pH对砂柱反硝化脱氮的影响

在不同的初始pH条件下,72h后砂柱中不同深度溶液的pH值,都出现了上升的现象;但是在不同初始pH条件下,砂柱中同一深度溶液pH值变化幅度不同。在不同的初始pH条件下,砂柱中硝酸盐的去除效率各不相同;当初始pH=7．00时,在砂柱的400mm、800mm深度处的取样样品中分别测得硝酸盐浓度为44．89mg／L、14．98mg／L,砂柱对硝态氮的脱除效果最好;当初始pH=5．00时,在砂柱的400mm、1200mm深度处的取样样品中分别测得硝酸盐浓度为132．56mg／L、56．68mg／L,砂柱对硝态氮的脱除效果最差。     

Plugging behavior of gellan in porous saline media

In this article, the hydrodynamic behavior of dilute aqueous solutions of a natural polysaccharide—gellan in the porous media under the modeled oilfield conditions is described. The hydrodynamic properties of gellan and poly(acrylamide) solutions in saline porous media are compared. The influence of inorganic salts NaCl, KCl, CaCl₂, MgCl₂, and BaСl₂ on sol–gel and gel–sol transitions of dilute gellan solutions was evaluated. The mechanism of sol–gel transition in the presence of individual alkaline and alkaline‐earth metal salts is described on the basis of literature data. The viscometric measurements revealed that the effectiveness of salts to enhance gelation of gellan changes in the following order: BaСl₂ > CaCl₂ ≈ MgCl₂ > KCl > NaCl. The sol–gel and gel–sol phase transitions of gellan solution were also observed upon addition of oil field water containing 73 g L^?1 of alkaline and alkaline earth metal ions. During the injection of gellan solutions into the porous media saturated by saline water an oscillation of the injection pressure was observed. Such behavior of gellan is explained by either the sol‐to‐gel and the gel‐to‐sol transitions of the polymer taking place in saline water or the step‐by‐step plugging of high permeable channels until all high permeable channels of sand packs are plugged due to gellan invasion. The application of brine‐initiated gelation of gellan for water shutoff operations (WSO) in field conditions was demonstrated. Higher technological effectiveness of gellan injection in comparison with existing gelation systems was shown. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41256.     

Analysis of stability of food emulsions by Eyring's theory: Influence of different biopolymers

Eyring's kinetic theory of liquids was applied to the study of flow behavior of low oil content mayonnaises at different temperatures. These food emulsions were formulated with different biopolymers as stabilizers (polysaccharides such as modified starch, gellan gum, and pectin). The analysis of the values obtained for the parameters of the Eyring equation for viscosity determined the emulsion containing only starch as a stabilizer is the most unstable to stirring. Replacement of part of the starch with gellan gum or pectin enhances the stability of the emulsion. The results for activation energy are quite similar for high shear rates, which can be explained by the evolution of the average drop size distribution. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2653–2657, 2004     

Self-Compacting Concrete: Theoretical and experimental study

This paper addresses experiments and theories on Self-Compacting Concrete. First, the features of “Japanese and Chinese Methods” are discussed, in which the packing of sand and gravel plays a major role. Here, the grading and packing of all solids in the concrete mix serves as a basis for the development of new concrete mixes. Mixes, consisting of slag blended cement, gravel (4-16 mm), three types of sand (0-1, 0-2 and 0-4 mm) and a polycarboxylic ether type superplasticizer, were developed. These mixes are extensively tested, both in fresh and hardened states, and meet all practical and technical requirements such as medium strength and low cost. It follows that the particle size distribution of all solids in the mix should follow the grading line as presented by Andreasen and Andersen. Furthermore, the packing behaviour of the powders (cement, fly ash, stone powder) and aggregates (three sands and gravel) used are analysed in detail. It follows that their loosely piled void fraction are reduced to the same extent (23%) upon vibration (aggregates) or mixing with water (powders). Finally, the paste lines of the powders are used to derive a linear relation between the deformation coefficient and the product of Blaine value and particle density.     

