Fabricating pine needles derived spherical nanocellulose with polyaniline and montmorillonite clay for simultaneous removal of cationic and anionic dyes from binary mixtures

Herein, pine needles derived spherical nanocellulose (SNC) was combined with aniline to form SNC-polyaniline (SNC-PANI), followed by modification with montmorillonite (MMT) to form SNC-PANI-MMT composite. The as-synthesized materials were characterized by FTIR, XRD, XPS, TGA, FESEM, and EDS and evaluated for the simultaneous adsorption of cationic and anionic dyes, malachite green (MG), and Congo red (CR) from MG-CR mixture, and fuchsin basic (FB) and methyl orange (MO) from FB-MO mixture. Non-linear kinetics of adsorption showed the anionic dyes, CR and MO to follow pseudo-first order kinetics with 91.30 % and 85.50 % removal, respectively, while the cationic dyes, MG and FB followed Elovich model with 95.10 % and 83.10 % removal, respectively. Non-linear isotherm analysis showed all the dyes to follow Langmuir isotherm with maximum adsorption capacity of 282.394 and 298.420 mgg^-1 (120 min, 25 °C, 7.0 pH) for MG and CR, respectively, whereas the same for FB and MO were 194.126 and 185.757 mgg^-1, respectively. The dyes were adsorbed through electrostatic, π-π, ion-dipole interactions, and hydrogen-bonding. The SNC-PANI-MMT showed regeneration and reusability upto nine cycles with high cumulative adsorption capacity. Thus, the composite has appreciable cost-effectiveness, high sustainability, environmental friendliness, and holistic characteristics for the treatment of real dyes-polluted wastewater.