The textile industry produces about 700,000 tons of synthetic dyes annually, contributing to 20% of global wastewater as estimated by the World Bank Group.
Azo dyes' persistence in ecosystems is due to their robust molecular structure, which lacks natural enemies in the form of degrading enzymes typically found in the environment. This resilience allows them to endure in water and soil, posing long-term contamination risks. The breakdown products of azo dyes, sometimes more toxic than the dyes themselves, can degrade into carcinogenic aromatic amines, affecting aquatic life and potentially entering the human food chain.
Given these risks, many countries regulate azo dyes, imposing limits and controlling industrial discharges into water systems. However, enforcement varies, particularly in developing regions where the textile industry plays a crucial economic role. Innovative solutions like genetically engineered bacteria to break down azo bonds and enhanced chemical treatments are needed to manage these pollutants effectively.
Addressing the challenge of removing azo dyes like Crystal Violet (CV) from wastewater has led to various methods, each with limitations. Electrocoagulation, which forms metal hydroxide flocs to capture dye molecules, requires high energy and careful sludge management. Coagulation-flocculation, another common method, adds chemicals to neutralize and aggregate dye particles, simplifying their removal but producing chemical sludge. Biodegradation uses microorganisms to break down dyes, offering an environmentally friendly alternative, though it often fails to completely remove dyes and is operationally complex.
Emerging as a promising solution to these environmental challenges, electrospun nanowebs, especially those modified with nitrocellulose (NC), offer a high-efficiency approach to dye removal. These nanowebs leverage the high surface area of nanofibers, combined with the chemical properties of NC, to effectively adsorb and remove dyes from wastewater. Notably, adding NC derived from waste tissue paper enhances these properties, providing both a sustainable and effective solution.
Electrospun nanowebs are created by extracting NC from organic waste and integrating it with polyacrylonitrile. The synthesis involves dissolving polyacrylonitrile in dimethylformamide (DMF), mixing it with NC, and then electrospinning it into nanowebs. These webs are characterized by techniques such as scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR), confirming their structural integrity and functional efficacy.
The nanowebs have shown high efficacy in removing the dye crystal violet from water, with removal efficiencies reaching up to 91%. The adsorption process primarily follows a pseudo-second-order kinetic model, indicating that it is chemically driven. Furthermore, these materials demonstrate excellent reusability, maintaining high dye removal efficiency over multiple cycles. This reusability, coupled with the sustainable sources of NC, marks a significant step forward in developing environmentally friendly water treatment technologies.
The use of electrospun nanowebs modified with NC presents a robust and sustainable approach to mitigating the environmental impact of synthetic dyes in wastewater. Looking forward, further research into the scalability of this technology and its application across various types of synthetic dyes could broaden its utility in industrial applications. This innovative approach not only addresses current environmental challenges but also paves the way for future advancements in water treatment technologies.