Monosize polystyrene microbeads by dispersion polymerization

Monosize Polystyrene microbeads were prepared by dispersion polymerization in different alcohol/ water media. Azobisisobutyronitrile and polyacrylic acid were utilized as initiator and steric stabilizer, respectively. The polymerizations were performed in three kinds of dispersion media having different polarities: isopropanol/water, 1-butanol/water, and 2-butanol/water. The effects of initiator and stabilizer concentrations, alcohol/water ratio, and monomer/dispersion medium ratio on the size and monodispersity of the polymeric microbeads were investigated. By dispersion polymerization, polystyrene (PS) microbeads were obtained in the size range of 1.0–4.0 μm with narrow size distribution or in the monosize form. The average size and size distribution of microbeads with increasing polarity of the dispersion medium. The average size and size distribution increased with increasing initiator concentration in all dispersion media. The increase in the stabilizer concentration in homogeneous dispersion media resulted in a decrease in average size and size distribution of the microbeads. A clear increase was observed in the average size with increasing monomer/dispersion medium ratio. Isopropanol/water dispersion medium provided monosize microbeads with higher values of monomer/dispersion medium ratio. © 1993 John Wiley & Sons, Inc.     

进水中硝酸盐浓度对砂柱脱氮的影响

实验研究了在不同进水浓度下,砂柱中物质对硝酸盐的脱除效果和砂柱深层水体遭受污染情况。分别设置初始进水硝酸盐浓度为100 mg/L、200 mg/L、300 mg/L,72 h后,在砂柱的不同深度取样测量硝酸盐剩余浓度。结果表明,在一定的范围内,进水浓度越高,反硝化速度越快。而初始进水硝酸盐浓度为300 mg/L时,在砂柱600 mm深度处测出硝酸盐浓度为125.4 mg/L,反硝化脱氮速率不再提升。     

Gellan gum–O,O′‐bis(2‐aminopropyl)‐polyethylene glycol hydrogel for controlled fertilizer release

A gellan gum–Jeffamine superabsorbent hydrogel was obtained with different crosslink densities using different amounts of (1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide hydrochloride) and N‐hydroxysuccinimide. Infrared spectroscopy and thermal analysis confirm the crosslinking. A morphology analysis indicates denser structures for samples with higher crosslinking points. The swelling degree in high‐acyl gellan gum hydrogels was equivalent to 145 times their dry weight, and 77 times when low‐acyl gellan gum was used. Hydrogels also showed a 450 min water retention, as opposed to 280 min for pure water, evidencing good humidity control, suitable for use in arid climates. They also demonstrated a maximum release of commercial fertilizer of about 400 mg per gram for KH₂PO₄ and about 300 mg per gram for NPK 20‐5‐20. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45636.     

Gelcasting of alumina suspension using gellan gum as gelling agent

As one of the excellent colloidal ceramic forming methods for fabricating complex shaped ceramic components, gelcasting has been extensively investigated in the past two decades. In this article, a novel nontoxic system for gelcasting of ceramics was investigated using gellan gum as gelling agent. The rheological and gelling properties of gellan gum solutions with different types of cations and different concentrations of divalent magnesium ions were studied. Influences of concentration of gellan gum and solid loading of alumina suspension on the rheological properties and gelling properties of alumina suspension were investigated. The rheological properties of concentrated alumina suspension mixing with gellan gum and magnesium chloride were evaluated. Dense ceramics prepared by gellan gum gelation showed homogeneous microstructure and good mechanical properties.     

