Engineering slow-release fertilizers with tunable dissolution behavior offers a promising strategy for improving crop nutrition while simultaneously reducing production and application costs. Struvite (MgNH4PO4·6H2O) is widely recognized as a sustainable recovered phosphate fertilizer, yet limited attention has been given to control the release kinetics of all nutrient components (Mg2+, NH4+, and PO43–). This study examines the synthesis and dissolution behavior of struvite precipitated with sodium dodecyl sulfate (SDS), trisodium citrate (TC), sodium alginate (NaAlg), and competing ions (Ca2+ and Al3+) to tailor crystal morphology and multinutrient release. Structural analysis confirmed phase-pure struvite with additive-dependent diffraction patterns indicating preferred orientation and altered surface morphology. Ion release experiments showed that surfactants enhanced the exposure of Mg2+, NH4+, and PO43– rich planes, accelerating the dissolution behavior, whereas Ca and Al modified struvite displayed prolonged dissolution, with Al-modified samples releasing only 50% PO43– at 144 h. Kinetic analysis showed that ion release was predominantly diffusion-controlled, with strong agreement to the Ritger–Peppas model (R2 = 0.9977) for pure struvite. Plant assays demonstrated that Ca and Al-modified struvite sustained nutrient supply, producing ∼65 mm roots, comparable to +P controls. These results highlight the potential of ion-modified struvite as a sustainable slow-release fertilizer.
Thota et al. (Thu,) studied this question.