Rashtreeya Sikshana Samithi Trust R V College of Engineering Bangalore – 560 059

Rashtreeya Sikshana Samithi Trust
R V College of Engineering
Bangalore – 560 059
(Autonomous Institution affiliated to VTU, Belgaum)
Department of Chemistry
Student’s NameV.AdharshUSN 18UG1REG0152Semester IBranch ECE Section-Roll No N
Course Title Engineering Chemistry Course Code 18CH12/22
Course Outcomes CO1 CO2 CO3 CO4
CO Attainment
in marks COs Explain the principles of chemistry in engineering ; technology Apply the knowledge of chemistry in solving socio-economic and environmental issues. Identify and analyze engineering problems to achieve practical solutions Develop solutions for problems associated with technologies
Certificate
This is to certify that V.ADHARSH ( 18UG1REG0152 ) II Semester Electronics And Communication Engineering Branch has satisfactorily completed the Assignment/Seminar presentation prescribed by the Institution in the course Engineering Chemistry (18CH12/22) for the academic year 2018 – 2019.

Title of Topic: REMOVAL OF HEAVY METALS FROM WASTE WATER USING NANO-MATERIALS
Max. Marks Marks Obtained
50 Signature of the Student Signature of the Faculty Signature of H.O.D.

REMOVAL OF HEAVY METALS FROM WASTE WATER USING NANO-MATERIALS
INTRODUCTION
One of the most abundant resources found on the surface of the Earth is water. It covers about 70.9 percent of Earth’s surface however only 1 percent of it available for human consumption. WHO estimates that 1.1 billion people don’t have access to adequate drinking water this caused mainly due to raise in prices of potable water, growing population and climate and environmental changes.
A huge amount of water can be saved year by treating waste water with efficient waste water treatment methods. A huge amount of waste water generated is due to factories, chemicals run off from fertilizers and toxic chemicals from e-waste. This waste water often consists of heavy metals dissolved in it (example arsenic, lead, mercury etc). This water containing heavy metals can cause severe health issues such as organ damage and cancer. The traditional waste water treatment methods aren’t effective on heavy metals present in waste water. On a large scale these methods are expensive, they don’t remove pollutants completely and they generate toxic sludge hence we should adopt nanotechnology to treat waste water more effectively.
Nanomaterials are the smallest scale of structures humans have developed. These are structures with one dimension at least less than 100 nm. Nanomaterials have been developed in various forms such as nanowires, nanotubes, membranes, particles, quantum dots and colloids. Its proven to be an efficient, cost effective and eco-friendly method of waste water management.
Nanotechnology has been referred as a standout amongst the most exceptional procedures for wastewater treatment. It might be grouped dependent on the nano-materials nature into three principle classifications: nano-adsorbents, nano-catalysts and nano-membranes.
In nano adsorption innovation, various and powerful works have been distributed as of late with the mean to research the expulsion of heavy metals from wastewater utilizing nano-adsorbent materials. Nano-adsorbent can be created utilizing the molecules of those components which are synthetically dynamic and have high adsorption limit on the surface of the nano-material). The utilized materials for advancement of nano-adsorbents incorporate initiated carbon, silica, earth materials, metal oxides and altered mixes as composites. The below average of the nanomaterials is nano-impetuses. The nanomaterials, for example, metal oxides and semiconductors have picked up a significant consideration of the researchers in creating wastewater treatment advances. Diverse kinds of nano-impetuses are utilized for corruption of toxins in wastewater, for example, electrocatalysts, Fenton based impetuses for enhancing compound oxidation of natural contaminations) and impetuses having antimicrobial properties.
The second-rate class of the nano-materials utilized in the wastewater treatment forms is utilizing nano-membranes. In that innovation, the weight driven treatment of wastewater has been demonstrated perfect for enhancing water nature of want. Among different sorts of film filtration, the nano-filtration (NF) is broadly connected for treatment of wastewater in businesses as a result of little pore sizes, minimal effort, high productivity and ease of use. Nanomembranes can be produced from nano-materials, for example, nano metal particles, non-metal particles and nano-carbon tubes among others. Various investigations have been looked into featuring the effectiveness of different recently created nano-materials. The present audit centred on four primary classes of nano-materials in use of wastewater treatment. These incorporate nano-adsorbents, nano-catalysts, nanomembranes and the mix of previously mentioned nanotechnologies with organic strategies.

