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Engineers at the University of Michigan and Rice University have developed a new technology for removing boron from seawater, an important step in turning seawater into safe drinking water.

Boron is a natural component of seawater that remains a toxic contaminant in drinking water after conventional filters remove salts from seawater. The boron levels in seawater are about twice as high as the World Health Organization’s most lenient limits for safe drinking water and 5 to 12 times higher than what many agricultural plants can tolerate.

Boron passes through the reverse osmosis membranes used in desalination plants in the form of boric acid. To remove it, the desalination plants normally add a base to the treated water that causes the boric acid to become negatively charged. An additional membrane then removes the charged boron, and an acid is then added to neutralize the water. All of this is expensive and complicated.

The new technology uses electrodes that remove boron by trapping it inside pores studded with oxygen-containing structures that bind with boron but let other ions pass through. Capturing boron with electrodes enables treatment plants to avoid the need for a second stage of reverse osmosis.

Global desalination capacity reached 95 million cubic meters a day in 2019. The new membranes could save nearly $7 billion a year. Such savings could make seawater a more accessible source of drinking water for a thirsty world. Freshwater supplies are expected to meet only 40% of the world’s demand by 2030.

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New water purification technology helps turn seawater into drinking water without tons of chemicals

Photo, posted August 21, 2018, courtesy of Alachua County via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

The production of cement – which is the world’s leading construction material – is a major source of greenhouse gas emissions, accounting for about 8% of global man-made emissions.

Cement production produces carbon dioxide in two ways: from a key chemical process and from burning fuel to produce the cement. The process of making “clinker” – the key constituent of cement – emits the largest amount of CO2. Raw materials, mainly limestone and clay – are fed into huge kilns and heated to over 2,500 degrees Fahrenheit, requiring lots of fossil fuel. This calcination process splits the material into calcium oxide and CO2. The so-called clinker is then mixed with gypsum and limestone to produce cement.

A team of researchers at MIT has come up with a new way of manufacturing cement that greatly reduces the carbon emissions. The new process makes use of an electrolyzer, where a battery is hooked up to two electrodes in water producing oxygen at one electrode and hydrogen at the other. The oxygen-evolving electrode produces acid and the hydrogen-evolving electrode produces a base. In the new process, pulverized limestone is dissolved in the acid at one electrode and calcium hydroxide precipitates out as a solid at the other.

High-purity carbon dioxide is released at the acid electrode, but it can be easily captured for further use such as the production of liquid fuels or even in carbonated beverages and dry ice. The new approach could eliminate the use of fossil fuels in the heating process, substituting electricity generated from renewable sources.

The process looks to be scalable and represents a possible approach to greatly reducing one of the perhaps lesser known but nevertheless very significant sources of greenhouse gas emissions.

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New approach suggests path to emissions-free cement

Photo, posted March 26, 2014, courtesy of Michael Coghlan via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

A new way to help purify water

Engineers at the University of Michigan and Rice University have developed a new technology for removing boron from seawater, an important step in turning seawater into safe drinking water.

Web Links

Emissions-Free Cement

The production of cement – which is the world’s leading construction material – is a major source of greenhouse gas emissions, accounting for about 8% of global man-made emissions.

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