Characterization of Compost with Respect to its Content of Heavy Metals. Part II: Sample Preparation

Abstract

This paper forms part of a study aimed at the development of a procedure for the determination of heavy metals in compost. The present paper deals with the sample preparation stage, including subdividing laboratory samples and reduction of the particle size.

The effect of particle size reduction on the random error due to the analysis of test portions was examined. It was found that milling for 20min in a quartz planet ball mill yields sufficiently homogeneous test samples. As the milling capacity of this device is too small, prior to milling subdivision of the laboratory sample is required. Subdivision before drying is recommended for practical reasons.     

Synthesis and Characterization of Hydrogel Nanoparticles Through Inverse Microemulsion Polymerization of 2-Acrylamido-2-methyl-1-propanesulfonic Acid

Nanosized hydrogel particles prepared through inverse microemulsion polymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid, using the combination of an oil soluble emulsifier (SPAN80) with a water soluble emulsifier (TWEEN 80), and precise determination of HLB range related to the formation of stable single phase microemulsions.

The effect of crosslink density, water phase to oil phase ratio, and the hydrophilic-lipophilic balance (HLB) value on polymerization rate, particle size, and swelling ratio were investigated. It found that polymerization rate and particle size are strongly dependent on the water phase to oil phase ratio. Hydrogel samples prepared using oil soluble and water soluble initiators and the results showed that the initiator type had a great influence on monomer conversion and particle size. Effect of pH on equilibrium swelling of hydrogels was studied by dynamic light scattering and hydrogels showed pH-independent swelling behavior in a broad range of pH values. We also reported and discussed the crosslink density distribution in nanogels prepared by inverse microemulsion polymerization.     

Chromatography of Suspensions. An Absolute Particle Size Detector Based on Turbidity-Spectra Analysis

Abstract

Herein is reported the theoretical basis for an absolute particle size detector based on turbidity-spectra analysis for the chromatography of spherical suspensions in the submicron range. A suitable detector for this purpose would be a variable wavelength spectrophotometer with very rapid scan in the wavelength range, 200–900 nm. It is proposed that such a detector be used with a liquid chromatograph which separates a spherical particle suspension according to size. An absolute detector of this kind would, to a large extent, overcome limitations of the chromatographic technique such as relatively poor resolution, flow rate variations and the lack of a particle diameter-retention volume calibration curve.     

Analyse Hydrometallurgique et Caracterisation de Miner Secondaires

Abstract

Two copper ores (containing between 1% and 2% of the metal) were analyzed by UV emission spectroscopy, infrared spectroscopy and X-ray diffraction yielding - per se - inconclusive results. The ores were subsequently classified by particle size into three “granular fractions”. Determination of copper, dissolved from each fraction by anaerobic and aerobic digestion with 5% aqueous sulphuric acid, produced illuminating information on the presence of sulfide-and oxide-type copper compounds. Fractionation was further refined by magnetic separations.     

Polymer-Protected Palladium Nanoparticles and Their Use in Catalysis

Abstract

Stable palladium colloids were prepared by the in-situ reduction of palladium chloride (PdCl₂) in the presence of protective water-soluble polymers and cationic polyelectrolytes. The particle sizes, morphologies, and particle-size distributions were determined by transmission electron microscopy and found to be in the nanometer size range. The catalytic activity of these colloidal metal-polymer systems was tested by the hydrogenation of cyclohexene as a model reaction. Most of the polymer-protected palladium nanoparticles were found to be catalytically active, and final conversions up to 100% were obtained in many cases.     

Particle size distribution of major inorganic species in atmospheric aerosols from Majorca (Spain)

Atmospheric aerosols collected by means of a cascade impaction system at the campus of the University of the Balearic Islands (Majorca, Spain) from November 1993 to February 1994 were analysed for chloride, nitrate, sulphate, ammonium, calcium, magnesium, sodium and potassium. Based on particle size distribution, the species studied were classified into three groups: (a) concentration decrease with particle size (sulphate and ammonium), (b) concentration increase with particle size (chloride, calcium, magnesium and sodium), and (c) independent of particle size (nitrate and potassium). A principal component analysis (PCA) revealed a clear relationship between particle size and analyte origin. Also, the origin of sulphate and potassium fine and coarse particles was found to be different.     

