Development of a selective adsorption process based on the use of innovative molecularly imprinted polymers for phosphate recovery from an acidogenic reactor treating food wastes

Phosphorus is considered a critical raw material by the EU because it is a nonrenewable source, with high economic importance and envisage a critical supply risk. In addition, the use of phosphorus is inefficient at different stages of the life cycle, causing both the waste of a wide range of resources and severe water pollution leading to eutrophication. Moreover, conventional recovery methods result in a P-complexation as struvite, which is usable only as a fertilizer. This thesis aimed to study the recovery of phosphate from wastewater of an acidogenic reactor treating food waste, through the development of smart polymer using a green technology. A Molecularly Imprinted Polymer (MIP) with affinity for (P)-based molecules was synthesized for the first time using supercritical carbon dioxide (scCO2) technology. The polymerization reactions took place in a high-pressure reactor, using 1:5:20 molar ratio of template/functional monomer/crosslinker and 2% (w/w) by weight of thermal initiator at a pressure of 200 bar and a temperature of 65 °C. The polymeric particles, obtained as a free-flowing material and with an average yield of 54 %, were characterized by morphological, chemical and physical analyses. The binding performance of the materials produced was evaluated through static binding tests and solid phase extraction experiments; several adsorption isotherms have been studied (Langmuir, Freundlich, Langmuir -Freundlich and Temkin model). The best promising device in the static binding experiments was MIP that could capture 8.8 mg P/g polymer and the results of the solid phase extraction showed that the recovery – even 100% - was not much affected by the presence of other competing chemical species in the media (9.2 % reduction in sorption capacity). MIP showed to be very promising polymeric device with the ability to work as a single-use device for P recovery, from biological reactors with high yields.