A study of silicon carbide synthesis from waste serpentine

There are 60000 tons of serpentine wastes produced in year 2004 in Taiwan. This is due to the well-developed joints in the serpentine ore body as well as the stringent requirements of the particle size and chemical composition of serpentine by iron making company. The waste also creates considerable environmental problems. The purpose of this study is reutilization of waste serpentine to produce a high value silica powder after acid leaching. These siliceous microstructure products obtained from serpentine would be responsible for high reactivity and characteristic molecular sieving effect. In this study, the amorphous silica powder was then synthesized to silicon carbide with the C/SiO(2) molar ratio of 3. The experiment results show that silicon carbide can be synthesized in 1550 degrees C. The formed silicon carbide was whisker beta type SiC which can be used as raw materials for industry.     

Sulfur-oxidizing autotrophic and mixotrophic denitrification processes for drinking water treatment: elimination of excess sulfate production and alkalinity requirement

The activity of copper oxide, titanium carbide and silicon nitride nanoparticles for the oxidative degradation of environmentally relevant concentrations (μg L⁻¹ range) of enrofloxacin - an important veterinary antibiotic drug - in aqueous solutions was investigated. With hydrogen peroxide as an oxidative agent, both copper oxide and titanium carbide decrease the concentration of enrofloxacin by more than 90% over 12 h. Addition of sodium halide salts strongly increases the reaction rate of copper oxide nanoparticles. The mechanism for the formation of Reactive Oxygen Species (ROS) was investigated by Electron Spin Resonance (ESR).     

基于自碳黑的水化硅酸钙制备及其磷回收特性

以白碳黑、硅灰、硅藻土和硅胶筛选硅质原料,并与钙质原料电石渣制备了水化硅酸钙。借助XRF、BET、FT—IR等表征手段,通过多次重复除磷实验,研究了硅质原料特性对水化硅酸钙回收磷性能的影响。结果表明,白碳黑具有极高的反应活性,因此可作为制备具有磷回收特性的水化硅酸钙的硅质原料。结合XRD等表征发现,白碳黑的有效利用率是影响水化硅酸钙回收磷性能的关键,该利用率取决于白碳黑与电石渣的摩尔配比以及水热反应温度。当电石渣与白碳黑的摩尔比为1．6：1,反应温度为170℃时,白碳黑具有最佳的利用效率。该条件制备的水化硅酸钙可作为晶种,在其表面结晶形成羟基磷灰石,从而达到磷回收的目的,磷回收后固体物质中的磷含量为19．05％。     

Microwave Process for Volatile Organic Compound Abatement

ABSTRACT

The CHA Corporation has completed the U.S. Air Force Phase II Small Business Innovation Research program to investigate the feasibility of using a novel microwave-based process for the removal and destruction of volatile organic compounds (VOCs) in effluents from noncombustion sources, such as paint booth ventilation streams. Removal of solvents by adsorption, followed by the regeneration of saturated granular activated carbon (GAC) by microwave energy, was achieved in a single fixed-bed reactor. Microwave regeneration of the fixed-bed-saturated carbon restored the original GAC adsorption capacity. After 20 adsorption/regeneration cycles, the adsorption capacity dropped from 13.5 g methyl ethyl ketone (MEK)/100 g GAC to 12.5 g MEK/100 g GAC. During microwave regeneration of the GAC fixed bed, the concentrated desorbed paint solvent was oxidized by passing the solvent mixture through a fixed bed of an oxidation catalyst mixed with silicon carbide in a microwave reactor. A 98% oxidation efficiency was consistently achieved from the oxidation of VOCs in the microwave catalytic reactor.     

Microwave process for volatile organic compound abatement

The CHA Corporation has completed the U.S. Air Force Phase II Small Business Innovation Research program to investigate the feasibility of using a novel microwave-based process for the removal and destruction of volatile organic compounds (VOCs) in effluents from noncombustion sources, such as paint booth ventilation streams. Removal of solvents by adsorption, followed by the regeneration of saturated granular activated carbon (GAC) by microwave energy, was achieved in a single fixed-bed reactor. Microwave regeneration of the fixed-bed-saturated carbon restored the original GAC adsorption capacity. After 20 adsorption/regeneration cycles, the adsorption capacity dropped from 13.5 g methyl ethyl ketone (MEK)/100 g GAC to 12.5 g MEK/100 g GAC. During microwave regeneration of the GAC fixed bed, the concentrated desorbed paint solvent was oxidized by passing the solvent mixture through a fixed bed of an oxidation catalyst mixed with silicon carbide in a microwave reactor. A 98% oxidation efficiency was consistently achieved from the oxidation of VOCs in the microwave catalytic reactor.     

