METHOD FOR PRODUCTION OF ORGANO-MINERAL FERTILIZER Russian patent published in 1995 - IPC

FIELD: agriculture. SUBSTANCE: sediments of sewage with high content of heavy metals presents a serious ecological problem due to its difficult utilization. Method provides for removal of heavy metals from sewage sediments with the help of nitric acid solutions in apparatus with stirrer and heating. Leaching is accomplished with solution of nitric acid with concentration of 1.00-1.25 mole/cu. dm at temperature of 50-70 C for 10-20 min. Process conducted with solid-to-liquid phase ratio of 1:5 and Reynolds numbers ≥ 1·10⁵ results in remaining heavy metal content admissible for such fertilizers. High temperature makes it possible to obtain coagulated sediment that simplifies its filtering and accelerates the process of removal of heavy metals. After filtration by means of drum-type vacuum filter of leaf press-filter, residual acidity is neutralized with alkalis such as KOH, NH₄OH and CaCO₃ to obtain the desired organo-mineral fertilizer. Separated metals are precipitated from solution and processed into slime from which they are regenerated. EFFECT: higher efficiency. 1 tbl