ABSTRACT
The extraction of metal values from some ores requires the use of hydrometallurgical techniques which employ ammoniacal lixiviants. The metal values are recovered from the pregnant liquors, leaving an aqueous wastewater which is high in dissolved solids and ammonia. The possible methods of removing ammonia from wastewaters include biological nitrification-denitrification, break point chlorination, evaporation, reverse osmosis, ion exchange, air stripping, and steam stripping. This chapter presents a study that focuses on steam stripping which has been reported to be capable of removing over 99% of ammonia in high-strength industrial wastes. The selection of a model for the study was based on several criteria. These include: the model should be able to predict the distribution of inorganic chemical species, both in dissolved and precipitated forms, before and after pretreatment for pH adjustment. The model should be based on the state-of-the-art theories and principles on chemical speciation and reaction-path estimates. The variability of wastewater composition has a significant effect on the overall treatment process.