Effect of decabromodiphenyl ether and antimony trioxide on controlled pyrolysis of high-impact polystyrene mixed with polyolefins

The controlled pyrolysis of polyethylene/polypropylene/polystyrene mixed with brominated high-impact polystyrene containing decabromodiphenyl ether as a brominated flame-retardant with antimony trioxide as a synergist was performed. The effect of decabromodiphenyl ether and antimony trioxide on the formation of its congeners and their effect on distribution of pyrolysis products were investigated. The controlled pyrolysis significantly affected the decomposition behavior and the formation of products. Analysis with gas chromatograph with electron capture detector confirmed that the bromine content was rich in step 1 (oil 1) liquid products leaving less bromine content in the step 2 (oil 2) liquid products. In the presence of antimony containing samples, the major portion of bromine was observed in the form of antimony bromide and no flame-retardant species were found in oil 1. In the presence of synergist, the step 1 and step 2 oils contain both light and heavy compounds. In the absence of synergist, the heavy compounds in step 1 oil and light compounds in step 2 oils were observed. The presence of antimony bromide was confirmed in the step 1 oils but not in step 2 oils.     

Fenton氧化/高浓度泥浆法处理矿山废水

为了解决某大型铜矿废水COD不达标问题,采用Fenton氧化对原有高浓度泥浆（HDS）工艺进行改进。探讨了Fenton氧化矿山废水各指标的去除效果以及H₂O₂浓度对出水COD去除效果的影响,结果表明,Fenton氧化-电石乳中和絮凝沉淀工艺处理矿山废水是可行的,最优实验条件为：pH稳定在3.0～4.5,H₂O₂投加量0.5 mL/L,电石乳投加量8.5 g/L,PAM投加量1.5 mg/L;系统对废水COD的去除机理是加入的H₂O₂和矿山酸性废水中的Fe²⁺离子在低pH下形成Fenton试剂;系统对TFe、Zn²⁺、Cu2+ 的去除效果比Mn²⁺的去除效果更稳定。     

Photocatalytic activity of TiO2 films grown on different substrates

Titanium dioxide films were prepared on glass, indium-tin oxide (ITO) glass and p-type monocrystalline silicon and studied for the photocatalytic degradation of rhodamine B in an aqueous medium. Raman, AFM, and XPS spectroscopic investigations of these films indicated that microstructure of titanium oxide films were greatly affected by the substrate materials. Rutile was confirmed to be easily formed on the surface of ITO glass, and TiO2 tended to grow as closely packed particles that were elongated strips with an average size of 20 nm, and had lovely contrast with the perfectly round particles grown on p-type monocrystalline silicon. Charge transfer between the film and silicon substrate was verified by surface photovoltage spectra. This may be the real reason why the films grown on ITO glass and silicon substrates exhibit higher photocatalytic reactivity than the film on glass substrate. Moreover, the different surface properties also seem to be responsible for the different activity.     

危险固体废物焚烧残渣的稳定化处理研究

采用常规危险固体废物稳定剂Na3 PO4、Na2S、腐殖酸以及工业固体废物电石渣对台州典型危险固体废物焚烧残渣进行稳定化处理.以残渣中污染最严重的重金属Pb、Ni、Cu、Zn的去除率为衡量指标,进行稳定化时间优化试验.结果表明,Na3 PO4、电石渣可在7d后达到较好的稳定化效果,且随着时间的延长效果稳定;而Na2S和...     

