Development of Thiol-Norbornene Based Polymeric Gels for Efficient Removal of Dyes from Aqueous Solutions

Bhattacharya, Sayantani (2020) Development of Thiol-Norbornene Based Polymeric Gels for Efficient Removal of Dyes from Aqueous Solutions. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Sayantani Bhattacharya (12IP002)) 12IP002.pdf - Submitted Version Restricted to Repository staff only Download (15MB)

Abstract

Urbanisation has led to an increased industrialisation. Industries provide employment, promote the growth of local income for the development of the nation. At the same time, they often contribute to the pollution of the ecosystem. The untreated industrial effluents comprising several hazardous components such as: toxic dyes, heavy metals, organic solvents, etc. when discharged directly into the waterways, cause severe water pollution. Direct discharge of the wastewater not only leads to an undesirable appearance of the water but also damages the aesthetic aspects of the receiving waters. The dye contaminated water is a major threat to mankind as well as aquatic lives and can no longer be used in agricultural or urban affairs due to the severe toxicity and carcinogenicity associated with the dyes. Thus it is absolutely necessary to remove toxic dyes from wastewater for the sustainability of life on earth. Amidst all the dye removal methodologies, adsorption is considered as the most reliable approach without involving any fancy equipment. However, this approach can be challenging at times if the adsorbent is expensive and not recyclable. Hence, appropriate choice of adsorbents is crucial for the success of this strategy. Preferably, the synthesis of the adsorbent must be facile without involving any rigorous procedure. Moreover, the adsorbent must be regenerated for a few cycles in order to keep the overall dye removal process economically feasible. In conjunction with these features, the adsorbent must also be nontoxic in nature to prevent any chances of secondary pollution. These concerns have motivated us to develop polymeric gel based adsorbents fabricated via facile, environmentally-friendly thiol-norbornene photoclick chemistry technique and explore their efficiency towards removal of toxic dyes from aqueous solutions. The entire thesis is divided into five chapters. Chapter 1 offers a general introduction of polymeric gels, enumerating them in terms of differences in synthesis or crosslinking mechanism. To broaden the possibility of these polymeric gels to decontaminate textile effluents comprising toxic dyes, the scope of commonly used dye removal methodologies are discussed in this chapter. Adsorption is recognised as the most reliable, commercially viable, and eco-friendly technique for dye removal. In this context, the efficiency of gel based adsorbents are discussed in detail. Chapter 2 describes the design and synthesis of photoinitiated thiol-norbornene click based organogel. The fundamental properties of a gel such as solvent uptake, viscoelasticity, porous morphology, thermal, mechanical stability, etc. are thoroughly investigated. The results reveal that the as-synthesised organogel, though does not swell in water, is capable of removing toxic cationic dyes from aqueous solutions. Chapter 3 illustrates the fabrication of a gel system based on thiol-norbornene photoclick chemistry. Norbornene is strategically functionalized with different poly (ethylene glycol) chains to produce PEG functionalized crosslinkers. In this chapter, we have investigated the impact of incorporating poly (ethylene glycol) (PEG) of different chain lengths in the network structure. The influence of incorporating PEG in the cross-linked network is evaluated in detail on the basis of their several physical properties such as solvent uptake, rheological behaviour, thermal stability, etc. Furthermore, the beneficial effect of the increased PEG chain in the network regarding dye removal efficiency from aqueous solutions are also thoroughly analysed in this chapter. Chapter 4 describes the development of thiol-norbornene based ingenious gels with pendant quaternary ammonium substituents on the norbornene backbone that are conducive to remove toxic anionic azo dye (acid orange 7) from wastewater. Three different alkyl side chains on the dangling quaternary ammonium moiety are prudently chosen and their performance towards removal of azo dye was scrutinised. The relationship between the composition of quaternary ammonium moiety on the gels and their influence on the physical properties are realised in this chapter. Chapter 5 focuses on the removal of toxic anionic azo dye (acid orange 7) from wastewater. To facilitate the removal, we have prudently introduced quaternary ammonium as well as triphenylphosphonium functionalities in the cross-linked network. In-depth analysis has been performed to recognise the dye removal process that is boosted by enhanced swelling of the gel in water.

Actions (login required)

View Item