langmuir equation, respectively. The percent removal of Cu(II) by the HTlc was strongly dependent on the initial pH of bulk solution. It increased sharply with the increase of initial pH value in the range of 5–7, and was relatively small in the initial pH range of 4–5, while it reached about 100% after initial pH was higher than 7. The presence of AlCl3 might obviously lower the equilibrium sorption amount (qe) of Cu(II) on the HTlc. However, the presences of NaCl and MgCl2 might increase the qe. The presences of ligands (citric acid and EDTA) in the studied concentration range might obviously decrease the qe of Cu(II) on the HTlc. The removal mechanism of Cu(II) cations by HTlc in the presence of SO42? anions may be attributed to the surface‐induced precipitation of Cu(II) hydroxides and the surface complex adsorption by the linking effect of SO42? between the HTlc and Cu(II) cations, and the removal ability arising from the surface‐induced precipitation is much higher than that from the linking effect of SO42?. 相似文献
4.
Ion, precipitate and adsorbing colloid flotation of cobalt(II) have been investigated at different pH values, using N-dodecylpyridinium chloride (DPCl), A strong cationic surfactant, and sodium lauryl sulfate (NaLS), a strong anionic surfactant, as collectors. In case of adsorbing colloid flotation, hydrous manganese dioxide was used as an adsorbent. The precipitate flotation curves experimentally obtained with the two tested collectors were compared with the corresponding theoretical one calculated from the data published for Co(II) hydrolysis. The effects of the collector concentration, ageing of the water-MnO2–Co(II) system, bubbling time period, cobalt(II) concentration and foreign salts on the percent removal of Co(II) by adsorbing colloid flotation using DPCl as collector were determined. Removals approaching 100% could be achieved under the optimum conditions. 相似文献
5.
Changqing Ye Dongsheng Wang Baoyou Shi Xiaopeng Ge Jiuhui Qu 《Journal of Sol-Gel Science and Technology》2007,41(3):257-265
Al13 is one of the novel nanospecies in partially neutralized Al(III) solution and Al-OH sol or precipitate could be generated
simultaneously in the neutralization. Unfortunately, the precipitate is believed to be harmful to the formation of Al13 due to the consumption of Al(OH)4
−, which was regarded as the precursor of Al13. In this paper, the feasibility and potential of transformation of freshly formed Al-OH precipitate into Al13 species were studied by using ferron colorimetric method and 27Al NMR spectroscopy. The Al-OH precipitates were produced by two ways: injection of base solution into Al(III) solution gradually
and mixing of Al(III) and base solutions instantaneously. The re-dissolving behaviors of the freshly formed precipitates were
examined under different basicities (OH/Al molar ratio) and temperatures. It has been shown that Al13 could be formed through the re-dissolution of intermediate Al-OH precipitate generated in partially neutralized Al(III) solution.
A possible formation mechanism of Al13 was suggested. Easily transformable precipitate was developed when the OH/Al molar ratio was less than 2.5. Rapid re-dissolution
of freshly formed precipitate was favorable for Al13 formation, which could be enhanced by heating. 相似文献
6.
A method is described where the simultaneous measurement of a thermal flow (by means of Tian-Calvet type calorimetry) and of a gas flow (by means of constant decomposition rate thermal analysis) allows the knowledge at any time of the instantaneous enthalpy of thermal dissociation. The method is used to study the thermal decomposition of an industrial Al(OH)3 gibbsite sample. 相似文献
7.
