Developing ligands to extract copper and silver from waste waters

Chapter 3 Literature Review

Literature Review

Developing ligands to extract copper and silver from waste waters

3.0 Overview

Since 1978, the United States Environmental Protection Agency (USEPA) has already categorized silver and copper ions like pollutants found in wastewater that constitute serious health hazards. These heavy metal ions are use in various industries notably jewelry manufacturer and copper smelting as include in table 3.1 that has been highlighted some possible occurrences bearing in their wastewaters and contaminants together (Selin KUTLU (2005)). N. F. Gray (2004) in their study about Biology of wastewater has suggested that the toxicity of metals has been examined by using biochemical oxygen demand (BOD) inhibition test. Metals were found to decrease in toxicity in the following order; mercury, silver, copper, chromium, iron, aluminum, cadmium, cobalt and nickel, tin and zinc. Likewise many researchers and also U.S. GEOLOGICAL SURVEY CIRCULAR 1133 (1995) have classified copper and silver among the high toxic metal as shown in table 3.2. Silver and copper ions are dangerous to man and aquatic life because they easily tend to bio-accumulate of any living tissues (J. Chil. Chem. (2007)). One example of same scenario is the most famous cases of heavy metal pollution occurred in Minamata, Japan in the 1950s. The reason of this disaster has been traced to the dumping of about 27 tons mercury compounds by the Chisso Corporation into Minamata Bay during the 1950s and 1960s. The people of Minamata consumed fish and shellfish from the Bay in their diet and this led to an accumulation of toxic methyl mercury in their bodies. Over 3,000 victims have been recognized as having “Minamata Disease”. As copper and silver have more less same characteristics of mercury and their toxic pollution has received a great deal of attention due to the increased industrialization and higher contaminant production; treatment of these waterborne wastes is therefore of paramount importance

Chelating technique integrated with gravimetric or volumetric analysis as well as spectrophotometric methods is a solution that can easily estimate and identify copper and silver toxic ion. The dissertation is based upon the development of ligands to chelate with copper and silver ions in order to remove to toxic metal and recovery of these precious metals from wastewater.

Table 3.1 Industries with possible occurrences of certain metals in industrial wastewaters (Water Pollution Control Federation, 1981).

Industry

As

Ba

B

Cd

Cr

Co

Cu

Fe

Pb

Mn

Hg

Ni

Se

Ag

Zn

Metallurgical industry

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Nonferrous Smelting

X

X

X

X

X

X

X

X

Metal Mining

X

X

X

X

X

X

X

X

X

Wire Drawing

X

X

X

Metal Plating

X

X

X

X

X

X

X

X

X

X

X

Alloying

X

X

X

X

X

X

X

X

X

Porcelain Industry

X

X

X

X

X

X

X

X

X

X

X

Inorganic Chemicals industry

X

X

X

X

X

X

X

X

Fertilizer Manufacture

X

X

X

X

X

X

Disinfectant Production

X

X

X

Petroleum Refining

X

X

X

X

Dye Manufacture

X

X

X

X

X

X

X

X

X

Wood Preservative Manufacture

X

X

X

X

X

Pigment Formulation

X

X

X

X

X

X

X

X

Paint Manufacture

X

X

X

X

X

X

X

X

X

X

Ink

Manufacture

X

X

X

Animal-glue Manufacture

X

X

X

Photographic Supplies

X

X

X

X

X

X

X

Textile manufacture

X

X

X

X

X

Food/Beverage Processing

X

X

Electrical/Electronics Manufacture

X

X

X

X

Source: Selin KUTLU (2005)

Table 3.2 Classification of naturally occurring metals by toxicity and hydrologic availability.

(Metals that normally do not exist as dissolved species in natural waters or are very rare in crystal rocks are in italics)

Non toxic

Low toxicity

Moderate to high toxicity

Aluminum

Magnesium

Barium

Praseodymium

Actinium

Indium

Polonium

Uranium

Bismuth

Manganese

Cerium

Promethium

Antimony

Iridium

Radium

Vanadium

Calcium

Molybdenum

Dysprosium

Rhenium

Beryllium

Lead

Ruthenium

Zinc

Iron

Potassium

Erbium

Rhodium

Boron

Mercury

Sliver

Zirconium

Lithium

Strontium

Europium

Samarium

Cadmium

Nickel

Tantalum

Rubidium

Gadolinium

Scandium

Chromium

Niobium

Thallium

Sodium

Gallium

Terbium

Cobalt

Osmium

Thorium

Germanium

Thulium

Copper

Palladium

Titanium

Gold

Tin

Hafnium

Platinum

Tungsten

Holmium

Ytterbium

Neodymium

Yttrium

Source: Heavy Metals Toxicity; U.S. GEOLOGICAL SURVEY CIRCULAR 1133, (1995).

