Chemical upcycling of phosphoric acid recovered from sewage waste

16 November 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Global concerns surrounding the depletion and strategic importance of phosphorus resources have heightened the demand for the recovery and recycling efforts. However, the phosphorus compound obtained from waste exists primarily as chemically inert phosphoric acid or its salts, and the direct conversion into high-value chemicals has remained largely elusive. Our objective was to develop an innovative technology that bypasses the use of white phosphorus and enables the direct esterification of phosphoric acid, leading to the production of phosphate triesters widely utilized across versatile applications. Tetraalkyl orthosilicates emerged as highly effective reagents for the direct triple esterification of 85% phosphoric acid, as well as the esterification of organophosphinic and phosphonic acids. Through both experimental and theoretical investigations, we have elucidated a novel mechanism governing the reaction, wherein tetraalkyl orthosilicate not only serves as an alkyl transfer reagent but also facilitates the formation of multimolecular aggregates as a reaction template, assisting the proton shuttle process. By optimizing the recovery method of phosphoric acid from sewage sludge ash, we successfully achieved the direct esterification of the recovered phosphoric acid with tetraalkyl orthosilicate, thus pioneering a groundbreaking upcycling pathway from sewage waste to valuable phosphorus chemicals.


Green Chemistry
Phosphate Esters
Phosphoric acid
White Phosphorus
Sewage Sludge Ash
Chemical Upcycling
Recovery and Recycling

Supplementary materials

Supplementary information
General Information, Experimantal Details, Computational Details and 1H & 13C{1H} NMR Spectrum of Products.


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