Abatement of Sulfur Hexafluoride Emissions from the Semiconductor Manufacturing Process by Atmospheric-Pressure Plasmas

Abstract

Sulfur hexafluoride (SF₆) is an important gas for plasma etching processes in the semiconductor industry. SF₆ intensely absorbs infrared radiation and, consequently, aggravates global warming. This study investigates SF₆ abatement by nonthermal plasma technologies under atmospheric pressure. Two kinds of nonthermal plasma processes—dielectric barrier discharge (DBD) and combined plasma catalysis (CPC)—were employed and evaluated. Experimental results indicated that as much as 91% of SF₆ was removed with DBDs at 20 kV of applied voltage and 150 Hz of discharge frequency for the gas stream containing 300 ppm SF₆, 12% oxygen (O₂), and 40% argon (Ar), with nitrogen (N₂) as the carrier gas. Four additives, including Ar, O₂, ethylene (C₂H₄), and H₂O_(g), are effective in enhancing SF₆ abatement in the range of conditions studied. DBD achieves a higher SF₆ removal efficiency than does CPC at the same operation condition. But CPC achieves a higher electrical energy utilization compared with DBD. However, poisoning of catalysts by sulfur (S)-containing species needs further investigation. SF₆ is mainly converted to SOF₂,SO₂F₄, sulfur dioxide (SO₂), oxygen difluoride (OF₂), and fluoride (F₂). They do not cause global warming and can be captured by either wet scrubbing or adsorption. This study indicates that DBD and CPC are feasible control technologies for reducing SF₆ emissions.     

Effect of Refractory on the Thermal Stability of SF6

The thermal decomposition of SF₆ is known to be oxygen-independent. Nevertheless, because of its high stability, the use of SF6 as a "conservative" surrogate in incinerator performance evaluation has been advocated and researched. This paper shows that refractory decreases markedly the stability of SF₆. The resulting increase in SF₆ decomposition was from 0 percent to 95 percent at 900°C, and the temperatures at which 90-99 percent decomposition occurred were lowered by 300-150°C. Refractory also decreased the stability of CCl₄ and C₂Cl₄, but to a lesser extent. The difference between the decompositions of C₂Cl₄ and SF₆ was reduced from several orders of magnitude to a factor of 2-4. Such a drastic and adverse change in relative stability could render SF₆ unsuitable as a "conservative" surrogate. The requirements for a "conservative" surrogate and the need for caution in its use are discussed, and further research areas are indicated.     

Decomposition of SF6 in an RF plasma environment

Sulfur hexafluoride (SFd)-contained gas is a common pollutant emitted during the etching process used in the semiconductor industry. This study demonstrated the application of radio-frequency (RF) plasma in the decomposition of SF6. The decomposition fraction of SF6 [etaSF6 (C(in)-C(out))/C(in) x 100%] and the mole fraction profile of the products were investigated as functions of input power and feed O2/SF6 ratio in an SiO2 reactor. The species detected in both SF6/Ar and SF6/O2/ Ar RF plasmas were SiF4, SO2, Fe2, SO2F2, SOF2, SOF4, S2F10, S2OF10, S2O2F10, and SF4. The results revealed that at 40 W, etaSF6 exceeded 99%, and the reaction products were almost all converted into stable compounds such as SiF4, SO2, and F2 with or without the addition of oxygen. Sulfur oxyfluorides such as SO2F2, SOF2, SOF4, S2OF10, and S2O2F10 were produced only below 40 W. The results of this work can be used to design a plasma/chemical system for online use in a series of a manufacturing process to treat SF6-containing exhaust gases.     

Dissociation of Sulfur Hexafluoride Tracer Gas in the Presence of an Indoor Combustion Source

ABSTRACT

As an odorless, nontoxic, and inert compound, sulfur hexafluoride (SF₆) is one of the most widely used tracer gases in indoor air quality studies in both controlled and uncontrolled environments. This compound may be subject to reactions with water vapor under elevated temperature to form acidic inorganic compounds such as HF and H₂SO₄. Thus, in the presence of unvented combustion sources such as kerosene heaters, natural gas heaters, gas log fireplaces, candles, and lamps, the SF₆ dissociation may interfere with measurements of the emissions from these sources. Tests were conducted in a research house with a vent-free natural gas heater to investigate these potential interferences. It was observed that the heater operation caused about a 5% reduction of SF₆ concentration, which can be an error source for the ventilation rate measurement and consequently the estimated pollutant emission rates. Further analysis indicates that this error can be much greater than the observed 5% under certain test conditions because it is a function of the ventilation flow rate. Reducing the tracer gas concentration has no effect on this error. A simple theoretical model is proposed to estimate the magnitude of this error.

