81,956 research outputs found

    Balancing soil nutrient availability on commercial organic farms

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    Soils from two commercial farms were analysed for cation exchange capacities with the aim of improving the balance of available nutrients at soil level, and to support the basic organic principle of maintaining and improving the long-term fertility and microbiological activity of the soil

    Preparation of New Versatile and Implantable Titanate Nanofiber-Bioscaffolds via Efficient Cation Exchanges

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    For the first time in the implantable biomaterials field, efficient hydrothermal cation exchange methods were developed suitable for mass-production of implantable material. The cation exchange conditions were performed by various methods of temperature, pressure, and time exposure. To confirm both chemical and physical alteration of the scaffold, XRD shift analysis, EDX atomic composition, and SEM imaging were conducted. The optimal results are to use aqueous solutions of 0.5 M chloride salts in sealed heated containers at 180 ̊C for eight hours. Cation exchange capacities are determined for K+, Na+, Li+, Ca2+, and Sr2+; future studies demanding durable, highly specific composition of a biocompatible material are needed

    Oxometalate-glass composites and thin films

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    New glass-composites with ion exchange properties have been developed. Ammonium 12-molybdophosphate (AMP) (ΝΗ4)3ΡΜοΐ2θ4ο, and ammonium 12-tungstophosphate (AWP) (Nh4)3PW12O40, known for their ion exchange capabilities, are included either in preformed aerogels with defined pore size, or are added to sol-gel mixtures during the process of gel formation. Characterization is carried out by FTIR, Raman and EXAFS spectroscopy. Ion exchange capacities for the oxometalate precursors are determined for silver and rubidium and are compared to those of the glass composites. Glass composites show high ion exchange capacity, but some portion of the metalate complexes leaches from the glass during the procedure. This is in contrast to thin composite films, which have almost no porosity and do not show loss of metalate. EXAFS spectroscopy demostrates that the oxometalate microstructure is maintained in glass composites and that rubidium ions after ion exchange in glasses occupy similar cation positions as in the precursor compounds

    Determination of Uptake and Release of 2,4-Dichlorophenol on the Nigerian Clay Soil using Gas-Liquid Chromatography

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    The uptake and release of 2,4-dichlorophenol on Nigerian clay soil was studied by introducing varying concentrations of the chlorophenol in 0.01 M aqueous calcium chloride solution at pH 4.5 into pretreated clay (0.6% OM) samples. The clay soil was treated with hydrogen peroxide followed by varying  concentrations of sulphuric acid (0.1, 2.0, 4.0 and 6.0 N). The uptake of 2,4-dichlorophenol was higher for treated clay soil samples with lower cation exchange capacity. The sorption isotherm plots were  non-linear, suggesting that sorption of sorbate onto sorbent is by adsorption mechanism and that charged species are involved. The sorption process was well described by the Freundlich isotherm. Clay soil samples with higher cation exchange capacities released smaller amounts of the adsorbed chlorophenols, therefore retaining close to half of the adsorbed amount due to strong adsorption of the charged species on the clay surface. The clay soils with lower cation exchange capacities released higher amounts of the adsorbed chlorophenols, due to the higher contribution of hydrophobic interaction between organic matter and hydrophobic sites on the clay surface.KEYWORDS: 2,4-dichlorophenol, adsorption, sulphuric acid treatment, hydrophobic interaction, desorption

    Log-derived cation exchange capacity of shaly sands : application to hydrocarbon detection and drilling optimization

