4. Conclusions
The recovery of P from MSWI fly ash with acidic leaching and
precipitation (Method I) and acidic and alkaline leaching (Method
II) was investigated in this study. Method I resulted in a recovery of
70% of P content of the ash and the final product contains about 3%
P, which is slightly higher than the content of sewage sludge and
the low grade phosphate ore. However, the trace metal content
limits direct application of this product on agricultural land. It is
suggested that the P product is used as a secondary resource for
phosphates production, thereby mitigating the use of this nonrenewable
mineral resource. The method is currently optimized
by complementing the P recovery with extraction of metals, and,
usage of industrial liquid wastes instead of chemicals and reduction
of materials requirements.
Method II resulted in