A group of researchers from Hokkaido University announced a significant advance in the recovery of phosphorus from the ashes resulting from the incineration of sludge in wastewater treatment plants , used for the generation of electrical energy . The study details an innovative method that overcomes the environmental and economic challenges of conventional techniques, such as chemical contamination and processing complexity.
Role of volatilization in sludge thermal treatment
The team has built on previous research on the recovery of essential nutrients such as calcium, iron and magnesium through thermal treatment of sludge . Through detailed analysis, they discovered that the volatilization process (the selective conversion of elements to gaseous forms during treatment) could be key to effectively separating phosphorus from the rest of the ash .
To delve deeper into this discovery, researchers at Hokkaido University experimented with different chemical conditions in the sludge ash, especially looking at the effects of adding carbon in a process that also involves chlorine. This approach allowed them to refine a method to isolate useful phosphorus compounds using alternating chlorination steps, with and without carbon.
Green technology in wastewater treatment plants
According to Yuuki Mochizuki, lead author of the study, this technique promises to be more energy efficient, in addition to generating fewer CO₂ emissions and being more economical compared to traditional methods that extract phosphorus from phosphate minerals. The process produces high-quality phosphorus chloride, which can then be transformed into phosphoric acid simply by dissolving it in water.
Whereas the amount of phosphorus in secondary resources such as steel slag, livestock manure and sewage sludge in Japan accounts for nearly half of all phosphorus imported into the country , Mochizuki and his team plan to evaluate whether their method could significantly decrease the nation’s dependence on phosphorus imports.
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Source: mining
Photo: Shutterstock
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