Synthesis and Characterization of a Novel Series of Cross-Linked (Phenol, Formaldehyde, Alkyldiamine) Terpolymers for the Removal of Toxic Metal Ions from Wastewater

A novel series of cross-linked terpolymers synthesized from phenol, formaldehyde and four alkyldiamines via Mannich reaction in n-hexane at 90∘C is introduced for the removal of lead(II) ions in the concentration range of 50–136 mgL⁻¹ from aqueous solutions. The synthesized terpolymers were characterized by spectroscopic techniques such as ¹³C-NMR, FT-IR and elemental analysis. The surface morphology, composition and crystallinity were investigated by scanning electron microscopy and powder X-ray. The adsorption of lead(II) ions was studied by batch equilibrium technique. The experimental data for the adsorption of lead(II) ions fitted Freundlich and Temkin isotherm models. The maximum adsorption capacity of lead(II) ions was found to be 222.2 mg g⁻¹ for Ph–Buta with a removal of 98 % within 4 h of adsorption. Adsorption kinetics for Ph–Buta were investigated and fitted pseudo-second-order kinetic model. The adsorption mechanism was studied by intraparticle diffusion model and found to follow film diffusion and intraparticle diffusion simultaneously. The adsorption of lead(II) ions was spontaneous and endothermic in nature with an increase of adsorption capacity as temperature increased. Ph–Buta terpolymer showed high efficacy in the removal of toxic metal ions from spiked [1 mg L⁻¹ solution of lead(II) ions] and unspiked wastewater samples with ~100 % removal of lead(II) ions. The excellent adsorption capacity of Ph–Buta provides a new, efficient adsorbent for treatment and separation of lead(II) ions from contaminated aqueous solutions and wastewater solutions.