Simultaneous solidification of potassium and phosphorus using rice straw charcoal and saturated phosphorus adsorbent

Phosphorus (P) ore is an expensive and limitedresource that will be depleted in a few decades if the currentglobal consumption rate continues. Japan, one of themost developed countries in the world, relies completely onimported phosphate rock for P. Potassium (K) ore, which isequally important for continuous development, is also becomingincreasingly expensive. The recovery of P and K istherefore important for continuous and sustainable development.In this study, concentrated P (obtained from eluent)and K (obtained through alkali leaching of rice strawcharcoal) were recovered as potassium magnesium phosphate(PMP) through the controlled addition of magnesium(Mg). A PMP crystal was produced when an equimolar(with respect to P) Mg solution was added to the leachingsolution (rich in P and K) at a pH range of 11–12. Thus, theproduction of PMP in a crystalline form demonstrates thehuge scope for the recycling of limited resources.