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211.
To solve the problem of shortened backwashing intervals in groundwater plants, several disinfectants including ozone (O3), hydrogen peroxide (H2O2) and chlorine dioxide (ClO2) were examined to peel off the film from the quartz sand surface in four pilot-scale columns. An optimized oxidant dosage and oxidation time were determined by batch tests. Subsequently, the optimized conditions were tested in the four pilot-scale columns. The results demonstrated that the backwashing intervals increased from 35.17 to 54.33 (H2O2) and to 53.67 hr (ClO2) after the oxidation treatments, and the increase of backwashing interval after treatment by O3 was much less than for the other two treatments. Interestingly, the treatment efficiency of filters was not affected by O3 or H2O2 oxidation; but after oxidation by ClO2, the treatment efficiency was deteriorated, especially the ammonia removal (from 96.96% to 24.95%). The filter sands before and after the oxidation were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. Compared with the oxidation by O3 and H2O2, the structures on the surface of filter sands were seriously damaged after oxidation by ClO2. The chemical states of manganese on the surfaces of those treated sands were only changed by ClO2. The damage of the structures and the change of the chemical states of manganese might have a negative effect on the ammonia removal. In summary, H2O2 is a suitable agent for film peeling. 相似文献
212.
Experiments were conducted in a fixed-bed reactor containing a commercial V2O5/WO3/TiO2 catalyst to investigate mercury oxidation in the presence of HCl and O2. Mercury oxidation was improved significantly in the presence of HCl and O2, and the Hg0 oxidation efficiencies decreased slowly as the temperature increased from 200 to 400°C. Upon pretreatment with HCl and O2 at 350°C, the catalyst demonstrated higher catalytic activity for Hg0 oxidation. Notably, the effect of pretreatment with HCl alone was not obvious. For the catalyst treated with HCl and O2, better performance was observed with lower reaction temperatures. The results showed that both HCl and Hg0 were first adsorbed onto the catalyst and then reacted with O2 following its adsorption, which indicates that the oxidation of Hg0 over the commercial catalyst followed the Langmuir–Hinshelwood mechanism. Several characterization techniques, including Hg0 temperature-programmed desorption (Hg-TPD) and X-ray photoelectron spectroscopy (XPS), were employed in this work. Hg-TPD profiles showed that weakly adsorbed mercury species were converted to strongly bound species in the presence of HCl and O2. XPS patterns indicated that new chemisorbed oxygen species were formed by the adsorption of HCl, which consequently facilitated the oxidation of mercury. 相似文献
213.
An experimental study has been conducted to investigate the effects of hydrogen addition on the fundamental propagation characteristics of methane/air premixed flames at different equivalence ratios in a venting duct. The hydrogen fraction in the methane–hydrogen mixture was varied from 0 to 1 at equivalence ratios of 0.8, 1.0 and 1.2. The results indicate that the tendency towards flame instability increased with the fraction of hydrogen, and the premixed hydrogen/methane flame underwent a complex shape change with the increasing hydrogen fraction. The tulip flame only formed when the fraction of hydrogen ranged from 0 to 50% at an equivalence ratio of 0.8. It was also found that the flame front speed and the overpressure increased significantly with the hydrogen fraction. For all equivalence ratios, the stoichiometric flame (Φ = 1.0) has the shortest time of flame propagation and the maximum overpressure. 相似文献
214.
Most of the numerical benchmarks on combustion in large scale volumes for hydrogen safety, which were performed up until today have demonstrated, that current numerical codes and physical models experience poor predictive capabilities at the industrial scale, both due to under-resolution and deficiencies in combustion modeling. This paper describes a validation of the EUROPLEXUS code against several large scale experimental data sets in order to improve its hydrogen combustion modeling capabilities in industrial settings (e.g. reactor buildings). The code is based on the Euler equations and employs an algorithm for the propagation of reactive interfaces, RDEM, which includes a combustion wave, as an integrable part of the Reactive Riemann problem, propagating with a fundamental flame speed (being a function of initial mixture properties as well as gas dynamics parameters). Validation of the first combustion model implemented in the code is based on obstacle-laden channels, interconnected reactor-type compartments, vented enclosures and covers all major premixed flame combustion regimes (slow, fast and detonation) with an aim to obtain conservative results. An improvement of this model is found in a direction of transient interaction of flame fronts with regions of elevated integral length scales presented in the velocity gradient field due to e.g. interactions with geometrical non-uniformities and pressure waves. 相似文献
215.
