Enhanced toxic dye removal from wastewater using biodegradable polymeric natural adsorbent

Abstract

In this study, the toxic cationic dye of methylene blue (MB) was encapsulated by the polymeric natural carbohydrate of turmeric powder (TP) adsorbent. The natural TP adsorbent was characterized to define the functional groups existing for complexation ability to the MB dye molecules. The MB dye adsorption system was optimized by varying the parameters of contact time, pH, initial concentration, competing ions and elution operations. The contributions of adsorption and complexation on MB dye removal by TP adsorbent was quantified at wide pH ranges for the determination of optimum condition and the maximum overall MB dye removal of 99.5% was obtained at pH 7.0. In the acidic pH region, the positively charged protonated TP adsorbent did not favor the adsorption of positively charged protonated MB due to electrostatic repulsion. In the neutral pH area, the dye molecule adsorption of positively charged MB dye onto negatively charged deprotonated TP adsorbent via electrostatic attraction and the complexation of MB dye with TP adsorbent via the formation of complexation and ion-exchange mechanism. The adsorption data were highly fitted to the Langmuir adsorption isotherm, and the maximum adsorption capacity was 157.33 mg/g. The ethanol was used an eluent in the elution operation, and the TP adsorbent was used in many cycles without loss in its original performances. Therefore, the carbohydrate polymeric TP adsorbent has shown favorable dye capturing ability from water samples, and this could be used as efficient adsorbents in potential practical applications for organic dye removal from wastewater to keep the water quality in safe for human health.