Yusov A. B. Fedoseev A. M. Astafurova L. N. 《Russian Journal of Coordination Chemistry》2002,28(4):264-271
The interaction of Np(VI), Pu(VI), Np(V), Np(IV), Pu(IV), Nd(III), and Am(III) with Al(III) in solutions at pH 0–4 was studied by the spectrophotometric method. It was shown that, in the range of pH 3–4, the hydrolyzed forms of neptunyl and plutonyl react with the hydrolyzed forms of aluminium. In the case of Pu(VI), the mixed hydroxoaqua complexes (H2O)3PuO2(-OH)2Al(OH)(H2O)3
2+ or (H2O)4PuO2OAl(OH)(H2O)4
2+ are formed at the first stage of hydrolysis. Np(VI) also forms similar hydroxoaqua complexes with Al(III). The formation of the mixed hydroxoaqua complexes was also observed when Np(IV) or Pu(IV) was simultaneously hydrolyzed with Al(III) at pH 1.5–2.5. The Np(IV) complex with Al(III) has, most likely, the formula (H2O)
n
(OH)Np(-OH)2Al(OH)(H2O)3
3+. At pH from 2 to 4.1 (when aluminium hydroxide precipitates), the Np(V) or Nd(III) ions exist in solutions with or without Al(III) in similar forms. When pH is increased to 5–5.5, these ions are almost not captured by the aluminium hydroxide precipitate. 相似文献
8.
Yusov A. B. Budantseva N. A. Fedoseev A. M. Astafurova L. N. 《Russian Journal of Coordination Chemistry》2001,27(11):776-782
Interaction of U(VI) with Al(III) in solutions at pH 2 and in precipitates obtained at pH 5 was studied using spectrophotometry, luminescence, and IR spectroscopy. It was shown that in the range of pH 3–4, hydrolyzed forms of uranyl and of aluminium come into interaction. The mixed hydroxoaqua complexes (H2O)3UO2(-OH)2Al(H2O)3+
4,(H2O)3UO2(-OH)2Al(OH)(H2O)2+
3, or (H2O)4UO2OAl(OH)(H2O)2+
4are likely to form in the solution. With an increase in pH, mixed polymers of a large size (oligomers) can form which further take part in the precipitate formation. The reaction between U(VI) and Al(III) in precipitates is confirmed by the data of IR spectroscopy and by the changes in the physico-chemical properties of these precipitates as compared with the properties of a mechanical mixture of separately precipitated uranium and aluminium. The important role of the oligomeric mixed forms in the formation of precipitate remains at pH levels varying from 5 to 14. 相似文献
9.
Al(OH)3- and ZrO(OH)2-coated magnetites were prepared and used for fluoride removal from aqueous samples. The influence of pH, sorbent mass, and ions such as chloride, sulfate, and phosphate on the removal of fluoride was characterized. The sorption process was highly pH dependent, and the optimal sorption was obtained from pH 4 to 5 for ZrO(OH)2- and pH 4 to 7 for Al(OH)3-coated magnetites. The sorption isotherm was well described by the Langmuir equation for the sorbents. The maximum adsorption capacity of ZrO(OH)2-coated magnetite (57.47?mg-F?g?1-sorbent) was higher than for Al(OH)3-coated magnetite (23.87?mg-F?g?1-sorbent). The ion-exchange reaction occurred in 5?min and more than 99% of fluoride was removed from solution. When the ZrO(OH)2-coated magnetite was used, the presence of foreign ions negatively affected the fluoride removal. The prepared sorbents showed an excellent performance for the removal of fluoride in water samples. 相似文献
10.
The separation behavior of mercury by a flotation system consisting of ammonium sulfate, ammonium thiocyanate and ethyl violet, and the conditions for the separation of Hg(II) with other common metal ions have been studied. The studies show that in aqueous solutions, Hg(II) combines with NH4SCN and ethyl violet(EV) into dissoluble ternary ion‐association complex [Hg(SCN)42?]?(EV)2. In the presence of ammonium sulfate, the precipitate is floats well on the surface of the water phase and separates from water thoroughly. It shows that Hg(II) can be separated completely from Cd(II), Fe(II), Co(II), Ni(II), Mn(II) and Al(III) by flotation at pH1.0. The flotation mechanism of Hg(II) is described in this paper. 相似文献
11.
