Effect of MgO and CaO/SiO2 on the immobilization of chromium in synthetic slags

This work investigated the chemical and mineralogical properties of CaO–SiO₂–Cr₂O₃–CaF₂–MgO slags. Synthetic slags were prepared and the effect of the slag basicity (mass ratio CaO/SiO₂) and MgO contents on the stability of the mineralogical species formed was analyzed. The morphology and composition of the slags were analyzed by X-ray powder diffraction (XRD) and scanning electron microscope-energy dispersive spectroscopy (SEM–EDS), whilst their chemical stability was evaluated by leaching with an aqueous acetic acid solution. It was found that in slags with CaO/SiO₂?=?1, the main Cr-compound was MgCr₂O₄ spinel, which forms octahedron crystals. Small amounts of CaCr₂O₄ and CaCrO₄ were also observed. It was found that with increasing the slag basicity from 1 to 2 the compounds MgCr₂O₄ and CaCr₂O₄ were formed together with the Cr(V)-containing compound complex Ca₅(CrO₄)₃F which forms hexagonal crystals. The results showed that the highest Cr concentration levels in the leaching liquors corresponded to slags with CaO/SiO₂?=?2, probably owing to the formation of CaCrO₄ and Ca₅(CrO₄)₃F, whilst the lowest chromium concentration levels corresponded to MgO-based slags owing to the stable binding of chromium in spinel with MgO. Additionally, potential–pH diagrams for the Ca–Cr–H₂O and Mg–Cr–H₂O systems at 25?°C were calculated.     

膨润土-钢渣复合吸附剂对Fe2+的吸附性能

研究了膨润土-钢渣复合吸附剂对模拟酸性矿山废水中Fe²⁺的吸附去除效果、Fe²⁺在吸附剂表面的赋存形态及其吸附机理和规律。结果表明：复合吸附剂在处理含Fe²⁺模拟酸性矿山废水时,不仅能释放碱性物质中和酸,且发生了吸附-聚沉协同作用;Fe²⁺可与膨润土发生晶格置换,还可通过静电吸附作用形成硅酸盐类矿物相,还有一部分通过配合作用生成多金属氧化物,最后一类是通过化学沉淀作用生成的 Fe（OH）₂或Fe（OH）₃受热分解而形成Fe₂O₃;被吸附的Fe²⁺中98.62%以残渣态形式存在于复合吸附剂中;复合吸附剂对Fe²⁺的吸附行为符合BET等温吸附模型和准二级动力学模型。     

Fe/SiO_2复合材料的制备及其对Cd~(2+)的吸附

以Na_2SiO_3为原料、聚乙二醇-2000为结构导向剂,采用溶胶-凝胶和高温煅烧两步法制备SiO_2微球,再以其为载体,采用液相还原法负载零价纳米铁,制得Fe/SiO_2复合材料。采用SEM,FTIR,XRD技术对Fe/SiO_2复合材料的形貌结构进行表征,研究了Fe/SiO_2复合材料对Cd~(2+)的吸附性能。表征结果显示,纳米铁以毛绒状负载在SiO_2微球上。实验结果表明,在溶液pH为5、n(SiO_2):n(Fe)=2、老化温度为70℃的最佳工艺条件下制备的Fe/SiO_2复合材料在25℃时处理Cd~(2+)初始质量浓度为35 mg/L的模拟含Cd~(2+)废水,Cd~(2+)吸附容量为28.10 mg/g。Fe/SiO_2复合材料对Cd~(2+)的吸附作用较符合准二级吸附动力学方程,对Cd~(2+)的等温吸附过程更符合Langmuir模型。     

Conversion of Mixed Low-Density Polyethylene Wastes into Liquid Fuel by Novel CaO/SiO<Subscript>2</Subscript> Catalyst

Plastic wastes disposal can be done by various methods such as landfill, incineration, mechanical and chemical recycling but these are restricted due to some environmental, economic and political problems. Conversion of these plastic wastes into valuable products by degradation is the best option. In the present work waste low density polyethylene was degraded by catalytic process using CaO/SiO₂ as mixed catalyst. The conditions for catalytic degradation were optimized for the production of maximum liquid fuel. It was found that the yield of liquid product was up to 69.10 wt% at optimum condition of temperature (350 °C), time (90 min) and catalyst feed ratio (1:0.4). Liquid fuels obtained from the catalytic degradation were further separated into various fractions by fractional distillation. Composition of liquid fuels was analyzed by FTIR spectroscopy, which showed that the liquid fuels mostly consist of paraffinic and naphthenic hydrocarbons. Different fuel properties such as density, specific gravity, American petroleum institute gravity (API gravity), viscosity, kinematic viscosity, refractive index, refractive intercept and flash point of both the parents and various fractional fuels were determined. All the properties of the obtained fuels are in close agreement with the fuel properties of gasoline, kerosene and diesel. It was found that our catalyst is very much efficient in terms of time, degradation temperature and amount of catalyst.     

