High Cation Exchange Capacity Research Articles

Fabrication and optical properties of photochromic compound/clay hybrid films

A cationic spiropyran iodide derivative (SPI) was synthesized as a photoresponsive compound, and SPI/montmorillonite clay hybrid films were prepared using ion- and guest-exchange intercalation methods. When the ion-exchange method was applied to clay with a low cation-exchange capacity (CEC), intercalation of SPI into clay interlayers did not occur. Using the clay with a high CEC, SPI was intercalated into clay interlayer and the interlayer distances were elongated. Upon UV and visible light irradiation, SPI in hybrid film photoisomerized reversibly and the interlayer distance also changed reversibly. On the other hand, intercalation by the guest-exchange method using cethyltrimethylammoniumbromide (CTAB) as a pre-exchanging reagent was independent on the CEC. After the addition of SPI, the CTAB in the clay interlayers was exchanged for SPI, but a partial CTAB remained in the interlayer. SPI in the hybrid films prepared by the guest-exchange method photoisomerized reversibly without any change in interplanar distance due to the coexisted CTAB.

Zeolite from alkali modified kaolin increases NH 4+ retention by sandy soil: Column experiments

Sandy soils have low water and nutrient retention capabilities so that zeolite soil amendments are used for high value land uses including turf and horticulture to reduce leaching losses of NH 4 + fertilisers. MesoLite is a zeolitic material made by caustic treatment of kaolin at 80–95 °C. It has a moderately low surface area (9–12 m 2/g) and very high cation exchange capacity (494 cmol(+)/kg). Laboratory column experiments showed that an addition of 0.4% MesoLite to a sandy soil greatly (90%) reduced leaching of added NH 4 + compared to an unamended soil and MesoLite is 11 times more efficient in retaining NH 4 + than natural zeolite. Furthermore, NH 4-MesoLite slowly releases NH 4 + to soil solution and is likely to be an effective slow release fertiliser.

Biosorption of chromium, copper and zinc by wine-processing waste sludge: Single and multi-component system study

Wine-processing waste sludge (WPWS) has been shown to have powerful potential for sorption of some heavy metals (i.e., chromium, lead and nickel) in single-component aqueous solutions. But although most industrial wastewater contains two or more toxic metals, there are few sorption studies on multicomponent metals by WPWS. This study has two goals: (i) conduct competitive adsorption using Cr, Cu and Zn as sorbates and examine their interaction in binary or ternary systems; and (ii) determine the effects of temperature on the kinetic sorption reaction. The sludge tested contained a high amount of organic matter (38%) and had a high cation exchange capacity (CEC, 255 cmol c kg −1). Infrared analysis reveals that carboxyl is the main functional group in this WPWS. The 13C NMR determination indicates alkyl-C and carboxyl-C are major organic functional groups. At steady state, there are about 40.4% (Cr), 35.0% (Cu) and 21.9% (Zn) sorbed in the initial 6.12 mM of single-component solutions. Only pseudo-second-order sorption kinetic model successfully describes the kinetics of sorption for all experimental metals. The rate constants, k 2, of Cr, Cu and Zn in single-component solutions are 0.016, 0.030 and 0.154 g mg −1 min −1, respectively. The sorption of metals by WPWS in this competitive system shows the trend: Cr > Cu > Zn. Ions of charge, hydrated radius and electronic configuration are main factors affecting sorption capacity. The least sorption for Zn in this competitive system can be attributed to its full orbital and largest hydrated radius. Though the effect of temperature on Zn sorption is insignificant, high temperature favors the other metallic sorptions, in particular for Cr. However, the Cr sorption is lower than Cu at 10 °C. The Cr sorption by WPWS can be higher than that of Cu at 30° and 50 °C.

Optimization of the mechanical properties of polypropylene-based nanocomposite via the addition of a combination of organoclays

The properties of polypropylene (PP) nanocomposites are dependent on the quaternary ammonium salt in the montmorillonite (MMT). A nanocomposite with C-15A, which has a high cation exchange capacity (CEC), exhibits an increase in its impact properties, while one prepared with C-20A, which has a low CEC, shows an increase in the flexural modulus. In order to obtain enhancements in both properties, PP nanocomposites were prepared using a combination of 1:1 of C-15A/C-20A. X-ray, TEM, thermal properties, dynamical mechanical analysis (DMA), and mechanical tests were used to evaluate the properties of this novel mixture. Nanocomposites of partially exfoliated morphology were obtained, especially when 5 wt% of poly(propylene- graft-maleic anhydride) (PP-g-MA) was used. The mechanical tests showed that the use of a 1:1 mixture of C-15A/C-20A caused a simultaneous gain of approximately 12% in flexural modulus and a five times higher impact strength. In addition, the dispersion of the clay was more homogeneous, with the absence of agglomerated structures that were present when either the individual C-15A or C-20A was used. The DMA results showed that while the organoclay improved the modulus of PP, the T g was decreased slightly.

