Impact of pH on Release of Ni in Cement Product from Coprocessing Waste in Cement Kiln
Clinker was produced by simulating cement calcinations test,and concrete samples were also prepared. Impact of pH on the release of Ni in the concrete samples was studied using similar method of EA NEN 7375,with five different leachants. Results showed that the cumulative release amount of Ni in the concrete was 1.64,0.167,0.038,0.019 and 0.025mg/kg when pH of leachant was 2.00,3.50,5.00,7.35 and 10.0 respectively. In the acid condition,the cumulative release amount decreased with the increase of pH,and reached the minimum at weak alkaline condition. In the alkaline condition,the measured cumulative release amount increased with the increase of pH. pH could affect the release process of Ni. Diffusion control was the major release mechanism of Ni in the leachants with pH 3.50 and 7.35,and release curves fit the standard line which slope was 0.5 very well and slopes of different increments were all between 0.35 and 0.65. In the prophase and metaphase,diffusion control was the major release mechanism of Ni in the leachants with pH 2.00 and 5.00,but depletion occurred in the anaphase. In the leachants with pH 10.0,delayed diffusion occurred in the prophase,diffusion control was the major mechanism in the metaphase and depletion occurred in the anaphase.