Batik is a technique of wax-resist dyeing applied to whole cloth. The applied wax resists dyes and therefore allows the artisan to color selectively by soaking the cloth in one color, removing the wax with boiling water, and repeating if multiple colors are desired. UNESCO classification of Indonesian batik as part of the cultural heritage in 2009 significantly increases the popularity and demand of batik. The batik industry needs high volumes of high quality water, resulting it into large amounts of highly colored wastewater. These dyes contain functional groups which make them quite stable in the environment and can cause environmental pollution and human illnesses if not treated properly. In this study, synthetic batik wastewater containing 32mg/L reactive orange 16, 32mg/L reactive black 5, and 2g/L sodium silicate was treated by using ozonation in a 2L batch reactor. In 5 minutes of ozonation (12g/m~3 , 4L/min), the color unit of wastewater significantly reduced from over 1000 to below 50. Three-dimensional fluorescence spectroscopy analysis indicated degradation of reactive orange 16 and reactive black 5. The TOC concentration reduced from 19.72 mg/L to 14.76 mg/L. Reactive dyes were alkaline and pH value was not affected by the ozonation process.
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