PH-dependent ciprofloxacin sorption to soils: Interaction mechanisms and soil factors influencing sorption

A study of ciprofloxacin sorption to 30 soils from the eastern United States revealed a statistically significant effect of pH on the solid–water distribution coefficient ( K d). Cation exchange capacity was the key soil factor influencing the extent of sorption at all pH values (3–8), with soil metal oxide content playing a smaller role at higher pH. Although, cation exchange, cation bridging and surface complexation mechanisms all appeared to contribute to the net extent of ciprofloxacin sorption to soils, the ciprofloxacin molecule appeared to be best suited for cation exchange. Notably, the ciprofloxacin cation (dominant at pH ≤ 5) exhibited a greater potential for cation exchange than the net neutral zwitterion (relevant at pH > 6). In addition to ciprofloxacin speciation in aqueous solution, the availability of surface sites for cation exchange (cation exchange capacity) and surface complexation (metal oxide content) played a key role in determining the shape of the pH edge and the potential contributions from individual sorption mechanisms to the net extent of sorption. Soils not limited by the availability of cation exchange sites and possessing a high effective cation exchange capacity (ECEC > 20 cmol c/kg), exhibited distinct pH edges (general decrease in sorption with pH) and the highest extent of sorption at all pH values. In these soils, cation exchange was found to be a dominant mechanism of sorption, with potential contributions from cation bridging and surface complexation being either unimportant or not discernable. In soils of lower cation exchange capacity (ECEC < 20 cmol c/kg), limited with respect to the availability of cation exchange sites, sorption initially increased with increasing pH, peaked at pH 5.5 and decreased at pH 7–8. In these soils, a specific contribution from surface complexation to the net extent of sorption was surmised at high pH values in metal oxide-rich soils, possessing low cation exchange capacities.

Bacterial Community Composition in Brazilian Anthrosols and Adjacent Soils Characterized Using Culturing and Molecular Identification

Microbial community composition was examined in two soil types, Anthrosols and adjacent soils, sampled from three locations in the Brazilian Amazon. The Anthrosols, also known as Amazonian dark earths, are highly fertile soils that are a legacy of pre-Columbian settlement. Both Anthrosols and adjacent soils are derived from the same parent material and subject to the same environmental conditions, including rainfall and temperature; however, the Anthrosols contain high levels of charcoal-like black carbon from which they derive their dark color. The Anthrosols typically have higher cation exchange capacity, higher pH, and higher phosphorus and calcium contents. We used culture media prepared from soil extracts to isolate bacteria unique to the two soil types and then sequenced their 16S rRNA genes to determine their phylogenetic placement. Higher numbers of culturable bacteria, by over two orders of magnitude at the deepest sampling depths, were counted in the Anthrosols. Sequences of bacteria isolated on soil extract media yielded five possible new bacterial families. Also, a higher number of families in the bacteria were represented by isolates from the deeper soil depths in the Anthrosols. Higher bacterial populations and a greater diversity of isolates were found in all of the Anthrosols, to a depth of up to 1 m, compared to adjacent soils located within 50-500 m of their associated Anthrosols. Compared to standard culture media, soil extract media revealed diverse soil microbial populations adapted to the unique biochemistry and physiological ecology of these Anthrosols.

