The testa (seed coat) plays an important role in the regulation of seed dormancy and germination as well as the exchange of water, gas and solutes from the environment. In this study, we investigated testa permeability and its relationship with germination kinetics in contrasting populations of three weedy Amaranthus spp.: A. palmeri, A. retroflexus and A. tamariscinus. The microstructure of the testa was observed for two of these species using scanning electron microscopy, and a bespoke image analysis solution was developed to quantify the thickness of the testa in different regions of the seed. The permeability of the testa in contrasting populations was assessed using a range of pesticidal compounds with varying physicochemical properties, and germination responses to gibberellic acid and norflurazon were evaluated. Our results revealed both within- and between-species differences in testa thickness and permeability; however, it was challenging to associate these differences with responses to germination stimulants. Burial experiments demonstrated that testa permeability is a dynamic trait which can change over time depending on the solute. This work provides insights for colleagues using germination stimulants or inhibitors to study seed physiology as well as a fundamental understanding for developing more effective weed management strategies. Future work could focus on the biochemical and molecular basis of differential testa permeability in seeds.

Wastewater treatment is critically important and ceramic-membrane engineering is one of the most effective technologies for water filtration and purification. However, the materials used in the preparation of ceramic membranes are usually expensive, e.g. ZrO and Al2O3 membranes, reverse osmosis materials such as carbon-based thin-film nanocomposite TFNC ‘carbon nanotube, graphene-oxide’. Delicate, thin membranes employed for small-scale filtration usually require optimal supports for effective operation. The purpose of the present research, therefore, was to find a less expensive material for membrane supports while, at the same time, enhancing performance. Membrane supports were thus prepared from local clay materials and (25 wt.%) CaCO3 using an extrusion technique, which enabled the production of tubular supports. The CaCO3 is responsible for creating the pores in the samples during heat treatment due to the evolution of CO2 gas. Some characteristics of the supports were evaluated using X-ray diffraction, which identified quartz, gehlenite, sillimanite, H-bearing aluminous stishovite, and wollastonite. The support treated at 1000°C displayed significant mechanical properties (flexural strength, 11.58 MPa, measured using three-point bending tests) compared with supports treated at other temperatures. Moreover, the support sintered at 1000°C had an estimated permeability factor of 1052 L/h m2.bar after performing both time- and pressure-dependent flux measurements. Such properties make it possible to use these supports as multi-scale filtration membranes for purification and filtration applications after performing a standard filtration application on dirty water, resulting in a significant difference in terms of turbidity and waste content.

Despite substantial scientific research efforts, accurate determination of the petrophysical effects of clay minerals on reservoir sands remains problematic. Diagenetic clays such as smectite and illite are of particular interest because of the pronounced effects these clays can have on reservoir quality. Here, results are reported from an experimental study based on the hydrothermal growth of smectite in synthetic sands. The sands contained quartz, dolomite and kaolinite, and were reacted at 175–200°C, for 19–45 d. The hydrothermal reaction can be written as follows:

$$dolomite + kaolinite + quartz \to smectite + calcite + CO<Subscript>2</Subscript>$$

The long-term impermeability of clay barriers in waste disposal facilities and hydraulic structures is of critical importance to environmental, agricultural, and industrial concerns. Changes in the oxidation state of Fe in the constituent clays of compacted clay barriers may degrade the hydraulic conductivity of these structures because other properties related to hydraulic conductivity, such as swelling, gel microstructure, and particle size, are greatly altered by the oxidation state. Two Na-saturated smectites (SWa-1 and API 25) were reduced by sodium dithionite (Na2S2O4), both in suspension and in situ after consolidation, to examine the effects of structural Fe reduction on hydraulic conductivity. Results indicated that the hydraulic conductivity depended on both the oxidation state and the consolidation history of the clay. The hydraulic conductivity of clay reduced in suspension before consolidation was lower than that of oxidized clay. Initially reduced smectite, thus, may be compactable to a less-permeable material with higher bulk density. But reduction of smectite in situ after consolidation increased the hydraulic conductivity and its variability. The oxidized state of clay liners should, therefore, be preserved.

