Contenu connexe


Separation of Solids.pptx

  1. SEPARATION & CLASSIFICATION OF SOLIDS Manufacturing Processes and Plant Visits
  2. SEPARATION OF SOLIDS Techniques used to separate one material from the other is called separation. Separations are extremely common in chemical manufacture. In fact, much processing equipment is devoted to separate one phase or one material from the other. Diffusional separation is a technique used for the separation of homogeneous mixtures. This separation includes the transfer of material between the phases including distillation, crystallization and absorption. Mechanical separation is used for the separation of heterogeneous mixtures. These are based on the physical differences between the particles such as size, shape or density. It can be applied for separating solids from solids, solids from liquids and also solids from gases.
  3. SEPARATION TECHNIQUE S Sieving Magnetic Separation Mechanical Screening Leaching Cetrifuging Froth Floatation
  4. Sieving Sieves, or sifters, are devices for separating wanted elements from unwanted material typically using a mesh. Sieving is a simple technique for separating particles of different sizes. Coarse particles are separated or broken up by grinding against one-another and screen openings. Depending upon the types of particles to be separated, sieves with different types of holes are used. Sieving plays an important role in food industries where sieves (often vibrating) are used to prevent the contamination of the product by foreign bodies
  5. Magnetic Separation A process in which magnetically susceptible material is extracted from a mixture using a magnetic force. This separation technique can be useful in mining iron as it is attracted to a magnet. In the machine, the raw ore is fed onto a conveyor belt which passes underneath two pairs of electromagnets under which further belts run at right angles to the feed belt. The first pair of balls are weakly magnetized and served to draw off any iron ore present. The second pair are strongly magnetized and attracted the wolframite, which is weakly magnetic. These machines are capable of treating 10 tons of ore a day.
  6. Mechanical Screening The practice of taking granulated ore material and separating it into multiple grades by particle size. This practice occurs in a variety of industries such as mining and mineral processing, agriculture, pharmaceutical, food, plastics, and recycling. A screening machine consist of a drive that induces vibration, a screen media that causes particle separation, and a deck which holds the screen media and the drive and is the mode of transport for the vibration.
  7. Leaching The process of extracting substances from a solid by dissolving them in a liquid, either naturally or through an industrial process. In the chemical processing industry, leaching has a variety of commercial applications, including separation of metal from ore using acid, and sugar from sugar beets using hot water.
  8. Froth Floatation Is another method to remove solids from liquids used in mineral processing and wastewater treatment. The froth flotation process is all about exploiting the natural hydrophobicity of liberated metals and playing with making them individually hydrophobic in order to accurately separate them from one another. The particles of metal sulphide are hydrophobic. Due to this property, they are primarily wetted by oil. The gangue particles, on the other hand, are hydrophilic and are wetted by water. As a result of stirring the solution in the tank, sulphide ore rises to the surface while the gangue particles settle. We use chemical reagents for this purpose.
  9. Centrifuging Centrifuging is a common separation technique that exploits the density differences of different substances. When solids are suspended in a liquid gradually the densest substance will settle on the bottom known as sedimentation. Centrifuging is an accelerated sedimentation.
  10. CLASSIFICATION OF SOLIDS 1. Crystalline Solids a. Ionic Solid b. Covalent Solid c. Metallic Solids d. Molecular Solid 2. Amorphous Solids
  11. Crystalline Solids The solids having sharp edges and well-defined planes are called crystals or crystalline solids. Crystalline solids are also called true solids. Sodium chloride, quartz, gold, copper, and iron are some examples of crystalline solids.
  12. Classification of Crystalline Solids 1. Ionic Solids In an ionic solid, the cations and anions are the constituent particles. These ions are systematically arranged in three-dimensional space. The strong electrostatic force of attraction between cations and anions is the binding force in an ionic solid. Example of ionic solids- Sodium chloride, potassium chloride, and lead bromide. Characteristics i). Ionic solids are hard, brittle, and have high melting points and very high enthalpy of fusion. ii). Ionic solids are insulators in solid state. But in the molten state and in aqueous solutions, they conduct electricity.
  13. Classification of Crystalline Solids 2. Metallic Solids The metals like iron, copper, gold, silver, sodium, potassium exist in the solid state at room temperature. In a metallic crystal, the atoms are held together by a strong force of attraction called metallic bonding. In the metallic crystals, the metal occupies the fixed positions, but their valence electrons move. Characteristics i). They are hard but malleable and ductile. ii). They are good conductors of heat as well as electricity. iii). They are lustrous. iv). They have high melting and boiling points.
