# Osmotic and diffusio-osmotic flow generation at high solute concentration. I. Mechanical approaches

## TL;DR

This paper investigates osmotic and diffusio-osmotic flows at high solute concentrations using a mechanical perspective, deriving generalized expressions for osmotic pressure and mobilities beyond dilute regimes.

## Contribution

It introduces a mechanical approach to osmotic transport at high concentrations, extending classical thermodynamic results to mixtures with arbitrary solute levels.

## Key findings

- Derived generalized osmotic pressure expressions for high concentration mixtures.
- Obtained new formulas for rejection coefficients and diffusio-osmotic mobilities.
- Connected mechanical balance with thermodynamic frameworks for non-dilute solutions.

## Abstract

In this paper, we explore various forms of osmotic transport in the regime of high solute concentration. We consider both the osmosis across membranes and diffusio-osmosis at solid interfaces, driven by solute concentration gradients. We follow a mechanical point of view of osmotic transport, which allows us to gain much insight into the local mechanical balance underlying osmosis. We demonstrate in particular how the general expression of the osmotic pressure for mixtures, as obtained classically from the thermodynamic framework, emerges from the mechanical balance controlling non-equilibrium transport under solute gradients. Expressions for the rejection coefficient of osmosis and the diffusio-osmotic mobilities are accordingly obtained. These results generalize existing ones in the dilute solute regime to mixtures with arbitrary concentrations.