3.1 Historical and Background

In order to understand the synthesis of ligands to extract toxic copper and silver ion, it is necessary to have brief theoretical chemistry acknowledge about their history. These studies do not have a precise discovery but Dwyer and Mellor (1964) claimed that they are made soon after the birth of structural organic chemistry.

However, O.Costisor and W.Linert (2004) had interpreted that in 1840, Ettling studied a dark green crystalline product from the reaction of cupric acetate, salicylaldehyde and aqueous ammonia. Few years later in 1869, Schiff found that the salicylaldimine complex caused by reaction of performed metal-salicylaldehyde with ammonia. Pfeifer and co-workers have realized the systematic study of Schiff's base complexes in the period 1930-1940 and notices the role of metal ions. Einchorn and Latif studied the self-consideration of o-aminobenzaldehyde in the presence of divalent transition metal ion but they were unable to separate and identify the macrocyclic complexes in the reaction mixture. However, the importance of the metal ion became certain and the accumulated qualitative information allowed to notice that a new synthetic way was discovered, that which involves the metal ions in organic synthesis and the first example of a deliberated ligands synthesis was described by Butch in 1964

The father of modern biochemistry was the French-Swiss chemist, Alfred Werner; who in 1893 developed the theory of coordination compounds, today referred to as chelates. For this turning point in reclassifying inorganic chemical compounds, Werner received the Nobel Prize in 1913. He went on to create accounting for the process by which metals bind to organic molecules, which is the basis for chelation chemistry.

3.1.1 Nature of silver and copper metal ligands

In aqueous form, copper and silver metals are not only present as “free” ions but also some other ions called as ligands are able to interact with them to form complex compounds. Such as the most essential ligands in natural waters and in industrial effluents are Cl-, HS- or H2S and OH-. However, NH3, F-, S2O32-, Sx2-, SO32-, CN-, SCN-, PO43- and also organic ligands can have an important influence on the complexation of metals (Bohumil Volesky (1990)).

In ligands field theory, many chemists have investigated various interest properties of metal complexes that would determine the suitability of organic reagents for its use in gravimetric or volumetric analysis as well as spectrophotometric methods for the estimation and identification of toxic ionized heavy metal (Muhammad, Karamat (1994)). The interaction between the softness and hardness of ligands and metals ions is term as Lewis acid-base concept. (Dr. Arlene Courtney (2001)).

As John Olmsted and Gregory M. Williams (1997) interpreted in their study of molecular science chemistry that metal cations are electron deficient. Thus, ligands by having lone pair of electrons, they will donate to form bonds to the metal ion. Briefly, Metals are Lewis acids that accept electron pairs from donating ligands that act as Lewis bases.

The development activities of a ligand to form a metallic complex depend in several parameters such as concentration, temperature, ionic strength, acidity and potential of the solution (Bohumil Volesky (1990)). Therefore; ‘ligand' is defined as anions, molecules, clusters, polymers and small particulates to which a metal cations binds and also called as coordinate compound (D.S. Smith et al (2002)).

Similarly, copper and silver ions as heavy metals properties; are very stable by producing metal-complexes. This is possible because an acceptor metal cations form coordinate bond with electron-donation. Bohumil Volesky (1990) has suggested these processes as Lewis acid-Lewis base neutralization under the theory of hard and soft acids and bases (HSAB). He also explained these impressions as the principle of electron mobility or polarizability.

As such, Tabassum, Hamida (1994) give detail that the atoms, ions, molecules which act as the ligands have the property to stabilize the lower oxidation states. Furthermore this property is related with the fact that these ligands possess vacant pi orbitals in addition to the lone pairs, to form a type of pi bonding that supplements the sigma bonding arising from the lone pair donation, high electron density on the metal atom is thus delocalized on the ligands. This ability of the ligands to accept electron density into low lying empty pi orbitals can be called as pi acidity in the Lewis sence. Such ligands form the bonds with the metals by using sigma orbitals and exercise their pi orbitals acidity by using their pi orbitals whose nodal plane includes the axes of the sigma bond.

3.1.2 Complexation and Chelation

Martell and Calvin (1952) have well specified in their chemistry study of the metal chelate compounds that when a metal ion combines with an electron donor, the resulting substance is assumed to be complex or coordination compound. If the chemical which combines with the metal contains two or more donor groups so that one or more rings are formed, the resulting structure is said to be a chelate compound or metal chelate, and the donor is said to be chelating agent.

Copper

Development of ligands for extraction copper and silver from waste water Chenassi Munbodh

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