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1.
The removal of sulfur dioxide (SO2) from simulated flue gases streams (N2/O2/H2O/SO2) was experimentally investigated using microgap discharge. In the experiment, the thinner dielectric layers of aluminum oxide (Al2O3) were used to form the microgap discharge. With this physical method, a high concentration of hydroxyl (OH*) radicals were produced using the ionization of O2 and H2O to further the conversion of SO2 into sulfuric acid (H2SO4) at 120 degrees C in the absence of any catalysts and absorbents, which were captured with the electrostatic precipitator (ESP). As a result, the increase of discharge power and concentrations of O2 and H2O increased the production of OH. radicals resulting in enhanced removal of SO2 from gas streams. With the test and analysis, a number of H2SO4 droplets were produced in experiment. Therefore, a new method for removal of SO2 in semidry method without ammonia (NH3) additive was found. 相似文献
2.
Photocatalytic degradation of bisphenol A (BPA) in waters and wastewaters in the presence of titanium dioxide (TiO 2) was performed under different conditions. Suspensions of the TiO 2 were used to compare the degradation efficiency of BPA (20 mg L ?1) in batch and compound parabolic collector (CPC) reactors. A TiO 2 catalyst supported on glass spheres was prepared (sol–gel method) and used in a CPC solar pilot plant for the photodegradation of BPA (100 μg L ?1). The influence of OH·, O 2 ·?, and h + on the BPA degradation were evaluated. The radicals OH· and O 2 ·? were proved to be the main species involved on BPA photodegradation. Total organic carbon (TOC) and carboxylic acids were determined to evaluate the BPA mineralization during the photodegradation process. Some toxicological effects of BPA and its photoproducts on Eisenia andrei earthworms were evaluated. The results show that the optimal concentration of suspended TiO 2 to degrade BPA in batch or CPC reactors was 0.1 g L ?1. According to biological tests, the BPA LC 50 in 24 h for E. andrei was of 1.7?×?10 ?2 mg cm ?2. The photocatalytic degradation of BPA mediated by TiO 2 supported on glass spheres suffered strong influence of the water matrix. On real municipal wastewater treatment plant (MWWTP) secondary effluent, 30 % of BPA remains in solution; nevertheless, the method has the enormous advantage since it eliminates the need of catalyst removal step, reducing the cost of treatment. 相似文献
3.
采用臭氧辅助光芬顿法处理电镀添加剂生产废水,考察双氧水、FeSO 4·7H 2O、pH和反应时间等因素对废水COD和UV 254去除的影响。实验结果表明,pH=4,臭氧通入量为0.25 g,双氧水的投加量93.3 mL/L,FeSO 4·7H 2O投加量为5.3 g/L,最佳反应时间为30 min,COD和UV 254去除率分别达到92.64%和87.95%。这表明,臭氧辅助光芬顿法对电镀添加剂生产废水处理效果显著,处理时间大大减少。 相似文献
4.
研究了辉光放电等离子体降解水中典型的环境内分泌干扰物邻苯二甲酸二丁酯(DBP)及降解过程中过氧化氢(H2O2)的生成规律。考察了电解质种类、共存污染物(甲醇、叔丁醇)及催化剂等条件对DBP降解及H2O2生成的影响。结果表明,在硫酸钠溶液中DBP降解效率和H2O2生成速率最高;甲醇、叔丁醇等共存污染物对DBP降解和H2O2生成有抑制作用;Fe2+,Fe3+和Cu2+对DBP的降解有催化作用,其催化效果为Fe2+>Fe3+>Cu2+。用高效液相色谱、离子色谱及气质联用仪等仪器分析了降解中间产物,提出了可能的降解机理。 相似文献
5.
