Surface modified polymer-magnetic-algae nanocomposite for the removal of chromium- equilibrium and mechanism studies

The present work explains the sorption ability of a novel nano-composite, Polypyrrole -iron oxide-seaweed (PPy - Fe3O4 – SW), for Cr(VI) removal. The influence of operating parameters, namely pH, contact time, nanocomposite dosage, initial Chromium concentration and operating temperature, on the hexavalent chromium removal was studied. The novel nano-composite was analyzed using FTIR, SEM and EDS to confirm the sorption of Cr(VI) and to understand the mechanism of sorption. PPy - Fe3O4– SW nano-composite removed 96.36% of Cr(VI) at the optimized conditions of pH = 2, temperature = 30 °C, initial Cr(VI) concentration = 50 mg/L, nanocomposite dosage = 100 mg and contact time = 30min. PPy-Fe3O4-SW nanocomposite has a maximum sorption capacity of 144.93 mg/g. The kinetic studies revealed that the metal adsorption obeys pseudo second order (PSO) model and the sorption was found to be monolayer in nature as confirmed by Langmuir isotherm (R2 > 0.9985). Electrostatic interaction and ion-exchange are identified as the fundamental mechanisms for Cr(VI) sorption on PPy-Fe3O4-SW composite. [Display omitted] •Fe3O4 - Polypyrrole - Ulva lactuca nanocomposite was applied for Cr(VI) sorption.•Nanocomposite has a maximum Cr(VI) uptake of 144.93 mg/g.•Sorption mechanism of Cr(VI) is electrostatic interaction and ion-exchange process.•Langmuir isotherm suitability confirms single layer of sorbent-sorbate interaction.•Desorption shows a removal efficiency of more than 72% for the first two cycles.