Desalination Technology is developing globally very fast these days. More and more desalination technologies getting applied into the conventional water treatment business today. DME does follow and support this development on an international basis starting from the first idea up to commodity products.
In Capacitive Deionization (CDI), charged ionic species are removed from aqueous solutions. The ions are adsorbed onto the surface of a pair of electrically charged electrodes, usually composed of highly porous carbon materials, upon applying an electrical voltage difference. Upon charging the electrodes with a voltage difference of typically 1-1.4 V, the salt ions present in the feed migrate to the electrode of opposite charge, cations to the cathode and anions to the anode, and form electrical double layers (EDLs) along the pore surface. Thus, the water flowing through the CDI cell is partially desalinated. In a discharging step, where either the applied voltage is shorted or the polarity reversed, the salt ions are released in a brine stream. The system architecture can be in flow-by or flow-through mode with the feed either streaming past the electrodes in parallel direction or streaming vertically through the electrode. New developments propose floating electrodes suspended in the aqueous solution that enable continuous operation. Various porous carbon materials have been suggested as electrode material, such as carbon aerogels, activated carbon and carbon nanotubes. An important factor is the sorption performance. The technology has been previously applied to brackish and seawater desalination, wastewater remediation and water softening, but has proven to be highly effective for solutions with low molar concentration such as brackish water. CDI does not require high pressure or temperature, as in membrane or thermal desalination, making the technology more energy efficient in comparison. It also has a higher accuracy in removing only particular salts and ions that enables the recovery of valuable compounds such as lithium among others. However, problems may arise in the regeneration phase as during reversed-polarity, repelled ions might be attracted to the oppositely charged electrode and by electrical shorting the only driving force is diffusion, which is slow and inefficient. The special applicability to brackish water offers a great potential for development, as the demand for desalination of brackish water is increasing due to salt intrusions into the groundwater in many regions worldwide. Nonetheless, many basic settings have not been uniquely defined until now and have to be further optimized.
The hidden talent of mushrooms for solar steam generation Read more: The hidden talent of mushrooms for solar steam generation
In this work, for the first time, researchers utilize living organisms – mushrooms – to generate steam under sunlight. It turns out that the micro- and macrostructures of mushrooms possess all the needed characteristics for a good solar steam-generation device: high solar absorption; efficient water supply and vapor escape; and good thermal management. Interestingly, a mushroom is an unlikely candidate as it typically lives in the shadow, i.e. it doesn’t get to see sunlight that much.
The mushroom maintains its hydrophilicity before and after carbonization because of its components, which include carbohydrates and proteins; the nitrogen functional groups exist even after carbonization.
The scientists attributed mushrooms’ capability of high-efficiency solar steam generation to their unique natural structures, including their umbrella-shaped black pileus, porous context, and fibrous stipe with a small cross section.
First, the umbrella-shaped black pileus can absorb a huge amount of solar energy. Second, the hydrophilic fibrous stipe working as efficient water supply path can pump water into the mushroom context by capillary force. Third, the porous context not only acts as a bridge to pump the water further into the top pileus but also provides sufficient vapor channels.
“What’s more” as Zhu points out, “the geometry of mushrooms is naturally