Scientists said yesterday they had made a nanotech device to strip salt from seawater, paving the way to small-scale or even battery-powered desalination for drought-hit regions and disaster zones.
The tiny prototype was reported on the eve of the UN’s World Water Day, which aims to highlight the worsening problems of access to clean water.
Desalination by conventional means works by forcing water through a membrane to remove molecules of salt. This process, however, is an energy-gobbler and the membrane is prone to clogging, which means that de-sal plants are inevitably big, expensive, fixed pieces of kit.
The new device has been given a proof-of-principle test by Jongyoon Han and colleagues of the electrical engineering and computer science department at Massachusetts Institute of Technology.
It works through so-called ion concentration polarization, which occurs when a current of charged ions is passed through an ion-selective membrane.
The idea is to create a force that moves charged ions and particles in the water away from the membrane.
When the water passes through the system, salt ions — as well as cells, viruses and micro-organisms — get pushed to the side. This saltier water is then drawn off, leaving only de-salted water to pass through the main microchannel.
The tiny device had a recovery rate of 50 percent, meaning that half of the water used at the start was desalinated. Ninety-nine percent of the salt in this water was removed.
Energy efficiency was similar to or better than state-of-the-art large-scale desalination plants.
“Rather than competing with larger desalination plants, the methods could be used to make small or medium-scale systems, with the possibility of battery-powered operation,” the researchers said in their paper, published by the journal Nature Nanotechnology.
In an e-mail, Han said the experiment entailed a tiny microfluidic chip, just a few square millimeters, that desalted just 10 microliters per minute.
“The idea toward the real-world application is that we would make many of these devices, thousands or tens of thousands of them, on a plate, and operate them in parallel, in the same way semiconductor manufacturers are building many small electronic chips on a single large wafer,” Han said.
“That would bring the flow rate up to around 100 milliliters per minute level, which is comparable to typical household water purifiers and therefore useful in many applications,” he said.
Four people jailed in the landmark Hong Kong national security trial of "47 democrats" accused of conspiracy to commit subversion were freed today after more than four years behind bars, the second group to be released in a month. Among those freed was long-time political and LGBTQ activist Jimmy Sham (岑子杰), who also led one of Hong Kong’s largest pro-democracy groups, the Civil Human Rights Front, which disbanded in 2021. "Let me spend some time with my family," Sham said after arriving at his home in the Kowloon district of Jordan. "I don’t know how to plan ahead because, to me, it feels
Polish presidential candidates offered different visions of Poland and its relations with Ukraine in a televised debate ahead of next week’s run-off, which remains on a knife-edge. During a head-to-head debate lasting two hours, centrist Warsaw Mayor Rafal Trzaskowski, from Polish Prime Minister Donald Tusk’s governing pro-European coalition, faced the Eurosceptic historian Karol Nawrocki, backed by the right-wing populist Law and Justice party (PiS). The two candidates, who qualified for the second round after coming in the top two places in the first vote on Sunday last week, clashed over Poland’s relations with Ukraine, EU policy and the track records of their
‘A THREAT’: Guyanese President Irfan Ali called on Venezuela to follow international court rulings over the region, whose border Guyana says was ratified back in 1899 Misael Zapara said he would vote in Venezuela’s first elections yesterday for the territory of Essequibo, despite living more than 100km away from the oil-rich Guyana-administered region. Both countries lay claim to Essequibo, which makes up two-thirds of Guyana’s territory and is home to 125,000 of its 800,000 citizens. Guyana has administered the region for decades. The centuries-old dispute has intensified since ExxonMobil discovered massive offshore oil deposits a decade ago, giving Guyana the largest crude oil reserves per capita in the world. Venezuela would elect a governor, eight National Assembly deputies and regional councilors in a newly created constituency for the 160,000
North Korea has detained another official over last week’s failed launch of a warship, which damaged the naval destroyer, state media reported yesterday. Pyongyang announced “a serious accident” at Wednesday last week’s launch ceremony, which crushed sections of the bottom of the new destroyer. North Korean leader Kim Jong-un called the mishap a “criminal act caused by absolute carelessness.” Ri Hyong-son, vice department director of the Munitions Industry Department of the Party Central Committee, was summoned and detained on Sunday, the Korean Central News Agency (KCNA) reported. He was “greatly responsible for the occurrence of the serious accident,” it said. Ri is the fourth person