α-Fe2O3/AC催化剂的制备及光Fenton反应降解双酚A

采用温和的无模板溶液反应合成了α-Fe₂O₃/AC复合催化剂,作为光Fenton降解双酚A反应的催化剂。通过XRD、SEM、FTIR、DRS、BET、XPS等方法对催化剂的形貌和理化特性进行了分析。结果表明：该催化剂晶型良好,为介孔材料,能够有效吸收和利用紫外光和可见光;该催化剂具有较高的催化活性,稳定性良好;在初始双酚A质量浓度为30 mg/L、溶液pH为4、H₂O₂加入量为320 mg/L、反应温度为40 ℃、催化剂加入量为1.33 g/L的条件下,双酚A降解率可达91.4%。     

Development and Characterization of the Reinforced Soy Protein Isolate-Based Nanocomposite Film with CuO and TiO2 Nanoparticles

Journal of Polymers and the Environment - The present study aimed to develop and characterize the soy protein isolate (SPI) nanocomposite film incorporated with CuO and TiO2 nanoparticles (NPs) for...     

A model for quantifying construction waste in projects according to the European waste list

The new EU challenge is to recover 70% by weight of C&D waste in 2020. Literature reveals that one major barrier is the lack of data. Therefore, this paper presents a model which allows technicians to estimate C&D waste during the design stage in order to promote prevention and recovery. The types and quantities of CW are estimated and managed according to EU guidelines, by building elements and specifically for each project. The model would allow detection of the source of the waste and to adopt other alternative procedures which delete hazardous waste and reduce CW. Likewise, it develops a systematic structure of the construction process, a waste classification system and some analytical expressions which are based on factors. These factors depend on technology and represent a standard on site. It would allow to develop a database of waste anywhere. A Spanish case study is covered. Factors were obtained by studying over 20 dwellings. The source and types of packaging waste, remains, soil and hazardous waste were estimated in detail and were compared with other studies. Results reveal that the model can be implemented in projects and the chances of reducing and recovery C&D waste could be increased, well above the EU challenge.     

Photochemical Kinetic Modeling of Degradation of Aqueous Polyvinyl Alcohol in a UV/H<Subscript>2</Subscript>O<Subscript>2</Subscript> Photoreactor

This study presents a photochemical kinetics model to describe the degradation of water-soluble PVA (Polyvinyl Alcohol) polymer in a UV/H₂O₂ batch reactor. Under the effect of UV light, the photolysis of hydrogen peroxide into hydroxyl radicals can generate a series of polymer scission reactions. For a better understanding and analysis of the UV/H₂O₂ process in the cracking of the PVA macromolecules, a chemical reaction mechanism of the degradation process and a relevant photochemical kinetics model are developed to describe the disintegration of the polymer chains. Taking into account the probabilistic fragmentation of the polymer, the statistical moment approach is used to model the molar population balance of live and dead polymer chains. The model predicts the PVA molecular weight reduction, the acidity of the solution, and hydrogen peroxide residual. In addition to previously published data collected in this laboratory, a new set of experiments were conducted using a 500 mg/L PVA aqueous for different hydrogen peroxide/PVA ratios for model validation. Measurements of average molecular weights of the polymer, hydrogen peroxide concentrations and pH of the PVA solution were determinant factors in constructing a reliable photochemical model of the UV/H₂O₂ process. Experimental data showed a decrease in the PVA molecular weight and a buildup of the solution acidity. The experimental data also served to determine the kinetics rate constants of the PVA photochemical degradation and validate the model whose predictions are in good agreement with data. The model can provide a comprehensive understanding of the impact of the design and operational variables.     