The second type of interference comes from the primary and secondary products of the SF₆ dissociation, mainly H₂SO₄, SO₂, HF, and fine particulate matter (PM). In the presence of ~5 ppm SF₆, the total airborne concentrations of these species increased by a factor of 4-10. The tests were performed at relatively high SF₆ concentrations, which is necessary to determine the interferences quantitatively. The second type of interference can be significantly reduced if the SF₆ concentration is kept at a low ppb level.     

Stability of 6:2 fluorotelomer sulfonate in advanced oxidation processes: degradation kinetics and pathway

Perfluorooctane sulfonate (PFOS), a widely used mist suppressant in hard chrome electroplating industry, has been listed in the Stockholm Convention for global ban. 6:2 Fluorotelomer sulfonate (6:2 FTS) acid and salts have been adopted as alternative products in the market, but no data about their abiotic degradation has been reported. In the present study, the degradability of 6:2 FTS potassium salt (6:2 FTS-K) was evaluated under various advanced oxidation processes, including ultraviolet (UV) irradiation, UV with hydrogen peroxide (H₂O₂), alkaline ozonation (O₃, pH = 11), peroxone (O₃/H₂O₂), and Fenton reagent oxidation (Fe²⁺/H₂O₂). UV/H₂O₂ was found to be the most effective approach, where the degradation of 6:2 FTS-K followed the pseudo-first-order kinetics. The intermediates were mainly shorter chain perfluoroalkyl carboxylic acid (C₇ to C₂), while sulfate (SO₄ ^2?) and fluoride (F^?) were found to be the final products. The high yields of SO₄ ^2? and F^? indicate that 6:2 FTS-K can be nearly completely desulfonated and defluorinated under UV/H₂O₂ condition. The degradation should firstly begin with the substitution of hydrogen atom by hydroxyl radicals, followed by desulfonation, carboxylation, and sequential “flake off” of CF₂ unit. Compared with PFOS which is inert in most advanced oxidation processes, 6:2 FTS-K is more degradable as the alternative.     

The air pollution caused by the burning of fireworks during the lantern festival in Beijing

The effects of the burning of fireworks on air quality in Beijing was firstly assessed from the ambient concentrations of various air pollutants (SO₂, NO₂, PM_2.5, PM₁₀ and chemical components in the particles) during the lantern festival in 2006. Eighteen ions, 20 elements, and black carbon were measured in PM_2.5 and PM₁₀, and the levels of organic carbon could be well estimated from the concentrations of dicarboxylic acids. Primary components of Ba, K, Sr, Cl⁻, Pb, Mg and secondary components of C₅H₆O₄²⁻, C₃H₂O₄²⁻, C₂O₄²⁻, C₄H₄O₄²⁻, SO₄²⁻, NO₃⁻ were over five times higher in the lantern days than in the normal days. The firework particles were acidic and of inorganic matter mostly with less amounts of secondary components. Primary aerosols from the burning of fireworks were mainly in the fine mode, while secondary formation of acidic anions mainly took place on the coarse particles. Nitrate was mainly formed through homogeneous gas-phase reactions of NO₂, while sulfate was largely from heterogeneous catalytic transformations of SO₂. Fe could catalyze the formation of nitrate through the reaction of α-Fe₂O₃ with HNO₃, while in the formation of sulfate, Fe is not only the catalyst, but also the oxidant. A simple method using the concentration of potassium and a modified method using the ratio of Mg/Al have been developed to quantify the source contribution of fireworks. It was found that over 90% of the total mineral aerosol and 98% of Pb, 43% of total carbon, 28% of Zn, 8% of NO₃⁻, and 3% of SO₄²⁻ in PM_2.5 were from the emissions of fireworks on the lantern night.     