Nano Adsorbents:
Lately, Nano-molecule materials have been examined for their potential as adsorbents. The littler size of the nanoparticles builds the surface territory which improves the synthetic movement and adsorption limit of Nano-particles for the adsorption of metals on their surface Adsorption process relies upon adsorption coefficient Kd and recitation dividing of toxin i.e. heavy metals or organic pollutants under balance conditions. In addition, for constant inorganic contaminations redox response is favoured to begin the ionic structure change. In any case, a few specialists emphatically concur that adjustments in redox condition impact the poisonous quality of these contaminations. The much of the time utilized nano-particles for the adsorption of substantial metals are initiated carbon and carbon nanotubes, manganese oxide, grapheme, zinc oxide, magnesium oxide, titanium oxide and ferric oxides. Nano-adsorbents have two principle properties: natural surface and outer functionalization. Their physical, synthetic and material properties are additionally identified with their extraneous surface structure, clear size and characteristic organization. In the fluid condition, the variables influencing the adsorption procedure are high surface region, adsorption action, concoction movement, area of particles on surface, absence of inner dissemination opposition and high surface restricting vitality. Nano-particles utilized as adsorbent for the evacuation of heavy metals ought to be nontoxic, high adsorption limit, can adsorb contaminations in less focus (ppb), adsorbed contaminations that can be effortlessly expelled from adsorbent surface and can be reused for various occasions.

Nano Membranes:
Among the ebb and flow propelled wastewater treatment systems, layer filtration innovation manufactured by nanomaterials is a standout amongst the best procedures. Nanotechnology ideas go past best in class execution of water treatment membranes and empower new usefulness, for example, synergist reactivity, high porousness, and fouling obstruction. The primary purposes behind selection of this innovation are their advantages as far as quality treated water, powerful cleansing and low space necessity for plant. Also, it is exceptionally sparing, proficient and basic in configuration contrasted with other treatment methods. For wastewater treatment, nano-layer partition innovation is utilized for successful evacuation of colours, heavy metals and different contaminants. Adjacent to molecule partition from wastewater, nano-materials in novel film additionally assume an essential job in the synthetic decay of natural foulants detachment. The pieces of these kinds of layer are one-dimensional nanomaterials (containing natural and inorganic materials, for example, nanotubes, nanoribbons, and nanofibers).

Nano Catalysts:
The nano-catalysts, particularly those of inorganic materials, for example, semiconductors and metal oxides, are increasing significant consideration of the scientists in use of wastewater treatment. Different sorts of nano-catalysts are utilized for wastewater treatment, for example, photocatalysts, electrocatalysts and Fenton based impetuses for enhancing substance oxidation of natural contaminations and antimicrobial activities.

Nano adsorbents and nano-membrane in recent years have proven to be particularly effective in treatment and removal of heavy metals from waste water.

LITERATURE SURVEY
Similar to the case with numerous different controls, uses of nanotechnology (for instance, in making steel and making canvases) were being used a very long time before the field was formally characterized. Early supporters of the field incorporate James Clark Maxwell (Scottish physicist and mathematician, 1831-1879) and Richard Adolf Zsigmondy (Austrian-German scientific expert, 1865-1929). Zsigmondy contemplated colloids (compound blends where one substance is scattered equally all through another) and took a gander at gold sols and different nanomaterials. Other critical supporters in the main portion of the twentieth century incorporate Irvin Langmuir (American scientific expert and physicist, 1881-1957) and Katherine B. Blodgett (American physicist, 1898-1910).

The term ‘nanotechnology’ was utilized first by the Japanese researchers Norio Taniguchi (1912-1999) in a 1974 paper on generation innovation that makes protests and highlights on the request of a nano meter. The American designer K. Eric Drexler (b. 1955) is credited with the advancement of atomic nanotechnology, prompting nano systems hardware producing.
The development of examining burrowing magnifying instrument in the 1980s by IBM Zurich researchers and afterward the nuclear power magnifying lens enabled researchers to see materials at an uncommon nuclear level. The accessibility of an ever-increasing number of ground-breaking PCs around this time empowered extensive scale reproductions of material frameworks utilizing supercomputers. These investigations gave understanding into nanoscale material structures and their properties. The complementary activities of modelling and simulation, atomic scale visualization and characterization, and experimental synthesis activities fuelled nanoscale research activities in 1980s.