Dairy wastewater is characterized by a high content of hardly biodegradable dissolved, colloidal, and suspended organic matter. This work firstly investigates the performance of two individual electrochemical treatments, namely electrocoagulation (EC) and electro-oxidation (EO), in order to finally assess the mineralization ability of a sequential EC/EO process. EC with an Al anode was employed as a primary pretreatment for the conditioning of 800 mL of wastewater. A complete reduction of turbidity, as well as 90 and 81 % of chemical oxygen demand (COD) and total organic carbon (TOC) removal, respectively, were achieved after 120 min of EC at 9.09 mA cm ?2. For EO, two kinds of dimensionally stable anodes (DSA) electrodes (Ti/IrO 2-Ta 2O 5 and Ti/IrO 2-SnO 2–Sb 2O 5) were prepared by the Pechini method, obtaining homogeneous coatings with uniform composition and high roughness. The ·OH formed at the DSA surface from H 2O oxidation were not detected by electron spin resonance. However, their indirect determination by means of H 2O 2 measurements revealed that Ti/IrO 2-SnO 2–Sb 2O 5 is able to produce partially physisorbed radicals. Since the characterization of the wastewater revealed the presence of indole derivatives, preliminary bulk electrolyses were done in ultrapure water containing 1 mM indole in sulfate and/or chloride media. The performance of EO with the Ti/IrO 2-Ta 2O 5 anode was evaluated from the TOC removal and the UV/Vis absorbance decay. The mineralization was very poor in 0.05 M Na 2SO 4, whereas it increased considerably at a greater Cl ? content, meaning that the oxidation mediated by electrogenerated species such as Cl 2, HClO, and/or ClO ? competes and even predominates over the ·OH-mediated oxidation. The EO treatment of EC-pretreated dairy wastewater allowed obtaining a global 98 % TOC removal, decreasing from 1,062 to <30 mg L ?1. 相似文献
6.
Increasing attention has been paid to pyrite due to its ability to generate hydroxyl radicals in air-saturated solutions. In this study, the mineral pyrite was studied as a catalyst to activate molecular oxygen to degrade Acid Orange 7 (AO7) in aqueous solution. A complete set of control experiments were conducted to optimize the reaction conditions, including the dosage of pyrite, the AO7 concentration, as well as the initial pH value. The role of reactive oxygen species (ROS) generated by pyrite in the process was elucidated by free radical quenching reactions. Furthermore, the concentrations of Fe(II) and total Fe formed were also measured. The mechanism for the production of ROS in the pyrite/H 2O/O 2 system was that H 2O 2 was formed by hydrogen ion and superoxide anion (O 2 ·?) which was produced by the reaction of pyrite activating O 2 and then reacted with Fe(II) dissolved from pyrite to produce ·OH through Fenton reaction. The findings suggest that pyrite/H 2O/O 2 system is potentially practical in pollution treatment. Moreover, the results provide a new insight into the understanding of the mechanism for degradation of organic pollutants by pyrite. 相似文献
7.
Fe 2O 3 and CeO 2 modified activated coke (AC) synthesized by the equivalent-volume impregnation were employed to remove elemental mercury (Hg 0) from simulated flue gas at a low temperature. Effects of the mass ratio of Fe 2O 3 and CeO 2, reaction temperature, and individual flue gas components including O 2, NO, SO 2, and H 2O (g) on Hg 0 removal efficiency of impregnated AC were investigated. The samples were characterized by Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Results showed that with optimal mass percentage of 3 % Fe 2O 3 and 3 % CeO 2 on Fe3Ce3/AC, the Hg 0 removal efficiency could reach an average of 88.29 % at 110 °C. Besides, it was observed that O 2 and NO exhibited a promotional effect on Hg 0 removal, H 2O (g) exerted a suppressive effect, and SO 2 showed an insignificant inhibition without O 2 to some extent. The analysis of XPS indicated that the main species of mercury on used Fe3Ce3/AC was HgO, which implied that adsorption and catalytic oxidation were both included in Hg 0 removal. Furthermore, the lattice oxygen, chemisorbed oxygen, and/or weakly bonded oxygen species made a contribution to Hg 0 oxidation. 相似文献
8.
