彩管厂含氟废水处理工程实例及问题讨论

对某彩管厂含氟废水治理工程进行改造。由于投加磷酸盐对处理含氟废水效果影响不大,原工艺流程三级化学沉淀法可简化为二级化学沉淀法;一级化学沉淀法后取消中间沉淀池对反应效果不产生影响;设计时需考虑管道结垢问题。处理后出水的氟化物的质量浓度小于10mg/L。应用实践表明,工程取得了满意的效果。

Synthesis and photoluminescence of Y and Cd co-doped ZnO nanopowder

Y and Cd co-doped ZnO nanopowders were prepared via chemical precipitation method in order to modify the band gap and increase the luminescent intensity. The structures and optical properties of the as-synthesized samples were characterized by X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS） and photoluminescence （PL）. The effects of Y and Cd ions on the optical properties of the samples were studied. Doping of Y into ZnO evidently increases the intensity of UV emission, or co-doping of Y and Cd enhances the UV emission, narrows the band gap of ZnO and hence red shifts the UV emission at the same time. Therefore, Y and Cd co-doped ZnO nanopowders exhibit an intense violet emission in the room temperature PL spectrum, which could be a potential candidate material for optoelectronic applications.

Preparation of Zr-doped CaTiO_3 with enhanced charge separation efficiency and photocatalytic activity

A series of Zr-doped CaTiO3 powders were prepared with the mild co-precipitation method and calcined at 850℃ for 3 h. The as-prepared Zr-doped CaTiO3 samples were characterized by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, UV-Vis diffuse reflectance spectra （DRS） and X-ray photoelectron spectra （XPS）. XRD result revealed the presence of single perovskite phase of CaTiO3. UV-Vis diffusive reflection spectra of Zr-doped CaTiO3 indicated that the absorbance obviously increased in the visible light irradiation. XPS analysis showed that two types of oxygen existed on the photocatalyst surface, including lattice oxygen and absorbed oxygen. Their photocatalytic activity in the case of the degradation of methyl orange in water and photoelectrochemical activity were also tested. The 5%Zr-doped （mole fraction） CaTiO3 sample showed the highest photocatalytic activity. The enhanced photocatalytic activity was ascribed to the change of the lattice structure, existence of oxygen vacancies and increase of the photogenerated charge separation efficiency.

Boron Nitride Nanowires Produced on Commercial Stainless Steel foil

Chemical vapor deposition growth of one-dimensional nanomaterials usually demands substrates that have been coated with a layer of catalyst film. In this study, a green process to synthesize boron nitfide （BN） nanowires directly on commercial stainless steel foils was proposed by heating boron and zinc oxide powders under a mixture gas flow of N2 arid 15% H2 at 1100℃, and a large quantities of pure h-BN nanowires have been produced directly on commercial stainless steel foil. The stainless steel foils not only acted as the substrate but also the catalyst for the nanowire growth. The synthesized BN nanowires were characterized by X-ray diffraction, scanning and transmission electron microscopes, X-ray energy dispersive spectrometer and photoluminescence spectroscopy, The nanowires also possess strong PL emission bands at 515, 535, and 728 nm.

Removal of Nitrogen and Phosphorus from Animal and Municipal Wastewaters as Dittmarite

