IISER Bhopal Researchers develop Porous Organic Polymers to remove Micropollutants from Water

BHOPAL: Indian Institute of Science Education and Research Bhopal (IISERB) Researchers have developed organic polymers, which can remove highly polar organic micropollutants (POMs) from water. This process will render the water safe for consumption.

 

These polymers have already been tested for polar organic micropollutants removal at a laboratory scale. Large-scale fabrication of these materials in collaboration with industrial partners will open up a promising avenue for real-time scavenging of toxic polar organic micropollutants from water.

 

Called ‘Hyper-crosslinked Porous Organic Polymers’ (HPOPs), a teaspoon of the powder of these polymers will cover an internal surface area of 1,000-2,000 m2/g, which is close to 10 tennis courts.

 

The main advantages of these HPOPs include:

(i) Large-scale fabrication using cheap and simple aromatic precursors without requiring any transition metal-based exotic catalysts, and

(ii) High thermal and hydrothermal stability.

 

The Research was led by Dr. Abhijit Patra, Associate Professor, Department of Chemistry, IISER Bhopal, at the Functional Materials Laboratory of the Institute. The Team comprised Mr. Arkaprabha Giri, Ph.D. student, Department of Chemistry, IISER Bhopal, Mr. Subha Biswas, former BS-MS student of Department of Chemistry, IISER Bhopal, currently, pursuing Ph.D. at IISc Bangalore, Dr. MD. Waseem Hussain, former Ph.D. student of Department of Chemistry, IISER Bhopal, currently, pursuing post-doctoral research at Hanyang University, South Korea, Mr. Tapas Kumar Dutta, Ph.D. student, Department of Chemistry, IISER Bhopal, and Dr. Abhijit Patra. This project was funded by the Department of Science and Technology (DST), Government of India, under ‘Centre for Sustainable Treatment, Reuse and Management for Efficient, Affordable and Synergistic solutions for Water’ (WATER-IC for SUTRAM of EASY WATER) Initiative.

 

The findings have been published in the reputed, peer-reviewed journal of the American Chemical Society, ACS Applied Materials and Interfaces (https://doi.org/10.1021/acsami.1c24393)

 

Highlighting the critical need for such Research, lead author Mr. Arkaprabha Giri, Ph.D. Student, Department of Chemistry, IISER Bhopal, and Dr. Abhijit Patra, Associate Professor, Department of Chemistry, IISER Bhopal, said, “In India, the prime concern is water contamination due to anthropogenic waste discharged to surface and groundwater by domestic, agricultural, and industrial sectors. These wastes contain large numbers of organic/inorganic micropollutants. Organic micropollutants are a diverse set of ‘analytes’ whose presence in water, even in trace amounts, pose a serious threat to human health and aquatic lives.”

 

Dr. Abhijit Patra added, “A process called ‘Sorption’ is one of the most energy-efficient techniques to purify water from organic micropollutants. However, commonly-used carbonaceous adsorbents possess several bottlenecks such as slow uptake rate and tedious regeneration process. Therefore, we need efficient adsorbent materials that can not only scavenge highly polar organic micropollutants (POMs) from water rapidly but also can be synthesized easily on a large-scale through simple fabrication techniques. This was the problem the IISER Bhopal Researchers at Functional Materials Laboratory set out to tackle.”

The major organic micropollutants found in the surface water bodies are:

Ø Various pharmaceuticals such as antibiotics, and steroids, among others,

Ø Industrial chemicals such as dyes, food additives, endocrine disruptors and plastic precursors, among others,

Ø Agricultural disposals such as pesticides, herbicides, and fertilizers, among others.

 

Researchers at the Functional Materials Laboratory in IISER Bhopal developed a series of organic polymers called ‘Hyper-crosslinked Porous Organic Polymers’ (HPOPs) with distinct morphologies (spherical nanoparticles to the two-dimensional nanosheets) using paddle wheel-like aromatic monomer, triptycene, by varying the synthetic conditions.

 

Knitting triptycene units with halogen-containing organic solvent (dichloromethane) using a simple and cheap catalyst, anhydrous aluminium chloride, led to the HPOP with 2D sheet-like morphology having a remarkably high surface area of 2,400 m2/g. This solvent knitted HPOP contains numerous numbers of tiny pores (a few nanometers; 1 lakh times smaller than the cross-section of a human hair).

 

As a result, the 2D sheet-like HPOP can act as a sponge for the adsorption of various organic micropollutants from water. Further, the Researchers followed the ‘same likes same’ design strategy by decorating the walls of the tiny pores of the highly porous 2D sheets with polar functionalities (sulfonic acid group) to enhance the adsorption capacity and easy sequestration of highly polar organic micropollutants (POMs) from water.

 

The researchers showed, for the first time, the evolution process of 2D nanosheets of solvent knitted HPOP from nanospheres to nanoribbons to 2D nanosheets through electron microscopy. The adsorption rate for toxic cationic dye, methylene blue (carcinogenic, teratogenic, mutagenic) by solvent knitted HPOP is one of the highest among the well-known adsorbent materials reported in the literature (17.6 g mg-1 min-1). The 2D sheet-like HPOP could sequester a broad-spectrum of POMs, including antibiotics, endocrine disruptors, steroid-based drugs, ionic dyes, plastic precursors, pesticides, and herbicides within 30 seconds only.