The temporal evolution of pedogenic Fe–smectite to Fe–kaolin via interstratified kaolin–smectite in a moist tropical soil chronosequence

Fe-rich kaolins in soils of a terrace chronosequence in the moist tropics of Costa Rica are derived from the transformation of smectite via interstratified kaolin–smectite (K–S). The smectite is ferruginous smectite (10.1 ± 3.7% Fe 2O 3) that forms early during pedogenesis from basaltic–andesitic parent material and is the dominant mineral in < 5 ka soils. Interstratified K–S with 60–90% kaolin layers is the dominant mineral in 10 ka soils, while 125 ka soils contain a physical mixture of Fe–kaolin (6.0 ± 1.9% Fe 2O 3) and K–S with > 80% kaolin layers. K–S is indicated by X-ray diffraction (XRD) data that reveal asymmetric 001 peaks between 17.5 and 17.8 Å (ethylene glycol-solvated) and irrational 00 l peaks that exhibit Méring-like behaviour, and by transmission electron microscopy–analytical electron microscopy (TEM–AEM) data that document single crystals of K–S with compositions intermediate to those of end-member crystals of smectite and kaolin. Lattice fringe images from high resolution TEM (HRTEM) show lateral transitions from smectite layers to kaolin layers via a cell-preserved, layer-by-layer transformation mechanism, and changes in the compositions of tetrahedral and octahedral sheets, notably decreases in octahedral Fe and Mg and tetrahedral Al, indicate that the reaction is accompanied by localized dissolution of smectite 2:1 layers that proceeds laterally. Fourier transform infrared (FTIR) and XRD data indicate that kaolin layers are a mixture of kaolinite and halloysite, and differential thermal analysis–thermogravimetry (DTA–TG) combined with data from XRD and TEM–AEM indicate the development of Al-hydroxy-interlayers in K–S with time. The soil-forming factors that appear to control formation of K–S are (1) basaltic–andesitic parent that produces high concentrations of base cations and Si in young (< 5 ka) soils, and (2) moist tropical climate (3085 mm MAP, 27.3 °C MAT) with a short dry season that fosters formation of smectite in < 5 ka soils. By 125 ka, soils are dominated by Fe–kaolin and K–S, helping to constrain reaction rate. The relatively high cation exchange capacity (CEC) of the Fe-rich kaolins (18 ± 12 cmol c/kg) relative to many tropical kaolinites is attributed to small amounts of octahedral Mg and tetrahedral Al inherited from precursor ferruginous smectite layers. Accordingly, the origin (from smectite) and relatively high CEC of the K–S and Fe–kaolin has potentially important implications related to clay mineral reactions and elemental cycling in moist tropical soils.

Nutrient and Chemical Properties of Aging Golf Course Putting Greens as Impacted by Soil Depth and Mat Development

Nutrient and chemical changes in turfgrass sand-based root zones are not well understood. This study was conducted to characterize nutrient and chemical properties in putting greens influenced by root zone mixture and establishment treatment, putting green age, and soil depth. Putting greens were constructed and established with Agrostis stolonifera L. in sequential years from 1997 to 2000. Treatments included root zone mixtures of 80:20 (v:v) sand and sphagnum peat and 80:15:5 (v:v:v) sand, sphagnum peat, and soil, and accelerated versus controlled establishment. In the establishment year, the accelerated treatment received 2.6-, 3.0-, and 2.6-fold more nitrogen, phosphorus, and potassium, respectively, than the controlled treatment. Soil samples were taken in Fall 2001, Spring 2004, and Summer 2004 and were analyzed for nutrient and chemical properties such as pH, cation exchange capacity (CEC), organic matter (OM), total soluble salts (TSS), and 12 nutrients. The root zone mixture and establishment treatments had minimal effects on most nutrient and chemical properties with the exception of phosphorus and pH. Cation exchange capacity, OM, TSS, and all nutrients decreased with soil depth, whereas soil pH increased. The putting green age × soil depth interaction was significant for many of the nutrient and chemical properties, but separating soil samples into mat and original root zone instead of predetermined soil sampling depths eliminated most of these interactions. The mat layer had higher CEC and OM values and nutrient concentrations and lower pH values than the original root zone mixture.

