Phenolic vs. Styrene-based Adsorption resins: Differences and Application Analysis

Adsorption resin is a kind of high-molecular polymer with a three-dimensional network structure. It is insoluble in acids, bases and many organic solvents, and can adsorb specific substances through physical or chemical actions. Compared with traditional adsorption materials such as activated carbon, adsorption resins have advantages such as high selectivity, good strength and easy regeneration.

The working principle of adsorption resin is mainly based on:

Physical adsorption: Relying on intermolecular forces (van der Waals forces)

Chemical adsorption: Through specific chemical reactions of functional groups

Pore size sieving: Utilizing the matching property between the resin pore size and the size of the target molecule

Phenolic series vs styrene series adsorption resins:

Characteristics of phenolic resin skeleton:

The basic framework of phenolic adsorption resins is a three-dimensional network structure formed by the condensation reaction of phenolic compounds and aldehyde compounds. Its skeletal features include:

Chemical bond composition

1. The methylene bridge (-CH₂-) and  bond (-O-) are the main connecting units

2. Form a rigid benzene ring-methylene alternating structure

3. The skeleton contains a large number of phenolic hydroxyl groups, forming a highly polar environment

Spatial configuration

Highly cross-linked rigid skeleton

The benzene rings are connected by short-chain methylene groups, resulting in a dense structure

The inherent polar sites in the skeleton are evenly distributed

Characteristics of styrene-based resin skeleton:

Styrene-based resins take polystyrene as the basic framework and form a network structure through the cross-linking of divinylbenzene:

Chemical bond composition

1. Carbon-carbon single bonds form the main chain skeleton

2. The benzene ring is suspended from the main chain as a side group

3. The crosslinking point is achieved through the vinyl group of divinylbenzene

Spatial configuration

The flexible hydrocarbon main chain combines with the rigid benzene ring side groups

2. The degree of crosslinking can be precisely regulated (usually 8%-20%).

3. The skeleton is essentially non-polar, with its surface covered by benzene rings

Adsorption mechanism of phenolic resin:

Polar interaction dominance:

Hydrogen bonding: Phenolic hydroxyl groups form hydrogen bonds with compounds containing O, N, and F, with a strength of 20-40 kJ/mol

Dipole-dipole interaction: The directional arrangement of polar molecules with the polar skeleton of the resin

π-π stacking: The electron cloud between the benzene ring and the aromatic compound overlaps

Acid-base interaction: The weak acidity of phenolic hydroxyl groups can react with basic substances

Adsorption characteristics

High selectivity for polar substances

It still maintains good adsorption performance in aqueous solution

The adsorption heat is relatively large, and usually strong desorption conditions are required

Adsorption mechanism of styrene-based resins:

Hydrophobic effect dominant:

Hydrophobic effect: The affinity of a non-polar skeleton for hydrophobic substances

Van der Waals forces: The main contributor to non-specific physical adsorption

π-π interaction: The electronic effect between the benzene ring and aromatic compounds

Size exclusion effect: Molecular sieve separation based on pore size

Adsorption characteristics

It has a strong adsorption capacity for non-polar and weakly polar substances

Adsorption is driven by the hydrophobic effect in aqueous solution

The adsorption heat is relatively small and it is easy to desorb and regenerate