Technique of Phosphorus Recovery from Charcoal of the Water Sludge by Hot Alkali Water Extraction

In order to make utilize the charcoal of water sludge, charcoal of the sludge was mixed with a aq. solution of NaOH or KOH, and heated at 90°C - 120°C. Phosphorus was extracted by the addition of hot water, and separated by filtration. The phosphorus in the filtrate was recovered through crystallization followed by concentration and cooling at a low temperature. The recovered phosphorus was considered sodium phosphate (Na3 PO4 12H2 O) or potassium phosphate (K3 PO4 H2 O) from the recovered condition and X-ray analysis. The phosphorus recovery rate was estimated at about 60%-70% Reuse of the alkali which was not used in the recovery process, and the concentration method of the extracted phosphorus was investigated.