An energy-efficient and environmentally friendly microwave-assisted method was adopted for synthesis of butterfly-like CuO assembled by nanosheets through a Cu2Cl(OH)3 precursor, using no template. Formation mechanism of the butterfly-like CuO was explored and discussed systematically for the first time on the basis of both experimental results and crystal structure transformations in atomic level. The electrochemical sensing properties of the butterfly-like CuO modified electrode to ascorbic acid (AA) were studied for the first time. The results reveal that Cu(OH)2 nanowires were formed once the Cu2+ ions, located in between two CuO4 parallelogram chains of a Cu2Cl(OH)3 precursor, dissolve into the solution as Cu(OH)42− complex ions after ion exchange reactions and simultaneous assemble along a axis. Upon microwave irradiation, the adjacent CuO4 parallelogram chains of the Cu(OH)2 nanowires dehydrate and assemble along c axis, forming CuO nanosheets with (002) as the main exposed facet, which were further assembled to butterfly-like CuO under the action of microwave field, suggesting that microwave field functions like a ‘directing agent’. The butterfly-like CuO modified electrode shows good electrochemical sensing properties to AA with a low detecting limit, short response time and wide linear response range. 相似文献
12.
Maany M. Hamada Abdel-Hamid M. Shallaby Ola El-Shafai Ahmed A. El-Asmy 《Transition Metal Chemistry》2006,31(4):522-529
The complexes of thiosemicarbazide (HTS) have been prepared and characterized by spectral, thermal and magnetic studies. The
deprotonation constant of HTS and the formation constants of its complexes were evaluated pH-metrically. The Cu(II) acetate-HTS
system gave high stability. The catalytic activity of Co(II), Ni(II) and Cu(II) complexes was tested to decompose H2O2. The Co(II) complex has no activity whereas the Cu(II) complex was found to be more active than Ni(II). The different Cu(II)
complexes were tested; [Cu2(TS)(OH)2(OAc)] was highly active. All parameters affecting the reaction rate (concentration of H2O2, weight of catalyst, temperature and pH) were studied and the optimum conditions were evaluated. Attempts to increase the
activity of [Cu2(TS)(HO)2(OAc)] by mixing with superconducting cuprate sample, Nd0.1Y0.9Ba2Cu3O7-δ, will be the subject of further studies. 相似文献
13.
Dioctylarsinic acid (HDOAA) in chloroform solution has been investigated as a reagent for the extraction of Hg(II), Ag(I), Co(II), and Cd(II). Silver, cobalt and cadmium are not extracted below pH 7. An extraction coefficient of 1.1, constant over the pH range 1–6.5, was observed for Hg(II). With HCl concentrations of 1–8 M the extractability of mercury decreased slowly, reaching Ea0 = 0.05 at 8 M HCl. Silver formed a silver dioctylarsinate precipitate which collected at the interface. The extraction coefficients for Hg(II), Co(II) and Cd(II) increased above pH 7 to values of 20 (pH 9.1), 30 (pH 8.0), and 23 (pH 10), respectively. Reagent- and pH-dependence studies indicated that Co(II) and Cd(II) are extracted as M(DOAA)2 or M(DOAA)Cl through interaction of HDOAA with M(OH)2 or M(OH)+. Mercury was extracted from solutions of pH 1–6.5 as HgCl2 (HDOAA)2.5. 相似文献
14.
Weilun Hu Qian Shao Xingjun Xi Qiao Chu Tao Lan Fenfang Che Yuanyuan Liu Yanzhen Lu Yun Wei 《Biomedical chromatography : BMC》2019,33(1)
In this work, a general and novel separation technique gas‐assisted three‐liquid‐phase extraction was established and applied in separating and concentrating isoflavonoids from the actual sample of puerariae extract by one step. For the gas‐assisted three‐liquid‐phase extraction method, optimal conditions were selected: polyethylene glycol 2000 and ethyl acetate as the flotation solvent, pH 5, (NH4)2SO4 concentration 350 g/L in aqueous phase, N2 flow rate 30 mL/min, flotation time 50 min, and flotation twice. Five isoflavonoids compounds puerarin, 3′‐methoxydaidzin, puerarinxyloside, daidzin and daidzein were separated with recoveries of 82, 84, 80, 88 and 89%, respectively. The separated products were purified by preparative high‐performance liquid chromatography, and the purity of the final products was >96%. The established general gas‐assisted three‐liquid‐phase extraction was used to separate anthraquinones from Cassiae Semen under the optimal conditions, and the recoveries were >75%. The experimental results showed that the established gas‐assisted three‐liquid‐phase extraction method is a general technique for separating active compounds from herb extract. 相似文献
15.
