Molecular dynamics modeling and simulation of water desalination through a double-walled carbon nanotube with moiré pattern

Freshwater scarcity has emerged as a major challenge of our time. Under this context, the importance of an efficient and energy-saving water desalination method is highlighted. In recent years, carbon nanotube (CNT) membrane characterizing with high permeability has attracted much attention in research, and it is regarded as a promising alternative to the conventional reverse osmosis technology. This work aims at numerically investigating the water desalination ability of a novel type of CNT membrane structure, namely the double-walled carbon nanotube (DWCNT) with Moiré pattern. After establishing the physical CNT models and running the molecular dynamics (MD) simulation of the water desalination system, it is found that both the single-walled carbon nanotube (SWCNT) and DWCNT can desalinate the seawater successfully while the water permeability of DWCNT is at least 18.9% higher than that of SWCNT within the same time. As far as the Moiŕe pattern adopted in this study is concerned, the water permeability of DWCNT without Moiŕe pattern is 18.6% higher than that with Moiré pattern.

Experimental study on preparation of fuel by low-temperature pyrolysis of plastic waste combined with desiccated sludge after preforming

Take plastic waste and dried sludge as raw materials, use pressure testing machine and high temperature hot pressing mold to test under different parameters. The effect of raw material ratio, low-temperature pyrolysis temperature, molding pressure and heating time on the physical properties of the molded fuel after low-temperature pyrolysis, such as relaxation density, fall strength, compressive strength and water permeability, are studied. Single factor tests show that the general range of mixed molding parameters is: mixture ratio (dry sludge: composite plastics) 85:15~75:25, temperature 150~250°C, heating time 20~40min, compaction pressure 2~6MPa. Orthogonal test is designed on the basis of single factor test. The results show that the most important factor affecting the relaxation density of molding fuel is molding pressure, the most important factor affecting compressive strength is the ratio of raw materials, and the most important factor affecting water permeability is heating time. The fall strength is less affected by various factors. It is due to the stickiness of the molded plastic after softening, which strengthens the “cohesion” between the raw materials, and will not be explored in the orthogonal experiment. The optimal combination of relaxation density molding parameters is the ratio (dry sludge: composite plastics) 80:20, temperature 250°C, heating time 30min, compaction pressure 6MPa; the optimal combination of compressive strength molding parameters is 75:25, 250°C, 30min, 6MPa; the optimal combination of anti-moisture absorption performance molding parameters is 85:15, 150°C, 30min, 2MPa.

Seed-coat thickness explains contrasting germination responses to smoke and heat by Leucadendron species

Fire stimulates germination of most seeds in fire-prone vegetation. Fruits of Leucadendron (Proteaceae) are winged achenes or nutlets that correlate with their requirements for smoke and/or heat in promoting germination. We describe five possible smoke–heat dormancy-release/germination syndromes among plants, of which Leucadendron displays three (no response, smoke only, smoke and heat). As seed-coat thickness varies with seed-storage location (plant or soil) and morphology (winged or wingless), we tested its possible role in water uptake and germination. Species with winged seeds achieved 100% germination in the absence of smoke/heat, seed coats were an order of magnitude thinner, and their permeability greatly exceeded that of nutlets. As seed-coat thickness increased a) imbibitional water uptake declined at a decreasing rate, and b) the response to smoke, and to a lesser extent heat, increased linearly to reach levels of germination approaching those of winged seeds. For species responsive to smoke and heat, there was no additive effect when applied together, suggesting that they may have promoted the same physiological process. By what mechanisms a) the smoke response is greater the thicker the seed coat, and b) smoke chemicals could increase water permeability to explain the non-additive effect of smoke and heat, warrant further investigation.

Influence of Polymer Modifiers on Selected Properties and Microstructure of Cement Waterproofing Mortars

This paper presents the results of research on the influence of polymer modifiers: styrene-acrylic copolymer, vinyl acetate/ethylene (EVA), vinyl acetate/acrylic copolymer (VAAc), and VA/VeoVa/acrylic terpolymer on the water permeability and adhesion of cement-containing waterproofing mortars in concrete. The content of the polymers in the composition of the mortars was 15, 20 and 26% (m/m) in relation to the weight of the dry ingredients. Using microscopic methods, an attempt was made to analyse the relationship between the microstructure of the mortars and the properties of these polymers. The EVA and the vinyl acetate/acrylic copolymer, which were used in the form of dry powders, had the most favourable effect on water permeability and adhesion to the concrete substrate. They may prove to be useful for the production of one-component cement-containing waterproofing mortars. On the other hand, the VA/VeoVa/acrylic terpolymer modifier had the least favourable effect on the tested properties. For mortars with this modifier, the desired water-permeability parameters were not achieved. Depending on the amount of polymer modifier, the mortars were characterized by differences in watertightness, as established on the basis of changes in porosity and differences in the adhesion of the cement-polymer paste to the surface of aggregate grains. It was determined that the type of polymer and its dispergation properties influence the water permeability of mortars, as well as their adhesion to concrete substrates.