Synthesis of hydrogarnet from molten slag and its hydrogen chloride fixation performance at high temperature

Hydrogarnet was synthesized hydrothermally below 200°C using molten slag obtained from municipal solid waste. For comparison, it was also synthesized using pure-phase CaO–Al₂O₃–SiO₂–H₂O, as reported previously. The structural and textural properties of this material were investigated using various analytical and spectroscopic techniques such as X-ray diffraction, X-ray fluorescence spectrometry, atomic absorption spectrometry (AAS), thermogravimetry/differential thermal analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy. The Cl⁻ fixation ability of hydrogarnet was investigated in the temperature range 500–800°C in a fixed-bed flow reactor using a HCl concentration (1000 p.p.m.v.) similar to that of incinerator exhaust gas. Under these experimental conditions, the hydrogarnet was capable of reducing the HCl gas level to less than 1 p.p.m.v. Analysis of the spent catalyst revealed that the hydrogarnet was being transformed into wadalite and CaCl₂ at high temperatures. The elution test for chromium ions in hydrogarnet obtained from slag was also used, and it was found that chromium ions were not eluted from hydrogarnet. Received: January 27, 2001 / Accepted: October 11, 2001     

Hydrothermal-treated Pt/Al2O3 as an excellent catalyst for toluene total oxidation

The preparation of highly active supported noble metal catalysts with a low noble metal loading has always been the ultimate goal of researchers working on catalysis. Hydrothermally treated Pt/Al₂O₃ (Pt/Al₂O₃-H) exhibits better catalytic activity than that (Pt/Al₂O₃-C) treated via the conventional calcination approach. At the high space velocity of 100,000 mL/(g∙hr), the temperature that correspond to 50% toluene conversion (T₅₀) of Pt/Al₂O₃-H is 115°C lower than that of Pt/Al₂O₃-C, and the turnover frequency (TOF) value can reach 0.0756 sec⁻¹. The mechanism by which the hydrothermal approach enhances Pt/Al₂O₃ activity has been investigated. The structure associated with the high catalytic activity of Pt nanoparticles (NPs) can be retained via hydrothermal treatment. Furthermore, the support is transformed to AlO(OH) with numerous surface hydroxyl groups, which in turn can facilitate the adsorption of toluene. And the synergistic effects of Pt NPs and AlO(OH) increases the contents of Pt in oxidation state and active oxygen, which are beneficial for toluene oxidation.     

Arsenic and sulfur nanoparticle synthesis mimicking environmental conditions of submarine shallow-water hydrothermal vents

Arsenic and sulfur mineralization is a natural phenomenon occurring in hydrothermal systems where parameters like temperature and organic matter(OM) can influence the mobilization of the toxic metalloid in marine environments. In the present study we analyze the influence of temperature and OM(particularly sulfur-containing additives) on As and S precipitation based on the recent discovery of As-rich nanoparticles in the hydrothermal system near the coast of the Greek island Milos. To this end, ...     

不同母体制备的金属离子交换ZSM-5分子筛上C_3H_6选择催化还原NO反应的研究

 研究了由钠型及氢型ZSM-5母体制备的金属离子交换分子筛在过量氧存在下丙烯选择催化还原NO的反应。发现反应活性及活性温度范围取决于分子筛母体与金属离子的种类。在各种金属离子交换分子筛催化剂中，钴离子交换CoH－ZSM－5具有最高的活性，且随钴离子交换度的增加反应活性亦随之增加。     

Development of a hydrothermal time seed germination model which uses the Weibull distribution to describe base water potential

Seed germination has been modelled extensively using hydrothermal time (HTT) models, that predict time to germination as a function of the extent to which seedbed temperature, T, and water potential, Ψ, exceed the base temperature, T_b, and base water potential, Ψ_b, of each seed percentile, g. Within a seed population the variation in time to germination arises from variation in Ψ_b(g) modelled by a normal distribution. We tested the assumption of normality in the distribution of Ψ_b(g) by germinating seed of two unrelated species with non-dormant seed (Buddleja davidii (Franch.) and Pinus radiata D. Don) across a range of constant Ψ at sub-optimal T. When incorporated into a HTT model the Weibull distribution more accurately described both the right skewed distribution of Ψ_b(g) and germination time course over sub-optimal T than the HTT based on the normal distribution, for both species. Given the flexibility of the Weibull distribution this model not only provides a useful method for predicting germination but also a means of determining the distribution of Ψ_b(g).     

