Ever wondered how diapers can hold and absorb so much liquid? The simple answer is hydrogels. Disposable diapers have been on the rise in popularity in recent years because of their ease of use. Unfortunately with the sudden increase in popularity of diapers, waste management is a big issue all around the world. Everyone is trying to find new and innovative ways to decrease the generation of waste. Because of the short life span of disposable diapers, they end up in a waste field which causes very serious environmental impacts. Consequently, people are switching over to reusable diapers. While this is, in fact, a positive, the much bigger issue is in developing countries where the majority of disposable diapers are being used. In many of these developing countries, the used diapers are disposed of in either landfills or open dumpsites. The mismanagement of solid waste can lead to an increase in greenhouse gas emissions and water pollution from the open dumpsites. These hydrogels after being sanitized might have the possibility to be reused or repurposed for another product. Current research focuses on the reuse of hydrogels for soil irrigation.
A hydrogel is a chemically or physically bonded polymer. Chemically bonded hydrogels are permanent and chemically cross-linked together. Physically bonded hydrogels are reversible and are held together by hydrogen bonding from its interactions with water. The only difference between chemically and physically bonded hydrogel is that physically bonded hydrogels can be separated into individual components. How much water a hydrogel can hold is the point of equilibrium swelling which is the most important characteristic. When a hydrogel connects with water, the hydrophobic groups interact with the water molecules. The hydrophobic group tends to repel water, which leads to the swelling of the hydrogel. As the hydrogel swells, it is absorbing the surrendering water until it reaches its equilibrium swelling point. Every hydrogel has its own equilibrium swelling point. Once it reaches this point it will not swell anymore and the additional water will fill in the spaces between the bonds.
Traditionally, agricultural methods are based on irrigation methods such as drip and spray and, flood irrigation. This has some downfalls because not all the water is absorbed by the plants which can lead to runoff water. In some countries, this poses a bigger threat because of the scarcity of water. Sandy soils are impacted at a greater extent because they have low water carrying capacity which makes it hard for them to absorb water. This leads to most of the water being unabsorbed and the plant roots lacking sufficient water and nutrients. Since hydrogels are very absorptive, they can be used to absorb some of the excess water so the water does not go to waste.
Hydrogels can be used to improve agricultural management. Many studies are looking into if the hydrogels in diapers can be reused and repurposed after sanitation, but still, maintain the level of equilibrium swelling and have the ability to hold the water for a long period of time. Luckily, they were proven to have a larger equilibrium swelling capacity and a longer swell time. These two factors can greatly improve water retention in soil and irrigation efficiency. Because of the basic properties of a hydrogel, they are allowed to slowly release the water back into the soil, this allows improved water efficiency. This is because the plant’s roots are not drowning in large amounts of water which makes it harder for them to retain all of it. While the hydrogel is in the soil, it will wrap around the roots and will continue to give the roots the water supply it needs for photosynthesis. There still is a long way to go on researching this idea, but maybe in the future, we will be able to reuse hydrogels and many other everyday items.
Citations
Agaba, H., Orikiriza, L., Obua, J., Kabasa, J., Worbes, M., & Hüttermann, A. (2011, November 17). Hydrogel amendment to sandy soil reduces irrigation frequency and improves the biomass of Agrostis stolonifera. Retrieved November 24, 2020, from https://www.scirp.org/journal/PaperInformation.aspx?PaperID=8549
Al-Jabari, M., Ghyadah, R., & Alokely, R. (2019, March 20). Recovery of hydrogel from baby diaper wastes and its application for enhancing soil irrigation management. Retrieved November 23, 2020, from https://www.sciencedirect.com/science/article/pii/S0301479719303901
Ferronato, N., Nova Pinedo, M., & Torretta, V. (2020, June 21). Assessment of Used Baby Diapers Composting in Bolivia. Retrieved November 24, 2020, from https://www.mdpi.com/2071-1050/12/12/5055
Zekry, M., Abdallah, A., Salim, H., & Nassar, I. (2020, March 07). The Potential of super absorbent polymers from diaper wastes to enhance water retention properties of the soil. Retrieved November 24, 2020, from https://www.researchgate.net/publication/341756185_The_Potential_of_super_absorbent_polymers_from_diaper_wastes_to_enhance_water_retention_properties_of_the_soil