Numerous old urban communities had waste water frameworks, yet they were principally proposed to divert water from rooftops and asphalts. An eminent model is the sewage water arrangement of antiquated Rome. It included many surface courses that were associated with a huge vaulted channel called the Cloaca Maxima (“Great Sewer”), which conveyed sewage water to the Tiber River. Worked of stone and on a fabulous scale, the Cloaca Maxima is one of the most seasoned existing landmarks of Roman designing.

The development of incorporated sewage treatment plants started in the late nineteenth and mid twentieth hundreds of years, chiefly in the United Kingdom and the United States. Rather than releasing sewage specifically into an adjacent waterway, it was first gone through a blend of physical, natural, and compound procedures that evacuated a few or the vast majority of the toxins. Likewise starting in the 1900s, new sewage-accumulation frameworks were intended to isolate storm water from household wastewater, with the goal that treatment plants did not wind up over-burden amid times of wet climate.

Wastewater treatment plants turned out to be substantial, complex offices that required extensive measures of vitality for their activity. After the ascent of oil costs in the 1970s, worry for vitality protection turned into a more critical factor in the plan of new contamination control frameworks. Subsequently, arrive transfer and subsurface transfer of sewage started to get expanded consideration where plausible. Such “low-tech” contamination control strategies not exclusively may save vitality yet additionally may serve to reuse supplements and recharge groundwater supplies.

MATERIALS AND METHODOLOGY
Nano Adsorbents:
Nano adsorbents incorporates metallic nano-particles, nanostructured blended oxides, attractive NPs and metallic oxide NPs. Other than that, an ongoing advancement on carbonaceous nano-materials (CNMs) included carbon nanotubes, carbon nano-particles and carbon nanosheets. In addition, different kinds of silicon nano-material are likewise utilized as nano-adsorbents, for example, silicon nanotubes, silicon nanoparticles and silicon nanosheets. Also, Nano clays, polymer-based nano-materials, nanofibers, and aerogels are a portion of the nano-materials utilized for adsorption of heavy metals from wastewater.

Variables controlling the nano-adsorbents properties are measure, surface science, agglomeration state, shape and fractal measurement, synthetic synthesis, precious stone structure and dissolvability. Synthetic movement and fine grain estimate are two key properties of nano-particles that make its noticeable when contrasted with different substances, for example, typical scale titanium dioxide and alumina. In addition, adjustment in nano-particles can be done by some reagent to improve its properties for metals particles pre-focus.

Oxide Based Nano Adsorbents:
Oxide based nano-particles are inorganic nano-particles which are normally arranged by non-metals and metals. These nanoparticles are widely utilized for perilous toxins expulsion from wastewater. There incorporate titanium oxides, Titanium oxide/dendrimers composites zinc oxides, magnesium oxide, manganese oxides and ferric oxides. Oxide based nano-particles are portrayed by high BET surface zone, least natural effects, less solvency, and no auxiliary contaminations.

Carbon Nanotubes (CNT):
Carbon nanotubes (CNTs) are broadly considered material having the capacity to evacuate heavy metals and an assortment of natural contaminants from wastewater through adsorption (Ren et al., 2011). Be that as it may, poor scattering capacity, trouble in partition and little particles estimate are couple of issues exist for utilizing CNT as adsorbent. To defeat these issues specialists altered the standard CNT into changed CNT, for example, multi-divider carbon nanotubes (MWCNT). Altered attractive CNTs have high scattering capacity and can be effectively expelled from wastewater or utilized medium by utilizing magnet. A few investigations detailed the evacuation of substantial metals, for example, Pb(II) and Mn(II)), Cu(II) by utilizing MWCNTs.