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    Researchers at Louisiana State University, LSU, have introduced several petrophysical models expressing the electric properties of shaly sands. These models, to be used for hydrocarbon detection, are based on the Waxman and Smits concept of supplementing the water conductivity with a clay counterions conductivity. The LSU models also utilize the Dual Water theory, which relates each conductivity term to a particular type of water, free and bound, each occupying a specific volume of the total pore space. The main difference between these models and the other shaly sand models is that the counterion conductivity is represented by a hypothetical sodium chloride electrolyte. This study introduces a modified version of early LSU models. This modified model eliminates a questionable assumption incorporated in all previous shaly sand models. Previous models use same formation resistivity factor for all terms in the model. The proposed model considers that the electric current follows the effective porosity path in the term representing the free electrolyte and follows the clay porosity path in the term representing bound water. The differentiation between the two paths is accomplished by using two different formation factors one in the free water and another in the bound water term of the model. It also used two different cementation exponents to express formation factors in terms of porosity. The validity of the new model was checked using cation exchange capacities measured on core samples and drill cuttings. Calculated cation exchange capacities display good agreement with the measured cation exchange capacities. The water saturation calculated using the new model are more representative of hydrocarbon potential of the zones of interest. In addition, cation exchange capacity calculated using this modified model and log data acquired during drilling has shown potential for diagnosis of pending bit balling of PDC bits drilled with water based mud in overpressured shale

    Iminodiacetic acid (IDA) cation-exchange nonwoven membranes for efficient capture of antibodies and antibody fragments

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    There is strong need to reduce the manufacturing costs and increase the downstream purification efficiency of high-value therapeutic monoclonal antibodies (mAbs). This paper explores the performance of a weak cation-exchange membrane based on the coupling of IDA to poly(butylene terephthalate) (PBT) nonwoven fabrics. Uniform and conformal layers of poly(glycidyl methacrylate) (GMA) were first grafted to the surface of the nonwovens. Then IDA was coupled to the polyGMA layers under optimized conditions, resulting in membranes with very high permeability and binding capacity. This resulted in IgG dynamic binding capacities at very short residence times (0.1–2.0 min) that are much higher than those achieved by the best cation-exchange resins. Similar results were obtained in the purification of a single-chain (scFv) antibody fragment. As is customary with membrane systems, the dynamic binding capacities did not change significantly over a wide range of residence times. Finally, the excellent separation efficiency and potential reusability of the membrane were confirmed by five consecutive cycles of mAb capture from its cell culture harvest. The present work provides significant evidence that this weak cation-exchange nonwoven fabric platform might be a suitable alternative to packed resin chromatography for low-cost, higher productivity manufacturing of therapeutic mAbs and antibody fragments

    SIFAT KIMIA TANAH PADA BERBAGAI ZONASI HUTAN MANGROVE DI DESA TUMPAPA KECAMATAN BALINGGI KABUPATEN PARIGI MOUTONG

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    A study was conducted to determine soil chemical properties in zonation of mangrove forest, Tumpapa village, Balinggi district, Parigi Moutong regency, Central Sulawesi.We measured these effects by quantifying some chemical soil analysis were done on soil samples taken at depths 0-60cm. Soil samples were collected from the field by using paralon cylinders at four different zonation; transition zone (Rhizophora apiculata, Bruguiera, Ceriops and Xylocarpus), high tidal zone (Rhizophora apiculata and Bruguiera gymnorhiza), middle tidal zone (Rhizophora apiculata) and low tidal zone (Rhizophora styllosa and Rhizophora mucronata), respectively. The results showed that chemical soil properties in transition zone were pH 7.2, C-organic 0.75%, total N 0.13%, available P 8.68% and cation exchange capacities 22.17 me/100 g. At the high tidal zone were pH 6.4, C-organic 2.46%, total N 0.27%, available P 9.14% and cation exchange capacities 24.16 me/100 g. At the middle tidal zone were pH 6.1, C-organic 2.55%, total N 0.26%, available P 9.32% and cation exchange capacities 24.54 me/100 g. Hence, At the low tidal zone were pH 6.7, C-organic 1.71%, total N 0.15%, available P 10.41% and cation exchange capacities 23.11 me/100 g. Keywords : Zonation, Mangrove forest, Soil chemical properties

