Recyclable Poly(4-styrenesulfonic acid-co-maleic acid)-coated magnetite nanoparticles: Colloidal stability and interfacial inhibition of mineral scale formation

This work reports the synthesis and interfacial performance of poly(4-styrenesulfonic acid-co-maleic acid)-coated magnetite nanoparticles (Fe₃O₄@PSSMA) as a recyclable, environmentally benign material for inhibiting mineral scale formation in high-salinity aqueous systems. Magnetite nanoparticles were prepared by co-precipitation and coated with PSSMA, a dual-functional copolymer providing sulfonate and carboxylate groups for enhanced colloidal stability and surface binding to scale-forming ions. The resulting nanocomposite contained ~65 wt.% polymer and retained superparamagnetic properties, enabling magnetic separation and reuse. Comprehensive characterization (XRD, FT-IR, TGA) confirmed structural integrity and successful surface functionalization. Static and high-pressure dynamic tests demonstrated complete inhibition of gypsum at concentrations as low as 5 ppm, along with significant suppression of calcite and barite precipitation. SEM imaging revealed pronounced morphological disruption of scale crystals, indicating that inhibition occurs via interfacial adsorption and alteration of crystal growth pathways. The Fe₃O₄@PSSMA maintained full gypsum inhibition over four reuse cycles and remained stable in brines containing up to 10,000 ppm Ca²⁺. By integrating colloidal stability, interfacial control, and magnetic recoverability, this approach offers a sustainable platform for mitigating mineral scaling in industrial water systems.