【Frontiers of HaiChuan Chemical Technology】New breakthrough in the “magic straw”! Wuhan University team restores saline-alkali lands at low cost with zero emissions
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Our country is the third largest country in the world in terms of land salinization; 360,000 square kilometers of land are affected by salinization to varying degrees, and this phenomenon continues to spread. Traditional governance methods are costly and consume a large amount of water. Recently, a team from Wuhan University made a significant breakthrough by developing a \"salt-treatment straw\" that does not consume fresh water nor produce wastewater. With a cost of just 3 cents, this solution offers a new approach to addressing this global problem! In the laboratory of the School of Resources and Environmental Sciences at Wuhan University, this \"magic straw\" with filter paper was inserted into soil samples from saline-alkali lands, absorbing the salts in the soil like a sponge. Under the sunlight, the saltwater evaporates, and the salt crystals remain on the tubes; in this way, the saline-alkali soil is \"cured\". And the scientific name for this “magic straw” is paper-based solar desalinator. Dong Xiangyang, a postdoctoral researcher at the School of Resources and Environmental Sciences, Wuhan University: Just like the salt formed here, once the soil is restored to its normal state, it can be used for planting or other purposes, and its effectiveness can last for two to three years. This straw is made from agricultural waste such as straws and rice husks, costing only 3 cents; it saves more than 60% compared to traditional treatment methods. Moreover, with slight modifications to the existing straw production lines, 300 straws can be produced per minute, which means that the materials needed to restore 10,000 mu of saline-alkali land can be gathered in just a few days. At the same time, the straw draws soil brine directly, without using a single drop of fresh water; once it is used, it can degrade naturally and return nutrients to the soil. Deng Hongbing, Professor and Deputy Dean of the School of Resources and Environmental Sciences at Wuhan University: Zero pollution, zero waste, zero emissions. If such tubes are installed densely in one mu of land, the soil can likely be restored within three to four days, making it possible to grow crops there. At present, the Qingdao test site has already been equipped with the first batch of “salt treatment straws,” and these will be deployed on more saline-alkali marshes next year. The team is focusing on more types of \"damaged soil\"; in the future, this technology will be used to help more degraded lands regain their vitality.
Over a period of two years, the team developed a contactless solar interfacial evaporation soil desalinator with zero wastewater discharge, using readily available materials such as filter paper, straws, and plastic film (Figures a and b). In other words, a soil desalinator is created by inserting straws wrapped in filter paper into saline-alkali soil covered with plastic film. Through the separate design of a black plastic film (photothermal layer) and a paper-covered straw (evaporation layer), sunlight is converted into 10 μm infrared radiation to drive the desalinator, thereby preventing a decline in light absorption performance caused by salt accumulation at the evaporation interface ； The random fiber structure of the filter paper significantly reduces the apparent diffusion coefficient of salts; combined with the increased diffusion distance due to the columnar design and the evaporation-convection effect, this enables one-way migration of salts from the soil to the desalination unit, resulting in zero wastewater discharge. Ultimately, under direct use of saline water, the soil salt content decreased from 11.04 mg/g to 0.95 mg/g (a reduction of 93%), with no significant difference compared to the effect of freshwater treatment (Figure c); this level fully met the requirements for wheat growth (Figures d and e). After the repair was completed, visible salt particles formed on the surface of the straw, indicating that the salts in the soil had been ‘drawn out’ by the straw. Moreover, this method is applicable to various types of saline-alkaline soils, and it works well on sandy soil, loam, and clay. It truly transforms \"waste biomass\" into a tool for restoring saline-alkaline lands, allowing straw to once again play a role in ensuring food security for the Chinese people.
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