Response of a solid-liquid two-phase partitioning bioreactor to transient BTEX loadings

A two-phase partitioning bioreactor (TPPB) consisting of an aqueous phase containing a bacterial consortium and a polymeric phase of silicone rubber pellets (solid volume fraction 0.1) was used to treat a gaseous waste stream containing benzene, toluene, ethylbenzene and o-xylene (BTEX). The function of the solid polymer phase was to absorb/desorb the gaseous volatile organic compounds providing a buffering effect to protect the cells from high transient loadings and to sequester the BTEX for subsequent degradation. The TPPB was subjected to high and fluctuating inlet loadings of BTEX in the form of 4h step changes of 2, 4, 6 and 10 times the nominal inlet loading of 60 gm(-3) h(-1) total BTEX in approximately equal amounts, and removal efficiencies and elimination capacities were determined. It was found that overall removal efficiencies of greater than 95% can be achieved while obtaining overall elimination capacities of up to 282 gm(-3) h(-1) during transient operation and TPPB operation succumbs to toxic substrate levels between step changes of 6 and 10 times the nominal loading value (360-600 gm(-3) h(-1)). BTEX concentrations in the aqueous phase and the polymer phase of the TPPB were monitored throughout the imposed step changes to determine the extent to which the sequestering phase can buffer the aqueous phase from BTEX. With the polymer phase comprising only 10% of the total working volume of the reactor, the polymer beads accounted for up to 93%, 91% and 70% of the total BTEX present in the working volume for step changes of 2, 4 and 6 times the nominal loading, respectively.     

Pyrolysis of tetrabromobisphenol-A containing paper laminated printed circuit boards

Tetrabromobisphenol-A (TBBA) is the most common brominated fire retardant. In this study, a TBBA containing paper laminated printed circuit board (PCB) prepared from novolac was pyrolysed by both TGA and in a quartz glass reactor between 40 and 1,000 degrees C. The products were online detected by MS. It was found that the PCB degraded in three steps. Step one (<270 degrees C) consisted of the evolution of water and CO(2) from the paper laminate. In the second step, between 270 and 370 degrees C, the fire retardant decomposed, releasing HBr and brominated aromatics. In the third step, at temperatures above 370 degrees C, the phenol resin decomposed and char was formed. Compared to pure TBBA, which mainly produces brominated phenols, the brominated products enclosed in the char released HBr during the last degradation step as well as during the second step. Most of the bromine left the resin in the form of HBr, with about 14% of the bromine being fixed in brominated aromatics and less than 2% remaining in the residue.     

外源硅对不同pH水田土壤吸附铅的影响

通过等温吸附实验,研究了加硅对2种不同pH水田土壤吸附铅特性的影响。实验中用硝酸中和硅酸钠的碱性,各处理间钠离子和硝酸根离子的差异以硝酸钠补齐,消除了因硅酸盐的加入改变体系pH及伴随离子对土壤吸附铅可能产生的影响。结果表明,在本实验条件下,Langmuir方程、Freundlich方程和Temkin方程都能较好地描述不同硅浓度条件下两种土壤对铅的吸附特征,但以Freundlich模型为最优;加硅促进了酸性土壤对铅的吸附,抑制了碱性土壤对铅的吸附。     

Enhancing Diatom Growth by Using Zeolites to Change Seawater Composition (4 pp)

- Aims and Scope. The purpose of this study was to test whether two zeolites produced synthetically (products of zeolitic nature, PZN) could influence either the yield of a diatom culture or the chemical changes in the cultures. For this purpose, Phaeodactylum tricornutum was used as test organism in a culture medium of natural seawater enriched with N and P having negligible amounts of ammonia. Methods The PZN ZEBEN-06 and ZESTEC-56 were used in parallel experiments. The composition of trace metals and organic compounds with chelate activity in the culture media, were determined by anodic or cathodic stripping voltammetry. The impact of leaching silicon on the algal yield was evaluated by comparing the growth in the presence or absence of PZN, in seawater enriched or not-enriched with silicon. Results and Conclusions Both PZN significantly promoted the algal yield even in the absence of added silicon, a limiting nutrient for diatom growth. The PZN acted as a silicon buffer while providing a source of silicon required for growth. In addition, PZN released into the seawater small but significant amounts of the limiting micro-nutrient manganese (its concentration doubled during the experiments), while simultaneously removing relatively high quantities of zinc from the seawater. The presence of PZN inhibited the releasing of chelated compounds. These changes (sorption/desorption) caused by the PZN in the concentrations in the solutions used as culture media of P. tricornutum were probably responsible for the differences in both the diatom and exudation observed in the tested cultures.     

