1、 Basic principles

When pure water and saltwater are separated by an ideal semi permeable membrane, which only allows water to pass through and prevents salt from passing through, the water on the pure water side of the membrane will spontaneously flow into the saltwater side through the semi permeable membrane. This phenomenon is called permeation. If pressure is applied to the saltwater side of the membrane, the spontaneous flow of water will be suppressed and slowed down. When the applied pressure reaches a certain value, the net flow rate of water through the membrane is equal to zero. This pressure is called osmotic pressure. When the pressure applied to the saltwater side of the membrane is greater than the osmotic pressure, the flow of water will reverse, and at this time, the water in the saltwater will flow into the pure water side. The above phenomenon is the basic principle of reverse osmosis (RO) treatment of water.

2、 Reverse osmosis mechanism model

There are several classic models for the unified "dry closed wet open" reverse osmosis mechanism model

1. Priority adsorption of capillary pore model: Under the weak spot dry film electron microscope, no pores were found. Wet membrane specimens are not electron microscopy samples.

2. Dissolution diffusion model: does not consider pores.

3. Dry closed wet open model: proposed by Deng Yu et al. in the 1980s and 1990s, it is the most appropriate modern reverse osmosis mechanism model that can explain the unity of models 1 and 2. The "dry closed wet open" reverse osmosis model unifies two of the most classic reverse osmosis mechanism models, the pore model and the dissolution diffusion model. approach

When the membrane is dry, the pores shrink and become dense, and the pores are closed. Under electron microscopy, the dry film prepared for microscopic examination cannot be seen;

When the membrane is wet, the membrane material swells, the pores of the membrane are swollen by the solvent, and the pores open. Merger is the "dry closed wet open" desalination model.