(381c) Iron-Doped Porous Carbon Beads for the Removal of Methylene Blue Dye Molecules and Lead (II) Ions from Water

Rapid industrial activities are responsible for the discharge of heavy metals in to the water bodies. Synthetic azo dyes like Methylene Blue (MB) and heavy metals like lead (Pb) are non-degradable and toxic for humans. The effluents from various industries such as electroplating, textiles, pigments, leather, tanning, chemicals, automotive, mines, and refineries release lead in significant amounts. Several techniques including chemical precipitation, membrane filtration, ion exchange, biosorption, and adsorption have been adopted for the removal of MB molecules and divalent lead (Pb(II)) ions from aqueous solutions. Industries such as textile, leather, paper, plastics, etc., use dyes in order to colour their products and also consume substantial volumes of water. As a result, they generate a considerable amount of coloured wastewater. Adsorption is found to be the cheapest route for the efficient remediation of lead ions and MB dye from aqueous solution. Herein, we demonstrate the synthesis of Fe-catalysed growth of carbon nanofibers (CNFs) supported on phenolic resin-based activated carbon beads (CBs) for the adsorptive removal of Pb (II) ions and MB dye from water bodies. The phenolic resin-based carbon beads were synthesized by polymerization method using phenol, formaldehyde, triethyl amine, hexa-methylene tetraamine, poly vinyl alcohol, iron nitrate nonahydrate as the monomer, solvent, catalyst, cross-linking agent, suspension stabilizer, and the Fe-precursor salt, respectively. The synthesized beads were subjected to carbonization in N₂-environment and the steam-activation at 900^o C with an aim to improving its surface area. The activated beads were then reduced at an optimized temperature of 500 ^o C to convert iron-oxides into its elemental form and finally catalytic chemical vapor deposition (CVD) at 650 ^o C in the presence of acetylene facilitated the growth of CNFs over CBs. The final material was denoted as Fe-CNFs/CBs. The surface morphology and elemental composition of the materials at various stages of preparation were studied by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopic analysis. The synthesized material was further tested for its adsorption efficiency towards MB dye molecules and Pb(II) ions in aqueous solution. The adsorption equilibrium was achieved within 2 hours at an initial MB concentration of 100 mg/L. The batch kinetic adsorption study followed pseudo-second-order kinetics. Additionally, isotherm studies were performed over the MB concentration range of 25–300 mg/L. The study demonstrates that the prepared nano-adsorbent had an excellent maximum adsorption capacity of 318 mg/g for MB at a solution pH of 12 at 298 K. The synthesized material was further tested for its adsorption efficiency towards Pb (II) ions. The adsorption equilibrium was achieved within 4hour at an initial Pb(II) concentration of 100 mg/L. The batch kinetic adsorption study followed pseudo-second-order kinetics. Additionally, isotherm studies were performed over the Pb (II) concentration range of 10–200 mg/L. The study demonstrates that the prepared nano-adsorbent had an excellent maximum adsorption capacity of 272 mg/g for Pb(II) at a solution pH of 5 at 298 K. The maximum adsorption capacity data obtained for MB and Pb(II) systems in the present study are found to be superior to most of the literature data.