Dual responsive superparamagnetic nanocomposites: Synthesis, characterization and adsorption of nitrate from aqueous solution

Abstract In this work, a diblock polymer, poly (methacrylic acid)-block-poly (N-isopropylacrylamide) P(MAAc-b-NIPAM) was synthesized. Fourier transform infra-red (FTIR) and  1HNMR spectroscopy and gel permeation chromatography (GPC) were used for characterization of the polymer. The polymer was coated with magnetic nanoparticles as characterized via X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), vibration sample magnetometry (VSM), thermogravimetric analysis (TGA), and dynamic light scattering (DLS). The adsorption of nitrate from aqueous solution was studied in detail and the performance of the nanoparticles was evaluated. The adsorption conditions were optimized by changing different variables such as pH, concentration of NO3 - anion, contact time, and adsorbent dose. The adsorbent exhibited maximum efficiency for removal of the nitrate at pH 4, initial concentration of 40 mg/L, and amount of adsorbent of 0.08 g/L at room temperature (23 ± 2 °C). Langmuir, Frenudlich, Temkin and Dubinin–Radushkevich equations were used to interpret adsorption equilibrium. Langmuir Type (II) isotherm showed the best correlation (R 2 = 0 .9998). Lagergren pseudo-first-order, pseudo-second-order, the Elovich model, Ritchie second order and intraparticle diffusion models were used to explain adsorption kinetics. The experimental data showed best fit to pseudo-second-order (R 2 = 0 .999) kinetics.