Preparation and characterization of polyelectrolyte complex of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-trimethyl chitosan/gellan gum: evaluation for controlled release of ketoprofen

N,N,N-Trimethyl chitosan, a highly water soluble derivative of chitosan, has been made by reductive methylation of chitosan by a three-step process reported in literature. A novel polyelectrolyte complex of this derivative with gellan gum has been made by mixing the aqueous solutions of the two polymers. The complex was characterized by FTIR, TGA, DSC and SEM techniques. Maximum yield of the complex was obtained at pH 2.0 with a gellan gum:trimethylchitosan ratio of 3:1. The swelling study indicated pH responsiveness of the polyelectrolyte complex sample, with higher swelling under neutral or slightly basic conditions. In vitro studies on the release of the drug ketoprofen from the polyelectrolyte complex matrix were conducted in simulated gastric and intestinal fluids. The results indicated release of 85–90 % of the entrapped drug in the media of pH 6.8 and 7.4 and less than 7 % release in the medium of pH 1.2. The kinetic analysis indicated the drug release to be a first-order process. The mechanism of water transport and drug diffusion is shown to be of Fickian type. The results prove the suitability of the polyelectrolyte complex as a matrix material for delivery of drugs with short half life such as ketoprofen in the slow release mode.     

Effects of Microbial Polysaccharides on the Oil Absorption and Quality Characteristics of a Deep-Fried Snack Namkeen

This study investigates the potential of microbial polysaccharides (MP) gellan gum and pullulan to reduce oil uptake in a deep-fried snack (Namkeen). The concentration of MP in refined wheat flour varied between 1–10% (w/w) and the frying time and temperature are optimized. The results reveal that MP added namkeens showed a maximum relative oil reduction of 33.87% with gellan gum and 26.93% with pullulan at 10% (w/w). Gellan gum and pullulan result in oil reduction of 23.19% and 15.97% with 5% (w/w). The results reveal that gellan gum added namkeens exhibited 1.45 times lower oil uptake than pullulan added namkeen indicating potential oil reduction capabilities. The hardness of namkeen is observed to increase with an increase in MP concentration. Sensorial and textural characteristics of control and MP incorporated fried samples are comparable up to 5% (w/w) with MP concentration. The results for the control samples and MP incorporated samples are statistically significant. Furthermore, overall sensorial acceptability of pullulan added namkeens (7.74 ± 0.53) is slightly higher than that of gellan gum added namkeens (7.64 ± 0.36). Practical Application: Low-fat diet and functional foods are expected to help in managing the conditions of hyperlipidaemia. This study focuses on the potential of MP in reducing the oil content of deep-fried snacks. The efficacy of MP gellan gum and pullulan as functional ingredients for oil reduction in fried snacks demonstrates its aid in formulating low-fat foods thereby retaining sensorial characteristics.     

Gellan gum capped silver nanoparticle dispersions and hydrogels: cytotoxicity and in vitro diffusion studies

The preparation of highly stable water dispersions of silver nanoparticles using the naturally available gellan gum as a reducing and capping agent is reported. Further, exploiting the gel formation characteristic of gellan gum silver nanoparticle incorporated gels have also been prepared. The optical properties, morphology, zeta potential and long-term stability of the synthesized silver nanoparticles were investigated. The superior stability of the gellan gum-silver nanoparticle dispersions against pH variation and electrolyte addition is revealed. Finally, we studied the cytotoxicity of AgNP dispersions in mouse embryonic fibroblast cells (NIH3T3) and also evaluated the in vitro diffusion of AgNP dispersions/gels across rat skin.     

Production and characterization of poly(ethylene glycol dimethacrylate-styrene-glycidyl methacrylate) microbeads

