Water Purification by Green Synthesized Nanomaterials

BACKGROUND

Water pollution is one of the important causes of human fatality in the world, particularly in underdeveloped or developing countries. Moreover, with rapid industrialization and urbanization, the problem of water pollution is posing a severe threat to health and livelihood. The pollutants found in water are of varied nature and depend on the source of the water. Several techniques have so far been adopted to purify contaminated water. All the techniques have one or the other disadvantages, limiting their applications on large scale, sustainability, and long-term usage. The advances in the field of nanoscience and technology have opened a new horizon for replacement/improvement of conventional ways with more efficient methods. Presently, green synthesized nanomaterials are being used for water purification.

METHODS

Plant extracts and microbes are being used to synthesize nanomaterials, which are used as catalysts, adsorbents and membranes for water purification.

RESULTS

Nanomaterial-based techniques could create problems for the environment due to various chemicals used in their production step, thus defeating the ultimate purpose. In this regard, green nanomaterials can prove to be extremely useful both in terms of sustainability and efficiency.

CONCLUSION

This review illustrates various ways of how green nanomaterials can be utilized for water remediation and summarizes the recent work done in this emerging research area.

Applications of Green Synthesized Nanomaterials in Water Remediation

Water is the most important component on the earth for living organisms. With industrial development, population increase and climate change, water pollution becomes a critical issue around the world. Its contamination with different types of pollutants created naturally or due to anthropogenic activities has become the most concerned global environmental issue. These contaminations destroy the quality of water and become harmful to living organisms. A number of physical, chemical and biological techniques have been used for the purification of water, but they suffer in one or the other respect. The development of nanomaterials and nanotechnology has provided a better path for the purification of water. Compared to conventional methods using activated carbon, nanomaterials offer a better and economical approach for water remediation. Different types of nanomaterials acting as nanocatalysts, nanosorbents, nanostructured catalytic membranes, bioactive nanoparticles, nanomembranes and nanoparticles provide an alternative and efficient methodology in solving water pollution problems. However, the major issue with nanomaterials synthesized in a conventional way is their toxicity. In recent days, a considerable amount of research is being carried out on the synthesis of nanomaterials using green routes. Nanomaterials synthesized by using the green method are now being used in different technologies, including water remediation. The remediation of water by using nanomaterials synthesized by the green method has been reviewed and discussed in this paper.

Infrared-optical double resonance spectroscopic measurements on 2-(2'-pyridyl)benzimidazole and its hydrogen bonded complexes with water and methanol

The H(2)O and MeOH complexes of 2-(2'-pyridyl)benzimidazole (2PBI) were investigated using laser induced fluorescence and IR-UV double resonance spectroscopic techniques. The 0(0)(0) band for the S(1) <-- S(0) electronic transition of 2PBI was observed at 31,616 cm(-1), and corresponding transitions for the H(2)O and MeOH complexes show substantial red shifts of 1059 and 1203 cm(-1), respectively. A long progression up to v' = 5 in the 92 cm(-1) vibrational mode was observed for bare 2PBI, which is considerably shortened to v' = 2 and v' = 1 for the H(2)O and MeOH complexes, respectively. The combined experimental and theoretical results suggest that both H(2)O and MeOH form cyclic complex with 2PBI incorporating N-H...O and O-H...N hydrogen bonds. Comparison with other known hydrogen-bonded H(2)O complexes of bifunctional aza-heteroaromatic molecules suggest that 2PBI-H(2)O is probably one of the strongest of all known complexes. Further, the experimental data in combination with calculations suggests that the hydrogen atom/proton transfer leading to tautomeric form might be thermodynamically spontaneous in the electronic excited state, due to explicit solvent (H(2)O and MeOH) participation.