Tea industry waste activated carbon as a low-cost adsorbent for methylene blue removal from wastewater

Abstract

The possible utilization of tea industry waste activated carbon (TIWAC) as an inexpensive, eco-friendly bio adsorbent for methylene blue (MB) removal from wastewater was studied. Phosphoric acid was used as the activating agent for the preparation of TIWAC and Scanning Electron Microscopy and Fourier Transformed Infrared Spectroscopy were used to characterize TIWAC. In this work batch experiments were carried out at pH 7 and at temperature of 30±2 r to study the efficiency of MB adsorption on to TIWAC under different conditions such as TIWAC dosage, MB concentration, pH of the solution, and agitation time. The adsorption characteristics of the sorbent was tested with Freundlich and Langmuir adsorption models and the kinetic studies were conducted to determine the order of the adsorption process. The adsorption capacity of MB and the maximum % removal of MB by TIWAC were found to be 233.51 mg g and 77.8% respectively at the optimized adsorption conditions (TWAC dosage= 0.001 g, MB concentration= 300 mg/L, agitation time=6 hrs) at pH 7. Isotherm data were satisfied Langmuir model than Freundlich model and kinetic data were best fitted with the pseudo first order model. Most importantly, the Langmuir constant, the maximum adsorption capacity value (q0); obtained for adsorption of MB onto 77WAC was 303.3 mg g4 , which is significantly greater than that of the adsorption of MB by various other bio¬sorbents reported in the literature. Bench-scale fixed-bed column experiments were also carried out at various flow rates to study the practical usability of the adsorbent and it was found out that the breakthrough time was decreased with increasing flow rate. The results of this study indicate that TIWAC is an effective and environmental friendly adsorbent for removal of dye from wastewater.