RECOVERY OF METALS FROM EFFLUENT

Presented by : Arvind Singh Heer MSc-II(Sem-IV)Analytical ChemistryPaper-III MITHIBAI COLLEGE

RECOVERY OF METALS FROM EFFLUENT

CONTENTINTRODUCTIONMODERN METHODSION EXCHANGE CHROMATOGRAPHYELECTRODIALYSIS

INTRODUCTION What does recovery of metals from effluents means?Separation of metals ions froman outflowing of water or gas from a natural body of water, or from a manmade structure is known as recovery of metals from effluents There are physical or chemical processes that fall under the designations of recovery, recrystallisation and grain growth are often difficult to distinguish in a precise manner

MODERN METHODSModern methods for recovering of metals from effluents are - ION EXCHANGE CHROMATOGRAPHY - ELECTRODIALYSIS, etc.

ION EXCHANGE CHROMATOGRAPHYIon-exchange chromatographyis achromatographyprocess that separatesionsandpolar molecules based on their affinity to theion exchanger. It works on almost any kind ofcharged moleculeincluding largeproteins, smallnucleotides, andamino acids. It is often used in protein purification, water analysis, and quality control.

PRINCIPLEIon-exchange chromatography retainsanalytemolecules on the column based oncoulombic(ionic) interactions. The stationary phase surface displays ionic functional groups (R-X) that interact with analyte ions of opposite charge. This type of chromatography is further subdivided into cation exchange chromatography andanion-exchange chromatography. The ionic compound consisting of the cationic species M+ and the anionic species B- can be retained by the stationary phase.Cation exchange chromatography retains positively chargedcationsbecause the stationary phase displays a negatively charged functional group:

Anion exchange chromatography retains anions using positively charged functional group:Note that the ion strength of either C+ or A- in the mobile phase can be adjusted to shift the equilibrium position, thus retention time.The ion chromatogram shows a typical chromatogram obtained with an anion exchange column

ELECTRODIALYSISElectrodialysis(ED) is used to transportsaltionsfrom onesolutionthroughion-exchangemembranes to another solution under the influence of an appliedelectric potentialdifference. This is done in a configuration called an electrodialysis cell. The cell consists of a feed (dilute) compartment and a concentrate (brine) compartment formed by ananionexchange membrane and acationexchange membrane placed between twoelectrodes. In almost all practical electrodialysis processes, multiple electrodialysis cells are arranged into a configuration called an electrodialysis stack, with alternating anion and cation exchange membranes forming the multiple electrodialysis cells.

Electrodialysis processes are different thandistillationtechniques and other membrane based processes (such asreverse osmosis(RO)) in that dissolved species are moved away from the feed stream rather than the reverse. Because the quantity of dissolved species in the feed stream is far less than that of the fluid, electrodialysis offers the practical advantage of much higher feed recovery in many applications.Electrodialysis reversal(EDR) is an advanced electrodialysis process which utilizes a flow and polarity reversal to de-scale membrane surfaces and enable high concentration operation.EDR is used in higher salinity commercial applications where brine volume and scaling is a concern.

Electrode reactions: Small amounts of hydrogen gas are generated at the cathode: At the anode small amounts of oxygen gas are generated:

REFERENCE INSTRUMENTAL METHODS OF ANALYSIS WILLARD MERRITT DEAN SETTLE

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