Spinel ferrites have recently emerged as a new class of adsorbents that are preferred for water treatment.(1−3) These materials have a high surface area and great active sites for interaction with contaminants, and therefore offer a high adsorption capacity. Spinel ferrites possess special superparamagnetic properties (SPM), allowing them to be easily recovered from the reaction mixture by application of an external magnetic field.(4,5) Spinel ferrites have been investigated to remove various contaminants in water such as organic compounds,(6−8) nutrient salts,(9) and toxic metals.(10−13)

Pasted from <https://pubs.acs.org/doi/10.1021/acsomega.9b04126#>







Lead and water: reaction mechanisms, environmental impact and health effects
Seawater contains trace amounts of lead (2-30 ppt). On average rivers contain between 3 and 30 ppb. Phytoplankton contains approximately 5-10 ppm lead (dry mass), freshwater fish approximately 0.5-1000 ppb, and oyster approximately 500 ppb.
The World Health Organization (WHO) stated a legal limit of 50 ppb for lead in 1995, which is decreased to 10 ppb in 2010.

In what way and in what form does lead react with water?
Under normal conditions lead does not react with water. However, when lead comes in contact with moist air reactivity with water increases. A small lead oxide (PbO) layer forms at the surface of the metal. When both oxygen and water are present, metallic lead is converted to lead hydroxide (Pb(OH)2):
2Pb(s)+ O2(g) + 2H2O(l) -> 2 Pb(OH)2(s)

Solubility of lead and lead compounds
Elementary lead does not dissolve in water under normal conditions (20oC, and pressure = 1 bar). It may however occur dissolved in water as PbCO3 or Pb(CO3)22-. A well-known example of a water soluble lead compound is lead sugar (lead(II)acetate), which derived its name from its sweet nature.
Lead frequently binds to sulphur in sulphide form (S2-), or to phosphor in phosphate form (PO43-). In these forms lead is extremely insoluble, and is present as immobile compounds in the environment. Lead compounds are generally soluble in soft, slightly acidic water.


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What are the health effects of lead in water?
The human body contains approximately 120 mg of lead. About 10-20% of lead is absorbed by the intestines. Symptoms over overexposure to lead include colics, skin pigmentation and paralysis. Generally, effects of lead poisoning are neurological or teratogenic. Organic lead causes necrosis of neurons. Inorganic lead causes axonal degeneration and demyelination. Both species of lead may cause cerebral oedema and congestion. Organic lead compounds are absorbed quicker, and therefore pose a greater risk. Organic lead derivates may be carcinogenic. Women are generally more susceptible to lead poisoning than men. Lead causes menstrual disorder, infertility and spontaneous abortion, and it increases the risk of stillbirth. Foetuses are more susceptible to lead poisoning than mothers, and generally foetuses even protect mothers from lead poisoning. A long time ago lead was applied as a measure of birth control, for example as a spermicidal, and to induce abortion.
Children may absorb a larger amount of lead per unit body weight than adults (up to 40%). Consequently, children are generally more susceptible for lead poisoning than adults. Symptoms include lower IQs, behavioural changes and concentration disorder.
Lead accumulates in leg tissue. The most severe type of lead poisoning causes encephalopathy.
Lead toxicity is induced by lead ions reacting with free sulfydryl groups of proteins, such as enzymes. These are deactivated. Furthermore, lead may interact with other metal ions.

Which water purification technologies can be applied to remove lead from water?
Lead removal from water may be established applying coagulation, sand filtration and ion exchange. Additionally, active carbon, KDF media filtration and reverse osmosis may be applied.
Literature and the other elements and their interaction with water
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Efficient removal of Pb(II) from aqueous solution by a novel ion imprinted magnetic biosorbent: Adsorption kinetics and mechanisms

Pasted from <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6437713/>



Effective removal of Pb(ii) using a graphene@ternary oxides composite as an adsorbent in aqueous media†

Pasted from <https://pubs.rsc.org/en/content/articlelanding/2017/nj/c7nj03064a#!divAbstract>



https://onlinelibrary.wiley.com/doi/abs/10.1002/ep.670130124