PURPOSE: To effectively utilize toxic sulfuric acid sludge being a by-product from a process for re-treating used oils by forming intermediate sludge from the sulfuric acid sludge without environmental pollution by adjusting the sulfuric acid sludge to a pH in a specified range.
CONSTITUTION: First, a high-pH material (desirably, water) is added to sulfuric acid to adjust it to a pH, desirably 3-7, being high enough for the sludge to form particles and keep a molten state at a high temperature, especially, near 190°C and being not such high as to cause the sludge to become particulate at ordinary temperature and to insolubilize the sludge. Thus, an intermediate mixture containing a highly acidic substance layer comprising a liquid containing sulfuric acid, etc., and an intermediate sludge layer of a H of 3-7 from the sulfuric acid sludge, and the highly acidic substance layer and the intermediate layer are separated from each other by a process such as decantation to obtain the intermediate sludge. It is suitable that bronze asphalt being a bitumen material is obtained by heating the intermediate sludge at 200-275°C.
JPS5440849A | 1979-03-31 | |||
JPS51111207A | 1976-10-01 |
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