Ultrafiltration method for purifying water-insoluble aluminum hydrates

摘要

A process and apparatus for purifying water-insoluble particles is disclosed. The process comprises the steps of continuously recirculating a fluid aqueous suspension of the water-insoluble particles between a filtration system and a suspension reservoir; continuously conducting ultrafiltration of the recirculating suspension at the filtration system to separate an aqueous permeate containing the water- soluble impurities from the recirculating fluid aqueous suspension; continuously discharging the permeate generated by ultrafiltration; adding water to the recirculating fluid aqueous suspension undergoing ultrafiltration at approximately the same volumetric rate per hour as permeate is being discharged; monitoring the purity of the recirculating fluid aqueous suspension; and recovering the purified fluid aqueous suspension after the recirculating fluid aqueous suspension has reached a predetermined purity condition. An apparatus is also disclosed for carrying out the above process. Preferred water-insoluble particles may include lakes (particles with absorbed dye) and particles used to make lakes such as finely divided aluminum hydrate. Advantages of this invention include the ability to consistently produce high purity water- insoluble particles at low cost and with savings in manual labor. Purification according to this invention requires substantially less water than prior art methods, reducing purified water consumption and waste product disposal costs.