Photochemical Degradation of Aqueous Polyvinyl Alcohol in a Continuous UV/H<Subscript>2</Subscript>O<Subscript>2</Subscript> Process: Experimental and Statistical Analysis

Polyvinyl alcohol (PVA), being a dominant contributor of total organic carbon (TOC) in textile wastewater, is not easily degradable by conventional methods of wastewater treatment. This study investigates the degradation of aqueous PVA in a continuous UV/H₂O₂ photoreactor since the feeding strategy of hydrogen peroxide proves to have considerable effects on the process performance. Response surface methodology involving the Box–Behnken method is adopted for the experimental design to study the effects of operating parameters on the process performance. Experimental analysis shows that the TOC removal varies from 16.11 to 42.70 % along with a reduction of the PVA molecular weights from 56.7 to 95.3 %. The TOC removal is significantly lower than the molecular weight reduction due to the generation of the intermediate products during oxidation. Operating the UV/H₂O₂ process in a continuous mode facilitates the degradation of highly concentrated polymeric solutions using a relatively small hydrogen peroxide concentration in the feed with a small residence time ranges from 6.13 to 18.4 min.     

Effect of Nanoscale SiO<Subscript>2</Subscript> and TiO<Subscript>2</Subscript> as the Fillers on the Mechanical Properties and Aging Behavior of Linear Low-Density Polyethylene/Low-Density Polyethylene Blends

Linear low-density polyethylene (LLDPE) was blended with low-density polyethylene (LDPE) at a fixed ratio (80 wt LLDPE and 20 wt %LDPE) and filled with nanoparticles of SiO₂ and TiO₂ at a ratio up to wt 5%, so as to develop the polymeric composites suitable to preparing the agricultural micro-irrigation pipes having good environmental adaptability. These compounds were blended using calcium stearate, polyethylene wax, and titanate coupling agent as the auxiliary dispersants, and ethylene-vinyl acetate copolymer (EVA) as the toughness improver. The LLDPE/LDPE composites filled with the nanoparticles were extruded and injected to prepare the composites specimens for the performance evaluations and micro-irrigation pipe field test. The mechanical properties, thermostability, and processibility of the injected composites were investigated. The effect of heating in an oven and irradiating by ultraviolet on the mechanical properties of the composites was explored. The environmental adaptability of the micro-irrigation pipes made of the filled LLDPE/LDPE composites was evaluated making use of long-term outdoor field test in northwest China where the arid and harsh natural conditions are of great concerns. It was found that the LLDPE/LDPE blend with the LLDPE mass fraction fixed as 80% showed balanced mechanical and thermal properties and flexibility, and was suitable to be used as the basic resin matrix. The incorporation of nano-TiO₂ contributed to effectively improving the resistance to heating and ultraviolet irradiation of the composites. The composite made from 91% basic resin matrix, 6% EVA, and 3% mixed nano-SiO₂ and TiO₂, showed balanced comprehensive properties. The micro-irrigation pipes made of this filled LLDPE/LDPE composite had good environmental adaptability and service behavior in a three-year field test and were suitable to be used in arid area.     

改性SiO2气凝胶对废水中Fe3+的吸附性能

制备了改性SiO₂气凝胶,考察了经不同类型、不同配比的改性剂改性的SiO₂气凝胶对模拟含Fe³⁺废水的吸附处理效果。实验结果表明：改性SiO₂气凝胶的最佳制备条件为三甲基氯硅烷（TMCS）作改性剂,V（TMCS）#x02236;V（正己烷）=1#x02236;5;当改性SiO₂气凝胶加入量为75g/L、吸附时间为4h、Fe³⁺质量浓度为10mg/L时,模拟含Fe³⁺废水的Fe³⁺去除率为98.32%,剩余Fe³⁺质量浓度为0.168mg/L;采用改性SiO₂气凝胶动态吸附处理流量为420mL/h、Fe³⁺质量浓度为100mg/L的模拟含Fe³⁺废水,吸附后废水中剩余Fe³⁺质量浓度仅为0.196mg/L。     

H2O2复合体系及其在环境治理中的应用

介绍了过氧化氢的基本性质,就过氧化氢在污水治理以及烟气污染防治方面的应用进展进行了评速,并展望了过氧化氢复合体系(H2O2/UV)同时脱硫、脱硝的前景及可能存在的问题.     

