Application of Extracellular Polymeric Substances Extracted From Wastewater Sludge for Reactive Dyes Removal

Abstract

The aim of this study was to investigate the adsorption of three commercial reactive dyes using extracellular polymeric substances (EPS) extracted from the waste sludge of a beer wastewater treatment plant in Hanoi, Vietnam. EPS was extracted from sludge by HCHO-NaOH method and characterized by the measurement of kaolin flocculation activity, dry weight, chemical composition and functional groups. Adsorption of dyes on EPS was conducted by Jartest at different pH, reaction time and EPS dosage. The EPS was composed of 25% of sludge weight. The FTIR analysis showed the present of amine and carboxyl group in the EPS structure. The removal efficiencies of reactive dyes were high at pH below 6, the contact time was from 30 to 60 min and EPS dosage of 200 – 250 mg/L. At optimum condition, the removal efficiency of 85%, 99% and 99% were obtained for Reactive Yellow 176 (RY 176), Reactive Blue 21 (RB 21) and Reactive Red 241 (RR 241), respectively. The adsorption process could be described by both Langmuir and Fruendlich isothermal equations. The maximum dye adsorption capacity for RY 176, RB 21 and RR 241 was 0.50 g/g, 0.72 g/g and 0.95 g/g, respectively. This study revealed that the EPS in wastewater sludge can be utilized as an effective adsorbent for dyes removal, thereby, enhancing the value of sludge in wastewater treatment.