Access to clean and drinkable water has now become not just a local, but a global problem as well. Water contamination is one of the world’s leading causes of death and the problem is only getting worse. The Indian Institute of Science Education and Research (IISER), Pune, has come up with a unique solution to tackle this issue – a custom-designed molecular sponge-like material that can swiftly clean polluted water by soaking up sinister contaminants. The results were recently published in the journal Angewandte Chemie.
Systematic studies have identified various organic (organic dyes, antibiotics, pesticides, etc.) as well as inorganic toxic pollutants such as iodides, oxo-pollutants like perrhenate that are carcinogenic in fresh water sources and can pose direct threat to humanity and living organisms. Commonly utilized sorbent materials often trap these pollutants through ion-exchange strategy to purify water but suffer from poor kinetics and specificity.
To mitigate this issue, the research team at IISER, Pune prepared a newly engineered material called viologen-unit grafted organic-framework (iVOFm). The material employs the amalgamation of electrostatics driven ion-exchange combined with nanometer-sized macropores and specific binding sites for targeted pollutants.
The size and number of tunable macropores along with the strong electrostatic interaction of iVOFm can quickly remove various toxic pollutants from water.
Development of iVOFm
To develop this unique material, the team employed a make-and-break strategy to grow a charged porous organic polymer (POP) as a sponge-like infinite framework on silica nanoparticles that are used as a template.
After this, the silica nanoparticles were strategically removed to create ordered hierarchical interconnected macro/microporosity throughout the material.
The material features inherent cationic nature and macroporosity to allow fast diffusion of pollutants. When tested for a wide array of water pollutants, it showed ultrafast capture of all pollutants – both organic and inorganic – with over 93% removal in just 30 seconds. Among all the tested pollutants, the new material showed ultrafast removal of sulfadimethoxine antibiotic from water almost completely.
Even in the presence of other co-existing anions such as nitrates, chloride, and bromide, the removal of sulfadimethoxine antibiotic was extremely high within a minute. The engineered material could remove sulfadimethoxine antibiotic with high efficiency when tested using different real water samples.
Selectivity and Reusability
The material was found to be very selective toward toxic pollutants in the presence of co-existing ions present in waste water, even at low concentrations. It can also be used several times to clean contaminated water, just like a bath sponge can be utilized to tackle multiple water spills.
The cationic compound iVOFm is adaptable for sequestering various pollutants and is a possible solution to the water pollution problem. These results open up a new avenue for the creation of numerous sophisticated sorbent materials for practical water filtration. The fast pollutant trapping capacity of the material is attributed to the faster diffusion of pollutants through the ordered interconnected presence of macropores in the material. This is a promising step in the direction of finding sustainable solutions for the global water pollution problem.