Remediating TCE‐contaminated groundwater in low‐permeability media using hydraulic fracturing to emplace zero‐valent iron/organic carbon amendment

A field pilot test in which hydraulic fracturing was used to emplace granular remediation amendment (a mixture of zero‐valent iron [ZVI] and organic carbon) into fine‐grained sandstone to remediate dissolved trichloroethene (TCE)‐contaminated groundwater was performed at a former intercontinental ballistic missile site in Colorado. Hydraulic fracturing was used to enhance the permeability of the aquifer with concurrent emplacement of amendment that facilitates TCE degradation. Geophysical monitoring and inverse modeling show that the network of amendment‐filled fractures extends throughout the aquifer volume targeted in the pilot test zone. Two years of subsequent groundwater monitoring demonstrate that amendment addition resulted in development of geochemical conditions favorable to both abiotic and biological TCE degradation, that TCE concentrations were substantially reduced (i.e., greater than 90 percent reduction in TCE mass), and that the primary degradation processes are likely abiotic. The pilot‐test data aided in re‐evaluating the conceptual site model and in designing the full‐scale remedy to address a larger portion of the TCE‐contaminated groundwater plume. © 2012 Wiley Periodicals, Inc.     

CuO/γ-Al2O3联合脱硫脱硝技术研究进展

综述了CuO／γ-Al2O3吸收／催化剂的制备发展过程，吸附的流程化学及原理和该项技术由固定床、流化床到移动床的发展过程。分析了该项技术在实际应用中存在的问题，并指出了以后的发展方向。     

Influence of H<Subscript>2</Subscript> on the decomposition of halides by nonthermal plasma incorporated with in situ alkaline absorption

To control the emission of halides into the environment, an experiment on the nonthermal plasma decomposition of the halides CF₄, CHF₃, C₂HCl₃, and CHClF₂ was conducted in a wire-in-tube corona reactor. It was found that the decomposition of C₂HCl₃ and CHClF₂ was easy compared with the decomposition of CF₄ and CHF₃. With the addition of H₂ in N₂ gas, the decomposition ratio of CF₄, C₂HCl₃, and CHClF₂ increased. In contrast, the decomposition ratio of CHF₃ in a hydrogen-rich atmosphere was lower than that in an N₂ atmosphere. It was demonstrated that the yields of HF and/or HCl formed during halide decomposition clearly increased in the presence of H₂ in N₂ gas. Furthermore, in order to prevent the production of unwanted products from halide decomposition, a combination of plasma decomposition and in situ alkaline absorption was devised by coating a layer of Ca(OH)₂ onto the surface of the grounding electrode. It was demonstrated that the Ca(OH)₂ sorbent played an effective role as a scavenger, participating in halide decomposition by capturing reaction products such as HCl and HF, therefore resulting in increased halide decomposition.     

DTC类改性糯米淀粉的制备及其吸附水中Pb2+性能

采用碱法从天然糯米中提取糯米淀粉（SS）,经环氧氯丙烷交联、醚化,邻苯二胺胺化,CS₂亲核加成,最终制备出一种新型Pb²⁺吸附剂——二硫代氨基甲酸盐（DTC）类改性糯米淀粉（DTCS）。在吸附剂加入量2.0 g/L、Pb²⁺质量浓度30 mg/L的条件下,不同阶段改性产物吸附Pb²⁺的最佳pH均为7.0,吸附平衡时间为30 min。SS对Pb²⁺的吸附去除率仅为9.1%,经改性后吸附能力逐步提高,最终产物DTCS对Pb²⁺的吸附效果最佳,Pb²⁺去除率高达99.9%,平衡吸附量为14.97 mg/g。DTCS对Pb²⁺的吸附过程符合准二级吸附动力学模型,以化学吸附为主。     

低碳经济下燃煤电厂CO_2捕集技术

随着中国经济发展,温室气体排放量大幅增加。温室气体中,CO2的排放对气候的负面影响十分巨大,CO2排放已成为燃煤发展的瓶颈问题之一。针对电力工业CO2排放状况,介绍了几种火电厂CO2排放捕集措施：燃烧前脱碳、富氧燃烧以及燃烧后脱碳技术,分析了各项技术的优势和可行性;指出了低碳经济下火电厂的CO2减排方向。     

经济手段在火电厂SO2污染控制中的应用

阐述了环境管理中经济手段的特点,类型及各国在控制火电厂SO2排的应用,对我国采用的经济手段及其效果与存在问题进行了简要分析,并提出了在我国实施环境经济手段的原则与建议。