Hydrolysis And Dechroming Of Chrome Shavings And Recycling

In this paper , alkali, hydrogen peroxide and enzyme were used to dechrome and hydrolyse the shavings containing chrome. An optimal dechroming process was obtained through single factor analysis method and orthogonal.The results show that : Chrome shavings can be hydrolyzed with alkali or hydrolyzed with enzyme after oxidation dechroming using hydrogen peroxide.The collagen products recovered can be used as feed.When the shavings were treated with CaO 7% at 90℃for 6 hours,chromium content in hydrolyzate was 4.63mg/L,collagen recovery was 38%,molecular weight was about 14000 dalton. When the shavings were treated with MgO 7% at 90℃for 6 hours,chromium content in hydrolyzate was 0.53mg/L,collagen recovery was 21%,molecular weight was about 52000 dalton.The Optimize process for hydrolyzed with enzyme after oxidation dechroming using hydrogen peroxide was : the shavings were treated 8 times under ultrasonic condition with 9% H2O2, 3.0% CaO at 50℃for 70 minutes per time.Then the dechromed shavings were treated with 2709 alkaline protease 4% at 60℃for 2 hours. After treated chromium content in hydrolyzate was 1.26mg/L,collagen recovery was 45%,molecular weight was about 3000 dalton.Waste solution produced by Oxidation dechroming can be recycled .Chromium recovery was 85%. Recycled products can be used as retanning agent to enhance value and reduce the hexavalent chromium pollution.