Simultaneous adsorption of Cr(VI) and phenol onto tea waste biomass from binary mixture: Multicomponent adsorption, thermodynamic and kinetic study

Abstract

During this investigation simultaneous removal of Cr(VI) and phenol using tea waste biomass is studied in a batch reactor. The influences of process parameters such as pH, adsorbent quantity, contact time, initial concentration on the percentage removal have been studied. The optimal pH condition for the adsorption of Cr(VI) was found acidic while that for phenol was basic but at pH 7 both phenol and Cr(VI) were adsorbed to maximum extent simultaneously onto the surface of tea waste biomass. At an optimum pH 7, temp 30 °C, adsorbent dose 15 g L-1, 99.19% of 100 mg L-1 Cr(VI) and 95.07% of 50 mg L-1 phenol were removed. The equilibrium was reached after 12 h for Cr(VI) and 24 h for phenol. The maximum adsorption capacity of tea waste biomass, according to extended Langmuir isotherm model was 199.523 and 9.487 mg g-1 for Cr(VI) and phenol, respectively. Multicomponent adsorption isotherms such as non modified competitive Langmuir, modified competitive Langmuir, extended Langmuir, extended Freundlich, competitive non modified Redlich Peterson and competitive modified Redlich Peterson model were used to study the equilibrium process at the initial concentration range of 100-450 mg L-1 of Cr(VI) and 50-225 mg L-1 of phenol. The experimental results demonstrated that both Cr(VI) and phenol were well described by pseudo second order model. Thermodynamic study depicted that adsorption of phenol onto tea waste biomass was spontaneous and exothermic while for Cr(VI) was endothermic in nature. © 2015 Elsevier Ltd. All rights reserved.