    Physico-chemical characterization of dietary fiber sources

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    The physico-chemical characteristics of several dietary fiber sources—wheat bran, corn bran, peanut hull, oatmeal, alfalfa and alpha-cell (cellulose) were studied. All samples were dried in a vacuum-oven and ground until the particles would pass a U.S. Std. Sieve No. 30 but would not pass U.S. Std. Sieve No. 80. The ground samples were analyzed for acid-detergent fiber, acid-detergent lignin, water-holding capacity, bile salt binding, cation-exchange and emulsifying capacities. Proximate analysis of all samples was performed. Based on the results of this experimental study, the following con-clusions were made: Of the six samples, alpha-cell (cellulose) had the highest and oatmeal the lowest acid-detergent fiber content. Peanut hull had the highest and oatmeal the lowest acid-detergent lignin content. There were significant differences among the means of all samples (p\u3c0.05). Among all samples, alfalfa possessed the highest water-holding capacity and oatmeal the lowest. There were significant differences among all means (p\u3c0.05). Alfalfa possessed the highest bile salt binding capacity, followed by oatmeal, but little variation among the means was observed (p\u3c0.05). For cation-exchange capacity oatmeal showed an unusually high cation-exchange capacity, followed by alfalfa. Peanut hull had the lowest cation-exchange capacity. No significant differences among the means of the five groups were observed (p\u3c0.05). As for emulsifying capacity, alfalfa possessed the highest emulsifying capacity. Peanut hull showed the least emulsifying capacity and Duncan\u27s Multiple Range test allowed partitioning of the means into three unique groups (p\u3c0.05). Acid-detergent fiber and acid-detergent lignin did not exhibit strong correlation with any of the functionalities studied. A significant linear relationship was observed between ash and bile salt binding (r = 0.84). No significant relationship was observed among different functionalities (water-holding capacity and bile salt binding, water-holding capacity and cation-exchange capacity and cation-exchange capacity and bile salt binding capacity) except for water-holding capacity and cation-exchange capacity (r = -0.83)

    The Ion Exchange Properties of Monoclinic Zirconia: A Study with Ion Selective Electrodes

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    The amphoteric ion exchange and sorptive properties of monoclinic zirconia are studied here in detail. Microcrystals of zirconia have been prepared and systematically charaterized to give a full understanding of the method for crystal growth. A novel algorithm for calculation of ion exchange capacity employing a single pH electrode is utilized. Results are obtained which support the Donnan model for the exchange process. Anion and cation exchange capacities are shown to be a single valued function of the acid pA or base pB. Reversibility is demonstrated and enchancement of exchange capacity is accomplished through common ion addition. A titration system is developed which incorporates additional ion selective electrodes and includes computer programs for calibration, ion exchange capacity calculations and graphic display of results. This system confirms previous work by showing chloride uptake to match proton uptake. Fluoride uptake by monoclinic crystals of zirconia is revealed to be ten times higher than typical capacities for exchangers of this kind. Again uptake is demonstrated to be reversible, and a single valued function of the acid pHF. Exchange properties of zirconia for fluoride ion are expained by ligand exchange and incorporation in the framework of the oxide

    Radiation-grafted cation-exchange membranes:an initial ex situ feasibility study into their potential use in reverse electrodialysis

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    A variety of radiation-grafted cation-exchange membranes (RG-CEM) were synthesised, using a high-dose rate electron-beam peroxidation method, for an initial evaluation of their applicability to reverse electrodialysis cells (RED, a type of salinity gradient “blue” energy). The RG-CEMs were adequately conductive (to Na+ cations) but without the incorporation of crosslinking co-monomers, the permselectivities were too low (≤80%). In contrast, when ETFE-based RG-CEMs were synthesised with incorporation of 10% mol bis(vinylphenyl)ethane (BVPE) crosslinking co-monomer into the styrene-containing grafting mixture, permselectivities of >90% were obtained without a significant decrease in conductivity. The use of BVPE in the grafting mixture also resulted in the RG-CEMs exhibiting enhanced ion-exchange capacities without any increase in water uptakes (cf. uncrosslinked variants). In contrast, the use of less flexible divinylbenzene crosslinker led to prohibitively large decreases in RG-CEM conductivity. This study highlights that the future development of both radiation-grafted cation-exchange and anion-exchange membranes for RED (and other electrodialysis applications) should utilise flexible crosslinkers (such as BVPE) to ensure adequate permselectivities
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