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 (CH 3SCH 3, or DMS). Odor was diminished effectively via reforming DMS into mainly carbon disulfide (CS 2) or sulfur dioxide (SO 2). The removal efficiencies of DMS elevated significantly with a lower feeding concentration of DMS or a higher applied rf power. A greater inlet oxygen (O 2)/DMS molar ratio slightly improved the removal efficiency. In an O 2-free environment, DMS was converted primarily to CS 2, methane (CH 4), acetylene (C 2H 2), ethylene (C 2H 4), and hydrogen (H 2), with traces of hydrogen sulfide (H 2S), methyl mercaptan (CH 3SH), and dimethyl disulfide. In an O 2-containing environment, the species detected were SO 2, CS 2, carbonyl sulfide, carbon dioxide (CO 2), CH 4, C 2H 4, C 2H 2, H 2, formal-dehyde, and methanol. Differences in yield of products were functions of the amounts of added O 2 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. 相似文献
9.
This study revealed a dual pathway for the degradation of tris(1-chloro-2-propanyl) phosphate (TCPP) by zero-valent iron (ZVI) and persulfate as co-milling agents in a mechanochemical (MC) process. Persulfate was activated with ZVI to degrade TCPP in a planetary ball mill. After milling for 2 h, 96.5% of the TCPP was degraded with the release of 63.16, 50.39, and 42.01% of the Cl?, SO42?, and PO43?, respectively. In the first degradation pathway, persulfate was activated with ZVI to produce hydroxyl (·OH) radicals, and ZVI is oxidized to Fe(II) and Fe(III). A substitution reaction occurred as a result of the attack of ·OH on the P–O–C bonds, leading to the successive breakage of the three P–O–C bonds in TCPP to produce PO43?. In the second pathway, a C–Cl bond in part of the TCPP molecule was oxidized by SO4·? to carbonyl and carboxyl groups. The P–O–C bonds continued to react with ·OH to produce PO43?. Finally, the intermediate organochloride products were further reductively dechlorinated by ZVI. However, the synergistic effect of the oxidation (·OH and SO4·?) and the reduction reaction (ZVI) did not completely degrade TCPP to CO2, resulting in a low mineralization rate (35.87%). Moreover, the intermediate products still showed the toxicities in LD50 and developmental toxicant. In addition, the method was applied for the degradation of TCPP in soil, and high degradations (>?83.83%) were achieved in different types of soils. 相似文献
10.
采用Fenton法处理MBR-NF浓缩液,考察了FeSO4·7H2O投加量、n(H2O2)/n(Fe2+)投加比、初始pH对渗滤液MBR-NF浓缩液处理效果的影响,并在最佳实验条件下,探讨浓缩液富里酸(FA)、亲水性有机物(HyI)组分在Fenton氧化前后组成的变化。研究结果表明,在FeSO4·7H2O投加量为0.055 mol/L、n(H2O2)/n(Fe2+)投加比为4、初始pH为7.58时,对COD、腐植酸(UV254)、色度(CN)的去除率分别为79.6%、93.7%和97.8%。Fenton氧化后,浓缩液中有机物组分含量发生了较大变化,腐植酸含量下降,HyI成为渗滤液溶解性有机物主要成分。紫外-可见光谱表明,Fenton法对FA去除效果较好,而对HyI氧化效果较差;傅立叶红外光谱显示,经Fenton氧化后,FA的结构发生了明显变化,而HyI则变化不明显。 相似文献
11.
Abstract Sulfur hexafluoride (SF 6) is an important gas for plasma etching processes in the semiconductor industry. SF 6 intensely absorbs infrared radiation and, consequently, aggravates global warming. This study investigates SF 6 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 SF 6 was removed with DBDs at 20 kV of applied voltage and 150 Hz of discharge frequency for the gas stream containing 300 ppm SF 6, 12% oxygen (O 2), and 40% argon (Ar), with nitrogen (N 2) as the carrier gas. Four additives, including Ar, O 2, ethylene (C 2H 4), and H 2O (g), are effective in enhancing SF 6 abatement in the range of conditions studied. DBD achieves a higher SF 6 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. SF 6 is mainly converted to SOF 2,SO 2F 4, sulfur dioxide (SO 2), oxygen difluoride (OF 2), and fluoride (F 2). 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 SF 6 emissions. 相似文献
12.