A Novel in situ Cascade Ultrafiltration Unit Specifically Designed for Field Studies of Anoxic Waters

Abstract

The effect of sample handling and the experimental conditions used during a filtration experiment are critical factors, which must be assessed, if truly representative size distributions of natural particulates are to be obtained. This is particularly the case when colloidal sized, reactive (coagulation, oxidation, precipitation) species such as those found in anoxic lake waters are investigated. Furthermore, such samples are generally rich in both H₂S and CO₂ and losses by volatilization may alter the pH and lead to changes in the species distribution between the dissolved, colloidal and particulate species. In this paper, we describe a submersible in situ cascade ultra-filtration unit which has been specifically developed to enable the study of particle size distributions in situ. This system has been used to investigate the particle size distributions of colloidal sized iron and manganese species in oxygen depleted and totally anoxic reduced water strata found in a well stratified hypereutrophic lake (Lake Bret, Vaud, Switzerland).     

High Performance Size Exclusion Chromatography on Microparticulate Silicas and its Application to Forensic Analysis

Abstract

Size exclusion chromatography (SEC) on irregular silicas of 5–10 um particle size and 60–130 Å average pore size is shown to provide a rapid method for the comparison of a variety of forensically significant samples. Use of dual detectors (UV/fluorescence of UV/Refractive Index) was found to enhance the value of the technique for forensic screening.     

Nanoemulsion of Myrtus communis essential oil and evaluation of its larvicidal activity against Anopheles stephensi

PurposeExcessive use of chemical insecticides has caused environmental pollution and vector resistance. Herbal essential oils with larvicidal properties are good alternatives to synthetic insecticides.mIn this study, larvicide properties of Myrtus communis essential oil and its nanoemulsion against Anopheles stephensi were investigated.MethodsComponents of Myrtus communis essential oil were identified by GC–MS. Nanoemulsion of essential oil was made with Tween 80, Span 20, and water. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) determined particle size and morphology of nanoemulsions. The larvicide activity compared with bulk essential oil.ResultsA total of 107 M. communis essential oil compounds were discovered. The morphology of a selected nanoemulsion was spherical. LC₅₀ and LC₉₀ of M. communis essential oil were calculated as 26.1 and 46.2 µg/ml, respectively. The larvicide activity of nanoemulsion increased by 40% compared to the bulk essential oil. The nanoemulsion's larvicide activity (100%) lasted up to 3 days, while the essential oil had larvicide properties only for up to 24 h.ConclusionsMyrtus communis essential oil was found to be an effective larvicide and classified as an active larvicide. The residual efficacy of the nanoformulation of M. communis significantly increased compared with the bulk essential oil.     

Nano Silicon from Nano Silica Using Natural Resource (Rha) for Solar Cell Fabrication

Abstract

High purity (～99%) nano silica with an average particle size of ～100 nm was extracted at pH 3 at 650°C from a natural resource, rice husk, using alkaline extraction followed by acid precipitation method. Using nano silica as a precursor, silicon (Si) nanoparticles have been synthesized by high-temperature magnesiothermic reduction method. The prepared sample was characterized by X-ray diffraction, particle size analyzer, Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray fluorescence analyzer, and UV–Vis spectroscopy. The comprehensive characterization studies indicate the pure phase formation of Si and the variation of particle size from 70 nm to 100 nm for samples synthesized at different sintering temperatures. Moreover, the silicon nanoparticles produced at 850°C have pure phase formation, high purity, and good absorption peaks. The efficiency calculated through IV characteristics is found to be increasing in silicon and ruthenium combination (2.67%), which is better than that achieved from the conventional solar cells. The produced silicon nanoparticles could be applied as an anode material for solar cell fabrication.     

Separation and Dispersion in Sedimentation Field-Flow Fractionation

Abstract

Contributions of separation and dispersion to the total zone width of a polydisperse latex sample under various flow rates and retentions were studied. Both the direct flow and the reverse flow techniques were employed and the experimental results were compared with theoretical relationships. The results showed a good agreement between the theory and the experiment under different conditions. A good agreement between the mean particle diameters calculated from our experimental data and those given by the producer was found. The width of the particle size distribution characterized by the standard deviation was found about two fold higher than that given by the producer.     

