A Delft researcher has found an ecologically sound way to win phosphoric acid for the production of fertiliser. Unfortunately it’s not (yet) necessary in Morocco and Tunis.
It’s now possible to reduce 70 to 90 percent of the known contaminants in phosphoric acid, like cadmium, arsenic, lanthanide’s, radium and fluor. All it takes to do this is an additional extraction and crystallisation step, according to Dr. Carla Koopman, whose PhD research arrived at this conclusion.
Koopman researched several methods. One method, which involved an ion exchange resin that ”fished” harmful metals out of phosphoric acid slurry, worked best, but was too expensive. The most elegant method was membrane extraction, in which the contaminated slurry is led through a hollow fibre. The heavy metals are diffused through the membrane and led away, while the phosphoric acid stays behind in the slurry.
In addition to contributing to other industries, this technology can be combined with another recent improvement: the ProGips process, which, when applied, means the most important by-product, gypsum, will be clean enough to use as a building material.
However, because the used membrane still requires some doctoring before it’s ready for action, the TU will continue to study the process, which, in itself, is remarkable, since the last two Dutch fertiliser production companies (and sponsors of the research project) closed their factories in the Netherlands three years ago. They relocated to Morocco and Tunis because it’s cheaper to produce the acid and environmental demands are less stringent.
”Yes, I was quite disappointed,” Koopman recalls ”But my tutor and employees at the fertiliser companies, Kemira Agro and Hydro Agri, were able to motivate me again.”
The young doctor still has hopes that the fertiliser industry will apply her method. ”Companies in China and Thailand have shown interest, and in these countries environmental legislation is also becoming stricter.”
It’s now possible to reduce 70 to 90 percent of the known contaminants in phosphoric acid, like cadmium, arsenic, lanthanide’s, radium and fluor. All it takes to do this is an additional extraction and crystallisation step, according to Dr. Carla Koopman, whose PhD research arrived at this conclusion.
Koopman researched several methods. One method, which involved an ion exchange resin that ”fished” harmful metals out of phosphoric acid slurry, worked best, but was too expensive. The most elegant method was membrane extraction, in which the contaminated slurry is led through a hollow fibre. The heavy metals are diffused through the membrane and led away, while the phosphoric acid stays behind in the slurry.
In addition to contributing to other industries, this technology can be combined with another recent improvement: the ProGips process, which, when applied, means the most important by-product, gypsum, will be clean enough to use as a building material.
However, because the used membrane still requires some doctoring before it’s ready for action, the TU will continue to study the process, which, in itself, is remarkable, since the last two Dutch fertiliser production companies (and sponsors of the research project) closed their factories in the Netherlands three years ago. They relocated to Morocco and Tunis because it’s cheaper to produce the acid and environmental demands are less stringent.
”Yes, I was quite disappointed,” Koopman recalls ”But my tutor and employees at the fertiliser companies, Kemira Agro and Hydro Agri, were able to motivate me again.”
The young doctor still has hopes that the fertiliser industry will apply her method. ”Companies in China and Thailand have shown interest, and in these countries environmental legislation is also becoming stricter.”
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