Adsorption of Chromium by Acid-Modified Dragon Fruit Peel

The research studied to use acid-modified dragon fruit peel (Selenicereus undatus) for
adsorption of chromium (III), chromium (VI) and chromium (III) mixed with chromium (VI)
in synthetic wastewater. The experimental conditions were studied consisting of contact
times, pH values and adsorbent dosages. Adsorption isotherms were evaluated. Moreover, the
laboratory wastewater was treated by this adsorbent. Adsorption column was setup to treat
the laboratory wastewater. From experimental results, the suitable contact times were 120
minutes for all types of chromium. Percent of chromium adsorption was increased when
increasing adsorbent dosage. The suitable pH values for chromium (III), chromium (VI) and
chromium (III) mixed with chromium (VI) adsorption were 3, 2 and 3, respectively.
Adsorption of chromium (III), chromium (VI) and chromium (III) mixed with chromium (VI)
were explained by Freundlich isotherm. When using acid-modified dragon fruit peel dosage
of 30 g/L, 35.40% of chromium in laboratory wastewater was adsorbed. Acid-modified
dragon fruit peel was more suitable for adsorption column than dragon fruit peel without
modification.