Adsorption of Reactive Red 141 from wastewater onto modified chitin

This research involved the adsorption of synthetic reactive dye wastewater (SRDW) by chitin modified by sodium hypochlorite and original chitin in batch experiments. The comparison of maximum adsorption capacity used the Langmuir model to describe SRDW adsorption onto chitin and modified chitin under a system pH of 11.0. Maximum dye adsorption by chitin increased from 133 mg g−1 to 167 mg g−1 at temperatures of 30-60 °C, respectively. For modified chitin, the capacity decreased from 124 mg g−1 to 59 mg g−1 when the temperature increased from 30 °C to 60 °C, respectively. Both Na2SO4 and Na2CO3 increased in dye adsorption. The spectra of attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectrometry confirmed the hydroxyl groups as functional groups of modified chitin, which affected the modification and the SRDW adsorption. The adsorbed dyes were eluted by distilled water and 1 M NaOH to confirm the dye adsorption mechanism. Total elution of modified chitin and chitin were 92.76% and 55.29%, respectively. Although modified chitin had a maximum adsorption capacity less than chitin, elution of the dye from modified chitin was easier than chitin. Therefore, modified chitin could be suitable in a column system for dye pre-concentration as well as wastewater minimisation. In addition, the column study showed that modified chitin could be used for more than four cycles of adsorption and elution by distilled water.