Regeneration of mineral sludges contg. soluble salts - by mixing with bitumen to agglomerate the particles and sepg. the water from the mastic

摘要

A bitumen, esp. a bitumen emulsion, is added to the sludge and the mixt. is stirred to agglomerate the particles. The aq. phase is then sepd. from the resulting mastic. The max. amt. of soluble salts initially present in the aq. phase to a value at which the salts remain dissolved in the aq. phase. The process is esp. useful for treating jarosite contg. sludges resulting from the hydrometallurgical prodn. of zinc. Jarosite is a complex of formula NH4 2 Fe6(SO4)4 (OH)12 . The sludge generally contains 70% solid materials and 30% residual water, with a content of about 2 wt.% (on dry sludge) of soluble zinc salts in the form of Zn++ ion. Using the process, up to 90% or more of the zinc can be reclaimed. The mastic contg. the pptd. jarosite is useful as an additive to paving asphalt to increase the hardness. In an example, a jarosite sludge contg. 193g solids, 87g water and 4g Zn++ in the aq. phase, was mixed at 60 degrees C with a bitumen emulsion contg. 54g bitumen and 20g water. 73g water was recovered contg.