Biofilter made from coffee grounds removes heavy metals from water
Coffee grounds can be used to filter heavy metals from water. To do this, biochar must be created through heating.
The starting material for the biofilter is washed, dried, and sieved coffee grounds.
(Image: Loughborough University)
A research team from Loughborough University, in collaboration with Banaras Hindu University, has discovered that coffee grounds can be effectively used to filter heavy metals such as lead, copper, and zinc from water. The porous plant-based material is suitable for producing biochar, which serves as a water filter. Up to 96 percent of heavy metals could be removed in this way.
Coffee is one of the most popular beverages worldwide. Consequently, a large amount of coffee grounds is produced, which is usually disposed of as waste. The scientists at Loughborough University investigated the extent to which the porous, plant-based material is suitable as an absorption material. They presented the results of their investigations in the studies „The Potential of Barista Coffee Waste to Adsorb Copper and Zinc from Aqueous Solutions“ and „Optimized valorization of spent coffee grounds into biochar for lead removal using Box-Behnken design,“ published in Clean Technologies and Biomass and Bioenergy, respectively.
From the coffee grounds of the in-house cafeteria of Loughborough University's Herbert Building, the researchers produced highly porous biochar by heating. This carbon-rich material is also used to improve soil quality. However, the scientists optimized the temperature and duration of heating used for biochar production to achieve the highest possible filtration performance. With the biochar filter, up to 98 percent of lead could subsequently be removed from the water. 4.9 mg of lead were absorbed per gram of biofilter.
Filter Performance
The researchers investigated the extent to which contact time with the filter, mixing with other absorption materials, and metal concentration in the water affected filter performance. Even pure coffee grounds without further processing can be used to remove heavy metals such as copper and zinc from water at low metal concentrations (2.5 ppm copper, 10 ppm zinc) and exhibit high filter performance at these low concentrations. The scientists also tested a mixture of coffee grounds and rice husks. This combination proved to be more effective at high metal concentrations of more than 5 ppm copper and more than 25 ppm zinc.
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Overall, up to 96 percent of the metals could be removed from the water, the scientists write. They believe that their cost-effective and environmentally friendly method can be used to free water from heavy metals. The process they proposed could be scaled up for industrial use.
(olb)
