This includes the purification of surface water, rivers, lakes, green algae, rural groundwater, deep purification in urban waterworks, pre-filtration in household central water purification systems, purification of household direct drinking water, and purification of bottled and barreled water.

Activated carbon, with its well-developed pore structure and strong adsorption capacity, has become a core material for drinking water treatment, especially in dealing with surface water pollution, sudden pollution incidents and improving terminal water quality, with remarkable effects. The following is a detailed description of the main application sections of activated carbon in the field of drinking water:

The principle of activated carbon in removing PFAS

Per- and polyfluoroalkyl substances (PFAS) are a class of artificially synthesized organic fluorochemicals in which all or part of the hydrogen atoms in carbon-hydrogen bonds have been replaced by fluorine atoms, with different functional groups attached at the ends. Depending on the type of functional group, they mainly include perfluoroalkyl carboxylic acids, perfluoroalkyl sulfonic acids, perfluoroalkyl phosphonic acids, perfluoropolyethers, fluoro-modulating polyols, and perfluorosulfonates, with the general structural formula CnF2n+1-R[3]. They possess characteristics such as hydrophobic and oleophobic properties, high temperature resistance, and the ability to reduce surface tension of water, and are widely used in the production fields of leather, textiles, paper, pesticides, fireproof materials, lubricants, coatings, personal care products, etc., earning them the nickname "permanent chemicals."

Research on the health and environmental impacts of PFAS began in the 1950s. It was not until the 21st century that the U.S. Environmental Protection Agency recognized their harm to health. On March 11, 2019, China's Ministry of Ecology and Environment and the State Administration for Market Regulation issued regulations prohibiting the production, circulation, use, and import and export of perfluorooctanesulfonic acid (PFOS) and its salts and perfluorooctanesulfonyl fluoride (PFOSF) except for acceptable uses. In June 2021, the United States proposed the "Prohibition of Perfluoroalkyl Substances in Cosmetics Act."

Starting from 2025, California and New York in the United States have already begun to ban the sale of clothing containing PFAS. An important reason for PFAS pollution is wastewater treatment and landfilling; they are highly stable, resistant to photolysis, hydrolysis, biodegradation, and metabolism by animals, posing a serious threat to the biological environment. Food, drinking water, indoor dust, and indoor and outdoor air are several main pathways for the general population to come into contact with PFAS. PFAS affect the health of organs such as the immune system, reproductive and developmental systems, liver, kidneys, pancreas, and are associated with cancer. Consumers find it difficult to determine the presence of fluorinated compounds in cosmetics based on their ingredients, so they should try to avoid using or limit the long-term use of makeup products that are too durable, waterproof, and difficult to remove.

Activated carbon (GAC/PAC) captures PFAS through physical adsorption and chemical interactions. The core mechanisms include:

1. Physical adsorption - Pore structure: The porous surface of activated carbon (micropores, mesopores) adsorbs PFAS molecules through van der Waals forces. Long-chain PFAS (such as PFOS, PFOA) are more easily adsorbed due to their stronger hydrophobicity.

2. Chemical interaction - Electrostatic interaction: PFAS carry a negative charge (such as sulfonic acid groups, carboxylic acid groups), and the surface charge of activated carbon can enhance adsorption through ion exchange or hydrogen bonding. Fluorine affinity: Some modified activated carbons (such as fluorinated ones) can selectively adsorb short-chain PFAS through fluorine-fluorine interactions.

Limitations of PFAS governance:

Activated carbon has a strong adsorption effect on long-chain PFAS (such as PFOS), but for short-chain PFAs (such as GenX), higher doses or modifications (such as loading metal oxides) are required. Natural organic matter (NOM) in water will compete with PFAS for the pores of activated carbon, reducing its efficiency.

The US EPA recommends the combined process of "activated carbon + reverse osmosis" (such as the Hoosick Falls project in New York State).

Regeneration issue: Waste activated carbon needs to be regenerated at high temperatures (>800℃), and PFAS may not be completely decomposed, posing a risk of secondary pollution.