In the present work, mesoporous simonkolleite–TiO2 composite was prepared with sol–gel method. The composite photocatalysts were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), and Raman spectroscopy. Also, surface area and particle size were analyzed using BET equation. The photocatalytic hydrogen production with simultaneous decolorization of Remazole Red (F3B) dye was investigated over TiO2 and simonkolleite–TiO2 composite under UV–vis light irradiation. It was worthy to be noted that the rate of hydrogen production over simonkolleite–TiO2 is higher that produced over TiO2. The maximum amount of photocatalytic-produced hydrogen was 2.1 mmol and 3.3 mmol within 240 min using TiO2 and simonkolleite–TiO2 composite, respectively. The specific production rate of hydrogen from photocatalytic conversion of dye was calculated. Improvement of apparent quantum yield (22.07%) after 5 h was achieved upon addition of simonkolleite to TiO2. This high apparent quantum yield proves that the system proposed in this study could be a hopeful approach toward using sunlight energy as outlook energy source. The obtained results suggested that a new process for H2 production from wastewater could be achieved. The process also provides a method for degradation of organic pollutants with simultaneous H2 production. 相似文献
216.
217.
An unexpected ignition of pyrophoric iron sulphide deposits took place in the fractionator of a Visbreaker unit. The distillation column had been chemically decontaminated prior to the event. The investigation of the event leads to conclusions concerning chemical decontamination limitations in vessels in coking service. Based on the lessons learned from this case, a prioritization of manual vessel cleaning works in coking service is proposed. 相似文献
218.
Yingying You Shaobin Huang Xuesong Zhao Han Li Fangqin Cheng Jinhua Wu Yongqing Zhang Shaofeng Zhou 《环境科学学报(英文版)》2019,31(9):39-45
This study for the first time proposed an efficient microbial electrolyte/UV system for Methyl Orange decomposition. With an external applied voltage of 0.2 V and cathode aeration of20 mL/min, H_2O_2 could be in-situ generated from two-electron reduction of oxygen in cathode, reaching to 8.1 mg/L in 2 hr and continued to increase. The pollutant removal efficiency of approximate 94.7% was achieved at initial neutral pH, with the activation of ·OH in the presence of UV illumination. Although the nature of its guiding principles remain on the vista of practical exploration, this proof-of-concept study provides an alternative operation pattern of solar–microbial hybrid technology for future wastewater treatment from a basic but multidisciplinary view. 相似文献
219.
Microwave and Fenton's reagent oxidation of wastewater 总被引:16,自引:0,他引:16
J.?Sanz J.?I.?Lombra?aEmail author A.?M.?De Luis M.?Ortueta F.?Varona 《Environmental Chemistry Letters》2003,1(1):45-50
We compared two H2O2 oxidation methods for the treatment of industrial wastewater: oxidation using Fenton's reagent [H2O2/Fe(II)] and microwave irradiation. Both methods were applied to the treatment of synthetic phenol solutions (100 mg L−1) and of an industrial effluent containing a mixture of ionic and non-ionic surfactants at high load (20 g L−1 of COD). The effects of initial pH, initial H2O2 concentration, Fenton catalyst amount and irradiation time were assessed. According to the oxidation of phenol, it has been
found that the oxidation by Fenton's reagent is dependent on the pH, contrary to the microwave system, which is not influenced
by this parameter. For both systems, a limiting amount of oxidant has been found; above this point the oxidation of phenol
is not improved by a further addition of peroxide. The oxidation of the industrial surfactant effluent has only been successful
with the Fenton's reagent. In this case, large amounts of ferrous ions are necessary for the precipitation of the ionic surfactants
of the effluent, followed by the oxidation of the non-ionic constituents of the solution.
Electronic Publication 相似文献
220.
An Experimental Study on the Effect of Electrolytic Concentration on the Rate of Hydrogen Production
The effects of concentration of electrolytes on hydrogen production rate (HPR) at different applied voltages were experimentally evaluated in this research paper. The rate of hydrogen production was found to be directly proportional to the concentration of total dissolved solids and the efficiency did not change much with the change in the concentration of solids. Sensitivity analysis of the electrolysis system was also carried out to understand the relative importance of concentration of total dissolved solids (TDS) on the HPR, which can help for an optimum design. 相似文献