Abstract This paper is particularly related to elemental mercury (Hg 0) oxidation and divalent mercury (Hg 2+) reduction under simulated flue gas conditions in the presence of nitric oxide (NO) and sulfur dioxide (SO 2). As a powerful oxidant and chlorinating reagent, Cl 2 has the potential for Hg oxidation. However, the detailed mechanism for the interactions, especially among chlorine (Cl)-containing species, SO 2, NO, as well as H 2O, remains ambiguous. Research described in this paper therefore focused on the impacts of SO 2 and NO on Hg 0 oxidation and Hg 2+ reduction with the intent of unraveling unrecognized interactions among Cl species, SO 2, and NO most importantly in the presence of H 2O. The experimental results demonstrated that SO 2 and NO had pronounced inhibitory effects on Hg 0 oxidation at high temperatures when H 2O was also present in the gas blend. Such a demonstration was further confirmed by the reduction of Hg 2+ back into its elemental form. Data revealed that SO 2 and NO were capable of promoting homogeneous reduction of Hg 2+ to Hg 0 with H 2O being present. However, the above inhibition or promotion disappeared under homogeneous conditions when H 2O was removed from the gas blend. 相似文献
13.
探讨了Fenton试剂石灰法处理苎麻脱胶前段混合废水工艺。试验表明,当FeSO 42O、H 2O 2(30%)、饱和石灰乳的投加量分别为3 g/L、2 mL/L和3 mL/L时,COD的去除率50%以上,色度去除率达到90%以上。更重要的是,处理后出水可部分回用于煮炼生产,从而节约生产用碱量,减少废水排放量, 还可提高废水可生化性,为后续生物处理创造条件。 相似文献
14.
A previously proposed technology incorporating TiO 2 into common household fluorescent lighting was further tested for its Hg 0 removal capability in a simulated flue-gas system. The flue gas is simulated by the addition of O 2, SO 2, HCl, NO, H 2O, and Hg 0, which are frequently found in combustion facilities such as waste incinerators and coal-fired power plants. In the O 2 + N 2 + Hg 0 environment, a Hg 0 removal efficiency (η Hg) greater than 95% was achieved. Despite the tendency for η Hg to decrease with increasing SO 2 and HCl, no significant drop was observed at the tested level (SO 2: 5–300 ppm v, HCl: 30–120 ppm v). In terms of NO and moisture, a significant negative effect on η Hg was observed for both factors. NO eliminated the OH radical on the TiO 2 surface, whereas water vapor caused either the occupation of active sites available to Hg 0 or the reduction of Hg 0 by free electron. However, the negative effect of NO was minimized (η Hg > 90%) by increasing the residence time in the photochemical reactor. The moisture effect can be avoided by installing a water trap before the flue gas enters the Hg 0 removal system. Implications: This paper reports a novel technology for a removal of gas-phase elemental mercury (Hg 0) from a simulated flue gas using TiO 2-coated glass beads under a low-cost, easily maintainable household fluorescent light instead of ultraviolet (UV) light. In this study, the effects of individual chemical species (O 2, SO 2, HCl, NO, and water vapor) on the performance of the proposed technology for Hg 0 removal are investigated. The result suggests that the proposed technology can be highly effective, even in real combustion environments such as waste incinerators and coal-fired power plants. 相似文献
15.
应用Fenton液相氧化吸收法进行同时脱硫脱硝实验。首先,利用单因素实验,分别考察了H2O2浓度、Fe2+投加量、初始pH值、UV照射和温度对脱硫脱硝的影响。结果表明,SO2和NO去除率随着H2O2浓度和Fe2+投加量的增大而提高;初始pH对SO2和NO的去除有较大影响;UV能促进SO2和NO的净化;温度对脱硫效率影响不大,但对NO的去除有显著作用,适当升温可以提高脱硝效率。随后,考察了SO2对NO去除率的影响。通过单独脱硝和同时脱硫脱硝的对比实验发现,SO2的加入对NO的去除有一定的促进作用,Fenton法可同时获得起始约80%的脱硝效率和98%以上的脱硫效率。 相似文献
16.
自行设计Fenton试剂法降解还原性气体异味的反应器,研究了Fenton试剂法处理餐厨垃圾异味主要成分(苯、乙酸乙酯、苯乙烯)的降解效果。以苯为典型代表物,优化得出该实验的最佳反应条件为:pH=3,FeSO4.7H2O投加量为1 g/L液相,30%H2O2投加量为10 mL/L液相,紫外光源辅助。结果证明,Fenton试剂法处理单一异味气体的效果较理想,在前180 min内能达到90%以上,该法在处理气态异味污染物方面具有广阔的应用前景。 相似文献
17.
