# Sorp‐Vection‐Based Membrane Silicone Oil Purification

## TL;DR

This paper introduces a new membrane separation technique called Sorp-vection to purify silicone oil by removing harmful cyclic siloxanes like D4.

## Contribution

The first Sorp-vection-based membrane system for industrial silicone oil purification, combining sorption and convective transport.

## Key findings

- A lab-scale Sorp-vection system achieved a separation factor above 15 for removing D4 from silicone oil.
- The system works with both lab-grade and industrial-grade silicone oil feeds.
- A predictive model aligned well with experimental results based on sorption data in crosslinked PDMS.

## Abstract

“Sorp‐vection” is a membrane separation technique that synergistically combines sorption with convective flow mechanisms. Beyond its conceptual discussion, we demonstrate a sorp‐vection separation achieved in a gas–liquid system, where permeation of a gas directly drives selective permeation of an organic solute across a dense polymer layer overcoming osmotic limitations of conventional membrane processes. Here, a long‐standing challenge in silicone oil production is addressed, in which residual cyclic oligosiloxanes are removed from silicone oil streams through permeation of CO2 across an optimally crosslinked PDMS selective layer. A lab‐scale 1st generation Sorp‐vection system demonstrated, with a separation factor above 15 to remove D4 (octamethylcyclotetrasiloxane) from low‐concentration feeds using both lab‐grade silicone oil (Sigma‐Aldrich) and an industrial‐grade feed (DOW‐SFD). Good agreement was found with a predictive model based on liquid D4 and high‐molecular‐weight silicone oil sorption data in crosslinked PDMS. This proof‐of‐concept study introduces the sorp‐vection strategy, expanding it from conventional two‐component systems to a three‐component configuration in which convective flow is introduced as an independent driving entity. Addressing concentration polarization in next‐generation versions of the sorp‐vection process is expected to ensure stable long‐term performance and to establish sorp‐vection as a transformative approach for industrial purification.

This work presents the first Sorp‐vection‐based membrane separation for silicone oil purification, coupling sorption‐driven selectivity with convective transport. Our strategy enables highly selective removal of residual cyclic siloxanes, particularly D4, overcoming the inherent trade‐offs and limitations associated with conventional membrane processes in the silicone industry.