Presentation topic:

Aqueous Elemental Pollution

byMaryum AtiqueM.Phill chemistryuniversity of AgricultureFSD.

Definition of Heavy Metals

• Heavy metals are those metal of relatively high density, or high relative atomic weight.

• Heavy metal can include elements lighter than carbon and can exclude some of the heaviest metals.

•    It mainly includes: 

- Transition

- Metals

- Some metalloids

- Lanthanides 

- Actinides.

COMMON HEAVY METALS CAUSING AQUEOUS POLLUTION

• Cadmium • Lead• Mercury• Aluminum• Antimony• Arsenic• Zinc and Copper• Nickel• Tin• Uranium

Sources of heavy metals pollution

• Primary sources of heavy metals are point sources: - Mines

- Foundries

- Smelters

- Coal-burning power plants

- Diffuse sources (combustion by-products and vehicle emissions)

• Waste-derived fuels are especially prone to contain heavy metals, so heavy metals are a concern in consideration of waste as fuel.

• Electronic waste is also a significant source of heavy metal contaminants

Sources and sink of heavy metals

Aluminium aqueous pollution

• The amount of aluminium in seawater is 0.013 and 5 ppb. River water generally contains about 400 ppb of aluminum.

• Regular aluminium concentration is 0.4ppm• Below pH 4.5 solubility increases and

concentration becomes upto 5ppm and so its pollution level is also increased.

Arsenic water pollution

• Arsenic contamination of groundwater is often due to naturally occurring high concentrations of arsenic in deeper levels of ground water

• Its sources are geochemical processes, mining activities • Industrial and manufacturing processes.• through the dissolution of minerals and ores, and as a result of

erosion from local rocks.• It can causes:• Irritation of the stomach and intestines• Red and white blood cells decreased production, skin changes and

lung irritation

Severe effects of arsenic pollution

Antimony aqueous pollution

• Major sources of antimony in drinking water is waste water from petroleum refineries; fire retardants; ceramics; electronics.

• It causes lung irritation, heart and lung damage, stomach pains, diarrhea, vomiting and stomach ulcers.

• Its elevated level adversely affect the plant growth.• Cadmium aqueous pollution:• Maximum contaminant level for cadmium is 0.005 mg/L or 5 ppb.• Cadmium applications- including electroplating and the

manufacture of batteries.• Contaminated foodstuffs can result in emphysema, renal failure,

cardiovascular disease, and perhaps cancer.

Antimony aqueous pollution

Lead aqueous pollution

• Action Level for Treatment Techniquein parts per million (ppm)Lead = 0.015 ppm

• Health EffectsInfants and children: Delays in physical or mental development; children could show slight deficits in attention span and learning abilities.Adults: Kidney problems; high blood pressure

• Sources of contaminationCorrosion of household plumbing systems, erosion of natural deposits. Industrial sources such as lead mining, smelting and coal combustion, the use of lead-based paint and lead containing pipes in water supply systems.

Quality Standard for Groundwater

Categories of Ground water

1

2 3 4 5

Lead ≤mg/L 0.005 0.01 0.05 0.1 >0.1

Cadmium ≤mg/L 0.0001 0.001 0.01 0.01 >0.01

• Category 1 and 2 reflects the low contents of chemical components for groundwater.

• Category 3 reflects that it is applicable to concentrative drinking water sources and industrial and agricultural water use.

• Category 4 is primarily applicable to the industrial use water and partial agricultural use water.

• Category 5 is not applicable for drinking purposes.

Mercury aqueous pollution

•  largest emitters 

cement plants

power plants

gold mining, and

industrial boilers in • In areas of mercury contamination, larger and older fish tend to have

higher levels of mercury.• Minamata disease  is a neurological syndrome caused by severe 

mercury poisoning by polluted water. Symptoms include ataxia, numbness in the hands and feet, general muscle weakness, narrowing of the field of vision, and damage to hearing and speech

Effects of mercury on health

Nickel aqueous pollution• The average concentration of nickel in drinking water in the United

States is between 2 and 4.3 ppb.• Metallic nickel and some other nickel compounds are teratogenic

and carcinogenic to mammals. Nickel concentrations in plants are usually 1 μg/g, and concentrations above 50 μg/g are toxic.

• Effects of nickel:• Increased red blood cells (cancer)• Increased protein in the urine• Chronic bronchitis• Reduced lung function• Stomach aches• Cancer of the lungs

Uranium aqueous pollution

• Uranium is a naturally and commonly occurring radioactive element and found in water coming from power plants causing uranium contained water pollution

• Uranium poisoning cause birth abnormalities including physical deformities, neurological and mental disorders.

• Copper and zinc:• Zn can lead to acute gastrointestinal and respiratory damages and acute

heart, brain and kidney damages, when they are in polluted aqueous form. • High concentrations of these heavy metals in ground water can negatively

affect on crop growth, as these metals interfere with metabolic functions in plants

• Cupper toxicity in water lead to Liver damage ,Kidney damage ,Neurologic damage, Weakness , Abdominal pain, Nausea, Vomiting,  Diarrhea,  Lung damage and Coma.

Methods to purify the water from elemental

pollution

Commonly used methods

- Chemical precipitation

- Biosorption

- Ion exchange

- Reverse osmosis

- Solvent extraction • Reverse Osmosis: 

It is a process in which heavy metals are separated by a semi-permeable membrane at a pressure greater than osmotic pressure caused by the dissolved solids in wastewater. The disadvantage of this method is that it is expensive.

RO CC

• Direct contact membrane distillation (DCMD). • Applicable to desalination. Heated seawater is

passed along the surface of a hydrophobic polymer membrane.

• Evaporated water passes from the hot side through pores in the membrane into a stream of cold pure water on the other side.

• The difference in vapour pressure between the hot and cold side helps to push water molecules through.

Ion-exchange• Ions exchange: In this process, metal ions from dilute solutions are

exchanged with ions held by electrostatic forces on the exchange resin.Different type of ion exchange resins used for every metal like Lead : carboxylic resin

Uranium: WBA and SBA • Chemical Precipitation:  Precipitation of metals is achieved

by the addition of coagulants such as alum, lime, iron salts and other organic polymers. The large amount of sludge containing toxic compounds produced during the process is the main disadvantage.

Heavy metals removal by biosorption

• The biosorption process involves a solid phase (biological material) and a liquid phase (solvent, normally water) containing a dissolved species to be sorbed.

• The degree of sorbent affinity for the sorbate determines its distribution between the solid and liquid phases.

• Many algae have immense capability to sorb metals, and there is considerable potential for using them to treat wastewaters

Heavy metals removal by Zeolites • Zeolites are nature's powerful detoxifiers that are so strong they

even binds all those heavy metals from the food and water we ingest.

• natural zeolites can safely remove heavy metals such as mercury, cadmium, lead, arsenic, aluminum, and tin, while also removing radioactive metals like cesium and Strontium-90.

• Zeolites are  microporous,  aluminosilicate minerals

 commonly used as commercial adsorbents.

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