Phosphorus and nitrogen are known causes of eutrophication in rivers, lakes streams and estuaries. The sources of these nutrients are diverse and they include chemical fertilizers, CAFOs （Confmed Animal Feeding Operations）, land application of animal and municipal as well as industrial wastewaters. Application of manure slurries to crop land beyond allowable limits could result in high levels of phosphorus and nitrogen in runoff that negatively impact aquatic animals. Municipal wastewater treatment plants are setup to remove these nutrients from domestic and industrial wastewater through a network of treatment processes. Controlling the discharge of phosphorus and nitrogen in wastewater is a key factor in preventing eutrophication. This paper presents work done to enhance a chemical precipitation process that removes over 90% of dissolved phosphorus and nearly 20% of dissolved nitrogen from both synthetic and municipal wastewaters. The objective of the study is to remove nitrogen and phosphorus from wastewater as dittmarite, a value-added mineral fertilizer found in nature. A laboratory procedure was developed that generated significant quantities of dittmarite from various wastewaters. Pure dittrnarite contains nitrogen, phosphorus and magnesium in approximate molar ratios of 1：1.2：1.2 that can support plant growth. It is produced as a wet precipitate from chemical reactions that occur in the wastewater treatment process; it can be dried for proper handling and utilization. Municipal wastewater treatment plants, high volume fish producers, CAFOs and individual rural homeowners could all benefit from this technology for on-site removal of nitrogen and phosphorus from produced wastewaters.

Quantum Chemistry Modeling of Formation of Graphene and Graphene Nanowalls for Emission Electronics

The system ＂substrate--graphene island on its surface＂ was modeled with using semi-empirical quantum chemistry methods for various substrates. Such system imitates the graphene nucleation and growth when using CVD （chemical vapor deposition） technique. Herewith the carbon atoms can enter the island from both the substrate and the bulk of the CVD reactor. The authors show that for a wide island size range the carbon nanowalls placed perpendicularly as to the substrate is the most favorable configuration. But a transfer to this configuration is only possible providing two conditions are realized： the CVD technique is stimulated by plasma, when a strong electrical field exists near the substrate surface and preliminary decomposition of carbon carrier is realized in the bulk of the CVD-reactor.

The discovery of surface runoff in the megadunes of Badain Jaran Desert,China,and its significance

The Badain Jaran Desert exhibits the greatest difference in altitude of all of the world's deserts.On the slopes of megadunes in the desert,there are physical and chemical deposits produced by surface runoff.In addition,we have observed rarely-seen infiltration-excess surface runoff in the megadune depressions as well as spring streams at the base of megadunes.We used electron microscopy,energy spectrum analysis,infiltration experiments,moisture content determinations and grain-size analysis to study the mineral and chemical composition of the runoff precipitates,and grain-size of the deposits associated with the runoff,together with the hydrological balance in the megadune area,and the atmospheric precipitation mechanism responsible for groundwater recharge and for supplying water to lakes.The observations of shallow runoff and infiltration-excess surface runoff indicate the occurrence of strong and effective precipitation in summer,which would provide an important source for groundwater recharge.Several lines of evidence,such as the physical and chemical deposits resulting from shallow subsurface runoff,spring streams,infiltration-excess runoff,and gravity capillary water with a moisture content of 3-6%,demonstrate that precipitation reaches the base of the megadunes through infiltration and subsequently becomes groundwater.The chemical deposits,such as newly-formed calcite and gypsum,and gray-black physical deposits,as well as different stages in the development of fan-shaped landforms resulting from shallow subsurface runoff,indicate that groundwater recharge in the area is the result of long-term precipitation,rather than intermittent individual major rainfall events.Fine sand layers with a low infiltration capacity lead to subsurface runoff emerging at the ground surface.Five factors play an important role in maintaining a positive water balance and in replenishing groundwater via rainfall:effective rainfall as a water source,the high infiltration capacity of the sands enabling rainfall to rapidly become capillary water in the dunes,low evapotranspiration rates due to the sparse vegetation,the fact that the depth of the sand layer influenced by evaporation is shallow enough to maximize the deep infiltration of rainfall,and rapidly-moving gravity capillary water in the sandy dunes.These five factors together constitute a mechanism for groundwater recharge from rainfall,and explain the origin of the groundwater and lakes in the area.Our findings represent a significant advance in research on the hydrological cycle,including groundwater recharge conditions and recharge mechanisms,in this desert region.

