PRODUCTION OF NEUTRALIZED MATERIAL HAVING HIGH BULK DENSITY

摘要

PROBLEM TO BE SOLVED: To obtain a neutralized material having a high bulk density from a solution containing zinc by preadding zinc oxide to the solution and then raising the pH to a specific value or above when neutralizing the solution containing the zinc. SOLUTION: Zinc oxide is preadded to a solution containing zinc and the pH thereof is then raised to >=9.5 when neutralizing the solution containing the zinc. The amount of the zinc oxide added at that time is preferably 0.03-1 expressed in terms of zinc oxide/zinc hydroxide (weight ratio) based on the amount of zinc in the solution and the pH thereof is preferably raised to 10.0-12.0. For example, various amounts of the zinc oxide (having 80μm average particle diameter) are added to 1.0L solution containing zinc sulfate in an amount of 1.0g/L expressed in terms of zinc and the pH thereof is then regulated to 10.5 by using Ca(OH)2 to precipitate the zinc. After completing the reaction, pH is reduced to 9.5 by using sulfuric acid and a nonionic flocculant is added in an amount of 0.35g/m<3> thereto. The resultant mixture is allowed to stand for 24hr to determine the volume occupied by the neutralized material in the aqueous solution and the amount of the neutralized material. Thereby, the slurry concentration is calculated.