Biosorption characteristics of methylene blue and malachite green from simulated wastewater onto Carica papaya wood biosorbent

Abstract

The present study reports the sequestration of the cationic dyes, methylene blue (MB) and malachite green (MG) from aqueous solutions using natural Carica papaya wood (CPW) in a batch biosorption process. Characterizations of CPW were achieved by Field Emission Scanning Electron Microscopy, X-ray Diffractometer and Fourier transform infrared spectroscopy. The influence of various parameters such as solution pH, biosorbent dose, contact time, initial dye concentration and temperature were examined and optimal experimental conditions were determined. The biosorption isotherm models and kinetics characteristic of dye biosorption onto CPW were investigated. The equilibrium data followed the Langmuir isotherm model, predicted the maximum biosorption capacities of 32.25 and 52.63 mg dye per gram of CPW for MB and MG, respectively. The biosorption kinetics of MB and MG removal using CPW was better described by the pseudo-second-order kinetic equation. The experimental data obtained at different temperature of 303, 313 and 323 K for the biosorption of each dyestuff using CPW were analyzed through the thermodynamic parameters of ΔG°, ΔH° and ΔS° respectively. Experiments on the regeneration studies indicated that the biosorption capacity of CPW was consistent towards MB and MG removal upto 5 recycles by subjecting 0.1 M HCl as the desorbing agent. The current investigation revealed that the simulated wastewater showed better removal of MB and MG under the studied experimental conditions. Hence, the biomass from Carica papaya wood could be employed as an efficient, eco-friendly and economical biosorbent for the removal of MB and MG from industrial wastewater.