Researchers have explored the adsorption conduct of alumina upheld on CNT for the treatment of lead watery arrangements. They revealed that the covered CNT showed preferred evacuation capacity over the uncoated CNT. Surface change of CNT expands its general adsorption movement. Different sorts of surface alteration systems are accounted for by various specialists which incorporate corrosive treatment, metals impregnation and practical particles/gather joining. The previously mentioned methods modify the qualities of CNTs surface like BET surface region, surface charge, scattering and hydrophobicity.
Corrosive treatment of CNTs was completed by utilizing various types of acids, which incorporate HNO3, KMnO4, H2O2, H2SO4 and HCl. Corrosive treatment evacuates the pollutions present on the surface of CNTs. In addition, it likewise presents new useful gatherings on the surface of CNTs, which brought about increment in its adsorption limit from wastewater. Moreover, oxygen-containing gathering can likewise be presented by microwave-energized surface wave plasma. Joining utilitarian atoms/bunches on the surface of CNTs are another approach to enhance their surface attributes. It tends to be done through various routes, for example, plasma method, compound adjustment and microwave. Any way among these methods, plasma strategy is truly outstanding because of less vitality request and ecological amicable process.
Graphene Based Nano Adsorbent:
Graphene is one of allotropy of carbon having uncommon highlights that make it profoundly positive for a few natural applications. Graphene oxide (GO) is a carbon nano-material having two-dimensional structure created by the oxidation of graphite layer through compound technique.
The most widely recognized strategy utilized for the blend of GO is Hummers technique. The hydrophilic gatherings were initiated in GO which required extraordinary oxidation process. The nearness of these hydroxyl and carboxyl gatherings as practical gatherings in GO expands the adsorption of heavy metals. GO as adsorbent for the expulsion of substantial metals is getting more consideration because of its high surface region, mechanical quality, light weight, adaptability and synthetic stability.

In addition, the nearness of utilitarian gathering on the surface of GO too impacts the adsorption procedure. GO has two principle includes when contrasted with different nanomaterials, for example, CNTs. Initial, a solitary layer GO has two dimensional basal planes accessible for the most extreme adsorption of heavy metals. Furthermore, it has basic union process, which can be done by synthetic shedding of graphite with no metallic impetus and convoluted instrument. In addition, GO did not require any further corrosive treatment to improve its adsorption limit as it as of now contains hydrophilic practical gathering.
Nano Membranes:
Among the current wastewater treatment methods, layer filtration innovation created by nanomaterials is a standout amongst the best methodologies. Nanotechnology ideas go past best in class execution of water treatment layers and empower new usefulness, for example, synergist reactivity, high penetrability, and fouling. The principle explanations behind appropriation of this innovation are their advantages regarding quality treated water, viable cleansing and low space prerequisite for plant. Also, it is very sparing, productive and straightforward in configuration contrasted with other treatment methods.
For wastewater treatment, nano-layer partition innovation is utilized for powerful expulsion of colours, heavy metals and other contaminants. Close to molecule partition from wastewater, nano-materials in novel layer likewise assume a fundamental job in the substance disintegration of natural foulants division. The pieces of these sorts of film are one-dimensional nanomaterials (including natural and inorganic materials, for example, nanotubes, nanoribbons, and nanofibers.
For specific filtration and nano-molecule evacuations, a film created with carbonaceous nanofibers (CNFs) indicated exceptional particular filtration/expulsion effectiveness under high weight. Besides, amassing beta cyclodextrins in CNF layers through straightforward filtration process have momentous potential for expulsion of phenolphthalein and fuchsin corrosive. For fluid osmotic partition, zeolite based nano-membranes can be utilized. The basic zeolite materials utilized in layers incorporate sodalite, MFI-sort and Linde Type A. The most normally connected zeolite in nano-layers is Zeolite ZSM-5 (MFI) which has a concoction synthesis as NanAlnSi96n-O192 16H2O (n 3) for a unit cell. Moreover, the catching capability of nano-particles and other little atoms can be emphatically upgraded by interconnection nano-particles and contrarily charged bodies on perceptible circle like titanate-nanoribbon layer.

Carbon Nanotube:
Carbon nanotubes are getting more significance as nanomaterials for union of polymer composite layers with most extreme execution. These composites have different highlights, for example, low mass thickness, to a great degree high quality and ductile modulus, high adaptability and expansive perspective proportion, which improve its execution. Based on its union structure it might be called as single-walled carbon nanotubes (SWCNTs) or multi walled tubes carbon nanotubes (MWCNTs) comprise of solitary and multi-walled tubes separately.

