Sustainable fertiliser mesh, ‘4D’-precision engineered by flow chemistry: minimising agrochemical pollution

Le, Tu Nguyen Quang; Lim, Chang Nong; Fisk, Ian; Tran, Nam Nghiep; Hessel, Volker; Robertson, Karen

Abstract

Flow chemistry is best when opening “novel process windows”, and one of six NPW paths is “new chemical transformations”. Flow chemistry has a large impact on syntheses which are particularly mixing-sensitive. Here we exploit the NPW offered by flow chemistry to generate a new kind of core-shell necklaced fertiliser which can be woven and used as a localised point source with low leachate rate to the surrounding environment. We report the flow synthesis of fertiliser capsules with a chitosan coating around a chitosan/citric acid matrix that comprises dispersed phosphorus (P) particles (apatite). These capsules are connected via a chitosan string, resembling necklaces, adding a 3rd hierarchy in scale (3D) to the two hierarchies of coating and matrix. The strings of necklaces were woven into a mesh-like structure, adding a 4th hierarchy scale (4D). A stack of those meshes has potential to enable precise and uniform fertiliser release over a soil volume - control both over the temporal and spatial domain. Controlled-release fertilisers of macronutrients as P are critical for agricultural efficiency to reduce non-point source pollution causing by nutrient runoff/leaching. Using combined sheath and segmented flow in a water/oil system, the capsules had a consistent composition and morphology with an average content for phosphate and potassium of 24.5 wt% and 7 wt%, respectively. The resulting fertiliser exhibited slower nutrient release and extended lifetimes in aqueous media with 62 days in mild acidic solution, against 2422 days in deionised water. Soil column experiments demonstrated a low leaching loss for the sheath-flow made P fertiliser (1.2%), which was 60 times less than for a commercial fertiliser.

Citation

Le, T. N. Q., Lim, C. N., Fisk, I., Tran, N. N., Hessel, V., & Robertson, K. (2025). Sustainable fertiliser mesh, ‘4D’-precision engineered by flow chemistry: minimising agrochemical pollution. Green Chemistry, 27(3), 696-715. https://doi.org/10.1039/d4gc04833d

• Journal Article Type: Article
• Acceptance Date: Dec 2, 2024
• Online Publication Date: Dec 7, 2024
• Publication Date: Jan 21, 2025
• Deposit Date: Feb 20, 2025
• Publicly Available Date: Dec 8, 2025
• Journal: Green Chemistry
• Print ISSN: 1463-9262
• Electronic ISSN: 1463-9270
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 27
• Issue: 3
• Pages: 696-715
• DOI: https://doi.org/10.1039/d4gc04833d
• Public URL: https://nottingham-repository.worktribe.com/output/42840833
• Publisher URL: https://pubs.rsc.org/en/content/articlelanding/2025/gc/d4gc04833d