Sustainable scale control via direct EDTMP functionalization of magnetite nanoparticles: Interfacial inhibition with magnetic recovery

ABSTRACT Oilfield scale control requires inhibitors that combine high efficiency with environmental compatibility and long-term deployability. Here, we hypothesize that direct functionalization of magnetite nanoparticles (Fe 3 O 4 ) with a non-polymeric phosphonate, ethylenediamine tetra(methylene phosphonic acid) (EDTMP), can preserve inhibitor activity while enabling magnetic recovery and reuse without the limitations of polymer-based coatings. Fe 3 O 4 @EDTMP nanocomposites containing ~49 wt.% EDTMP were synthesized via a simple co-precipitation and surface coordination approach. The material showed strong scale inhibition performance against gypsum and calcite, achieving complete inhibition at ≥10 ppm under static conditions and maintaining high efficiency over four reuse cycles. Under dynamic flow conditions (100 °C, 1000 psi), the system effectively suppressed gypsum and calcite scaling at low concentrations (1–5 ppm), while higher concentrations were required for barite, likely due to its rapid nucleation kinetics and the limited accessibility of surface-bound inhibitor groups. Importantly, Fe 3 O 4 @EDTMP demonstrated improved calcium compatibility compared to pure EDTMP, remaining stable up to 10,000 ppm Ca²⁺ without precipitation. These results indicate that the combination of inhibition performance, enhanced stability, and magnetic recoverability makes this system a promising candidate for more sustainable and low-discharge oilfield scale management.