Assessment of Ecotoxicity of Topsoils from a Wood Treatment Site

Abstract A series of 9 soil samples were taken at a timber treatment site in SW France where Cu sulphate and chromated copper arsenate (CCA) have been used as wood preservatives (Sites P1 to P9) and one soil sample was collected at an adjacent site on the same soil type (Site P10). Copper was a major contaminant in all topsoils, varying from 65 (Soil P5) to 2600 mg Cu kg −1 (Soil P7), exceeding background values for French sandy soils. As and Cr did not accumulate in soil, except at Site P8 (52 mg As kg −1 and 87 mg Cr kg −1) where CCA-treated posts were stacked. Soil ecotoxicity was assessed with bioassays using radish, lettuce, slug Arion rufus L., and earthworm Dendrobaena octaedra (Savigny). There were significantly differences in lettuce germination rate, lettuce leaf yield, radish root and leaf yields, slug herbivory, and earthworm avoidance. An additional bioassay showed higher negative impacts on bean shoot and root yields, Rhizobium nodule counts on Bean roots, and guaiacol peroxidase activity in primary Bean leaves for soil from Site P7, with and without fertilisation, than for soil from Site P10, despite both soils having a similar value for computed free ion Cu 2+ activity in the soil solution (pCu 2+). Beans grown in soil from Site P7 that had been fertilised showed elevated foliar Cu content and phytotoxic symptoms. Soils from Sites P7 (treatment plant) and P6 (storage of treated utility poles) had the highest ecotoxicity, whereas soil from Site P10 (high organic matter content and cation exchange capacity) had the lowest. Except at Site P10, the soil factor pCu 2+ computed with soil pH and total soil Cu could be used to predict soil ecotoxicity.

Polypropylene/clay nanocomposites: Effect of different clays and compatibilizers on their morphology

AbstractA set of organically modified clays (OLS) were mixed with different compatibilizers to alter their interactions with either homopolymer or heterophasic polypropylenes when they were melt‐mixed, and the relation between the OLS/compatibilizer system and the composite morphology was studied. X‐ray diffraction (XRD) showed that depending on the specific OLS/compatibilizer system, it is possible to obtain several morphologies in the composites. In particular, some samples prepared with compatibilizers based on itaconic acid and OLSs, which had the highest cation exchange capacity and were organically modified with a set of quaternary ammonium salts, presented longer clay interlayer distances than the original OLSs, whereas other composites showed a clay collapse associated with shorter interlayer distances. Moreover, some composites presented both kinds of morphologies together. By means of diffuse reflectance spectroscopy and thermogravimetric analysis, it was possible to show that the OLSs were stable under the operating conditions, so the decrease in the interlayer distance found in some samples was not related to degradation processes. On the other hand, high‐resolution transmission electron microscopy (HR‐TEM) showed that collapsed clays were formed by tactoid and immiscible structures with poor dispersion in the polymer matrix. However, samples with intercalate state from XRD presented very well dispersed multilayer stacks about 10 nm thick. Finally, those samples with both collapsed and intercalate morphologies presented tactoid and immiscible structures together with well dispersed multilayer stacks in the corresponding HR‐TEM images. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Ion Exchange Functional Nanofibers

AbstractWe have synthesized a series of ion exchange functionalized fibers (IXF) from polystyrene (PS) and polyacrylonitrile (PAN). To obtain strong-acid cation exchange fibers, polystyrene was sulfonated using specific sulfonation protocols. Micron sized fibers (average diameter of 100m) were then produced from the functionalized polystyrene using a single-screw extruder equipped with a 30 hole spinneret with orifice diameter of 0.5 mm with a precise screw speed of 5 rpm, pump speed of 15 rpm, and with a feed rate of 2.4 cc/min. The extruder zone temperature was kept at 250 – 270 °C. Fiber was drawn at 120 degree with a draw ratio of 2. Electrospinning of functionalized polystyrene was also carried out to produce ultrafine functionalized fibers of 100 nm in average diameter. We have also electrospun polystyrene and polyisoprene blended nanofibers to increase the strength of the resulting blend nanofibers compared to pure PS nanofibers. To synthesize weak-acid cation exchange fibers polyacrylonitrile (PAN) was electrospun and the nanofibers obtained were alkaline hydrolyzed with 2 N NaOH for 20 minutes at room temperature to convert nitrile bonds to carboxylate. Cation exchange capacity (CEC) of the microfibers and nanofibers was determined. Sulfonated PS microfibers show high CEC of 4.0 meq/gm compared to that of nanofibers with 2.5 meq/gm. CEC of blended nanofibers of PS and polyisoprene was 2.0 meq/gm. In case of PAN fibers, nanosized electrospun fibers were found to show a CEC of 1.5 meq/gm. Weak-base anion exchange fiber synthesis was undertaken using appropriate protocol and its CEC was measured. For all IXF synthesized, fiber diameter was measured using SEM, degree of functionalization was qualitatively determined using FTIR and ion exchange capacity was computed after mass balance on a binary exchange system after equilibrium.

