氯酸钠电解尾气中氢气的回收利用

介绍了氯酸钠电解尾气经除氯、除水、脱氧后回收氢气的工艺原理和方法。     

预碳化辅助双氧水沉淀高碱铝酸钠溶液强化薄水铝石合成工艺(英文)

Hydrogen peroxide (H2O2) precipitation from sodium aluminate (SA) solution at close-ambient temperature is an efficient method to synthesize boehmite and its derived alumina with high surface area, but the precipitation yield of Al2O3 is usually below 50% in highly alkaline SA solutions. Here the synthesis of boehmite is enhanced through a precarbonization-assisted H2O2 route in highly alkaline SA solutions. It is found that the crystal structure of the precipitation product is evidently influenced by the precipitation conditions. As the precipitation temperature increases from 273 to 325 K, a small amount of gibbsite by-product is formed. As the aging temperature increases from 301 to 333 K, the crystallinity of boehmite decreases and part of the boehmite dissolves due to an increase in the pH value. Based on the above results, a precarbonization-assisted H2O2 route is proposed to obtain pure boehmite with more complete recovery of Al2O3 from highly alkaline SA solutions. The route includes a controllable precarbonization step of SA solutions with a molar ratio of Na2O to Al2O3 higher than 2︰1, followed by the H2O2-precipitated step with a molar ratio of H2O2 to Al2O3 less than 7︰1. Because of its facile operation conditions, no extraneous impurity, time saving and a possible recycle of the filtrate, the route has great potential to be an alternative method for preparation of boehmite and its derived alumina.     

Cellulose stability and delignification after alkaline hydrogen peroxide treatment of straw

Neutron diffraction profiles for cellulose from different sources were compared before and after alkaline hydrogen peroxide (AHP) treatment. It was found that AHP treatment did not cause detectable changes in the structure of highly polymerized cellulose. In measurements on wheat straw, peaks were observed at the angles characteristic of pure cellulose. Changes, with AHP treatment, of the intensities, positions, and widths of these peaks were consistent with effects due to delignification, which frees the cellulose lattice from strains caused by the binding of lignin.     

过氧化氢在碱性条件下的稳定性研究

通过对碱性过氧化氢稳定性的研究，选定了过氧化氢在碱性条件下应用的稳定剂，稳定剂最佳配方为：1000mL 50%过氧化氢加入稳定剂C1．5g，稳定剂D3．5g，选择此配方后的过氧化氢溶液的稳定性明显改观，所配制的碱性过氧化氢溶液清洁透明，无气泡，满足了用户的需求。     

大有发展前景的氯酸钠工业

详细分析了国内外氯酸钠的产需现状，二氧化氯的广泛应用，为氯酸钠带来了广阔的市场空间，氯碱企业生产氯酸钠，可大大提高企业的经济效益。     

Comparison of wool bleaching with hydrogen peroxide in alkaline and acidic media

A merino wool top was bleached in both alkaline and acidic media, varying the hydrogen peroxide concentration in the bleaching bath. For the same peroxide concentration, bleaching in an alkaline medium leads to a whiter and more chemically attacked wool than bleaching in an acidic medium. For the same chemical attack, wool bleached in an alkaline medium is whiter than for bleaching in an acidic medium.     

Reactions of oxygen and hydrogen peroxide at silver electrodes in alkaline solutions

The intermediate peroxide scheme for the oxygen electrode has been tested by experiments on oxygen reduction and hydrogen peroxide decomposition at silver electrodes in potassium hydroxide solutions (0·1, 1·0 and 5·0 M) at 25°C. The scheme is found appropriate in interpreting the observations, and data are obtained for the specific rate of three of the four one-electron steps involved in the reduction of oxygen to water. The decomposition of hydrogen peroxide occurs at a diffusion-limited rate and gives a mixed potential, V(nhe) = 0·94–0·059 pH, when the peroxide concentration exceeds a low limit (10⁻⁶ M in 1 M KOH). The silver-dissolution reaction exhibits essentially pure diffusion polarization and with the oxygen-reduction reaction determines the open-circuit potential of silver when the peroxide content of the solution is low. The results are compared with previous data on silver and on other electrode materials.     

Reactions of hydrogen peroxide on a silver electrode in alkaline solution

Reactions with hydrogen peroxide on silver in alkaline solutions with H₂O₂ concentration 5 × 10^?7 mol/ml have been studied with the ring-disk electrode. The amount of oxygen formed on the disk as the result of catalytic decomposition of hydrogen peroxide and its oxidation was established on the ring-electrode made from pyrographite. The rate constants of H₂O₂ electrochemical reduction (k₃), its oxidation (k′₂) and catalytic decomposition (k₄) and their dependence on potential have been evaluated. The constant k₄ scarcely depends on potential; it is ca 10^?2 cm/s.     

