Abstract
dc:description.abstractPhosphate, one of the primary components in fertilizers, is a finite resource in current scarcity, mainly obtained by the mining of phosphate rocks. In 2014, this mineral was declared as one of the 34 critical resources in the European Union. Phosphate rocks are geographically concentrated but needed for the growth of plants and mammals. The latter ones excrete phosphate in urine, with a concentration between 260 and 900 mg/L. Current wastewater treatment plants receive a wide range of stream sources, with a phosphate inlet concentration up to only 20 mg/L. Current treatments focus on the removal of phosphate and not its recovery to avoid eutrophication, complying with standard discharge regulations. Removal of phosphate through chemical precipitation in plants consumes 49 MJ/Kg P. This thesis demonstrates a novel approach for the recovery and reuse of phosphate, focused on its extraction from decentralized wastewater systems (i.e. no-mix toilets) with recovery at the production point. For the application of this approach, an integrated process is developed focused on the synthesis of adsorbent materials for phosphate selective adsorption, its recovery through multiple adsorption and desorption cycles, followed by its reuse for fertilizer production. Overall, this thesis demonstrates the efficient recovery and reusability of phosphate from aqueous solutions with high phosphorous initial contents (PO<sub>4</sub>-P) to simulate the concentration of streams from decentralized wastewater systems and from urine streams. This work evaluates the synthesis of ZnO-based and layered metal hydroxide adsorbent materials for phosphate recovery. Layered metal hydroxides are analysed due to their metal composition tunability and positively-charged surfaces. In addition, a novel adsorbent synthesis approach was evaluated through the synthesis of ZnO-composite materials via atomic layer deposition. This synthesis technique produced ZnO clusters on the substrate’s surface, increasing the atom-efficiency in the adsorption process. Furthermore, through the adsorption mechanism investigation, it was observed that the presence of metallic species in the phosphate adsorbent materials increased the overall positive surface charge, resulting in the enhancement of the adsorption capacity via electrostatic attraction. The phosphate species were also adsorbed through chemisorption via surface complexation. Lastly, as a proof-of-concept investigation, this phosphate recovery approach was also successfully implemented using synthetic urine and human urine streams, where phosphate was removed not only by adsorption but also by chemical precipitation.
Degree
thesis:*- Name dc:type.qualificationname
- Doctor of Philosophy (PhD)
- Level dc:type.qualificationlevel
- Doctoral
- Grantor dc:publisher.institution
- University of Cambridge
- Year dc:date.issued
- 2023
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Avena Maia, Marina
- Advisor dc:contributor.advisor
-
- Torrente-Murciano, Laura
Subjects
dc:subject × 3Rights
dc:rightsIdentifiers
dc:identifier.*- DOI dc:identifier.doi
- https://doi.org/10.17863/CAM.108456
- OAI identifier oai:identifier
- oai:www.repository.cam.ac.uk:1810/368143