9 March, 2023
In this newsletter we highlight our recent progress of the water cleaning technologies we develop for the ultra-filtration prototype in the project GreenWaterTech (GWT). Ultra-filtration of water is the final step in water cleaning, and ensures that all resistent chemicals and microorganism that may still be present in the water are efficiently and safely removed. In GWT we employ three serial steps: 1) Enzymatic cleaning, 2) Nanoadsorbents, and 3) Photocatalysis.
Step 1: We use enzymes to catalyze degradation of chemicals of emerging concerns (CECs). Pharmaceuticals were chosen according to their appearance in different water bodies in Sweden and Europe, specifically: diclofenac, paracetamol and carbamazepine. The enzymes demonstrated great oxidation capacity for the selected pollutants. Horseradish peroxidase immobilized fly ash and perlite degraded diclofenac completely after 24h. The same immobilized enzyme showed also high degradation rates for paracetamol (≈90%). Immobilized Laccase was successful in carbamazepine degradation, reaching up to 38% degradation rate for high drug concentration 20 µg/mL. Enzymes are provided by Pharem Biotech, which will also assemble the Step 1 reactor.
Step 2: We employ nanoadsorbents based on metal oxides that able to adsorb and decompose CECs, including organophosphorus pesticides and various pharmaceuticals. We have synthesized the nanoadsorbents using simple “green” methods and tested their adsorption and degradation properties. CeO2-based nanoadsorbents have demonstrated extraordinary ability not only to adsorb selected micropollutants from water (eg. organophosphate pestcides), but also to decompose them into non-toxic products (Fig. 1). We have demonstrated that nanostructured CeO2 has dephosphorylation ability (and is able to decompose DNA-like substrates), which can be potentially used for abatement of antibiotica resistant bacterias (Fig. 1). The main results on CeO2 nanoadsorbents are summarized in two published articles [1,2]. Field test are done in collaboration with the Dekonta company.
Fig. 1 Schemcatic illustration of the photocatalyst used in Step 2 for ultra-filtration of water. Nanostructured ceria possesses high pseudo-enzymatic activity (Phospholipase C and D-like activity) and antiviral properties against herpes simplex virus (HSV-1) and Adenovirus 5 (Ad-5). Source: https://doi.org/10.1039/D2EN00173J
Fig. 2 Schemcatic illustration of the photocatalyst used in Step 3 for ultra-filtration of water. Sulfate groups blocks coordination sites, thereby decreasing the build-up of strongly bonded intrermediate degradation products, leading to sustained activity. Sulfate groups attracts photoexcited electrons, thereby prolonging the life-time of electron-holes yielding more ROS radicals. Additionally, the sulfate-coating increases surface acidity yielding protolytic catalyst properties. Source: F. Svensson, Catalysts-2223979, accepted.
Step 3: We utilize advanced oxidation processes to degrade CECs. In particular, we use surface-modified and so-called heterojunction photocatalysts. Sulfate-terminated anatase-TiO2 with enhaned surface acidity, TiO2-SO4, have been prepared by a simple one-step synthesis method [3]. The results demonstrate improved sustained degradation activity of the TiO2-SO4, photocatalysts compared with commercial TiO2 photocatalysts due to synergetic action of the sulfate-groups and the supporting titania (Fig. 2). Tests of TiO2-SO4 for removal of bisphenols A and C , and antibiotics in water show promising results, in particular, demonstrating broad-spctrum actity of different kinds of CECs compared to commercial TiO2 photocatalysts. Preliminary studied on virus inactivation by TiO2-SO4 coatings indicate higher antiviral inactivation (>99.99%) compared to commercial anatase-TiO2 (90%), and negligible cytotoxicity. Finally, photocatalysts will be coated on PMMA optical fibres provided by Brochier technologies and glass fibre mats provided by Treffler Prodution, both providing robust, high-surface area support. In case of fibres, the photocatalyst will be illuminated from “inside” by simple fibre coupling of UV light. The devices will be immersed in the Step 3 cleaning module.