Differential behaviour of combustion and gasification fly ash from Puertollano Power Plants (Spain) for the synthesis of zeolites and silica extraction

Coal gasification (IGCC) and pulverised coal combustion (PCC) fly ashes (FAs), obtained from two power plants fed with the carboniferous bituminous coal from Puertollano (Spain), were characterised and used as raw materials for zeolite synthesis by direct conversion (DC) and by alkaline fusion (Fu), and SiO 2 extraction (Si-Ex) at laboratory scale. The Puertollano FAs are characterised by a high SiO 2 content (59%) with respect to EU coal FAs. High zeolite synthesis yields were obtained from both FAs by using conventional alkaline activation. However, the Si extraction yields were very different. The results of the zeolite synthesis from the Si-bearing extracts from both FAs demonstrated that high purity zeolites with high cation exchange capacity (CEC, between 4.3 and 5.3 meq/g) can be produced. The solid residue arising from Si-Ex is also a relatively high NaP1 zeolite product (CEC 2.4–2.7 meq/g) equivalent to the DC products. The zeolitic materials synthesised from both FAs by Fu showed an intermediate (between the high purity zeolites and the DC products) zeolite content with CEC values from 3.4 to 3.7 meq/g. Low leachable metal contents were obtained from high purity A and X zeolites and zeolite material synthesised by Fu for PCC FA.

Agronomic and economic performance of reservoir sediment for rehabilitating degraded soils in Northern Ethiopia

Nutrient export through sediment is, often, not given due attention in improving the fertility of soils. A Randomized Complete Block Design (RCBD) (replicated three times) was conducted to assess the effect of sediment, collected from a microdam, on the yield of a local wheat cultivar (Triticum aestivum) grown on a Luvisol and a Vertisol during cropping season of 2003 and 2004 in Tigray, Ethiopia. In the first season, the treatments consisted of applying 34.3 Mg sediment ha−1 (T1), 0.1 Mg urea ha−1 (T2), 4 Mg manure ha−1 (T3) and a control plot (T4). The experiment was repeated in the 2004 cropping season using the same indicator crop but without the use of T1 and T3 inputs to evaluate the residual effect of these treatments on crop productivity. Plant height, plant density, spike length, straw and grain yield were compared among the treatments. After harvest, surface soil (0–25 cm) samples were taken and analyzed for total Nitrogen (Ntot), available Phosphorous (P), Soil Organic Carbon (SOC), Cation Exchange Capacity (CEC), and porosity to examine treatments effect on these soil properties. Higher CEC, exchangeable bases, SOC, Ntot, available P and micronutrients except Cu characterized sediment compared to the two soils used. Application of sediment increased the average grain and straw yield of wheat by 72% and 12%, respectively, in the Luvisol, and by 38% and 23%, respectively, in the Vertisol relative to the control. However, the application of sediment didn’t change the physicochemical properties of the Vertisol, but in the Luvisol CEC and available P were increased significantly. Like manure, sediment provided marginal rate of return above the minimum acceptable value (100%) by farmers, demonstrating the potential of these resources to improve degraded soils and boost farmers’ income.

Distribution of fungi and bacteria in the soils of the University of Ilorin Teaching and Research Farm

The occurrence of fungi and bacteria in Afon, Tanke, Badi, Bolorunduro and Ilemona soils of the University of Ilorin Teaching and Research Farm and the impact of some physicochemical properties of the soils on distribution of microorganisms were studied. The soil dilution technique was used to isolate bacteria and fungi on Nutrient Agar and Potato Dextrose Agar Plates respectively. Cultural and microscopic characteristics were employed in the identification of isolates. The population density of fungi in the soils was in the order Afon > Ilemona > Tanke > Bolorunduro > Badi series while that of bacteria was in the order of Afon > Tanke > Bolorunduro > Badi > Ilemona series. The high microbial load of Afon series was attributed to a combination of factors such as its relatively high organic matter content (0.20%) and Effective Cation Exchange Capacity (9.93), the sandy loam texture and the pH (5.7). A variety of fungal and bacterial species associated with nitrogen fixation and organic matter decomposition were isolated from all the soils. The mycoflora of Ilemona soil was dominated by saprophytic Aspergillus spp while plant pathogenic moulds such as Colletotrichum and Fusarium species occurred frequently in the other soils. The frequency of occurrence of Colletotrichum sp in Afon was 52%, while Fusarium spp was 87% in Badi, 36% in Tanke and 5% in Bolorunduro. The occurrence of enteric bacteria in high numbers in Bolorunduro and Ilemona soils was attributed to the presence of grazing cattle in the farmlands. It was concluded that for optimum crop yield, Afon, Badi, Tanke and Bolorunduro soils need to be treated with appropriate fungicides before the cultivation of crops. JARD Vol. 4 (2) 2005: pp. 218-227

