Sustained release of Zn from zinc sulfide nanoparticles (ZnS NPs) amplified the bioaccessibility of Zn in soil: Adsorption dynamics and dissolution kinetics

Controlled-release micronutrient supplementation to provide better bioavailable zinc (Zn) under alkaline soil conditions is a concept of commercial pertinence for sustainable agriculture. High pH stable nano-scaled ZnS is the material under study in the present investigation where the adsorption dynamics and dissolution kinetics of sono-chemically synthesized zinc sulfide nanoparticles (ZnS NPs) were evaluated in comparison to ZnSO4 in Lufa 2.2 soil for supplementation of Zn. The mechanism of adsorption of ZnS NPs and ZnSO4 onto Lufa 2.2 soil was well explained by fitting into the Freundlich adsorption model and pseudo-second order equation. ZnS NPs reflected the stronger ability to get adsorbed on the Lufa 2.2 soil as compared to metal ions, due to higher surface reactivity of NPs and higher Kf value (0.557) than ZnSO4 (0.463). Time relevant enhancement in extractability of Zn from ZnS NPs amended soil and diminution in extractability of Zn from ZnSO4 spiked soil was observed in bioavailability studies. The increased labile pool of Zn from ZnS NPs amended soil over time was due to their slow dissolution in soil and could be adjusted to consider as “sustained released ZnS NPs”. Dissolution of ZnS nanoparticles (NPs) in Lufa 2.2 soil adhered to the first-order extraction model, exhibiting extended half-lives of 27.72 days (low dose) and 28.87 days (high dose). This supported prolonged stability, increased reactivity, and reduced ecological risk compared to conventional Zn salt fertilizers, promoting enhanced crop productivity. Schematic illustration of adsorption dynamics of sono-chemically synthesized ZnS NPs onto lufa 2.2 soil and their slow dissolution in soil via controlled release of Zn for augmented bioavailability. [Display omitted] •ZnS NPs (10.42 ± 1.92 nm) reflected the stronger ability to get adsorbed on Lufa 2.2 soil as compared to ZnSO4.•ZnS NPs dissolute gradually in alkaline soil, increasing Zn bioavailability over time, unlike ZnSO4.•Dissolution of ZnS NPs in Lufa 2.2 soil followed first-order extraction model with half-life time of 27.72–28.87 days.•ZnS NPs can serve as “sustained release Zn supplement” in soil, boosting Zn availability for plants.