Nonswellable and swellable poly(ethyleneglycol dimethacrylate)-based microbeads that could react directly with the biological molecules were produced by a suspension polymerization procedure. For this purpose, ethyleneglycol dimethacrylate (EGDMA) was copolymerized with glycidyl methacrylate (GMA) in an aqueous suspension medium. Benzoyl peroxide and poly(vinyl alcohol) were used as the initiator and the stabilizer, respectively. The copolymerization provided nonswellable, tranparent, and spherical copolymer microbeads in the size range of 100–300 μm. On the other hand, swellable copolymer microbeads in the aqueous medium were obtained by using toluene as a diluent in the same copolymerization recipe. In a separate group of polymerizations, styrene (St) monomer was also included within the monomer phase to regulate the hydrophobicity of resulting microbeads. Nonswellable and swellable poly-(EGDMA-St-GMA) microbeads were obtained by changing the type and concentration of the ingredients within the monomer phase. The effects of glycidyl methacrylate, styrene, and toluene concentrations on the microbead yield, the average size, and the swellability of microbeads were investigated. In the second part of the study, the interaction of produced microbeads with a selected enzyme (i.e., chymotrypsin) was investigated. The most stable chymotrypsin immobilization was achieved with the swellable poly(EGDMA)-based microbeads including styrene. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1319–1334, 1998     

Qualitative and Quantitative Evaluation of Quartz in Different Granular Types of Ouargla Region Sand Dunes – Algeria

In this paper, it is shown that Ouargla region (Algeria) sand dunes are very rich in quartz. This study aims to assess the quartz in the different granular sand types, using XRD spectroscopy. Granulometric classification and the size distribution curve were carried out. The X’Pert HighScore program based on the Rietveld refinement was used in analyzing the XRD data. Qualitative and quantitative quartz evaluations were carried out. It was deduced that the quartz was of the α phase. The concentrations of quartz have been calculated as: the very fine sand (0.063-0.100 mm) possessing the highest value of 82.05 %, followed by the coarse sand (0.500-1.000 mm) with 78 %, while in both the medium (0.250-0.500 mm) and the fine (0.100-0.250 mm) the concentration was about 67 %, whereas, the lowest one was 18.2 % in the very coarse sand (1-2 mm). These results were confirmed by FTIR spectroscopy. Crystallite sizes of quartz have been estimated, and their distribution curve versus grain sizes has been illustrated. It was found that the crystallite sizes in the fine sand are less than 100 nm, and thus may be considered as nanometric particles.     

高酰基结冷胶在食品饮料中的应用研究

高酰基结冷胶的研究在国内逐步深入,应用优越性逐步被人们所认识,综合研究内容和行业信息,主要介绍了高酰基结冷胶的基本应用范围和应用效果的优越性,简要分析目前行业的研究和应用情况,为高酰基结冷胶的应用推广提供参考依据。     

The performance of pumice as a filter bed material under rapid filtration conditions

Deep bed sand filters are used extensively in drinking water and wastewater treatment. In this study, sand and pumice were used as a filtration media under rapid filtration conditions and performance results for both were compared. Turbidity removal performance and head losses were investigated as functions of filtration rate, bed depth and particle size. Under the same experimental conditions such as 750 mm bed depth, 7.64m³/m².h flow rate and, 0.5−1.0 mm grain size, turbidity removal rates for sand and pumice were found to be 85-90% and 98-99%, respectively. Furthermore, the head loss for sand and pumice were found to be 460 mm and 215 mm, respectively. The results obtained have shown that pumice has a high potential for use as a filter bed material.     

Sintered glass-ceramics from incinerator fly ashes. Part II. The influence of the particle size and heat-treatment on the properties

A composition obtained by mixing MSW ashes with sand and glass cullet was melted at 1500 °C and quenched in water. The obtained frit was sieved and separated in different fractions: L (large, 2–5 mm), I (intermediate, 1–2 mm) and S (small, <1 mm). The sintering of the glass particles, carried out in an alumina mould, occurred in the 700–950 °C range. The curve of the crystal growth rate as a function of the temperature was obtained by means of 1 h heat-treatment in the 850–1050 °C range. The crystal growth started at 850 °C and the maximum rate, 0.013 mm/min, occurred at 1020 °C. The ferrobustamite crystal phase was evaluated by XRD analysis and observed by optical microscopy. The mechanical, thermal and chemical properties of the L, I and S glass-ceramics were measured and discussed. They resulted to be influenced by the grain size of the glass particles and by the percentage of crystal phase.     

