Addressing the global problem of polluted water requires sustainable, efficient, and scalable remediation solutions, such as electrospun polyvinyl alcohol (PVA) membranes incorporating specific nanoadsorbents. The retention of contaminants depends on membrane swelling, morphology, and the adsorbent within the nanofiber. This study investigated the effect of relative humidity (RH) within the electrospinning chamber on the morphology of the resulting mats and how this affected the flow dynamics depending on whether or not the permeating liquid induced swelling in the membranes. An insolubilized PVA membrane was used as a hydrophilic filter model and a PVA membrane filled with iron oxide nanoparticles (IONPs) as a composite model (PVA + IONPs). The presence of IONPs increases the nanofiber diameter, which decreases when prepared under intermediate RH (IRH). Consequently, the nanofiber configuration, which is critical for filtration tortuosity, is influenced by RH. The initial swelling results in over 60% greater water flux through PVA + IONPs compared to PVA at an equivalent RH. This characterization helps to optimize membrane applications, highlighting that PVA + IONPs exhibit lower permeability values at IRH, indicating improved contaminant retention capabilities.

Effective arsenic remediation requires maximizing the loading and accessibility of active iron phases, a persistent challenge that has limited the development of practical superadsorbents. Here, a seed‐assisted anisotropic growth strategy is applied to electrospun poly(vinyl alcohol)/pectin nanofibers by sequentially introducing Fe ²⁺ and Fe ³⁺ ions. This dual‐ion approach generates ∼2‐nm iron seeds that direct the growth of rice‐grain‐like iron oxyhydroxide nanostructures (29 ± 6 nm × 110 ± 20 nm; aspect ratio ∼4), achieving loadings and surface accessibility unattainable with conventional single‐doping. The resulting morphology exhibits a high iron content (1.72% at, a 12‐fold increase over single‐ion doping [0.04%–0.14%]), yielding a superadsorbent that reduces As(V) from 1 mg L ⁻¹ at pH 6 to below the WHO guideline (10 µg L ⁻¹ , ∼99% removal) using only 1 g L ⁻¹ dose. High removal efficiency is retained at neutral and basic pH (∼30 µg L ⁻¹ ), substantially outperforming single‐doped materials ([245 ± 15] µg L ⁻¹ , ∼75% removal). Structural analysis (FE‐SEM, EDS, SAXS, WAXS) elucidates the seed‐mediated growth mechanism, whereas kinetic and isotherm studies indicate chemisorption and accelerated cooperative binding. The material is reusable over several cycles, and remains effective in the presence of competing ions, establishing seed‐mediated growth as a powerful route to high‐performance nanostructured superadsorbents.