三种混凝剂处理煤泥水的对比试验研究

本文介绍了石灰、电石渣及CaCl2 分别与聚丙烯酰胺联用处理煤泥水的对比试验研究结果。结果表明 ,三种方法对煤泥水均有较好的处理效果 ,其中CaCl2 法效果最好 ,但药剂费也最高 ,石灰法和电石渣法处理效果相差不大 ,但电石渣法药剂费较低。     

以粉煤灰和电石渣为催化剂的聚丙烯裂解模型研究

对粉煤灰和电石渣为催化剂的聚丙烯裂解进行模型研究.通过模型计算了裂解反应的表观活化能、频率因子、反应级数等.模型计算表明随着反应温度的升高反应速率增加,达到相同转化率所需反应时间减少.当剂塑比从0增加到30%时,聚丙烯裂解的活化能呈现降低的趋势,特别当剂塑比为30%时,其活化能降低约50%.说明粉煤灰和电石渣对聚丙烯裂解具有一定的催化效果.     

焦粉成型技术

冶金、化工、电石生产企业 ,因生产工艺要求需要将大块的焦炭破碎成一定粒度的块焦 ,破碎过程要产生2 0 %— 2 5 %的焦粉。本文针对目前工业废弃焦粉再利用问题 ,通过深入调查 ,反复试验 ,取得了很好的效果。为冶金、化工、电石生产企业废弃焦粉成型再利用找到一条切实可行的方法     

Desulphurization mechanism and engineering practice of carbide slag

Environmental Science and Pollution Research - In order to give full play to the alkaline neutralization value of carbide slag and reduce the environmental hazards of carbide slag, it is of great...     

新型硅镁胶（MgO·2SiO2）对模拟放射性废水中CO2＋的吸附性能

以泡花碱和氯化镁为原料合成出了一种新型硅镁胶（MgO-2SiO2）吸附材料,用傅里叶红外光谱仪对其进行了表征,并对模拟放射性废水中的Co2＋进行吸附实验。结果表明,控制合成pH在10．50～11．00,可以得到目标硅镁胶（MgO·2SiO2）,在460cm-1处出现了较强的吸收峰,这是由Mg-O伸缩振动和si—Mg-O弯曲振动引起。在500℃焙烧4h后,可以得到吸附性能良好的硅镁胶,随着溶液pit的升高,去除率增大,在pH为4～8时达到最大。25％时,最大吸附量可达135．5mg／g,吸附过程符合Langmuir等温吸附方程和准二级动力学方程。重复使用4次,对Co2＋的吸附量仍然达到130mg／g,说明硅镁胶是一种可重复利用的吸附剂。     

粉煤灰和电石渣对聚丙烯塑料裂解的影响研究

研究了粉煤灰和电石渣对聚丙烯塑料裂解的影响,讨论了加入量对裂解速度和裂解产物的影响.结果表明:粉煤灰和电石渣都使裂解产物中的轻质部分(汽油和裂解气)增加、重油降低;粉煤灰比电石渣更能加快反应的进行,而且加入量越多,反应越快,需时越短;粉煤灰比电石渣对聚丙烯塑料的裂解具有明显的催化促进效果.     

二级Fenton氧化高浓度有机硅废水研究

采用二级Fenton氧化技术对可生化性差的高浓度有机硅废水进行处理,考察了不同因素对COD去除率的影响,对比了一级氧化和二级氧化的效果。结果表明对于COD为9 600 mg/L的高浓度有机硅废水,pH为3,[H2O2]/[Fe2+]=2∶1为最佳的反应条件,COD去除率随着H2O2的投加量的增大先增大而后减小,每200 mL水样中先投加20%的硫酸亚铁12 mL,然后分2次投加30%的H2O2各4 mL,氧化完成后调整pH值为7~8静止沉淀,COD去除率达89.2%。对于某绝缘电器厂的生产废水经二级Fenton氧化处理后,出水有机物浓度显著降低,可生化性提高,Fenton二级氧化可以作为高浓度有机硅废水的预处理工艺。