流化床-输送床耦合装置中煤颗粒的气力分级

引言流化床内颗粒与流体混合激烈,传热与传质效果好,颗粒在全床内的温度和浓度均匀一致,故流化床广泛应用于燃烧、气化及热解过程中。然而,不同粒径颗粒的流化特征有所差别,且所需要的转化时间及转化温度不同。目前的热解技术使得各粒     

Axial mixing and scaleup of reciprocating plate columns

Axial mixing measurements in single phase (water) flow have been taken in open-type reciprocating plate columns of diameters 25.4 and 508 mm. In the case of the smaller column, two-phase axial mixing was measured, both in the dispersed phase (water dispersed in n-heptane) and the continuous phase (with n-heptane dispersed in water). Pulse injection of a tracer solution of ammonium chloride and methanol in water was used. Under single phase conditions, the axial dispersion coefficients were found to go through a minimum as the agitation level was increased from zero. The coefficients were nearly an order of magnitude higher in the 508 mm column than in the 25,4 mm column. In two phase flow in the 25,4 mm column, the continuous phase axial dispersion coefficients also went through a minimum as agitation was increased. The dispersed phase axial dispersion coefficients decreased monotonically as agitation was increased from zero. The results of this work and previous data are used in modelling the scale-up of reciprocating plate columns by means of Pratt's simplified technique. The existing empirical scale-up equation is consistent with an assumption that continuous phase mixing increased with column diameter but dispersed phase mixing remains unchanged.     

Preparation and Characterization of Poly(Methyl Methacrylate) Microbeads by Dispersion Polymerization: Effects of the Medium Composition,Monomer Concentration,Thermal, and Optical Properties

This study investigated the relationship between particle size, particle distribution, thermal, and optical properties of poly(methyl methacrylate) microbeads using dispersion polymerization under various methanol/water (MeOH/H₂O) dispersion medium ratios and methyl methacrylate acid concentrations. The particle size of the poly(methyl methacrylate) microbeads increased when the medium solubility and monomer concentration increased simultaneously. In addition, the molecular weight and polydispersity of the poly(methyl methacrylate) microbeads were increased as the methanol ratio increased. The refractive index increased as the content of the poly(methyl methacrylate) microbeads increased with wavelengths of 546 and 589 nm.     

石英砂粒径大小对甲烷水合物形成及分布的影响

为了研究不同粒径多孔介质体系中甲烷水合物的形成,本文采用粒径分别为0.075~0.5mm、0.5~1mm、1~2mm和2~3mm的石英砂作为多孔介质,在初始压力7.0MPa、温度0.5℃条件下进行水合物形成实验并进行取样观察、分层分解,得出不同粒径大小石英砂中甲烷水合物形成及分布的特征。结果表明：随着石英砂粒径的增大,石英砂砂体中的水合物形成量和初始水合物形成速率在逐渐减小;在粒径为0.075~0.5mm、1~2mm和2~3mm石英砂中,充气过程中水合物便开始形成,且并未出现明显的水合物大量形成阶段,而在粒径为0.5~1mm石英砂体系中出现了水合物大量形成的阶段;通过计算发现,0.5~1mm石英砂体系的气体消耗量最大,为0.47mol,2~3mm石英砂体系的气体消耗量最小,仅为0.05mol;在这4种粒径的石英砂体表面的甲烷水合物主要以分散状均匀分布于颗粒之间或胶结成块,但这一观察结果与通过分解的方法所得到的石英砂上部水合物形成量大于下部的结果存在差异;重复实验也发现,仅在粒径为0.5~1mm石英砂顶部出现了水合物大量富集的现象,因此推断认为在一定粒径的介质体系同时上部存在较大空隙时,水合物有可能会在空隙中大量富集存在。这一实验结果对自然环境中水合物的赋存区域及形态的预测具有一定的参考价值。