Calcined lotus leaf as a low-cost and highly efficient biosorbent for removal of methyl violet dye from aqueous media

Abstract

ABSTRACT In this investigation, methyl violet dye (MV) was removed from aqueous media using calcined lotus leaf (CLL). To do this, the characterisation of the CLL was determined using various analyses including XRD, SEM, EDX, Map, FTIR, and BET. Based on the BET analysis, the specific surface area of the bioadsorbent was evaluated as 123.95 m2/g. The crystal phases in the CLL can be attributed to the graphite structure with aromatic layers in the synthesised activated carbon. Also, the maximum removal efficiency of 99.73% was attained at a pH value of 7, sorbent dosage of 2 g/L, initial dye concentration of 1 mg/L, the contact time of 50 min, and 25ºC. The CLL indicated a remarkable removal efficiency ever achieved for MV. Moreover, the maximum biosorption capacity of 26.315 mg/g was obtained using the Langmuir model. The equilibrium study revealed that the Freundlich isotherm model describes a better model for the adsorption of the MV dye on the surface of the CLL. In addition, an investigation into the sorption kinetics indicated that the quasi second-order kinetic model could better illustrate the adsorption mechanism. Moreover, based on the thermodynamic study, the sorption process was spontaneous and exothermic.