WP2 deals with the design and manufacturing of filters based on smart materials and the development of methods to benchmark and validate the performance of smart materials filters against existing solutions.

Involved partners: RISE Acreo, Stockholm University (SU), Borregaard, MoRe Research, Swedish Aerogel, KTH, RISE Bioekonomi, NeoZeo, IVL, RISE Biovetenskap och material samt Boliden.

WP2 leader: RISE Acreo (Sandberg); WP2 Co-leader: SU (Matthew)

Below follows a summary in text and in illustrations on activities performed during the year combining all Tasks, with contributions from all parties.

Filter materials

Research work will be done to manufacture filter materials and how to integrate different cellulose grades into multilayered membranes has been focused on (SU, MoRe). The ambition for the coming year is to have in hand functionalized cellulose membranes manufactured from WP1, integrate the membranes with electrochemical sensors and study the permeability, mechanical properties, adsorption performance and scalability of the obtained smart filtering systems. In collaboration (SU, MoRe, Acreo), support layers of the membranes will be developed, and electrochemical tests of the prepared material will be conducted. The observations from these studies are expected to result to at least one publication by the end of 2019.

Electronic sensors in filter paper

Lab work on the integration of optical light guides and electronic sensors into filter paper has been performed. The results so far indicate that the challenges are non-trivial, and the plan is to develop improved ideas and concepts during 2019. Fig 1 illustrates illuminated optical fibers in paper.

Fig 1. Illuminated optical fiber in paper.

Photocatalytic activity in zink oxide paper

The photocatalytic activity in ZnO-paper based on photocatalytic activity indicator inks has been studied. The results are promising, and the plan is to submit a scientific article based on the finding during 2019.

Test reactor

A test reactor for sheet-formed photocatalysts for air purification in a plug-flow configuration has designed and built (Sandberg et al.). Compared to other evaluation tools for photocatalytic air purification, the MTC validation tool for photocatalysis has several distinguishing features. It is a reactor of plug-flow type with a high aspect ratio, and the photocatalytic sheets are illuminated directly by the light source without any barrier in between, such as quartz glass. The light source is a water-cooled UV-LED aggregate of own construct. Compact sensors are integrated into the reactor. Function of photocatalytic papers and the validation tool has been confirmed.

Design, manufacturing and testing of electrochemical in and at filter membranes

Sensor electrodes has been integrated into filter materials in one approach to realize smart and connected filter materials, to provide a new tool set for the development of “sensor-absorbent filter materials”.

Validation tool for sheet-formed photocatalysts for air purification

Fig 2. Two sets of electrochemical sensors printed directly on filtration media Insets show details of the electrode structure, a. Each set of sensors have one interdigit electrode structure for impedance measurements and one two electrode structure with a working electrode and a large reference counter electrode. Printing of materials for electrochemical sensors, b. Electrochemical response to metal ion absorption in the filter medium, c. The sensors can be facing into the filter medium or into the bulk liquid and can be applied on both sides of a membrane.

Unexpected results

The role of CO2 on irradiated ZnO surfaces is under debate and is of great importance for evaluation and operation of photocatalytic reactors. With the sensors mounted inside the reactor it become clear that the dynamics of CO2 release from an irradiated photocatalyst is slow, significant and must be considered.

Experiments have indicated that printing electrodes on membranes can be useful tool for understanding, development and economic operation of filter membranes. The conducting traces, i e the printed electrochemical sensors on filtration membranes, are well insulated by the printed dielectric. Metal ions in the membrane can be distinguished from metal ions in the bulk.

Meetings

The WP2 team participate regularly in the monthly WP2 Skype meetings.
A filter workshop was held at Camfil for the entire Consortium, with focus on air filters in Feb 2018.

Workshop on membranes (processing and testing) took place at SU, hosted by Aji Mathew at her lab. This full day event was very successful, with about 20 participants from the MISTRA TerraClean program seeing some of the lab work we conduct in the WP2 tasks.

At the Consortium meeting in Uppsala in October, 2018, the partners could benefit from a lecture on LCA, held by IVL.