  14. Classification of Crystalline Solids 3. Covalent Solids The solid substances in which covalent bonds bond the atoms throughout the crystal are known as covalent solids. Covalent solids are also known as atomic solids, network solids, macromolecular crystals or giant molecules. Asbestos, silicon carbide, mica, graphite, and diamond are examples of macromolecular crystals. Characteristics i). They are very hard, except graphite which is soft. ii). They have high melting points. iii). They are poor conductors of heat as well as electricity (except graphite which is an atomic solid and is a good conductor of electricity). iv). They have high heat of fusion.
  15. Classification of Crystalline Solids 3. Covalent Solids These are solid substances in which the molecules are the constituent particles. Iodine, ice, dry ice (solid carbon dioxide), and naphthalene are examples of molecular solids. These can be classified into three subgroups: Nonpolar, Polar, and Hydrogen- bonded.
  16. Type of solid Constituent particles Attracting force Examples (in solid state) Physical nature Melting point Electrical conductivity 1. Ionic solids Cations and anions Electrostatic (Coulombic) NaCl,MgO,ZnS, CaF2NaCl,MgO, ZnS,CaF2 Hard but brittle High Insulator as solid but conductor in molten state and in aqueous solution 2. Metallic solids Positive ions in a sea of electrons Metallic bonding Copper, silver, gold, iron Hard, but malleable and ductile Fairly high Conductor in solid and molten states 3. Covalent or Network solids Atoms Strong covalent bonding Graphite diamond, quartz, silicon carbide Soft Hard Very high Conductor Insulators 4. Molecular (i) Nonpolar molecules (ii) Polar molecules (iii) Hydrogen bonded Molecules Molecules Molecules Molecules Dispersion force Dipoledipole interaction Hydrogen bonding I2,I2, dry ice, H2,H2, Ar, CCl4NH3,SO2A r,CCl4NH3,SO2 Ice, alcohol, phenol, proteins Soft Soft Hard Very low Low Low Insulator Insulator Insulator Types of Crystalline Solids Based on the Type of Attracting Force
  17. Amorphous Solids The solids which lack in well- defined structure and shape are known as amorphous solids. Amorphous solids are also called supercooled liquids or pseudo solids. Glass, rubber, and plastics are some examples of amorphous solids. Uses of Amorphous Solids i. Amorphous solids are useful as inorganic glasses, fabrication of glass apparatus for laboratory, and making kitchen wares. ii. Amorphous silica is used as a photovoltaic to convert sunlight into electricity.
  18. Property Crystalline solids Amorphous solids Structure Crystals have a long- range order. Amorphous substances have short-range order. Melting point Crystalline solids have a sharp and characteristic melting point. Amorphous solids either decompose or change gradually into liquid over a range of temperatures on being heated. Cleavage Crystals when cut with a sharp edged tool, split into two pieces and the newly generated surfaces are plain and smooth. Cleavage of amorphous solids gives irregular fractures. Difference between Crystalline Solids and Amorphous Solids
  19. Classification of Solids Based on Their Electrical Conductivity i. Conductors A metallic atom has more valence orbitals than the number of valence electrons. Therefore, the electrons find more space to move and conduct electricity easily. This can easily be understood by band theory which is also called the molecular orbital theory. ii. Semiconductors In semiconductors, the energy gap between the valence band and conduction band is not very large. Therefore, The valence electrons have a tendency to jump into the conduction band. Thus when an electric field is applied, some electrons move to the conduction band and conduct electricity. iii. Insulators When the energy gap between the valence band and conduction band is very large, the valence electrons cannot jump into the conduction band. Therefore, they do not conduct electricity, and such substances are called insulators. The conductivity of metals is large, whereas the conductivity of an insulator is very less. Between these two are semiconductors.
  20. Classification of Solids With Respect to Magnetic Properties i. Diamagnetic – Diamagnetism is a property caused by an induced magnetic field of the orbital electron. It is present more or less in all substances, but it is more pronounced in materials like H2,KCl,NaClH2,KCl,NaCl and TiO2TiO2 in which all the electrons have paired spins. The magnetic field weakly repels the substances that have diamagnetic properties. ii. Paramagnetic - Paramagnetism is caused by the spin and orbital angular momentum of electrons. Paramagnetism is shown by all the solids in which atoms, ions, or molecules have unpaired electrons. Paramagnetic materials are weakly attracted to a magnetic field, and it is shown only in the presence of the magnetic field. O2,Cr3+,Cu2+,Fe3+O2,Cr3+,Cu2+,Fe3+ show paramagnetism . iii. Ferromagnetic - This property is caused by particles arranged on the lattice and the electrons with parallel spins. Iron (Fe),(Fe), cobalt (Co),(Co), and nickel (Ni)(Ni) are ferromagnetic elements. They are attracted very strongly by a magnetic field. It is a permanent property of the material at a given temperature.
  21. iv. Antiferromagnetic - This property is caused by particles arranged on two lattices with spins on one lattice antiparallel to those on the other lattice. This results in the cancellation of magnetic moments on the lattice. The materials like MnO,MnSe,KMnFe3MnO,MnSe,KMnFe3 are antiferromagnetic. v. Ferrimagnetic - The particles on interpenetrating lattices cause this magnetic property with the unequal number of electrons and with antiparallel spins. This represents a situation with a net magnetic moment. FeO.Fe2O3≡Fe3O4 is an example of ferrimagnetic material. Classification of Solids With Respect to Magnetic Properties
  22. 1. _____________ uses sifters for separating wanted elements from unwanted material typically using a mesh.

Notes de l'éditeur

  1. chalcopyrite, the most common copper mineral, a copper and iron sulfide, and a very important copper ore.