Different examinations have been directed for combination of changed nanotube membranes. In 2015 researchers announced the union of Carboxyl multi-walled carbon nanotubes/calcium alginate (CMWCNT/CA) composite by utilizing polyethylene glycol 400 as pore-framing specialist with hydrogel nanofiltration layer. CMWCNT/CA film had a high quality around 1.83 MPa. Besides, layer has great enemy of fouling property, as 96.87% was ox-like serum egg whites (BSA) arrangement motion of unadulterated water flux (PWF). Moreover, the examination on dismissal of Congo red appeared to 98.62% of evacuation proficiency. In concentrate by nanofibrous filtration membranes were created made out of Poly hydroxybutyrate-calcium alginate/carboxyl multi-walled carbon nanotube composite. The composite film builds the hydrophilic and tractable mechanical property, which increment the expulsion of chose contamination. It was watched the 32.95 L/m2h and 98.20% of transition and dismissal rate individually of composite layer for the colour Brilliant blue. Researcher arranged chitosan/Silica-covered carbon nanotubes (CS/SCNTs) composite membranes by using the chitosan and SCNTs which was set up by embracing a basic sol-gel technique. The CS/SCNTs composite layer indicated improved mechanical properties, oxidative and warm steadiness and proton conductivity.

RESULTS AND DECISIONS
Nano Adsorbents:
Nano-adsorbent is broadly utilized adsorbents for the expulsion of heavy metals from wastewater. CNTs and metal oxides are the most ordinarily utilized nano-particles for the expulsion of heavy metals from fluid arrangement. These nano-particles have some key highlights, for example, high BET surface region, microporous structure, high scattering capacity, financially and natural well disposed. Be that as it may, littler size of particles and troubles in partition from watery arrangement will prompt optional contamination). This further impacts the bioavailability and versatility of the substantial metals and causes danger in the earth. Likewise, temperate reuse and recovery is one of another test for these nano-particles. Any way alteration was done by various analysts, for example, Hydrous Manganese Oxide (HMO) and multi-divider carbon nanotubes (MWCNT), to beat these difficulties. By and by, new patterns in nano-adsorbents, for example, natural inorganic cross breeds are maintainable choice to beat the related impediments of nano-adsorption process.

Researchers detailed the expulsion of substantial metals from wastewater by utilizing changed CNTs joined with different practical gatherings. In addition, CNTs changed with metal/metal oxide, for example, MnO2 and press oxide likewise indicate promising outcomes for overwhelming heavy metals expulsion from wastewater.

Different scientists utilized graphene-based nanomaterials for the adsorption of overwhelming metals from waste water researchers contemplated the expulsion of heavy metals from wastewater by utilizing GO empowered sand channel in section reactor also. change the GO with TiO2 and utilized half and half composite for the adsorption of Pb2+, Cd2+ and Zn2+ particles from the water. The adsorption limit of half and half composite reaches up to 65.6 mg/g, 72.8 mg/g and 88.9 mg/g for Pb2+, Cd2+ and Zn2+ individually.

Nano Membranes
The fundamental explanations behind selection of layers filtration innovation are their advantages as far as quality water treatment, viable purification and low space prerequisite for plant. Also, it is very efficient and basic in configuration contrasted with other treatment strategies. Nano-membrane detachment innovation can be productively connected for evacuation of colours and substantial metals. As far as natural concerns, the nano-membranes have expansive biological impression amid their assembling procedure. Researchers found that the existence cycle of carbon nanofiber contributes 100 times more for each unit weight to danger, a worldwide temperature alteration and ozone exhaustion than traditional materials. Another hindrance is the issue of membrane fouling which is caused by cooperation of natural mixes in water with hydrophobic layer. The affidavit of particles on the film surface or inside the pores of layer expands the shot of film fouling which results in low quality treated water and lessens unwavering quality and life of layer hardware. Membrane fouling diminishes the water transition and, in this manner, needs a layer clean-up process by substance or mechanical means or even some time the entire substitution of film. To bring down these issues, the scientists are concentrating on alteration of layer by covering with a hydrophilic polymer layer, for example, poly-vinyl liquor and chitosan. Also, the nano-particles, for example, TiO2 might be consolidated to expand the hydrophilicity of layers, along these lines decreasing fouling and expanding the saturate motion.