A simulation of sulfur wet deposition and its dependence on the inflow of sulfur species to storms

Numerical precipitation scavenging models are used to investigate the relationship between the inflow concentrations of sulfur species to precipitation systems and the resulting sulfur wet deposition. Simulations have been made for summer and winter seasons using concentration ranges of SO₂, aerosol SO₄²⁻, H₂O₂ and O₃ appropriate for the eastern U.S. summer simulations use one-dimensional timedependent convective cloud and scavenging models; winter simulations use two-dimensional steady-state warm-frontal models. Sulfur scavenging mechanisms include nucleation scavenging of aerosol, aqueous reactions of H₂O₂, O₃ and HCHO with S(IV), and nonreactive S(IV) scavenging. Over the wide range of conditions that have been examined, the relation between sulfur inflow and sulfur wet deposition varies from nearly linear to strongly nonlinear. The degree of nonlinearity is most affected by aerosol SO₄²⁻ levels and relative levels of SO₂ vs H₂O₂. Higher aerosol SO₄²⁻ levels (as found in summer) produce a more linear relation. The greatest nonlinearity occurs when SO₂ exceeds H₂O₂. Winter simulations show more nonlinearity than summer simulations.     

Aktuelle und künftige Emissionen treibhauswirksamer fluorierter Verbindungen in Deutschland

Zusammenfassung  Die fluorierten Verbindungen Schwefelhexafluorid (SF₆), perfluorierte Fluorkohlenwasserstoffe (CF₄, C₂F₆) und wasserstoffhaltige Fluorkohlenwasserstoffe (H-FKW) z?hlen zu den atmosph?rischen Spurengasen mit extrem hohen Treibhauspotentialen. Untersucht werden für Deutschland ihre realen Emissionen für 1990–1995, und Prognosen für die Jahre bis 2020 werden aufgestellt. Diesen Prognosen zufolge vermindern sich die j?hrlichen Freisetzungen von CF₄/C₂F₆ von 1990 bis 2000 von 335 t/34 t auf 100 t/10 t infolge Automatisierungsma?nahmen an der Hauptquelle (Aluminiumhütten). Die Emissionen von SF₆ bleiben dagegen bis 2020 im Schwankungsbereich zwischen 200 und 300 t j?hrlich. Hauptemittenten sind nicht elektrische Schaltanlagen, da diese relativ dicht sind und über ein Entsorgungs-und Wiederaufarbeitungskonzept für gebrauchtes Gas verfügen, sondern mit gro?em Abstand Autoreifen und Schallschutzscheiben. Bei den erst seit 1990 gezielt als FCKW-Nachfolger eingesetzten H-FKW ist mit fortschreitender FCKW-Substitution in der station?ren und mobilen K?lte-und Klimatechnik, bei PU-Montageschaum und Asthmasprays mit einer sprunghaften Zunahme der Emissionen bis auf über 9700 t/a ab dem Jahr 2007 zu rechnen, sofern sich nicht halogenfreie Alternativen st?rker durchsetzen. Im Jahr 2020 werden bei Annahme dieser Trends die kumulierten Emissionen der genannten fluorierten Verbindungen der Treibhauswirkung von 25 Mio. t CO₂ entsprechen (GWP-Betrachtungszeitraum: 100 Jahre).      

The Inhibition of Photochemical Smog

Additional inhibitors for the conversion of NO to NO₂ in C3H6—NO—0₂ irradiated mixtures have been tested at 25°C. These mixtures initially contained 16 mTorr C₃H₆, 8 mTorr NO, 0.012 mTorr NO₂, additive, and enough O₂ to bring the total pressure to 100 Torr. The NO₂ pressure was monitored photometrically. In the absence of additive, the NO₂ pressure first increases with irradiation time reaching a maximum conversion at about 15 minutes. As the irradiation time increases beyond 15 min, the NO₂ pressure drops. Before adding the inhibitors, runs were done with 10 Torr of CO added, and in these runs the conversion was speeded so that the maximum in NO₂ pressure occurred at 10 min. This enhancement in conversion rate is considered to be diagnostic for the presence of HO radicals. Next 10-min irradiations were done with various amounts of hexafluorobenzene (C₆F₆), nitrobenzene (C₆H₅NO₂), or naphtha lene (C₁₀H₈) added. The NO₂ pressure was reduced to one-half its value in the absence of inhibitor with 270 mTorr C₆F₆’, 220 mTorr C₆H₅N0₂, or 4 mTorr C₁₀Hg. The C₁₀H₈ is a very efficient inhibitor, but additions of up to 1 8.5 mTorr C₁₀H₈ did not reduce the N0₂ pressure to zero. Studies of the percent conversion of NO to NO₂ vs. irradiation time were done with either 4.2 mTorr C₁₀H₈ or 40 mTorr 2,6-di-ferf-butyl-4-methylphenol (Ph) added. In the former case the peak conversion was delayed from 15 to 22 min, while in the latter case no delay occurred. However, with the Ph added, there appeared to be some reduction in the maximum value of percent conversion.     

