Surface modification of nanocellulose using polypyrrole for the adsorptive removal of Congo red dye and chromium in binary mixture.

In this study, nanocellulose was synthesised by acid hydrolysis of cellulose and was coupled with polypyrrole supporting matrix. The synthesised nanocellulose polypyrrole composite (NCPPY) was characterised by FESEM, XRD, FTIR, BET, TGA/DSC and NMR. These analysis showed the conversion of cellulose to nano sized crystalline structure with excellent thermal stability and higher surface area. The effect of different parameters like pH, temperature, contact time, adsorbent dosage and initial concentration of Chromium (Cr(VI)) and Congo Red (CR) were optimised in batch mode. Response Surface Methodology (RSM) has been employed as an optimization tool for the efficient removal of Cr(VI) and CR and the maximum removal efficiency was found to be 80% and 85% respectively. The Langmuir and Freundlich isotherm well fitted the equilibrium data for CR and Cr(VI) respectively. Thermodynamic data showed that the biosorption of Cr(VI) and CR on NCPPY is an endothermic, spontaneous, and entropy-driven process. The adsorption kinetic followed pseudo-second-order for Cr(VI) and intraparticle diffusion for CR. Effect of co-existing ions were checked using several common salts and heavy metals. Results indicated that NCPPY has great potential to remove Cr(VI) and CR binary mixture under simulated conditions.