Extensive investigation on the study for the adsorption of Bromocresol Green (BCG) dye using activated Phragmites karka

Abstract

Removal of Bromocresol green (BCG) dye from aqueous solution has been investigated using activated bio-sorbent Phragmites karka (PK). Batch adsorption method has been adopted and different parameters such as; pH of the solution, contact time, agitation speed, APK/BCG dose and temperature has been studied. From the resulted adsorption data the process is optimised and the transportation mechanism of BCG onto APK phase is proposed. In this study the bio-adsorbent PK is charred using H2SO4 to produce activated Phragmites karka (APK) which appears as an effective adsorbent on enhancing the loading efficiency of BCG than PK without activation. The BCG adsorption efficiency is increased from 16.05 to 84.2 % with increasing in acidity of the solution and maximized at pH 0.5 of solution. Maximum loading capacity of 392.3 mg/g is resulted using APK as adsorbent while removing BCG at ambient condition. The PK, APK, BCG loaded APK, and BCG are characterized by SEM, UV-vis and FTIR to ascertain the adsorption process as well as mechanism. The absorption peak obtained at 3450 cm-1 due to ν (O-Hstr) of BCG was shifted to a broad band at 3270 cm-1 shows the conjugation of BCG on surface of the APK, confirming the transporation of BCG to APK Phase as resulted from FTIR analysis. From the adsorption kinetics study, the rate of BCG adsorption shows well fit to the pseudo second order model than pseudo first order kinetic model. The positive value of, ∆Ho 2.49 kJ/ mole obtained by thermodynamic study reveals the endothermic nature of adsorption and and ∆So 24.87 J.K-1mol-1 shows the increase in degrees of freedom of BCG during adsorption. Equilibrium data are analysed by Langmuir, Freundlich and Tempkins adsorption isotherm to establish adsorption mechanism and the results shows best fit with Freundlich (R2=0.99) isotherm and reveals that the adsorption is of chemisorptions type.