Utilization of Chromium Waste from Tanning Industry as Ceramic Glaze
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Waste from tanning industry contains chromium. Inappropriate waste handling can cause environmental pollution because the waste is hazardous and toxic materials, where the concentration of chromium in waste was 56314.026 ppm. Chromium waste has potential as stain on ceramic industry and been known as chrome green. The objectives of research are to investigate leach ability of immobilized chromium and to investigate the glaze quality and its characteristic.
The research was conducted according to the variation of the chromium waste amount in the glaze mixture. The basic glaze composition was 35% of feldspar, 35% of borax, 15% of kaolin and 15% of quartz sand. Chromium waste as much as 0%, 15%, 30% and 45% was added to the basic glaze mixture. Glaze was applied by brush on the surface of ceramic body and fired at 1100 oC for 8 hours.
Based on TCLP test, the concentration of chromium was ranging from 0 ppm – 2.960 ppm. The more chromium waste was added, the chromium concentration increased. Based on tank leaching test, chromium concentration of D sample in the leachate was very low, ranging from 0.08 ppm – 0.13 ppm. The chromium concentration of TCLP and tank leaching test was lower than allowable limit (5 ppm) according to Peraturan Pemerintah No 85/1999. It means the immobilization of chromium was successful. The result of research showed that the hardness of glaze was 8 of Mohs scale, 6 of Mohs scale, 5 of Mohs scale, and 4 of Mohs scale. The more percentage of chromium waste was added, the lower hardness of glaze would be obtained. However, the hardness of each sample still meet the quality standard of SNI 15-4249-1996, that is minimum 4 of Mohs scale. The addition of chromium waste as much as 0%, 15%, 30% and 45% resulted variations of green colour. The more chromium waste was added, the green colour of glaze was darker.