Utilization of calcite and waste glass for preparing construction materials with a low environmental load

In this study, porous calcite materials are hydrothermally treated at 200 °C using powder compacts consisting of calcite and glasses composed of silica-rich soda-lime. After treatment, the glasses are converted into calcium aluminosilicate hydrates, such as zeolite phases, which increase their strength. The porosity and morphology of new deposits of hydrothermally solidified materials depend up on the chemical composition of glass. The use of calcite and glass in the hydrothermal treatment plays an important role in the solidification of calcite without thermal decomposition.     

Recovery of solid fuel from municipal solid waste by hydrothermal treatment using subcritical water

Hydrothermal treatments using subcritical water (HTSW) such as that at 234 °C and 3 MPa (LT condition) and 295 °C and 8 MPa (HT condition) were investigated to recover solid fuel from municipal solid waste (MSW). Printing paper, dog food (DF), wooden chopsticks, and mixed plastic film and sheets of polyethylene, polypropylene, and polystyrene were prepared as model MSW components, in which polyvinylchloride (PVC) powder and sodium chloride were used to simulate Cl sources.While more than 75% of carbon in paper, DF, and wood was recovered as char under both LT and HT conditions, plastics did not degrade under either LT or HT conditions. The heating value (HV) of obtained char was 13,886-27,544 kJ/kg and was comparable to that of brown coal and lignite. Higher formation of fixed carbon and greater oxygen dissociation during HTSW were thought to improve the HV of char.Cl atoms added as PVC powder and sodium chloride to raw material remained in char after HTSW. However, most Cl originating from PVC was found to converse into soluble Cl compounds during HTSW under the HT condition and could be removed by washing.From these results, the merit of HTSW as a method of recovering solid fuel from MSW is considered to produce char with minimal carbon loss without a drying process prior to HTSW. In addition, Cl originating from PVC decomposes into soluble Cl compound under the HT condition. The combination of HTSW under the HT condition and char washing might improve the quality of char as alternative fuel.     

可见分光光度法测定水质总氮的研究

水质总氮检测,对水资源保护、环境保护至关重要。文章以此为中心,对水质总氮检测方法进行改进,并从实验原理、消解速度、线性、准确性、干扰等方面进行分析讨论,提出了一种水质总氮检测的新方法。     

Tertiary metallogenesis in the Eastern Alps: the Waldenstein hematite deposit (Austria)

The specularite deposit at Waldenstein is an epigenetic replacement/vein-type hematite mineralization with distinct alteration zones. It is situated in highly metamorphosed schists and, gneisses of the Koralm Crystalline Complex. Sericitization and chloritization are strictly bound to this alteration and occur within a few meters of the hematite veins. Radiometric dating of the sericitization and the implicity of the mineralization yield a Middle Eocene age. Petrographic evidence proves an early, relatively reduced paragenesis (magnetite, ilmenite) being partly replaced by hematite and chlorite during the main phase of ore formation. Fluid inclusion and stable isotope investigations indicate that formation temperatures were approximately 300°C during the main stage and decreased to 200°C in the latest stage of the hydrothermal event. The H-isotope compositions of chlorites and of fluid inclusions in quartz indicate the influence of seawater. This also explains the high salinities determined by fluid inclusion studies (20–30% NaCl equiv.). According to the genetic model presented in this paper the hydrothermal activity started when the deformation accompanying the uplift of the Koralm Crystalline Complex passed from a ductile to brittle regime (Middle Eocene). The brittle faults acted as channelways for rising, deep fluids, probably of metamorphic origin. Temperature differences between the different uplifting crustal segments supported fluid circulation. Precipitation of the ore occurred at shallow crustal levels where the hydraulic regime was dominated by seawater, and oxidation of the original reducing fluids took place.