Influence of silica fume on the desiccation cracks of compacted clayey soils

Clayey soils containing smectites are widely used for construction of liner and cover systems to reduce the hydraulic conductivity in geotechnical applications because of their low permeability and high cation exchange capacity. However, the compacted clayey soils crack on drying because of their high swelling potential, and their hydraulic conductivities increase. To solve this problem, it is essential to stabilize the clayey soils using additive materials. The aim of this study is to examine the suitability of silica fume as a stabilization material to reduce the development of desiccation cracks in compacted clayey liner and cover systems. Natural clayey soil and clayey soil–silica fume mixtures were compacted at the optimum moisture content and subjected to laboratory tests. The results show that silica fume decreases the development of desiccation cracks on the surface of compacted samples. We concluded that silica fume waste material can be successfully used to reduce the development of desiccation cracks in compacted clayey liner and cover systems.

Greenhouse Gas Emissions from Two Soils Receiving Nitrogen Fertilizer and Swine Manure Slurry

The interactive effects of soil texture and type of N fertility (i.e., manure vs. commercial N fertilizer) on N(2)O and CH(4) emissions have not been well established. This study was conducted to assess the impact of soil type and N fertility on greenhouse gas fluxes (N(2)O, CH(4), and CO(2)) from the soil surface. The soils used were a sandy loam (789 g kg(-1) sand and 138 g kg(-1) clay) and a clay soil (216 g kg(-1) sand, and 415 g kg(-1) clay). Chamber experiments were conducted using plastic buckets as the experimental units. The treatments applied to each soil type were: (i) control (no added N), (ii) urea-ammonium nitrate (UAN), and (iii) liquid swine manure slurry. Greenhouse gas fluxes were measured over 8 weeks. Within the UAN and swine manure treatments both N(2)O and CH(4) emissions were greater in the sandy loam than in the clay soil. In the sandy loam soil N(2)O emissions were significantly different among all N treatments, but in the clay soil only the manure treatment had significantly higher N(2)O emissions. It is thought that the major differences between the two soils controlling both N(2)O and CH(4) emissions were cation exchange capacity (CEC) and percent water-filled pore space (%WFPS). We speculate that the higher CEC in the clay soil reduced N availability through increased adsorption of NH(4)(+) compared to the sandy loam soil. In addition the higher average %WFPS in the sandy loam may have favored higher denitrification and CH(4) production than in the clay soil.

Factors Controlling the Membrane Efficiency of Shales When Interacting With Water-Based and Oil-Based Muds

Summary This paper presents a comprehensive set of experimental data for the membrane efficiency of four shales when interacting with different water-based and oil-based muds. Pressure transmission tests were used to measure the membrane efficiency using three different cations and two different anions at different concentrations (water activities). It was found that the measured membrane efficiencies of shales, when exposed to salt solutions, were low—ranging from 0.18% to 4.23%. Useful correlations are presented between the membrane efficiency and other shale properties. Results suggest that the membrane efficiency of shales is directly proportional to the ratio of the cation exchange capacity and permeability of shales. Higher cation exchange capacities and lower permeabilities correlate very well with higher membrane efficiencies. Moreover, the ratio of the hydrated solute (ion) size to shale pore throat determines a shale's ability to restrict solutes from entering the pore space and controls its membrane efficiency. Cations and anions with large hydrated radii yielded higher membrane efficiencies, compared to ions with small hydrated diameters. Thus, the formulation of drilling fluids must take into account the types of cation and anion in the water-based fluid. It was also found that the membrane efficiency of oil-based muds was high, however, these membrane efficiencies were not 100 % as postulated by many researchers.

