Development of effective nano-biosorbent based on poly m-phenylenediamine grafted dextrin for removal of Pb (II) and methylene blue from water.

Novel nano-biosorbent was successfully prepared based on dextrin-g-poly m-phenylenediamine (DgPmPDA) and graphene oxide (GO) by using the solution blending technique and was found to be an effective adsorbent for Pb(II) and methylene blue (MB) dye. The nano-biosorbent was characterized by FTIR, CHN, XRD, SEM, AFM and TGA. The adsorption process depended on the pH of solution, adsorbent dosage, contact time, initial concentration of Pb(II) and MB, and temperature. Experimental results were in good agreement with Langmuir isotherm model for both Pb(II) and MB adsorption. The maximum adsorption capacity (Qmax ) of Pb(II) and MB was found to be 80 mg/g and 76.33 mg/g, respectively, at optimum conditions. Results showed that the kinetics of Pb(II) and MB onto the DgPmPDA@GO nano-biosorbent followed the pseudo-first-order and pseudo-second-order models, respectively. Thermodynamic parameters exhibited the endothermic and spontaneous nature of the sorption process. A possible mechanism of adsorption was suggested where π-π stacking interactions, H-bonding interaction and electrostatic attraction controlled the MB adsorption and chelation and electrostatic attraction controlled the Pb(II) adsorption.