Clayey soils are essential materials used to reduce hydraulic conductivity and pollutant migration, common at sites of waste disposal. This study investigates the possible use of a Tunisian soil as a lining material for disposal sites for acidic-fluoride wastes. A permeability test on a waste-solution sample (pH = 2.7) obtained from a disposal site in southern Tunisia was conducted over a period of about 2 years. The test results show that the permeability decreased with time until stabilized at 8.33 × 10−11 m/s. After the permeability test, the samples retrieved from the permeameter show a degradation state which varied with the thickness of the specimen. These samples can be classified into three zones (Z1: unaffected, Z2: moderately affected; and Z3: extensively affected). Physicochemical characterization of the three samples (Z1, Z2, and Z3), and of the original argillaceous soil, was by X-ray diffraction, Fourier transform infrared spectroscopy, differential thermal and thermal gravimetric analysis, 29Si and 27Al nuclear magnetic resonance, and N2-adsorption techniques. The original sample consists essentially of palygorskite, kaolinite, and quartz. Sample Z3 underwent complete dissolution of kaolinite which supports the precipitation of fluoroaluminate and the appearance of an X-ray amorphous silica phase. In samples Z1 and Z2, the soil adsorbs fluoride at a rate of ∼68.5 mg/g and is highly resistant to acidic attack.

Clays and their composites have been widely used for secondary containment walls for underground storage tanks and landfills. The pore-size changes occurring in the clay have a profound effect on its permeability. This study presents a new method for evaluating the use of an atomic force microscope (AFM) for studying wet clay in a non-aqueous state in order to determine the pore-size of clay at various water contents, a type of study typically performed by the more expensive environmental scanning electronic microscope. The method consists of mounting a sponge saturated with water under the sample in order to prevent drying by the heat generated by the AFM electronics. The micro-scale AFM image results show that the clay-particle separations reduce linearly as the water content increases. This change in pore-size is postulated to be attributed to the reduction in the size of the diffuse double layer and more extensive hydrogen bonds between clay particles and bipolar water molecules. The AFM was not able to produce nano-scale images due to excessive adhesion between the cantilever arm and the wet clay sample.

A wick structure is the core part of a heat pipe that produces capillaries to move liquid from a condenser to an evaporator. The purpose of the current study was to develop a wick structure from zeolite and kaolin using various sintering methods. Due to significant porosity and water-adsorption properties, zeolite and kaolin can produce a large capillary force inside the heat pipe. A porous wick specimen is developed from pure zeolite together with a mixture of zeolite and kaolin by using pressureless (loosely packed) and conventional pressurized sintering for thermosiphon heat-pipe applications. Major properties such as porosity, water adsorption, and permeability were noted to be better under pressureless sintering compared to pressurized sintering. Significant and uneven shrinkage in both radial and linear directions is a major problem in loosely packed sintering of pure zeolite. However, the addition of kaolin helps to overcome the problem of porosity and shrinkage in pure zeolite; but the permeability and strength of the wick structure are reduced with the addition of kaolin. A general trend is that increasing porosity causes increasing permeability. Due to grain size and compaction, however, permeability is reduced with the addition of kaolin. Based on the experimental results for porosity and permeability, the wick structure formed from zeolite with 5–10% of kaolin has better thermal properties for heat-pipe applications.

Short- and long-term exposure to inorganic solutions can cause significant degradation of the hydraulic properties of bentonite clay used in geosynthetic clay liners (GCLs). In particular, the increase in hydraulic conductivity due to cation exchange when Na-montmorillonite is subjected to leachates rich in Ca and Mg has caused problems in incinerator ash landfill liners located in wet environments, where large quantities of leachates are generated. Experimental results are presented to evaluate the immediate change in hydraulic conductivity of seven types of GCL clays upon permeation with leachate generated from three ash landfills. The composition of the ash, which is a by-product of the incineration of municipal solid waste (MSW), in turn influences the composition of the resulting leachate. Falling head permeability tests were performed on flexible-wall permeameter specimens, with back-pressure saturation. Chemical analysis shows that the three leachate products contain high, medium, and low concentration Ca and Mg cations. The clay component of GCL materials tested in this study consists of regular and polymer-treated bentonite. Polymer treatment is believed to render the clay non-reactive to many organic and inorganic chemicals. The results of this study indicate that: (1) polymer treatment is generally more beneficial if the clay is first saturated with water and not directly with the leachate; (2) high swell potential of the bentonite is more advantageous than polymer treatment, especially when low hydraulic conductivity is required in the short term and if the clay is pre-hydrated. Experiment setup and special specimen preparation procedures are also discussed.