Toxic metal contamination in aquatic systems commonly occurs as multicomponent mixtures, making competitive adsorption assessment essential for realistic adsorbent evaluation. This study investigated corn stalk-derived hydrochar functionalized with Mg-Fe layered double hydroxide (Mg–Fe-LDH@HC) for simultaneous Cd(II) and Zn(II) adsorption in aqueous bicomponent systems. The material was evaluated through pH and dosage optimization, kinetic assays, bicomponent equilibrium modeling, thermodynamic assessment, mixture-design experiments, regeneration tests, and applicability assays with interfering ions and real water matrices. Under the selected conditions, pH 6.75, 4 g L⁻¹ Mg–Fe-LDH@HC, 1 mM equimolar Cd(II)/Zn(II), 298.15 K, and 180 min, near-complete removal of both metals was achieved. Kinetic analysis showed rapid initial uptake followed by a slower approach to equilibrium. Bangham, Elovich, and Weber-Morris analyses supported a multistage adsorption process involving external surface uptake, diffusion-related resistance, and heterogeneous surface interactions, although intraparticle diffusion was not the sole rate-controlling step. Bicomponent equilibrium was better described by heterogeneous models, particularly the double-layer model and Extended Sips, indicating non-equivalent adsorption domains. Thermodynamic parameters showed favorable and mildly endothermic adsorption with limited temperature dependence. Mixture-design experiments demonstrated that metal proportion influenced adsorption more strongly than temperature, with increasing Cd(II) fractions reducing Zn(II) retention. Overall, Mg–Fe-LDH@HC showed promising performance for Cd(II)/Zn(II) removal under competitive conditions, although the adsorption pathway should be interpreted as an evidence-supported combined process rather than individually confirmed mechanisms.

Nano-enabled fertilizers and precision agriculture are increasingly framed as complementary strategies to enhance nutrient-use efficiency and reduce environmental footprints. However, their operational integration remains unclear because precision denotes either spatial field management or targeted nano-enabled release. This scoping review evaluated whether nanofertilizers have been operationally integrated into spatially explicit nutrient-management systems. Systematic searches in Scopus and Web of Science, complemented by citation tracing, identified 60 reports representing 59 unique evidence units. An operational framework disaggregated integration into spatial decision-making (S), differential nano-enabled deployment (N), and spatially resolved outcome validation (O), with validation maturity coded from V0 to V6. Of the 59 evidence units, 52 (88.1%) represented conceptual convergence, five (8.5%) technological proximity without operational coupling, and only two (3.4%) advanced partial integration. The review did not identify a fully assessed study that demonstrated the complete S–N–O sequence. The two most advanced cases followed complementary pathways: S-N without spatial outcome validation, and S-O with uniform nano-input application. Citation tracing also revealed that secondary claims often overstate operational maturity relative to primary evidence. Closing this gap requires establishing field-scale S–N–O workflows that explicitly link spatial diagnosis, differential nano-actuation, and multi-zone agronomic and environmental validation.