Fouling of ceramic membranes during microfiltration of model solutions

A model study of the microfiltration of fatty acids (C2 to C8) dissolved in a synthetic ultrafiltrate was performed. Ceramic membranes of 0.1 and 0.2 m were used. Results showed that minerals from the ultrafiltrate were involved in membrane fouling, while fatty acids were poorly rejected.On 0.1 m membranes, modelisation of fouling exhibited two different steps of fouling, a first one due to adsorption of solutes, and a second one involving particles deposit onto the membrane. On 0.2 m membranes, only fouling due to particles deposit was observed in modelisation. Results of fouling and rejection pointed out the great difference between 0.1 and0.2 m membranes.This revised version was published online in October 2005 with corrections to the Cover Date.     

草酸青霉对含钾矿物风化及钾溶出的影响

【目的】探讨含钾硅酸盐矿物在草酸青霉(Penicillium oxalicum)作用下的风化及钾溶出情况。【方法】利用等离子体发射光谱、X-射线能谱、X-射线光电子能谱分析了3种常见含钾硅酸盐矿物(钾长石、白云母和黑云母)在草酸青霉作用后浸出液和矿物表面元素含量的变化;通过X-射线衍射分析矿物晶相结构的变化;采用共聚焦激光扫描显微镜表征了草酸青霉在矿物表面形成的生物膜;测量了培养液中不同碳源与氮源组分对草酸青霉解钾的影响。【结果】草酸青霉对结构稳定的钾长石和白云母风化速率较低,相比而言黑云母容易被风化并释放可溶性钾元素;草酸青霉在矿物表面形成了网状结构的生物膜,有利于微环境的生成及有机酸在其内的富集,促进微环境内钾的释放,强化微生物对矿物的风化作用;草酸青霉对多种碳源及氮源都表现出较好的适用性。【结论】草酸青霉是一种能够促进多种含钾矿物风化和钾溶出的真菌,在堆肥和生物肥料领域具有广泛的应用前景。     

Effect of Immobilizing Substances and Salinity on Heavy Metals Availability to Wheat Grown on Sewage Sludge-Contaminated Soil

The objective of the investigation was to evaluate the effect of immobilizing substances and NaCl salinity on the availability of heavy metals: Zn, Cd, Cu, Ni, and Pb to wheat (Triticum aestivum L.). In greenhouse pot experiment, a sewage sludge amended soil was treated with the following immobilizing substances: three clay minerals (Na-bentonite, Ca-bentonite and zeolite), iron oxides (goethite and hematite), and phosphate fertilizers (superphosphate and Novaphos). The pots were planted with wheat and were irrigated either with deionized or saline water containing 1600 mg L^?1 NaCl. Wheat was harvested two times for shoot metal concentrations and biomass measurements. Metal species in soil solution were estimated using the software MINEQL+.

The addition of metal immobilizing substances to the soil significantly decreased metal availability to wheat. The largest reduction in metal bioavailability was found for bentonites. The irrigation with saline water (1600 mg L^?1 NaCl) resulted in a significant increase in metal chloride species (MCl⁺ and MCl₂ ⁰). The highest metal complexation with Cl occurred for Cd, which was about 53% of its total soil solution concentration. The total concentration of Cd (Cd_T) in soil solution increased by 1.6–2.8-fold due to saline water. The NaCl salinity caused a significant increase in uptake and shoot concentration of Cd for two harvests and small but significant increase in shoot Pb concentration for the second harvest. It was concluded that the use of bentonites is the most promising for the reduction of heavy metal availability to plants. Saline water containing 1600 mg L^{? 1} NaCl increased the availability of Cd and Pb to wheat and decreased the efficiency of bentonites to immobilize soluble Cd.     

Sensory evaluation of fruit quality and nutritional composition of 20 breadfruit (Artocarpus, Moraceae) cultivars

Twenty breadfruit cultivars growing in afield genebank at Kahanu Garden, National Tropical Botanical Garden, Hana, Maui, Hawaii, were evaluated for sensory attributes and nutrient composition. A taste panel scored eight flavor/aroma attributes, five textural attributes, and color. There were significant differences (P ≤ 0.01) in aroma, visual texture, flavor intensity, sweetness, starchiness, moistness, stringiness, firmness, and color. The greatest differences were in color and texture. Nutrient analyses showed significant differences (P ≤ 0.05) for energy, carbohydrates, ash, crude protein, potassium, magnesium, sodium, iron, copper, and zinc. Considering the versatility of breadfruit as a food, its ease of production, and its nutritional value, the numerous good quality flavorful cultivars available should be more widely grown for sustainable agriculture and food security.     

