Synthesis of Guar gum/bentonite a novel bionanocomposite: Isotherms, kinetics and thermodynamic studies for the removal of Pb (II) and crystal violet dye

In the present study, the performance of Guar gum/bentonite bionanocomposite was evaluated for the sequestration of Pb (II) and crystal violet (CV) dye from aqueous solution. The bionanocomposite was characterized by SEM, EDX, FT-IR, XRD, TGA, BET and TEM techniques. The bionanocomposite showed porous, crystalline nature with particle size ranging between 3 and 11 nm and increased thermal stability. The point of zero charge was found to be 2.2. The maximum adsorption was observed at pH 5.1, 7.6 and contact time 240 min, 300 min for Pb (II) and CV, respectively. The kinetic study revealed that the adsorption process of Pb (II) and CV onto the bionanocomposite followed the pseudo-second order model, confirming chemisorption as a rate determining step. The adsorption isotherm was in good agreement with the Freundlich for Pb (II) and Langmuir for CV isotherm model, respectively. Thermodynamic studies showed that the process was physiosorption, spontaneous and endothermic with increased in randomness. The desorption study of Pb (II) and CV exhibited the excellent regenerative efficacy (upto fifth cycle) of bionanocomposite using 0.1 M HCI. The bionanocomposite has also been successfully applied for the removal of heavy metals from electroplating, battery manufacturing and medical wastewater before and after spiking CV dye solution to it. (C) 2017 Elsevier B.V. All rights reserved.