Kinetics of Sulfur-Oxide Formation in Flames: II. Low Pressure H2S Flames

The microstructure of 1/10 and 1/20 atmosphere, lean H₂S—O₂—N₂ flames is developed using the mass-spectrometric flame-sampling technique. The flame mechanism developed is in agreement with that determined from an earlier study on 1-atm H₂S flames. The formation of SO₂ appears to be primarily related to the production of SH and the ensuing oxidation steps SH + O₂ = SO + OH and SO + O₂ = SO₂ + O. While there is some question whether SO₂ formation occurs via an SO or an S₂O intermediate, the present study does not give direct support to the role of S₂O in the oxidation mechanism. However, the presence of significant quantities of free sulfur in the pre-flame zone may be indicative of S₂O formation via SO + S → S₂O, and, possibly, via the disproportionation of SO, 3SO → S₂O + SO₂. Kinetic analyses of some of the pre-flame reactions indicate an apparent activation energy of 17,300 calories/mole for the decomposition of H₂S. The actual initiation process in the flame mechanism requires further examination. The specific rate for the reaction step H₂S + O = OH + SH is given by k ₆ = 1.45 × 10₁₅ exp ( – 6600/RT) cm³ mole^–1 sec^–1, and the specific rate for the oxidation of SO, SO + O₂ = SO₂ + O, is given by k ₅ = 5.2 × 10₁₄ exp (—19,300/RT) cm³ mole^–1 sec^–1.     

Azo-dyes photocatalytic degradation in aqueous suspension of TiO2 under solar irradiation

The photodegradation of two common and very stable azo-dyes, i.e. methyl-orange (C₁₄H₁₄N₃SO₃Na) and orange II (C₁₆H₁₁N₂SO₄Na), is reported. The photocatalytic oxidation was carried out in aqueous suspensions of polycrystalline TiO₂ irradiated by sunlight. Compound parabolic collectors, installed at the “Plataforma Solar de Almería” (PSA, Spain) were used as the photoreactors and two identical reacting systems allowed to perform photoreactivity runs for the two dyes at the same time and under the same irradiation conditions. The disappearance of colour and substrates together with the abatement of total organic carbon content was monitored. The main sulfonate-containing intermediates were found to be in lower number in respect to those obtained under artificial irradiation. In particular there were no more evidence of the presence of hydroxylated transients. The dependence of dye photooxidation rate on: (i) substrate concentration; (ii) catalyst amount; and (iii) initial pH was investigated. The influence of the presence of strong oxidant species (H₂O₂, S₂O₈²⁻) and some ions (Cl⁻, SO₄²⁻) on the process was also studied.     

Characterization of Fugitive Material within a Primary Lead Smelter

ABSTRACT

The primary production of Pb via the sinter plant-blast furnace method resulted in a large number of Pb and other phases, reflecting the complex reactions occurring within each of the processes. Optical microscopy and X-ray diffraction (XRD) techniques have been used to characterize fugitive emissions and dusts generated during sintering, smelting, Cu drossing, refining, and slag fuming at a primary Pb-Zn smelter. The results displayed a complex array of phases, with the mineralogy of the dusts and fume reflecting conditions of the particular metallurgical operation. The principal Pb species followed a transformation from PbS through PbSO₄ and PbO to Pb° (metal) from raw materials to the refinery. The fugitive emissions generated by the blast furnace were of a finer size with more complex chemistry than fugitive material from other source areas. XRD identified a mixture of PbS, ZnO, and ZnS, associated with one or more of the Cl-bearing phases Pb(OH)Cl, PbCl₂, Pb₄O₃Cl₂, Na₃Pb₂(SO₄)₃Cl, Pb₁₀(SO₄)Cl₂O₈, Pb₄SCl₆, and Pb₇S₂Cl₁₀. The presence of Cl-bearing phases in the fume has possible health implications.     

The formation of dithionate during the iron(III)-catalysed autoxidation of sulfur(IV)-oxides

The iron(III)-catalyzed autoxidation of sulfur(IV)-oxides results in the formation of two different oxidation products of sulfur(IV): dithionate, S₂O₆²⁻, and sulfate, SO₄²⁻. The yield of these reaction products depends on the experimental conditions. Under the studied conditions ([Fe(III)] : [SIV)] = 1:10, pH = 2–4) dithionate is the minor reaction product. The formation of dithionate is influenced by the initial pH but not by the initial O₂ concentration. The presence of CO²⁺, Mn²⁺, and Ni²⁺ have no influence on the yield of dithionate, whereas in the presence of Cr³⁺ less and, in the presence of Cu²⁺, no dithionate is formed.     