Compost Layering Effects on Poultry Litter Leaching: A Column Study

Incorporation of poultry litter (PL) into the nutrient management strategy of crop producers in South-western British Columbia is an important end-use for this agricultural waste product. Environmental and ecological concerns associated with leaching of nutrients by over-winter field storage of PL need to be addressed. To mitigate some of these concerns, some farmers store the manure on a base pad of City of Vancouver yard trimmings compost (YTC), with an additional covering layer of YTC. An outdoor column leaching study was designed to observe the effects of the YTC base pad and covering on the quality of leachate emanating from the PL, as well as to determine the maximum leachability of nutrients from these materials over the storage period. The YTC cover increased (P<0.05) the leaching of nitrogen (N), copper (Cu), and zinc (Zn) from the PL below. The YTC base pad under the PL decreased (P<0.05) the cumulative Cu, Zn and P leached as compared to the PL alone by 50%, 54% and 30%, but had little ability to retain N or soluble salts. Concentrations in the first flush of leachate out of the PL were reduced by the YTC base pad from 25 to 1.3 mg Cu L−1, 11 to 0.95 mg Zn L−1, and 430 to 40 mg P L−1. The high calcium content and cation exchange capacity of the YTC are credited with much of this retention. We recommend that farmers continue to store PL on a base pad of YTC with some improvements, and that the YTC cover is used to isolate the PL from wildlife.

Mineral nutrient economy in competing species of Sphagnum mosses

AbstractBog vegetation, which is dominated by Sphagnum mosses, depends exclusively on aerial deposition of mineral nutrients. We studied how the main mineral nutrients are distributed between intracellular and extracellular exchangeable fractions and along the vertical physiological gradient of shoot age in seven Sphagnum species occupying contrasting bog microhabitats. While the Sphagnum exchangeable cation content decreased generally in the order Ca2+ ≥ K+, Na+, Mg2+ &gt; Al3+ &gt; NH4+, intracellular element content decreased in the order N &gt; K &gt; Na, Mg, P, Ca, Al. Calcium occurred mainly in the exchangeable form while Mg, Na and particularly K, Al and N occurred inside cells. Hummock species with a higher cation exchange capacity (CEC) accumulated more exchangeable Ca2+, while the hollow species with a lower CEC accumulated more exchangeable Na+, particularly in dead shoot segments. Intracellular N and P, but not metallic elements, were consistently lower in dead shoot segments, indicating the possibility of N and P reutilization from senescing segments. The greatest variation in tissue nutrient content and distribution was between species from contrasting microhabitats. The greatest variation within microhabitats was between the dissimilar species S. angustifolium and S. magellanicum. The latter species had the intracellular N content about 40% lower than other species, including even this species when grown alone. This indicates unequal competition for N, which can lead to outcompeting of S. magellanicum from mixed patches. We assume that efficient cation exchange enables Sphagnum vegetation to retain immediately the cationic nutrients from rainwater. This may represent an important mechanism of temporal extension of mineral nutrient availability to subsequent slow intracellular nutrient uptake.

Transport of micelles of cationic surfactants through clinoptilolite zeolite

Natural clinoptilolite is capable of removing metal cations from water due to its high cation exchange capacity. The affinity of the zeolite for cations makes it a good candidate to remove cationic surfactants from water. The transport of hexadecyltrimethylammonium (HDTMA), at a solution concentration greater than its critical micelle concentration (CMC), through zeolite columns of different particle sizes resulted in a retardation factor of 50–60. The capacities of HDTMA sorption at the breakthrough point C B are 82–83 mmol kg −1 at 20–25 PVs and 140–160 mmol kg −1 at 40–45 PVs for the 1.4–2.4 mm and 0.4–1.4 mm zeolite, respectively. While, the capacities of HDTMA sorption at the exhaustion point C E are 185–187 mmol kg −1 at 110–120 PVs and 195–210 mmol kg −1 at 90–100 PVs, for the 1.4–2.4 mm and 0.4–1.4 mm zeolite, respectively. In the early stage of the transport experiment, the HDTMA effluent concentration was close to zero while the counterion Br − concentration was about 50% of the input concentration, indicating a complete removal of HDTMA but only a partial removal of bromide. At any given time, the amount of surfactant removed is about twice that of counterion Br − removed and twice that of metal cations released. The concurrent removal of counterion accompanying surfactant sorption was attributed to HDTMA admicellar sorption by the zeolite, indicating that both cation exchange and hydrophobic bonding are dominant mechanisms for HDTMA removal when its input concentration is greater than the CMC. Therefore, when designing an adsorption bed to remove surfactant from aqueous solutions with concentrations greater than the CMC, partially release of counterion needs to be taken into consideration.