Green Synthesis of Nano-particles for Waste Water Treatment


Today most of the countries are facing drinking water problems and conditions are very severe especially in developing countries. The world is facing formidable challenges in meeting rising demands of clean water as the available supplies of freshwater are depleting due to (i) extended droughts, (ii) population growth, (iii) more stringent health based regulations and (iv) competing demands from a variety of users. Various industries such as paper and pulp, tanneries, cosmetic, coffee pulping, pharmaceutical food processing, electroplating and dye manufacturing units, discharge colored and toxic effluents to water. Clean water (i.e., water that is free of toxic chemicals and pathogens) is essential to human health. The protection of water treatment systems against potential chemical and biological terrorist acts is also becoming a critical issue in water resources planning.

    Water treatment techniques:

    Today a number of techniques are used for treatment of water i.e. chemical and physical agent such as chlorine and it’s derivatives, Ultraviolet light, Boiling, Low frequency ultrasonic irradiation, Distillation, Reverse Osmosis, Water sediment filters (fiber and ceramic) Activated carbon, Solid block, Pitcher and faucet-mount filters, Bottled water, Ion exchange water Softener, Ozonating, Activated alumina 'Altered' Water. Halogens such as chlorine (Cl) and bromine (Br) are well known and widely used as antibacterial agents, but the direct use of halogens as bactericides has many problems because of their high toxicity and vapor pressure in pure form.

    The most common cation in water affecting human and animal health is NH4+. In drinking water ammonia removal is very important to prevent oxygen depletion and algae bloom and due to its extreme toxicity to most fish species. It can be replaced with biologically acceptable cations, like Na+, K+ or Ca2+ in the zeolite. During the past few decades, several investigations have been carried out concerning the use of synthetic and natural zeolites, polymer films and metal ions (Ag+, Cu2+, Zn2+, Hg2+, Ti3+, Ni2+, Co2+) as bactericides for water disinfection.

    Nanotechnology in water treatment:

    Advances in nanoscale science and engineering suggest that many of the current problems involving water quality could be resolved or greatly diminished by using nonabsorbent, nano catalysts, bioactive nanoparticles, nanostructured catalytic membranes, submicron, nano powder, nanotubes, magnetic nanoparticles, granules, flake, high surface area metal particle supramolecular assemblies with characteristic length scales of 9-10 nm including clusters, micro molecules, nanoparticles and colloids have a significant impact on water quality in natural environment.

    Nanotechnology used for detection of pesticides chemical and biological substances including metals (e.g., Cadmium, copper, lead, mercury, nickel, zinc), Nutrients (e.g., Phosphate, ammonia, nitrate, nitrite), Cyanide Organics, Algae (e.g., Cyanobacterial toxins) Viruses, Bacteria, Parasites, antibiotics, and biological agents are used for terrorism. Innovations in the development of novel technologies to desalinate water are among the most exciting and seem to have promise. Opportunities and challenges of using nanomaterials in the purification of surface water, groundwater and industrial wastewater streams is a matter of continuing concern. Misconceptions and One of the many impressions that people have about the future of nanotechnology is the expectation that nanoparticles can be used to kill harmful organisms, repair body tissue, in water quality improvement and to cure disease.

    Recent applications of nanoparticulate silver have included open wound and burn treatment and preliminary studies have shown that a 20-ppm silver colloidal suspension (~30 nm diameter) in purified water has a 100% cure rate for malaria. Titanium dioxide, especially as nanoparticulate anatase, is also an interesting antibacterial, with notable photocatalytic behavior. But ultrafine anatase has also been identified as cytotoxic and in-vivo studies have shown that it can be severely toxic in the respiratory system.  Nano capsules and nanodevices may present new possibilities for drug delivery, gene therapy, medical diagnostics, antimicrobial activity etc. The effect of particle size on the adsorption of dissolved heavy metals to iron oxide and titanium dioxide nanoparticles is a matter laboratory-scale experiments. Iron oxide and titanium dioxide are good sorbents for metal contaminants.

    Spherical aggregates of nanoparticles that have a similar size and shape to the resin beads already used in water purification. ligands, fluvic acids, hemic acids and their aggregates have a significant impact on contaminant mobility, reactivity, and bioavailability. Nanoparticles can also be designed and synthesized to act as either separation or reaction media for pollutants.

    Nanoparticles have two key properties that make them particularly attractive as sorbents. On a mass basis, they have much larger surface areas than bulk particles. Nanoparticles can also be functionalized with various chemical groups to increase their affinity towards target compounds.

    Advantages of Nanoparticles: 

    Nanoparticles have been increasingly tested as a potential alternative to traditional adsorbents due to their vast surface area, perfect mechanical rigidity, adjustable surface chemistry and feasible regeneration under mild conditions. Nanoparticles have few more significant advantages over other adsorbent materials; for example, they can be readily manufactured in a wide range of physicochemical properties.

    Waste water treatment via adsorption process
    Waste water treatment via adsorption process

    Challenges of recycling nanoparticles:

    Recovering and recycling nanoparticles is especially difficult because they tend to form complex, hard-to-separate mixtures with other substances. It is of prime importance to design a new process which is perfectly suited to recycling nanoparticle.

    Green Synthesis of Nano-particles for Waste Water Treatment
    Green Synthesis of Nano-particles for Waste Water Treatment

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