Salt-imposed restrictions on the uptake of macroelements by roots of Arabidopsis thaliana

The aim of this investigation was to identify the growth limiting factors in Arabidopsis thaliana subjected to a mild salt stress. Two natural accessions (Col and N1438) were compared. In spite of their morphological and developmental similarity, they have been previously shown to differ in the response of their superoxide dismutase genes to salt stress (Physiol Plant 132:293–305, 2008). Thirty-day-old seedlings were grown for 15 days using a split-root configuration in which the root system was divided into two equal parts: the first was immersed in a complete nutrient solution with 50 mM NaCl added, while the second part was immersed in either complete or incomplete K-, Ca-, or N-free medium. Using this approach, we demonstrated that K⁺ and Ca²⁺ uptake was impaired in the roots subjected to NaCl. There was no indication of the salt-induced inhibition of N uptake. If K⁺ or Ca²⁺ were available from salt-free medium, plants were able to grow at normal rate and accumulate large amounts of Na⁺ in the shoots. These results indicate that the sensitivity of Arabidopsis growth to mild salinity was probably due to an inhibition of K⁺ or Ca²⁺ root transport by salt rather than due to salt accumulation in shoots. Furthermore, the salt sensitivity of ion transport in roots seemed to depend on the genotype, since K⁺ was limiting for Col growth, in contrast to N1438, the growth of which was limited by Ca²⁺.     

Removal of Prymnesium parvum (Haptophyceae) and its toxins using clay minerals

Laboratory experiments were conducted to examine the ability of several clay minerals from Sweden to remove the fish-killing microalga, Prymnesium parvum Carter, from suspension. In their commercial form (i.e. after incineration at 400 °C), seawater slurries (salinity = 26) of the three minerals tested were generally ineffective at removing P. parvum from culture within a range of 0.01 to 0.50 g/L, and after 2.5 h of flocculation and settling. Dry bentonite (SWE1) displayed the highest removal efficiency (RE) at 17.5%, with 0.50 g/L. Illite (SWE3) averaged only 7.5% RE between 0.10 to 0.50 g/L, while kaolinite (SWE2) kept the cells suspended instead of removing them. Brief mixing of the clay-cell suspension after SWE1 addition improved RE by a factor of 2.5 (i.e. 49% at 0.50 g/L), relative to no mixing. The addition of polyaluminum chloride (PAC, at 5 ppm) to 0.50 g/L SWE1 also improved RE to 50% relative to SWE1 alone, but only minor improvements in RE were seen with SWE2 and SWE2 combined with PAC. In further experiments, P. parvum grown in NP-replete conditions were removed in greater numbers than cells in N- or P-limited cultures, at 0.10–0.25 g/L of SWE1 and 5 ppm PAC. With 0.50 g/L, RE converged at 40% for all three culture conditions. The toxin concentration of NP-replete cultures decreased from 24.2 to 9.2 μg/mL (60% toxin RE) with 0.10–0.50 g/L SWE1 treatment and 5 ppm PAC. A strong correlation was found between cell and toxin RE (r²=0.995). For N-limited cultures, toxin RE ranged between 21 and 87% with the same clay/PAC concentrations, although the correlation between cell and toxin removal was more moderate (r²=0.746) than for NP-replete conditions. Interestingly, the toxin concentration within the clay-cell pellet increased dramatically after treatment, suggesting that clay addition may stimulate toxin production in N-stressed cells. For P-limited cultures, toxin concentration also decreased following clay/PAC treatment (i.e. 36% toxin RE), but toxin removal was poorly correlated to cell removal (r²=0.462). To determine whether incineration affected SWE1’s removal ability, a sample of its wet, unprocessed form was tested. The RE of wet bentonite (SWE4) was slightly better than that of SWE1 (31% versus 17%, respectively, at 0.50 g/L), but when 5 ppm PAC was added, RE increased from 10 to 64% with 0.05 g/L of SWE4, and increased further to 77% with 0.50 g/L. There were no significant differences in RE among NP-replete, N-limited and P-limited cultures using PAC-treated SWE4. Finally, RE varied with P. parvum concentration, reaching a maximum level at the lowest cell concentration (1×10³ cells/mL): 100% RE with 0.10 and 0.50 g/L SWE4 + 5 ppm PAC. RE dropped as cell concentration increased to 1×10⁴ and 5×10⁴ cells/mL, but rose again when concentration increased to 1×10⁵ cells/mL, the concentration used routinely for the removal experiments above. Based on these results, SWE4 with PAC was the most effective mineral sample against P. parvum. Overall, these studies demonstrated that clay flocculation can be effective at removing P. parvum and its toxins only under certain treatment conditions with respect to cell concentration, clay type and concentration, and physiological status.     

Counteraction of Salinity Stress on Wheat Plants by Grain Soaking in Ascorbic Acid, Thiamin or Sodium Salicylate

The interactive effects of salinity stress (40, 80, 120 and 160 mM NaCl) and ascorbic acid (0.6 mM), thiamin (0.3 mM) or sodium salicylate (0.6 mM) were studied in wheat (Triticum aestivum L.). The contents of cellulose, lignin of either shoots or roots, pectin of root and soluble sugars of shoots were lowered with the rise of NaCl concentration. On the other hand, the contents of hemicellulose and soluble sugars of roots, starch and soluble proteins of shoots, proline of either shoots or roots, and amino acids of roots were raised. Also, increasing NaCl concentration in the culture media increased Na⁺ and Ca²⁺ accumulation and gradually lowered K⁺ and Mg²⁺ concentration in different organs of wheat plant. Grain soaking in ascorbic acid, thiamin or sodium salicylate could counteract the adverse effects of NaCl salinity on the seedlings of wheat plant by suppression of salt stress induced accumulation of proline.     

