Treatment of the caustic extraction waste stream of a sulfate pulp process

Abstract

The purpose of this investigation was to evaluate the use of NUCHAR activated carbon and aluminum sulfate as agents for removing a significant amount of color V from the caustic extraction waste of a sulfate pulp process.

After a thorough search of the related literature was completed, experimental tests were conducted using activated carbon and aluminum sulfate. Fourteen tests employing activated carbon were made at 25 °C, pH values of waste ranging from 3 to 11.4, carbon content of 0.1 and 0.3 gram per 100 milliliters of waste, and stirring times of 1, 3, 5, 10, 15, and 30 minutes.

Treatment of the waste with aluminum sulfate was s conducted at temperatures of 25, 60, 61, and 62 °C, pH values of waste of 6, 7, 8, 9, and 10, and alum additions of 0.6, 0.0, 1.2, and 1.5 grams alum per liter of undiluted waste, Stirring time for these e treatments was 5 minutes at 75 revolutions per minute and 25 minutes at 45 revolutions per minute. Filtration of the sludge from alum coagulation of the caustic waste was performed through a sand bed and by vacuum through filter aid. Filtration through filter aid indicates a greater possibility of development into a workable process.

It was concluded from this investigation that NUGHAR CEE-N activated carbon will not remove a significant amount of color free the caustic waste at the above conditions, but alum coagulation of the waste at pH of 6, temperature of 25 °C„ alum dosage of 1.5 gram per liter of waste, and stirring of 5 minutes and 25 minutes at 75 and 45 revolutions per minute, respectively, will decrease the color content of the waste approximately 90 per cent.