As the demand for fresh water increases worldwide, large-scale, new technologies for desalination are becoming increasingly sought after. Equally in wastewater treatment, the ability to remove industrial effluent, pesticides and hormones is becoming more important, especially when water re-use is considered.
Graphene-based desalination membranes.
In the natural world, aquaporins rapidly shuttle water molecules into and out of cells and mimicking this function could help improve the production of chemicals and pharmaceuticals.
One answer could be to use graphene, which is a sheet of carbon just one atom thick. Graphene is very strong, and sheets can be punctuated with sub-nanometre-sized pores that let water through while blocking salt.
While this works well for micrometre-sized membranes it is very difficult to make larger graphene sheets without defects, which act as large pores that let salt through.
Another approach is to create a membrane from a patchwork of small overlapping sheets of graphene oxide (also just one atom thick). Water can move through the membrane by permeating the gaps between the sheets, but the larger salt ions cannot.
While scientists have already made 0.4 in (1 cm) membranes this way, this material tends to swell-up when wet and let more salt through.
In Saudi Arabia, desalination researchers at King Abdullah University of Science and Technology have tailored the structure of graphene-oxide layers to mimic the hourglass shape of these biological channels, creating ultrathin membranes to rapidly separate chemical mixtures.
In China, Yanbing Yang and Xiangdong Yang at Wuhan University have developed a graphene-based desalination membrane with the potential to be scaled-up for practical applications. (en.whu.edu.cn)
In Australia, Mainak Majunder and a team at Nanoscale Science and Engineering Laboratory of Monash University, Melbourne, have developed a similar system that uses gravure printing, a widely available industrial printing process.
The technology will directly benefit Australian and international companies seeking energy savings and other cost advantages in water and wastewater filtration and industrial processes associated with pulp and paper, food and beverage, inks, pigments and dyes, pharmaceuticals and metals.
Supported by funding from the Australian Government’s Cooperative Research Centre (CRC) program of approximately US$1.2 million, and with investment from industry partners Clean TeQ Holdings in Melbourne and Ionic Industries, the technology entered the commercialisation phase after undergoing seven years of research and development.
In June 2019, Clean TeQ announced the successful completion of its hardness removal demonstration project in Inner Mongolia.
The demonstration program treated waste-water from a large coal-to-chemical refinery, producing DME (Dimethyl Ether) owned by Jiutai New Material located about 60 mi (100 km) from Hohhot, China.
The process requires large volumes of industrial grade water, putting a strain on sources of water supply in this water scarce region. The demonstration program confirmed that increasing water recovery by adopting Clean TeQ’s CIF (Continuous Ionic Filtration) system could substantially reduce the plant’s net water use.
Discover Solution 178: The Great Bubble Barrier!
Support 366solutions on Patreon and receive the ‘366solutions Insider Newsletter’ with updates on the monthly progress and successes of published solutions.