Catalytic ozonation of NH4+-N in wastewater over composite metal oxide catalyst

Large amounts of water containing-ammonium nitrogen(NH₄⁺-N)have attracted increasing attention.Catalytic ozonation technology,involving the generation of hydroxyl radical(OH)with strong oxidation ability,was originally utilized to degrade organic-containing wastewater.In this paper,Ce/MnOx composite metal oxide catalysts prepared with different preparation conditions were used to degrade wastewater containing inorganic pollutant(NH₄⁺-N).The as-prepared catalyst features were characterized using X-ray diffraction(XRD),Brunauer-Emmett-Teller method(BET),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS)and H₂-temperature programmed reduction(H₂-TPR)techniques.The results show that the catalyst,prepared by conditions with precipitant Na₂CO₃ and Ce/Mn molar ratio 1:2 calcined at 400℃for 3 h in pH 11.0,displays the optimal performance,with the removal rate of NH₄⁺-N and selectivity to gaseous nitrogen,88.14 wt%and 53.67 wt%,respectively.The effects of several operating factors including solution pH,initial NH₄⁺-N concentrations and scavengers were evaluated.In addition,XRD patterns of catalyst with the best performance and the comparative study on decontamination of NH₄⁺-N by various processes(O₃,catalyst and catalyst/O₃)show that the primary metal oxides are CeO₂ and MnO₂ in Ce/MnOx composite metal oxide catalysts,which have a synergistic effect on the catalytic ozonation of NH₄⁺-N,and the new phase MnO₂ plays a great role.After 5 consecutive use cycles,the degradation efficiency is declined slightly,and can still achieve better than 70 wt%over 1 h reaction.Additionally,the application of catalytic ozonation for actual wastewater on the removal rate of NH₄⁺-N was investigated.Possible mechanism and degradation pathway of NH₄⁺-N were also proposed.In a word,the application of CeO₂-MnO₂ composite metal oxide catalysts in catalytic ozonation can be regarded as an effective,feasible and promising method for the treatment of NH₄⁺-N.     

The internal nitriding behavior of Co-3Cr,Co-3Al,and Co-3Ti (a/o) over the range of 700–1100°C

Internal nitridation of Co containing 3 a/o of either Cr, Al, or Ti was studied over the range of 700–1100° C in NH₃/H₂ (694 ratio). The kinetics of thickening of the reaction zone followed the parabolic rate law, suggesting that solidstate diffusion was rate controlling. Activation energies obtained were 51.2 Kcal/molfor Co-3Cr, 46.6 Kcal/mol for Co-3Ti, and 27.9 Kcal/mol for Co-3Al. XRD showed only CrN, AlN, and TiN. Deep etching revealed that AlN formed hexagonal plates near the surface when formed at high temperature, the precipitates becoming more massive (blocky morphology) near the reaction front. TiN formed elongated dendritic precipitates, whereas CrN tended to form spheroids. The precipitate size varied with temperature, decreasing with decreasing temperature. In some cases, nitriding formed a case but no visible precipitates even at very high magnifications in the SEM. The solubility of nitrogen in cobalt was determined by long-time equilibration and subsequent chemical analyses. The diffusivity of nitrogen in cobalt was determined from measured permeabilities and the experimentally determined solubilities. Mechanisms are discussed, and the behavior of internal nitridation is compared with internal carburization and oxidation in cobalt alloys.     

Advances in the research of nitrogen containing stainless steels

The current status of nitrogen containing stainless steels at home and aboard has been introduced. The function and existing forms of nitrogen in the stainless steels, influence of nitrogen on mechanical properties and anti-corrosion properties as well as the application of nitrogen containing cast stainless steels were discussed in this paper. It is clear that nitrogen will be a potential and important alloying element in stainless steels. And Argon Oxygen Decarbonization (AOD) refining can provide an advanced manufacture process for nitrogen containing stainless steels with ultra-low- carbon and high cleanliness.     

Grinding-hardening with liquid nitrogen: Mechanisms and technology

This paper studies an innovative development of a steel grinding–hardening technology using an inert cryogen—liquid nitrogen. It was found that phase transformations took place during grinding with the application of liquid nitrogen and resulted in hardened surface layer in a ground component. The layer had a fine laths martensite structure which gave rise to a remarkably high hardness. It was also shown that the treatment can produce superior surface integrity, with compressive surface residual stresses and without surface oxidation. Due to the inert nature of the liquid nitrogen, the grinding process becomes environmentally conscious.     

水洗钽粉中氮的测定

针对水洗钽粉中杂质元素的干扰,采用EMGA-620W氧氮分析仪,测定了水洗钽粉中的氮,并与脉冲气相色谱法测氧氮(联测)进行了比较,认为该法快速、准确、可靠。     

Simulation of nitrogen dynamics and biomass production in winter wheat using the Danish simulation model DAISY

A dynamic simulation model for the soil plant system is described. The model includes a number of main modules, viz., a hydrological model including a submodel for soil water dynamics, a soil temperature model, a soil nitrogen model including a submodel for soil organic matter dynamics, and a crop model including a submodel for nitrogen uptake. The soil part of the model has a one-dimensional vertical structure. The soil profile is divided into layers on the basis of physical and chemical soil characteristics. The simulation model was used to simulate soil nitrogen dynamics and biomass production in winter wheat grown at two locations at various levels of nitrogen fertilization. The simulated results were compared to experimental data including concentration of inorganic nitrogen in soil, crop yield, and nitrogen accumulated in the aboveground part of the crop. Based on this validation it is concluded that the overall performance of the model is satisfactory although some minor adjustments of the model may prove to be necessary.     

肥料防结块缓释概况及性能快速表征方法探讨

介绍了颗粒肥料结块的原因机理、影响因素和传统的处理方法。简述了缓释肥料的特点、类型、加工方法以及国内外的研究发展状况。模拟肥料贮存、运输和施用环境以及设计装置，对颗粒肥料防结块、缓释性能快速表征方法进行了有益的探讨。对不同包膜尿素的测试结果表明，所设计的肥料养分释放模拟装置具有较好的应用前景。     

浅议我国钾肥工业的可持续发展

分析了我国可溶性钾盐资源短缺 ,钾肥工业发展速度缓慢 ,钾肥生产能力远远不能满足农业需求 ,国内庞大的钾肥市场长期依靠进口解决的现状 ,介绍了我国钾肥生产工艺技术、生产能力和消费情况。提出了加入WTO后 ,我国钾肥工业可持续发展的若干建议。     

影响PET树脂反应活性因素的分析

探讨了影响连续固相增粘产品活性的因素，提出了控制主反应器的温度、氮气流量、基础切片的端羧基、氮气露点等主要因素，实现生产的平稳控制，从而保证产品黏度的稳定。     

甲醛法测定铵盐含氮量

对甲醛法测定铵盐含氮量进行了研究，提出采用百里酚酞和酚酞混和指示剂进行测定。该法简单、快速、准确，能满足生产实际和样品检验需要。