Microscopic view of hydrogel network adsorbing pollutants from water.

The Science Behind Cleaner Water: How Advanced Hydrogels are Revolutionizing Pollution Removal

Soraya Malik in Climate & Environment August 2025 • 4 min read.

"Explore the innovative use of composite hydrogels in adsorbing pollutants like phenol from water, offering a promising solution for environmental conservation."

Water pollution caused by organic pollutants, such as phenolic compounds, poses a significant threat to global environmental health. These pollutants, released by industries like pharmaceuticals, petroleum, and plastics, contaminate both surface and groundwater, leading to adverse effects on ecosystems and human health. The U.S. Environmental Protection Agency (EPA) lists phenolic compounds as priority pollutants, highlighting the urgent need for effective wastewater treatment solutions.

Traditional methods of pollutant removal, including chemical oxidation, photochemical catalysis, and biological degradation, have been employed with varying degrees of success. However, adsorption is emerging as a particularly promising technique due to its efficiency and versatility in dealing with diverse pollutants. Polymeric hydrogels with tailored functional groups have garnered significant attention as effective adsorbents for organic pollutants, offering a sustainable and cost-effective approach to water purification.

Among the various polymers used in hydrogel preparation, natural polymers like polysaccharides stand out due to their non-toxicity, low cost, biodegradability, and wide availability. However, hydrogels are prone to swelling under specific conditions, which can compromise their mechanical properties. To overcome this limitation, researchers have been exploring novel network structures, such as double networks and nanocomposites, to enhance the mechanical strength and overall performance of hydrogels.

Decoding the Science: How Do These Hydrogels Work to Remove Pollutants?

Microscopic view of hydrogel network adsorbing pollutants from water.

Recent research has focused on developing double network composite hydrogels (DNCHs) that combine the unique characteristics of both double network hydrogels and nanocomposite hydrogels. These DNCHs are created by integrating crosslinked hydroxypropyl cellulose (HPC) with graphene oxide (GO). First, a single network composite hydrogel (SNCH) is formed through the crosslinking of HPC and GO using epichlorohydrin. Subsequently, the SNCH is treated with a polyethyleneimine (PEI) solution to create the DNCH. This innovative approach results in a material with enhanced adsorption capabilities due to its larger surface area and increased number of functional groups.

The DNCH exhibits a greater capacity for pollutant removal compared to SNCH, owing to its unique structural and chemical properties. The adsorption mechanism involves a combination of electrostatic interactions, hydrogen bonding, and π-π interactions between the hydrogel and the pollutant molecules. These interactions facilitate the efficient capture and removal of pollutants from aqueous solutions.

Electrostatic Interactions: Attractive forces between oppositely charged molecules.
Hydrogen Bonding: Interactions between hydrogen atoms and highly electronegative atoms like oxygen and nitrogen.
π-π Interactions: Attractive forces between aromatic rings in the hydrogel and pollutant molecules.

The dynamic adsorption behavior of these hydrogels reveals that the breakthrough time—the point at which the hydrogel's adsorption capacity is exhausted—is influenced by the initial concentration and feed flow rate of the pollutant. Specifically, the breakthrough time increases when the initial concentration and feed flow rate of the pollutant decrease. The DNCH consistently outperforms the SNCH in breakthrough time due to its superior adsorption capacity. These composite hydrogels can be reused multiple times without significant loss of their initial binding affinity, making them suitable for practical applications in water treatment.

The Future of Water Purification: A Sustainable Solution

The development of single and double network composite hydrogels represents a significant advancement in water purification technology. These materials offer an efficient, reusable, and environmentally friendly solution for removing pollutants from water sources. As research continues, these hydrogels hold immense potential for addressing water pollution challenges and ensuring access to clean and safe water for communities worldwide. Further exploration and refinement of these technologies will pave the way for a more sustainable and healthy future.

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This article is based on research published under:

DOI-LINK: 10.1557/jmr.2018.385, Alternate LINK

Title: Adsorptive Removal Of Phenol By Single And Double Network Composite Hydrogels Based On Hydroxypropyl Cellulose And Graphene Oxide

Subject: Mechanical Engineering

Journal: Journal of Materials Research

Publisher: Springer Science and Business Media LLC

Authors: Jingjing Wang, Nan Zhang, Chenye Jiang, Changsen Zhang

Published: 2018-10-23

Everything You Need To Know

How do composite hydrogels, like double network composite hydrogels (DNCHs), actually remove pollutants from water at a molecular level?

Composite hydrogels, particularly double network composite hydrogels (DNCHs), work through a combination of electrostatic interactions, hydrogen bonding, and π-π interactions. Electrostatic interactions involve attractive forces between oppositely charged molecules. Hydrogen bonding occurs between hydrogen atoms and electronegative atoms like oxygen and nitrogen. Pi-Pi interactions are attractive forces between aromatic rings in the hydrogel and pollutant molecules, all contributing to efficient pollutant capture.

What is the precise process of creating double network composite hydrogels (DNCHs) from hydroxypropyl cellulose (HPC) and graphene oxide (GO)?

Double network composite hydrogels (DNCHs) are created by integrating crosslinked hydroxypropyl cellulose (HPC) with graphene oxide (GO) to form a single network composite hydrogel (SNCH), using epichlorohydrin for crosslinking. Subsequently, the SNCH is treated with a polyethyleneimine (PEI) solution to create the DNCH, enhancing adsorption capabilities due to a larger surface area and increased functional groups.

What does 'breakthrough time' mean in the context of hydrogel adsorption, and how do factors like pollutant concentration affect it for double network composite hydrogels (DNCH)?

The breakthrough time refers to the point at which a hydrogel's adsorption capacity is exhausted. For double network composite hydrogels (DNCH), the breakthrough time is influenced by the initial concentration and feed flow rate of the pollutant. A lower initial concentration and feed flow rate result in a longer breakthrough time, indicating more efficient and prolonged pollutant removal. The DNCH consistently outperforms the SNCH in breakthrough time due to its superior adsorption capacity.

What exactly are phenolic compounds, and why are they considered a major threat requiring solutions like composite hydrogels?

Phenolic compounds are organic pollutants released by industries like pharmaceuticals, petroleum, and plastics. These substances contaminate surface and groundwater, leading to adverse effects on ecosystems and human health. The U.S. Environmental Protection Agency (EPA) lists phenolic compounds as priority pollutants, underscoring the need for effective wastewater treatment solutions, such as those using composite hydrogels.

Why does the development of single and double network composite hydrogels represent such a significant advancement in water purification technology?

Single and double network composite hydrogels represent a significant advancement because they offer an efficient, reusable, and environmentally friendly solution for removing pollutants from water sources. Unlike traditional methods, these hydrogels, particularly double network composite hydrogels (DNCHs), combine the benefits of double network hydrogels and nanocomposite hydrogels, leading to enhanced adsorption capabilities and mechanical strength. Their reusability and sustainable nature make them a promising technology for ensuring access to clean and safe water worldwide.