Emulsion polymerization. IV. Experimental verification of the theory based on slow termination rate within latex particles

A large body of data shows that the time dependence of conversion fits the equation P = At² + Bt in the interval where, according to the Smith-Ewart model, the relationship should be linear. For latexes of very small particle size the Smith-Ewart linear relationship (P = Bt) is often observed, and for latexes of very large particle size the conversion was found to be proportional to t². The experimental value of parameter B was in good agreement with independent theoretical predictions. From A and B the ratio between termination and propagation constants was calculated and was in the 5–200 range. Independent estimates of this ratio give the same order of magnitude. These independent estimates are from the literature and are obtained from the increase in conversion rate at catalyst post-addition during emulsion polymerization or from emulsion polymerization initiated by intermittent irradiation or from homogeneous polymerization in the presence of inert polymers of high viscosity. The conversion–time curves describing the whole conversion process generally have sigmoid shape. The molecular weight is often found to pass through a maximum as the conversion increases. In one experiment this maximum coincided with the calculated maximum in the average number of radicals per particle Q. The variation of experimental molecular weights with conversion accurately followed the theoretical predictions. The deviation from the Smith-Ewart model was often significant. The value of Q was not 0.5, as the Smith-Ewart model requires it to be, but often reached values much larger, as large as 10. The particle size distribution broadened with increasing conversion and became increasingly skew. Numerous data taken from the literature are in good quantitative or qualitative agreement with the theory proposed in Part III and for these data the observed deviations from the Smith-Ewart theory are readily explainable. The new data obtained with styrene, n-butyl methacrylate, and methyl methacrylate are also in quantitative agreement with the new theory. One experiment involving methyl methacrylate is analyzed in great detail. The variation of time, of Q, of molecular weight, of average particle size, and of particle size distribution with conversion are reported. The molecular weight distribution is also calculated from the conversion dependence of molecular weight.     

Behavior of Starches Derived from Varieties of Maize Containing Different Genetic Mutations. III. Effects of Biopolymer Source on Starch Characteristics Including Paste Clarity

Abstract

Starch was extracted from three mutant maize genotypes (waxy, (wx), waxy shrunken 1 (wxsh1), and dull waxy (duwx). Each starch was found to have distinct physical and functional properties. Starch from wxsh 1 was found to have a slower rate of retrogradation, enhanced freeze-thaw stability, and greater clarity when compared to either wx or duwx. This clarity was stable over time. Neither the degree of clarity of the wxsh 1 paste nor its stability was affected by the presence of salt or sugar. Starch from several different backgrounds containing duwx produced during several growing seasons, had a smaller particle size distribution than either wx or wxsh1. Starch especially from duwx, had a distinct Brabender Visco-Amylograph profile.     

Amino Acid and Poly(Ethylene Glycol) Based Self-Organizing Polymeric Systems: Chemo-Enzymatic Synthesis and Characterization

A chemo/regio selective enzymatic methodology has been designed to synthesize amphiphilic copolymers based on amino acid diesters and poly(ethylene glycol) [PEG]. The condensation polymerization was catalyzed by immobilized Candida antarctica lipase B (Novozyme 435) under solvent-less conditions. The synthesized polymers 3a–c were derivatized with long chain acid chlorides by chemical acylation to get the amphiphilic polymers 4a–c. The physical properties of the synthesized amphiphilic polymers viz: aggregation number, critical micelle concentration (CMC), radius of gyration (R_g), hydrodynamic radius (R_h) and particle size distribution were studied by static and dynamic light scattering (SLS and DLS) techniques. The polymers were found to be promising in drug delivery applications.     

Product distribution for flash pyrolysis of cellulose in a coil pyrolyzer

Objectives of this study were to (1) examine the performance of a commercial coil pyrolyzer as a flash pyrolysis instrument, (2) determine product distribution from cellulose under flash pyrolysis conditions, and (3) investigate the effect of cellulose type, particle size, heating rate, heating time, and final or soaking temperature on the distribution.It was found that the pyrolysis behavior of the products could be classified into two groups according to their similarity with the production of CO or CO₂. In the former, yield was an exponential function of weight loss, whereas in the latter, yield was an arithmetic function of weight loss. In the range studied, particle size and heating rate did not influence yield or its weight loss behavior. The type of cellulose, mainly degree of polymerization, influenced yield but not behavior.     