A small-scale flow alkaline fuel cell for on-site production of hydrogen peroxide

The behavior of a small-scale flow alkaline fuel cell (AFC) built-up for on-site production of HO₂⁻ using commercial gas-diffusion electrodes has been studied. It produces a spontaneous current due to the oxidation of H₂ to H₂O at the H₂-diffusion anode and the reduction of O₂ to HO₂⁻ at the O₂-diffusion cathode, while a fresh 1.0-6.0 mol dm⁻³ KOH electrolyte at 15.0-45.0 °C is injected through it. Under circulation of HO₂⁻+KOH solutions in open circuit, the flow AFC behaves as a two-electron reversible system. When it is shorted with an external load (R_ext), steady cell voltage-current density curves are found. The use of O₂/N₂ mixtures to fed the cathode causes a loss of its performance, being required to supply pure O₂ to yield a maximum HO₂⁻ electrogeneration. The current density and HO₂⁻ productivity increase with raising OH⁻ concentration, temperature and pressure of O₂ fed. At R_ext=0.10 Ω, a current efficiency close to 100% is obtained, and current densities >100 mA cm⁻² are achieved for 1.0 mol dm⁻³ KOH at 45.0 °C and for higher KOH concentrations at 25.0 °C. The flow AFC can work under optimum conditions up to 6.0 mol dm⁻³ KOH and 45.0 °C for possible industrial applications.     

Simultaneous oxidation of nitrogen oxides and sulfur dioxide with ozone and hydrogen peroxide

The use of ozone and hydrogen peroxide for the simultaneous oxidation of nitrogen and sulfur oxides was studied in experiments carried out in a stirred cell. It was found that in a gas mixture, containing both nitrogen and sulfur oxides, only the nitrogen oxides are oxidized by ozone. Contrary to earlier results, sulfur dioxide does not disturb the oxidation of nitrogen oxides under dry conditions. The consumption of ozone in the oxidation of nitric oxide was slightly below the stoichiometric level because the ozone was introduced into the reactor in the oxygen flow. When the molar ratio between ozone and nitric oxide was more than 0.4, some of the nitric oxide was oxidized to higher oxides of nitrogen, the final product being a solid mixture of N₂O₅ and (NO)₂S₂O₇. Some nitrosyl sulfuric acid was formed in the aqueous solution of hydrogen peroxide in addition to sulfuric acid under wet conditions. Some white solid was found on the walls of the reactor. This solid is said it the literature to consist of H₂SO₄, HNOSO₄ and (NO)₂S₂O₇.     

Infrared spectra of jute stick bleached with sodium chlorite and hydrogen peroxide

Jute stick was bleached with sodium chlorite and alkaline hydrogen peroxide solutions. The infrared (IR) spectra of bleached samples and jute stick were analyzed and compared. The bleached samples were characterized by higher absorbance intensity ratios (A_v/A₂₉₀₀) of the bands attributed to hemicellulose. Among the bleached samples the chlorite-bleached sample showed higher intensity for the bands mentioned. The bands attributed to lignin are either absent or very weak in the chlorite-bleached jute stick as compared to that of peroxide-bleached jute stick, although some residual lignin was present in the substrate. The 1635 cm^?1 band attribute to the vibration of adsorbed water molecules in the noncrystalline regions in cellulose appears as a sharp peak in chlorite-bleached jute stick and as a shoulder in peroxide-bleached jute stick. This can be attributed to the difference in the nature of the two bleaching processes.     

Pretreatment of sweet sorghum bagasse by alkaline hydrogen peroxide for enhancing ethanol production

Effects of severe and mild alkaline hydrogen peroxide (AHP) pretreatment on ethanol production from sweet sorghum bagasse via pre-simultaneous saccharification fermentation, and the chemical structure changes of the substrates were investigated. The results showed that the bagasse pretreated by severe AHP could produce more ethanol than that of mild AHP. The maximum ethanol concentration of the bagasses from mild and severe AHP pretreatment with 8% bagasse loading was 7.642±0.140 g/L and 19.330±0.085 g/L, respectively. Moreover, the FTIR and NMR analysis illustrated that the molecule and surface structures of the pretreated bagasse were significantly changed compared with the control. The potential biomass energy production of the effluent from the pretreatment was also briefly discussed for future utilization of waste solution.The heat energy potentials of waste solution with severe and mild AHP pretreatment were 367.2 kJ/L _effluent and 327.6 kJ/L _effluent , respectively.     

盐水中氯酸钠含量的控制

介绍了氯碱生产中盐水系统中氯酸钠的来源、危害及浓度的控制方法。为了保证氯酸钠的分解效率和操作安全性,对氯酸盐分解单元的操作及注意事项提出了建议。     

邻-联甲苯胺分光光度法测定氢氧化钠中的氯酸钠

介绍了邻-联甲苯胺分光光度法测定氢氧化钠中氯酸钠杂质含量的原理、操作步骤等,并分析了影响测定结果的因素,提出了操作过程中的注意事项。     

工业次氯酸钠溶液中氯酸钠含量的测定

利用次氯酸钠和氯酸钠的氧化能力不同,以双氧水消解次氯酸钠的影响,以硫酸中和次氯酸钠溶液中的氢氧化钠,以硫酸亚铁作还原剂,将试样中的氯酸钠还原,再用重铬酸钾标准溶液氧化过量的硫酸亚铁,从而测定工业次氯酸钠溶液中氯酸钠的准确浓度.方法简单可靠,测得的回收率高,检测极限（质量浓度）可达0.05g/L以下.     