CONCLUSION
In a momentum situation, there is a noteworthy requirement for cutting edge water advances to guarantee a high calibre of water, dispense with concoction and natural toxins, and strengthen mechanical generation procedures of wastewater. In such manner, nanotechnology is one of the perfect alternatives for development wastewater treatment forms. Different nano-materials have been produced and examined effectively for wastewater treatment. These incorporate nano-adsorbents (in view of oxides, Fe, MnO, ZnO, MgO, CNT), photocatalysts (ZnO, TiO2, CdS, ZnS: Cu, CdS: Eu, CdS: Mn), electrocatalysts (Pt, Pd), and nano-layers (multi walled CNTs, electrospun PVDF, PVC, Na-TNB). Moreover, these nano-particles can be coordinated with natural procedures (algal layer, anaerobic absorption, microbial power device) to enhance in water cleaning. Every innovation has its very own benefits and particular toxin expulsion effectiveness.

The nano-adsorbents can possibly evacuate heavy metals, for example, Cr, As, Hg, Zn, Cu, Ni, Pb and Vd from wastewater. Nano-molecule photocatalysts can be utilized for treatment of both dangerous toxins and heavy metals, where the change in impetus material can give the ability of utilizing unmistakable area of sun-based light rather than staggering expense counterfeit bright radiation. In electrocatalytic treatment of wastewater, the procedure could be enhanced by utilizing nano-particles to accomplish bigger surface region and uniform dissemination of impetus in the response media. Infiltration of wastewater, nanomembranes have been demonstrated exceptionally viable for lessening foulants, heavy metal and colours. Besides, if there should be an occurrence of natural treatment forms, nano-advances have been proficiently coordinated, as the utilization of nano-films in algal wastewater treatment encourages in proficient reaping of algal biomass, decreasing the layer fouling and utilization of coagulants.
There is no uncertainty of proficiency of usage nano-materials in wastewater treatment; in any case, this innovation has some genuine drawbacks that should be negotiated since nano-particles may discharge into the earth amid readiness and treatment forms, where they can collect for long time and cause genuine dangers. With the end goal to diminish the wellbeing hazard there is require a future research to get ready such impetuses having slightest harmfulness to the earth. More work is required to re-examine the ecotoxicity potential for each new adjustment in impetus and for existing materials. Likewise, life cycle evaluation of nano-materials is urgently required to address their general advantages and dangers.
Nano-innovation is once in a while received to mass procedures. Surrendered that up to this point, the greater part of the nano-materials has not been cost-aggressive when contrasted and customary materials, for example, initiated carbon, and in this manner future applications will centre around proficient procedures where just little amounts of nano-materials are required. Also, additionally work is required on building up a savvy strategy for blending nano-materials and testing the proficiency everywhere scale for fruitful field application.

FUTURE SCOPE
This paper centres solely around the potential outcomes of nanotechnology with respect to wastewater treatment. In any case, nanoparticles have another vital element that could make them a by and large worthy technique: it is their capacity to identify and avert defilement. Due to their size and different attributes, they can go about as sensors for some focused-on contaminants in wastewater. This property will be critical as far as recognizing pathogens or some newfound substances in water/wastewater.
At long last, future research should address the issue of similarity of nanotechnology with the current wastewater treatment techniques. In created nations, where a total sewerage connect with wastewater treatment plants is now set up, it cannot sensibly be normal that the current offices will be relinquished in the approaching time frame. Accordingly, it will be imperative to characterize how to fuse particular nanomaterials into the framework, with least changes to the current foundation.
In the meantime, autonomous nanotechnology procedures could be connected in undeveloped or creating nations that have not up ’til now characterized framework and wastewater treatment techniques.
Given the level of improvement and future prospects for enhancing productivity and monetary suitability, the accompanying three kinds of nanomaterials can be viewed as the most encouraging ones:
– Nano adsorbents
– nanomembranes
– Nano catalysts
The previously mentioned difficulties in regards to commercialization of nanomaterials are essential, however a significant number of them, including specialized qualities, cost of creation, natural effects, and so on might be considered as impermanent obstructions as it were. To beat these difficulties, close co-task between every single invested individual is fundamental. It very well may be normal this cutting-edge innovation, with watchful administration went for maintaining a strategic distance from bothersome outcomes, can make a tremendous commitment to this field, and set up itself as a decent wastewater treatment arrangement.

REFERENCE
Remediation of wastewater using various nanomaterials by Muzammil Anjum, R. Miandad, Muhammad Waqas, F. Gehany and M.A. Barakat
Britannica Encyclopaedia
www.trynano.org Methods of Removing Heavy Metals from Industrial Wastewater by Gunathilake S.K