Low-cost nanotechnology water filter

The effluents of tannery, paint, paper and textile industries containing different type of dyes are often discharged untreated into water bodies. The No. 1 polluter (after agriculture) of clean water is the textile industry, one of the most chemically intensive industries on the planet. The World Bank estimates that 17 to 20 percent of industrial water pollution comes from textile dyeing and finishing treatment given to fabric. This causes a serious environmental threat to aquatic and human life. Moreover, water treatment plants are very prone to fouling due to microorganism growth in the contaminated water, resulting in higher energy consumption and operating cost.

The development of sustainable, robust, energy-efficient and cost-effective water purification technologies is a challenging task. Conventional practices adopted for water purification – which can be classified into physical, chemical and biological methods – suffer from certain limitations such as high cost, low adsorption capacity, generation of toxic sludge, etc. These technologies – which include coagulation, flocculation, reverse osmosis, membrane separation, oxidation and ozonation, adsorption – are expensive or inadequate to remove dye. Adsorption with activated carbons, which is a cheap and effective method, has been demonstrated to remove dye from wastewater. But this approach is not suitable for industrial wastewater treatment because activated carbon can only be used once and then it is commonly disposed of in landfills. Moreover, removal of pathogens from treated water requires additional processes like chlorination, ozonation, etc., which increases the cost of treatment. A possible solution to tackle this problem has been demonstrated by scientists in India. They developed nanotechnology-based water purification using nano-silica-silver composite material as antifouling, antimicrobial and dye adsorptive material. Using this process, pathogenic bacteria and dye present in contaminated water can be treated simultaneously without using any chemicals, high-temperature, pressure or electricity.

The scientists synthesized a nano-silica supported silver nanocomposite material through eco-friendly protein mediated reduction of nano-silica bound silver ions. The proteins, extracted from Rhizopus oryzae – a zygomycetes fungi, served both as a reducing and a protecting agent for the silver nanoparticles and prevented their oxidation under environmental conditions. The result is a low-cost, highly effective nanomaterial for sustainable water purification. The nanocomposite removes the dyes at wide pH, temperature and dye concentration in solution. Moreover, the nanocomposite kills the microorganisms frequently present in the contaminated water. In addition, the nanocomposite material could be regenerated after treatment of dye bearing wastewater and the regenerated nanocomposite could be stored and reused for several more cycles

The nanocomposite also prevented attachment of floating microorganisms and inhibited the formation of biofilms on its surface. This makes it possible to use it for prolonged times in contaminated water. The long term antibacterial, antifouling and high dye adsorption properties of this functional nanomaterial are exceptionally promising for the development of high-efficiency and low cost water purification technologies.

(http://www.nanowerk.com/spotlight/spotid=35442.php)