Variability of SO2, CO,and light hydrocarbons over a megacity in Eastern India: effects of emissions and transport

The Indo-Gangetic plain (IGP) has received extensive attention of the global scientific community due to higher levels of trace gases and aerosols over this region. Satellite retrievals and model simulations show that, in particular, the eastern part IGP is highly polluted. Despite this attention, in situ measurements of trace gases are very limited over this region. This paper presents measurements of SO₂, CO, CH₄, and C₂–C₅ NMHCs during March 2012–February 2013 over Kolkata, a megacity in the eastern IGP, with a focus on processes impacting their levels. The mean SO₂ and C₂H₆ concentrations during winter and post-monsoon periods were eight and three times higher compared to pre-monsoon and monsoon. Early morning enhancements in SO₂ and several NMHCs during winter connote boundary layer effects. Daytime elevations in SO₂ during pre-monsoon and monsoon suggest impacts of photo-oxidation. Inter-species correlations and trajectory analysis evince transport of SO₂ from regional combustion sources (e.g., coal burning in power plants, industries) along the east of the Indo-Gangetic plain impacting SO₂ levels at the site. However, C₂H₂ to CO ratio over Kolkata, which are comparable to other urban regions in India, show impacts of local biofuel combustions. Further, high levels of C₃H₈ and C₄H₁₀ evince the dominance of LPG/petrochemicals over the study location. The suite of trace gases measured during this study helps to decipher between impacts of local emissions and influence of transport on their levels.     

Deodorization of Dimethyl Sulfide Using a Discharge Approach at Room Temperature

Abstract

The traditional technologies for odor removal of thiol usually create either secondary pollution for scrubbing, adsorption, and absorption processes, or sulfur (S) poisoning for catalytic incineration. This study applied a laboratory-scale radio-frequency plasma reactor to destructive percentage-grade concentrations of odorous dimethyl sulfide (CH₃SCH₃, or DMS). Odor was diminished effectively via reforming DMS into mainly carbon disulfide (CS₂) or sulfur dioxide (SO₂). The removal efficiencies of DMS elevated significantly with a lower feeding concentration of DMS or a higher applied rf power. A greater inlet oxygen (O₂)/DMS molar ratio slightly improved the removal efficiency. In an O₂-free environment, DMS was converted primarily to CS₂, methane (CH₄), acetylene (C₂H₂), ethylene (C₂H₄), and hydrogen (H₂), with traces of hydrogen sulfide (H₂S), methyl mercaptan (CH₃SH), and dimethyl disulfide. In an O₂-containing environment, the species detected were SO₂, CS₂, carbonyl sulfide, carbon dioxide (CO₂), CH₄, C₂H₄, C₂H₂, H₂, formal-dehyde, and methanol. Differences in yield of products were functions of the amounts of added O₂ and the applied power. This study provided useful information for gaining insight into the reaction pathways for the DMS dissociation and the formation of products in the plasmolysis and conversion processes.     

玻璃减薄蚀刻液中氟硅酸的选择性脱除方法

光电玻璃减薄蚀刻液中氟硅酸(H2SiF6)的累积,是导致蚀刻液无法连续使用而转化为废液的主要原因。尝试对蚀刻废液中氟硅酸进行选择性脱除工艺,探索刻蚀液循环利用的有效处理方法。鉴于氟硅酸的碱金属盐具有溶解度较低的特点,研究考察了利用钠盐或钾盐为沉淀剂,将废液中的H2SiF6以氟硅酸盐的形式沉淀去除,为实现蚀刻液的循环利用提供可能。结果表明,KCl相比NaCl对H2SiF6处理效果更好,但生成的K2SiF6的结晶颗粒过细,难以自然沉降,过滤效果较差;而Na2SiF6结晶沉降特性较好,且使用NaCl为沉淀剂具有价廉易得等特点,可作为氟硅酸的理想沉淀剂。H2SiF6去除率与碱金属盐H2SiF6摩尔计量比正相关,当摩尔计量比NaCl/H2SiF6=2,H2SiF6含量10%的模拟废液,其H2SiF6去除率可达到90%以上。     

Degradation of bisphenol A in aqueous solution by persulfate activated with ferrous ion