Abstract An activated sludge aeration tank (40 × 40 × 300 cm, width × length × height) with a set of 2-mm orifice air spargers was used to treat gas-borne volatile organic compounds (VOCs; toluene, p-xylene, and dichloromethane) in air streams. The effects of liquid depth ( Z), aeration intensity ( G/A), the overall mass-transfer rate of oxygen in clean water ( K L a O2 ), the Henry’s law constant of the tested VOC ( H), and the influent gaseous VOC concentration ( C 0) on the efficiency of removal of VOCs were examined and compared with a literature-cited model. Results show that the measured VOC removal efficiencies and those predicted by the model were comparable at a G/A of 3.75–11.25 m 3/m 2·hr and C 0 of ~1000–6000 mg/m 3. Experimental data also indicated that the designed gas treatment reactor with K L a O2 = 5–15 hr ?1 could achieve >85% removal of VOCs with H = 0.24–0.25 at an aerated liquid depth of 1 m and >95% removal of dichloromethane with H = 0.13 at a 1-m liquid depth. 相似文献
18.
Abstract The conversion of methane to liquid products, hydrogen (H 2), and ammonia (NH 3) was investigated experimentally using microgap discharge plasma at an environmentally friendly condition. The experimental results indicated that H 2 and NH 3 were detected as the main gas products. The highest yield and production rate of H 2 was 14.4% (v/v) and 2974.6 μmol/min, respectively, whereas the highest yield and production rate of NH 3 was 8000 ppm (v/v) and 165.1 μmol/min, respectively. Particularly, the liquid products were collected on the plate and consisted of pyrrole, 2-methyl-1,4-pentadiene, α-amidopyri-dine, 2,5-dimethylpyrrole, methylpyrazine, 1-hexyne, 1,4-heptadiene, and polycyclic organic compounds. Some liquid products were the intermediates of drug, ?avor, dye, and organic synthesis, as well as edible ?avor. The collection efficiency in mass and energy efficiency were 26.3% at once and 22.9 g/kWh, respectively. The whole reaction process was considered to be in line with green chemistry principles. 相似文献
19.
O, O, O-triethyl phosphorothioate ((C 2H 5O) 3PS, TEPT) is a widely used organophosphorus insecticide. TEPT may be released into the atmosphere where it can undergo transport and chemical transformations, which include reactions with OH radicals, NO 3 radicals and O 3. The mechanism of the atmospheric reactions of TEPT has not been fully understood due to the short-lifetime of its oxidized radical intermediates, and the extreme difficulty in detection of these species experimentally. In this work, we carried out molecular orbital theory calculations for the OH radical-initiated atmospheric photooxidation of TEPT. The profile of the potential energy surface was constructed, and the possible channels involved in the reaction are discussed. The theoretical study shows that OH addition to the PS bond and H abstractions from the CH 3CH 2O moiety are energetically favorable reaction pathways. The dominant products TEP and SO 2 arise from the secondary reactions, the reactions of OH-TEPT adducts with O 2. The experimentally uncertain dominant product with molecular weight 170 is mostly due to (C 2H 5O) 2P(S)OH and not (C 2H 5O) 2P(O)SH. 相似文献
20.
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 (H 2O 2), alkaline ozonation (O 3, pH = 11), peroxone (O 3/H 2O 2), and Fenton reagent oxidation (Fe 2+/H 2O 2). UV/H 2O 2 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 (C 7 to C 2), while sulfate (SO 4 2?) and fluoride (F ?) were found to be the final products. The high yields of SO 4 2? and F ? indicate that 6:2 FTS-K can be nearly completely desulfonated and defluorinated under UV/H 2O 2 condition. The degradation should firstly begin with the substitution of hydrogen atom by hydroxyl radicals, followed by desulfonation, carboxylation, and sequential “flake off” of CF 2 unit. Compared with PFOS which is inert in most advanced oxidation processes, 6:2 FTS-K is more degradable as the alternative. 相似文献
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