Complete nutrient composition of commercially raised invertebrates used as food for insectivores

A variety of invertebrates are commonly fed to insectivorous animals by both zoos and hobbyists, but information as to the nutrient composition of most commercially raised species is limited. Adult house crickets, house cricket nymphs (Acheta domesticus), superworms (Zophobas morio larvae), giant mealworm larvae, mealworm larvae and adult mealworms (Tenebrio molitor), waxworm larvae (Galleria mellonella), and silkworm larvae (Bombyx mori) were analyzed for moisture, crude protein, crude fat, ash, acid detergent fiber (ADF), neutral detergent fiber (NDF), minerals, amino acids, fatty acids, and vitamins. Earthworms (Lumbricus terresstris) were analyzed for moisture, crude protein, crude fat, ash, ADF, NDF, minerals, amino acids, and vitamins A and D₃. Proximate analyses were variable, with wide ranges found for moisture (57.9–83.6%), crude protein (9.3–23.7%), crude fat (1.6–24.9%), ADF (0.1–7.4%), NDF (0.0–11.5%), and ash (0.6–1.2%). Energy content ranged from a low of 674 kcal/kg for silkworms to 2,741 kcal/kg for waxworms.Using an amino acid scoring pattern for rats, the first limiting amino acid for all invertebrates tested was the total sulfur amino acid methionine+cystine. Deficiencies by nutrient (% of samples deficient vs. NRC requirements for rats on a dry matter (DM) basis) were as follows: calcium (100%), vitamin D₃ (100%), vitamin A (89%), vitamin B₁₂ (75%), thiamin (63%), vitamin E (50%), iodine (44%), manganese (22%), methionine‐cystine (22%), and sodium (11%). Deficiencies by invertebrate species (number of nutrients deficient vs. the NRC requirements for rats on a DM basis) were as follows: waxworms (9), superworms (8), giant mealworm larvae (7), adult mealworms (6), mealworm larvae (5), adult house crickets (4), house cricket nymphs (4), silkworms (4), and earthworms (4). These data provide a basis for determining nutrient intake of captive insectivores, and will aid in the development of gut‐loading diets to provide captive insectivorous animals with appropriate levels of necessary nutrients. Zoo Biol 21:269–285, 2002. © 2002 Wiley‐Liss, Inc.     

Molecular Modelling of The Mechanism of Action of Organic Clay-Swelling Inhibitors

Abstract

It is well known that the sodium smectite class of clays swells macroscopically in contact with water, whereas under normal conditions the potassium form does not. In recent work using molecular simulation methods, we have provided a quantitative explanation both for the swelling behaviour of sodium smectite clays and the lack of swelling of potassium smectites [1]. In the present paper, we apply similar modelling methods to study the mechanism of inhibition of clay-swelling by a range of organic molecules.

Experimentally, it is known that polyalkylene glycols (polyethers) of intermediate to high relative molecular mass are effective inhibitors of smectite clay swelling. We use a range of atomistic simulation techniques, including Monte Carlo and molecular dynamics, to investigate the interactions between a selection of these compounds, water, and a model smectite clay mineral. These interactions occur by means of organised intercalation of water and organic molecules within the galleries between individual clay layers.

The atomic interaction potentials deployed in this work are not as highly optimised as those used in our clay-cation-water work [1]. Nevertheless, our simulations yield trends and results that are in qualitative and sometimes semi-quantitative agreement with experimental findings on similiar (but not identical) systems. The internal energy of adsorption of simple polyethers per unit mass on the model clay is not significantly different from that for water adsorption; our Monte Carlo studies indicate that entropy is the driving force for the sorption of the simpler organic molecules inside the clay layers: a single long chain polyethylene glycol can displace a large number of water molecules, each of whose translational entropy is greatly enhanced when outside the clay. Hydrophobically modified polyalkylene glycols also enjoy significant van der Waals interactions within the layers which they form within the clay galleries.

In conjunction with experimental studies, our work furnishes valuable insights into the relative effectiveness of the compounds considered and reveals the generic features that high performance clay-swelling inhibitors should possess. For optimal inhibitory activity, these compounds should be reasonably long chain linear organic molecules with localised hydrophobic and hydrophilic regions along the chain. On intercalation of these molecules within the clay layers, the hydrophobic regions provide an effective seal against ingress of water, while the hydrophilic ones enhance the binding of the sodium cations to the clay surface, preventing their hydration and the ensuing clay swelling.