De-coloration of hazardous dye from water system using chemically modified Ficus carica adsorbent

Batch adsorption studies were carried out using a novel chemically modified Ficus carica fiber adsorbent for the removal of toxic methylene blue dye from aqueous solution. The modification of F. carica fiber was carried out using acrylic acid in the presence of ceric ammonium nitrate as the initiator to change the surface morphology of the natural fibers for the improvement of interfacial adhesion between matrix and fibers. The adsorbent was characterized by scanning electron microscopy and Fourier transformer infrared spectrometer. The effect of process parameters such as pH, adsorbent dosage, concentration, reaction temperature, contact time, electrolyte and surfactants were studied. The adsorption equilibrium was represented with Langmuir, Freundlich, Tempkin, and Harkin's-Jura and Dubinin-Radushkevich isotherm models. The maximum adsorption capacity of methylene blue onto adsorbent was 75.87 mg g ^{- 1}. The pseudo-first order, pseudo-second order and intraparticle diffusion models were tested and it is revealed that adsorption of methylene blue onto adsorbent follows the intraparticle diffusion model. Thermodynamic parameters such as enthalpy change (δH), entropy change (δS) and free energy change (δG) were evaluated to predict the nature of adsorption. The calculated values of δH, δS and ΔG for uptake of MB were 33.13 kJ mol ^{- 1}, 173.46 J mol ^{- 1} K ^{- 1} and - 19.43 kJ mol ^{- 1}, respectively. This indicated the endothermic and spontaneous nature of the adsorption process. The desorption experiment showed that 60.04% of dye was recovered from the aqueous system.