Fabrication, adsorption and photocatalytic properties of ZnTi0.6Fe1.4O4/Carbon nanotubes composites

ZnTixFe2-xO4 and ZnTi0.6Fe1.4O4/Carbon nanotubes （ZT0.6F1.4/CNTs） composites were prepared by chemical co-precipitation method. The composition, microstructure, magnetic property, adsorption and photocatalytic activity of the prepared samples were characterized by means of modem analytical techniques. The results indicated that ZT0.6F1.4CNTs composites not only held the original special structure and excellent adsorption properties of CNTs, but also had suitable magnetic property and excellent photocatalytic activity. The removal rate of the samples on Rhodamine B （RhB） depended on the adsorption of CNTs and the photocatalytic degradation of ZTo.6F1.4 in the composites. The maximum adsorption amount （qm） of ZT0.6F1.4/CNTs with the mass ratios of ZT0.6F1.4 to CNTs （mz/c）=l was up to 17.153 mg g-t for RhB, its adsorption behavior was in accord with Langmuir model, and its photocatalytic degradation activity on RhB had a positive correlation with the content of ZT0.6F1.4 in the sample. The experimental results indicate that the total removal rate of composite with rnz/c=l on RhB was more than 95% and the composite had good decontamination capability on industrial dye wastewater. In addition, the samples can be recovered conveniently, activated easily and had good performance for recycling.

Adjusting Na doping via wet-chemical synthesis to enhance thermoelectric properties of polycrystalline SnS

Tin sulfide (SnS) has analogous structural features to tin selenide (SnSe), but contains more abundant resources as compared with SnSe. SnS has elicited attention as a potential eco-friendly therm oelectric (TE) material. However, the intrinsic carrier concentration of SnS is very low, thereby hindering the performance improvement of the material. This study proposes that the TE properties of polycrystalline Nadoped SnS (synthesized through an improved chemical coprecipitation) can be significantly enhanced. The maximum power factor (PF) of 362 μW m^-1K^-2 at 873 K was achieved, presenting a state-of-the-art value for the polycrystalline SnS. Considering the merits of the improved electrical properties and lower thermal conductivity of SnS, the highest ZT was up to 0.52 at 873 K even without intentional chemical doping. This study offers an effective approach for improving the PF to achieve high ZT in SnS. Hence, we expect that this new perspective can be extended to other dopants and broaden the scope of synthesis technology.

Monodisperse Fe3O4 spheres: Large-scale controlled synthesis in the absence of surfactants and chemical kinetic process

Fe3 O4 has attracted tremendous interest in vast areas of biomedicine and catalysis as well as environment engineering.However,it is highly desired to fully understand the chemical kinetic process and propose a general,surfactantfree,large-scale synthesis approach for Fe3 O4 spheres.Herein,we developed a facile scalable solvothermal method in the absence of surfactants to produce Fe3 O4 spheres with the yield of 5.1 g,which present tunable sizes from 107 to 450 nm by modulated molar ratio of Fe3+/COO-in the solution.Particularly,it is observed that the reactants undergo a redox process,composed of a precipitation-dissolution equilibrium combined with a coordination reaction(termed as RPC),to the final product based on the LaMer model.It is worth noting that the generation of di-carboxyl group and its coordination with iron cations determine the formation of Fe3 O4 spheres.This work not only offers a strategy to precisely tailor the particle size in scalable synthesis process,but also gives the insight on the role of dihydric alcohol in the formation mechanism of Fe3 O4 spheres in the absence of surfactants.

Size influence on the fluorescence decay time of ZnS:Mn^(2+) nanocrystals

ZnS:Mn2+ nanocrystals(NCs) with particle size from 1.9 nm to 3.2 nm are synthesized via chemical precipitation method with different [S2-]/[Zn2+] ratios.The size-dependent decay for Mn emission exhibits a double exponential behavior.And two lifetime values,in millisecond time domain,can both be shortened with size increasing,which is attributed to enhanced interaction between host and Mn2+ impurity.A molecular structure model is proposed to interpret the tendency of two lifetime components,which is correlated to the number of S vacancy(Vs) defects around Mn2+.