十二烷基苯磺酸钠对燃料电池产过氧化氢的影响

用不同质量浓度的表面活性剂十二烷基苯磺酸钠(SDBS)对炭黑材料进行了改性,并制备了3种氧电极。通过极化曲线研究了其电化学活性,结果表明:加入适量的SDBS可以增加氧还原的过程。并放入燃料电池反应器里进一步研究其对产过氧化氢的影响。结果表明:过量的加入SDBS会减少过氧化氢的产量,而适量地加入SDBS,可以获得更大的电流和更高的过氧化氢产量,其过氧化氢浓度可以达到226 mmol/L;并且3个电极的电流效率都为100%。交流阻抗分析表明,适量地加入SDBS可以减小电子转移电阻和化学反应电阻,但其催化机理没有改变。     

Degradation of poly(vinyl alcohol) in strongly alkaline solutions of hydrogen peroxide

The action of hydrogen peroxide and sodium hydroxide independently as well as in combination together with stabilizer formulation–consisting of magnesium sulphate (5 g/L), ethylenediamine tetraacetic acid (2 g/L), gluconic acid (2 g/L), and nonionic/anionic wetting agent (1.5 g/L)–on poly(vinyl alcohol) (PVA) was investigated at 30°C and 95°C. The effect of sodium hydroxide (5–25 g/L) alone was to bring about an enhancement in the viscosity of PVA most probably due to gel formation. The latter was favored at higher sodium hydroxide concentrations and longer duration (30 min) of treatment. The opposite holds true when hydrogen peroxide (35% w/v) was used alone at concentrations ranging from 2 to 20 mL/L. The viscosity of PVA decreased as the hydrogen peroxide concentration increased. Nevertheless, hydrogen peroxide alone could not cause complete dissolution of PVA even at 95°C for 30 min. On the other hand, complete dissolution of PVA could be achieved under the influence of stabilized alkaline solutions of hydrogen peroxide at 95°C in less than 10 min. It was postulated that, under the conditions used, oxidation of PVA by hydrogen peroxide prevailed over gel formation under the influence of sodium hydroxide.     

Surface electrochemistry of UO2 in dilute alkaline hydrogen peroxide solutions

The reaction of H₂O₂ on SIMFUEL electrodes has been studied electrochemically and under open circuit conditions in 0.1 mol l⁻¹ NaCl (pH 9.8). The composition of the oxidized UO₂ surface was determined by X-ray photoelectron spectroscopy (XPS). Peroxide reduction was found to be catalyzed by the formation of a mixed U^IV/U^V (UO_2+x) surface layer, but to be blocked by the formation of U^VI (UO₂²⁺) species on the electrode surface. The formation of this U^VI layer blocks both H₂O₂ reduction and oxidation, thereby inhibiting the potentially rapid H₂O₂ decomposition process to H₂O and O₂. Decomposition is found to proceed at a rate controlled by desorption or reduction of the adsorbed O₂ species. Reduction of O₂ is coupled to the slow oxidative dissolution of UO₂ and formation of a corrosion product deposit of UO₃·yH₂O.     

Electrochemical oxidation of hydrogen peroxide at a bromine adatom-modified gold electrode in alkaline media

Bromine (Br)-adatom (Br_(ads)) was in situ fabricated onto polycrystalline gold (Au (poly)) electrode in Br⁻-containing alkaline media. The surface coverage of Br_(ads) (Γ_Br) varied only in the submonolayer coverage within the investigated potential window under potentiodynamic condition because of the coadsorption of hydroxyl ion (OH⁻) in alkaline media. The in situ fabricated Br_(ads)-submonolayer-coated Au (poly) electrode was successfully used for the electrochemical oxidation of hydrogen peroxide (H₂O₂). About five times higher oxidation current was achieved at the modified electrode as compared with the bare electrode. The enhancement of the electrode activity towards the electrochemical oxidation of H₂O₂ was explained based on the enhanced electrostatic attraction between the anionic HO₂⁻ molecules and Br_(ads)-adlayer-induced positively polarized Au (poly) electrode surface.     

过硫酸钠与双氧水催化降解印染废水的试验研究

为了考察Fe2+/Na_2S_2_O8/H_2O_2氧化体系对实际印染废水的处理效果,首先试验确定Fe2+/H_2O_2和Fe2+/Na_2S_2O_8氧化体系的最佳药剂投加量以及Fe2+/Na2S2O8/H2O2氧化体系的最佳p H,基于最佳p H条件下以药剂投加量为自变量,废水COD去除率为响应值,通过Box-Behnken设计方法设计试验,利用响应曲面分析优化,以优化结果为基础,改变氧化体系中药剂的投加时间与顺序,得出Fe2+/Na2S2O8/H_2O_2氧化体系最优工艺参数,经过90 min反应后,出水COD达到纺织染整行业废水排放限值。