Optical emission spectroscopy has been applied to study the OH radicals and O, H, and N active atoms produced by a high-voltage negative pulsed streamer corona discharge of N2 and H2O mixture gas in a needle-plate reactor at one atmosphere. The relative vibrational populations and the vibrational temperature of N2(C, v′) were determined. The effects of pulsed peak voltage, pulsed repetition rate, and the addition of O2 on the relative populations of OH(A2Σ) radicals, O(3p5P), Hα (3P), and N(3p4P) active atoms were investigated. It was found that the relative populations of those radicals increase with increasing pulsed peak voltage and pulsed repetition rate. The relative population of OH(A2Σ) radicals decreases with increasing O2 flow rate, while the relative populations of O (3p5P), Hα (3P), and N (3p4P) active atoms exhibit a maximum over the studied range of the O2 flow rate. The involved physicochemical processes have also been discussed. 相似文献
16.
Filip J Yngard RA Siskova K Marusak Z Ettler V Sajdl P Sharma VK Zboril R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(36):10097-10105
The reaction of potassium ferrate(VI), K2FeO4, with weak‐acid dissociable cyanides—namely, K2[Zn(CN)4], K2[Cd(CN)4], K2[Ni(CN)4], and K3[Cu(CN)4]—results in the formation of iron(III) oxyhydroxide nanoparticles that differ in size, crystal structure, and surface area. During cyanide oxidation and the simultaneous reduction of iron(VI), zinc(II), copper(II), and cadmium(II), metallic ions are almost completely removed from solution due to their coprecipitation with the iron(III) oxyhydroxides including 2‐line ferrihydrite, 7‐line ferrihydrite, and/or goethite. Based on the results of XRD, Mössbauer and IR spectroscopies, as well as TEM, X‐ray photoelectron emission spectroscopy, and Brunauer–Emmett–Teller measurements, we suggest three scavenging mechanisms for the removal of metals including their incorporation into the ferrihydrite crystal structure, the formation of a separate phase, and their adsorption onto the precipitate surface. Zn and Cu are preferentially and almost completely incorporated into the crystal structure of the iron(III) oxyhydroxides; the formation of the Cd‐bearing, X‐ray amorphous phase, together with Cd carbonate is the principal mechanism of Cd removal. Interestingly, Ni remains predominantly in solution due to the key role of nickel(II) carbonate, which exhibits a solubility product constant several orders of magnitude higher than the carbonates of the other metals. Traces of Ni, identified in the iron(III) precipitate, are exclusively adsorbed onto the large surface area of nanoparticles. We discuss the relationship between the crystal structure of iron(III) oxyhydroxides and the mechanism of metal removal, as well as the linear relationship observed between the rate constant and the surface area of precipitates. 相似文献
17.
Saad S. M. Hassan Nasser S. Awwad Awaad H. A. Aboterika 《Journal of Radioanalytical and Nuclear Chemistry》2006,269(1):135-140
Summary Synthetic Sorel's cement [3Mg(OH)2 . MgCl2 . 8H2O], is used as a new adsorbent material for removal of chromium(VI) ion from wastewater effluents. Parameters including contact
time, adsorbent dosage and pH are examined and optimized. The equilibrium data are fitted very well to the Langmuir and Freundlich
isotherms rather than linear. The adsorption isotherm indicates that the monolayer coverage is 21.4 mg Cr(VI) ion per g of
Sorel's cement. The adsorbent is considered as a better replacement technology for removal of Cr(VI) ion from aqueous solutions
due to its low cost, good efficiency, fast kinetics, and simple preparation. It offers remarkable efficiency for Cr(VI) removal
from wastewater compared with many other natural and synthetic adsorbents. 相似文献
18.