Degradation of bisphenol A (BPA) in aqueous solution was studied with high-efficiency sulfate radical (SO₄ ^?·), which was generated by the activation of persulfate (S₂O₈ ^2?) with ferrous ion (Fe²⁺). S₂O₈ ^2? was activated by Fe²⁺ to produce SO₄ ^?·, and iron powder (Fe⁰) was used as a slow-releasing source of dissolved Fe²⁺. The major oxidation products of BPA were determined by liquid chromatography-mass spectrometer. The mineralization efficiency of BPA was monitored by total organic carbon (TOC) analyzer. BPA removal efficiency was improved by the increase of initial S₂O₈ ^2? or Fe²⁺ concentrations and then decreased with excess Fe²⁺ concentration. The adding mode of Fe²⁺ had significant impact on BPA degradation and mineralization. BPA removal rates increased from 49 to 97 % with sequential addition of Fe²⁺, while complete degradation was observed with continuous diffusion of Fe²⁺, and the latter achieved higher TOC removal rate. When Fe⁰ was employed as a slow-releasing source of dissolved Fe²⁺, 100 % of BPA degradation efficiency was achieved, and the highest removal rate of TOC (85 %) was obtained within 2 h. In the Fe⁰–S₂O₈ ^2? system, Fe⁰ as the activator of S₂O₈ ^2? could offer sustainable oxidation for BPA, and higher TOC removal rate was achieved. It was proved that Fe⁰–S₂O₈ ^2? system has perspective for future works.     

Application of Computer Controlled High Resolution Mass Spectrometry to the Analysis of Air Pollutants

An AEI-MS9 high resolution mass spectrometer interfaced with a PDP-12 digital computer has been adapted for the multicomponent analysis of air pollutants. Air sampling techniques for particulate and gaseous pollutants have been developed which are compatible with the mass spectrometric system. A single stage impactor has been designed for sampling particulate matter of particle diameters greater than 1–2 μm. The remainder of the particulate matter is collected on a glass fiber filter. Gaseous pollutants are collected on a styrene-divinylbenzene copolymer (Chromosorb 102).

The particulate samples are introduced directly into the mass spectrometer utilizing a temperature programed insertion probe. Gaseous pollutants are desorbed from the copolymer directly into the mass spectrometer by heating. Analysis of composite mass spectral data is facilitated through the use of a digital computer utilizing newly developed computer programs. Final computer output yields qualitative and quantitative results for up to 300 pollutants. Organic pollutants identified in particulate matter include polycyclic aromatic compounds, alkyl chlorides, polychlorinated aromatics, substituted benzenes and organic acids. Composite quantitative results are reported for alkanes and alkenes in the following groups: C₁₅-C₃₀, C₃₀-C₅₀ and Cso-polymeric. Inorganic pollutants identified include As₄O₆, H₂SO_4/ (NH₄)₂SO₄, (NH₄)₂SO₃, NaHSO₄, NH₄NO_3/ NaNO₃, NH₄CI, SeO₂, I₂, elemental sulfur, and elemental cadmium.     

Ambient and Source SO2 Detector Based on a Fluorescence Method

The principle of this detector is based on the measurement of the intensity of the ultraviolet fluorescence of SO₂ produced by absorption of the Zn 2138 Å or Cd 2288 Å line. The fluorescence intensity was found to be linear from 0.1 to 500 ppm of SO₂ in air with the Zn lamp and from 0.1 to 1600 ppm with the Cd lamp. The detection limit at present is about 20 ppb. There is no detectable interference from O₃, H₂S, NO₂, CO₂, CO, or H₂, although the presence of a large concentration of CS₂ (500 times as much as SO₂) NO (500 times) or C₂H₄ (4000 times) interferes with the measurement. The presence of 2% H₂0 reduces the signal by 25%, while up to 1 % CH₄ has almost no effect.     

非均相Fenton体系中无机助剂对亚甲基蓝脱色的影响

直接使用有机过渡金属化合物二茂铁作为催化剂，研究了非均相Fenton反应中亚甲基蓝的降解，并考虑了实际排放的印染废水中存在的无机助剂，进一步分析了典型无机助剂CuSO4、NaCl、Na2CO3、Na2SO4、Na2S的存在对该非均相Fenton体系的影响，结果表明：直接使用二茂铁做催化剂反应120min后，亚甲基蓝的剩余率为0．6％，羟基自由基的表观生成率为83．4％。NaCl、Na2CO3、Na2SO4、Na2S的加入会阻碍反应的进行，而CuSO4的加入会促进反应的进行。