Semibatch Emulsion Polymerization of Butyl Acrylate: Effect of Functional Monomers

Abstract

The concentration of sodium lauryl sulfate (SLS) in the initial reactor charge is the most important parameter in determining the latex particle size during semibatch emulsion polymerization of butyl acrylate in the presence of acrylic acid (AA), methacrylic acid, or hydroxyethyl methacrylate. The final latex particle size decreases with increasing concentration of SLS, NP-40, or functional monomer. The carboxylic monomer AA is the most efficient functional monomer to nucleate and then stabilize the latex particles. The plot of log N _f vs log SLS shows a slope of 0.4–0.8, which is more consistent with Feeney's analysis based on the coagulative nucleation mechanism. Experimental data also show that the particle size first decreases to a minimum and then increases with an increase in the concentration of the neutralizing agent NaHCO₃. The optimal concentration NaHCO₃ for achieving the smallest latex particle size occurs at a point close to 0.15–0.29%. Experimental data of the particle size distribution and molecular weight distribution show that the aqueous phase reaction can play a very important role during the particle nucleation period.     

Effect of trimethylamine on the formation of anatase titania nanoparticles by gel-sol method

The anatase titania particles with controlled size and shape were prepared in large amount in the presence of trimethylamine (TMA) from the hydrolysis of a Ti-triethanolamine (TEOA) complex by gel-sol method. In the absence of TMA, ellipsoidal particles were obtained due to the anisotropic growth caused by the specific adsorption of TEOA onto the crystal planes parallel to the c-axis of a titania particle. TMA acted as a complexing agent of Ti(IV) ion to promote the growth of ellipsoidal particles and then inhibited the anisotropic crystal growth to produce ellipsoids of a low aspect ratio, rather than a shape controller to produce ellipsoids with a high aspect ratio. This may be explained in terms of the weak complexing between TMA (a tertiary amine) and Ti(IV) ion. The particle size was also controlled by seeding of anatase titania. Moreover, the seeding suggested that the rate-determining step of the gel-sol process was not the dissolution of the hydroxide gel, but the deposition of the monomeric precursor from the solution phase. Some cationic surfactants also promoted the particle grown to produce particles with a high symmetry in a similar way to TMA. The text was submitted by the authors in English.     

Morphological silica-supported acid catalyst for esterification of aliphatic fatty acid

Abstract

Silica-supported acid catalysts were synthesized and characterized for composition, morphology, particle size distribution, and crystallinity. The catalysts are used for the esterification of long-chain aliphatic acids with alcohol to produce the corresponding ester. Process parameters such as time, temperature, and solvent ratio influence the conversion of fatty acid to ester. A supported catalyst was found to show higher catalytic activity as compared to the conventional sulfuric acid catalyst.     

Evaluation of the Analytical Potentialities of a Composite Electrode Modified with Molecularly Imprinted Polymers

Abstract

The preparation of a methacrylate polymer molecularly imprinted (MIP) with paracetamol (APAP) was performed. After extraction of the APAP template molecule, the MIPs were incorporated into a graphite–polyurethane (GPU) matrix, and the resulting composites were used to prepare modified electrodes intended to be used in APAP determination. The best results were found using a 2.5% MIP in the GPU electrode and a 500-µm MIP particle size. This electrode was used in the determination of APAP in pharmaceutical formulations, reaching a 6.7 × 10^?8 mol L^?1 limit of detection. The 2.5% MIP-GPU-modified electrode showed better sensitivity than the nonimprinted methacrylate GPU-modified electrodes. Interference of phenacetin in the APAP response decreased remarkably when the proposed electrode was used.     

Fabrication of polyvinyl alcohol/chitosan oligosaccharide hydrogel: physicochemical characterizations and in vitro drug release study

Abstract

Hydrogel composites from polyvinyl alcohol and chitosan have been developed by various researchers as a function of their composition for various medical applications. Although, the solubility of chitosan in acidic solvents may limit its wide bioengineering applications. In this article, we demonstrate that polyvinyl alcohol-chitosan oligosaccharide (water soluble) to develop cross-linked hydrogel network using chemical cross linker. X ray diffraction, Fourier transform infrared spectroscopy, and wettability study of these hydrogels were also performed. Lomefloxacin drug was loaded into the hydrogels and its release profile was studied.