Superparamagnetic nanosorbent for water purification: Assessment of the adsorptive removal of lead and methyl orange from aqueous solutions

• Published in: The Science of the total environment 2020-04, Vol.711, p.134644-134644, Article 134644
• Main Authors: Gallo-Cordova, A., Lemus, J., Palomares, F.J., Morales, M.P., Mazarío, E.
• Format: Article
• Language: English
• Subjects: Adsorption; Iron oxide nanoparticles; Magnetic harvesting; Magnetic nanoparticles; Pollutant; Water treatment
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2019.134644

[Display omitted] •A 50.3 nm core/shell nanosorbent was synthesized for the removal of pollutants.•The 12.3 nm mesoporous silica shell was tuned to get a surface area of 570(5) m2/g.•The superparamagnetic core has a magnetization of 6 Am2/kg.•Methyl orange removal exhibited higher adsorption capacities with a qm of 240 mg/g.•Easy separation and 100% efficiency was achieved after four reusability cycles. The present study describes the preparation of 50.3 nm superparamagnetic nanosorbents with high surface area for the adsorptive removal of lead and methyl orange from water. This material is based on the surface modification of iron oxide superparamagnetic nanoparticles with a double-shell coating of mesoporous silica whose porosity was increased up to 570 m2/g by the addition of a porogenic material and its calcination. The adsorptive performance of the nanosorbent was evaluated as a function of several parameters (e.g. solution pH, pollutant initial concentration, and contact time), concluding that pHs around 5 are needed to avoid precipitation of Pb2+ as Pb(OH)2 and the equilibrium adsorption capacity is reached after 2 h in all cases. The experimental data on the adsorption capacity of lead and methyl orange onto the nanosorbent were fit to a pseudo-second order kinetic model and Langmuir isotherm model. The maximum adsorption capacity value increases from 35 up to 50 mg/gNS for lead removal with increasing nanosorbent surface area. Contrary, for methyl orange the maximum adsorption goes up to 240 mg/gNS, indicating a larger nanosorbent surface affinity for the organic matter that is able to diffuse through the silica pores as probed by the intraparticle diffusion model. In addition, we found an good reusability (100% recovering after 4 sorption/desorption cycles for methyl orange removal), which makes of this magnetic nanosorbent suitable for remediation technologies.