Ismagilov Z. R. Shkrabina R. A. Tsikoza L. T. Yashnik S. A. Shikina N. V. Sazonov V. A. Veringa H. 《Kinetics and Catalysis》2001,42(6):854-856
The effects of ion-exchange conditions and the zeolite Si/Al atomic ratio on the copper contents of Cu(80% ZSM-5 + 20%Al2O3) catalysts and on the catalytic activity in the selective reduction of NO with propane were studied. It was found that the synthesis of these catalysts exhibited the same behavior as in the case of bulk CuZSM-5 catalysts containing no Al2O3. The copper contents of the catalysts depend on the pH and concentration of copper solutions used for ion exchange, and the maximum activity (NO conversion) is attained even at an exchange level (Cu/Al) close to 100% regardless of pH and the zeolite Si/Al atomic ratio. At 300–400°C, the activity of the test catalysts is 10–20% lower than the activity of CuZSM-5 catalysts containing no Al2O3at equal exchange levels. This difference in the activity almost disappeared as the reaction temperature was increased. It was also found that in the Cu(80% ZSM-5 + 20%Al2O3) catalysts, an exchange level close to that in CuZSM-5 catalysts is attained by ion exchange from more concentrated solutions. An increase in the exchange level to 100% (by an increase in the pH of a copper solution from 6 to 10, as in the case of CuZSM-5 catalysts), had no effect on the activity. 相似文献
19.
《Arabian Journal of Chemistry》2020,13(4):5060-5074
A new species’ class of Cu-, Ga- and Zn-based rate catalysts was prepared by a systematic co-precipitation technique at the different related pH values (6.5–8.0) along with calcination functional conditions, influencing components’ physical properties, these were characterized, and their application performance for water–gas shift (WGS) reaction was researched. Substances were analysed by various experimental methods, namely chemisorption, temperature-programmed reduction (TPR) characterisation, diffraction, physisorption and microscopy. A homogenous size dispersion of the compounds with smaller granular particles was obtained for catalysis, implemented with high pH-resulting outputs. H2 TPR profiles revealed a tailored stronger effect of Cu–Zn on Ga for process, operated with low pH-conditioned forms. Over Cu/ZnGaOX, WGS was sensitive to Cu, which was primarily active. Catalytic chemical reactivity, activity and selectivity were also found to be critically dependent on material lattice structure, copper surface area and metal–support interaction phenomena. The temperature-programmed surface reaction with mass spectrometry (TPSR–MS) measurements showed that formulations, synthesised at the pH of 8.0, enabled reaching >99% of the equilibrium yield CO conversion at 260 °C. An increase in the converted CO, oxidation and H2 productivity with the integral steam content in gaseous feed flow was achieved. The heterogeneous phase processing at the correlated pH of 7.6 demonstrated the highest formed CO product at the temperature of 200 °C, compared with literature. This is particularly promising for reagent purity hydrogen-fed fuel cells. The kinetics for each co-precipitated solid was evaluated regarding the efficiency for the WGS in a fixed bed reactor. 相似文献
20.
The chemistry of magnesium precipitation preconcentration of Fe, Mn, and Co from seawater was investigated, and this analytical technique was adapted for use with the Element-2 inductively coupled plasma mass spectrometer (E2 ICP-MS). Experiments revealed that the scavenging efficiency of Mn using the precipitation protocol described here was ∼95% and similar to that previously observed with Fe. In contrast, the scavenging efficiency of Co was three-fold lower than that of Fe and Mn, resulting in poor recovery. An increase in sample size to 13 mL led to several desired effects: (1) an increase in the Fe and Mn signals allowing a final dilution of samples to 0.5 mL and the use of an autosampler, (2) an increase in precision to ∼1-2.5% R.S.D., and (3) an increase in signal relative to the blank. Experiments suggest metal concentration from seawater occurs during the formation of Mg(OH)2 precipitate, whereas P was scavenged by adsorption onto the Mg(OH)2 particles. Example vertical profiles are shown for dissolved Fe and Mn from the Equatorial Pacific. 相似文献