Module 2 States of Matter and Adsorption Isotherms PDF

10/5/2024 Module 2 States of mater and adsorption isotherms 1 States of mater 2 1 ...

10/5/2024 Module 2 States of mater and adsorption isotherms 1 States of mater 2 1  10/5/2024 States of Mater and Properties Traditionally three states, Gas, Liquid, and Solid. Plasma sate is the fourth state of matter Molecular Motions in Gas, Liquid, Solids Is interparticle attraction present in gas state or no? Gas Liquid Solid Rotational, translational and vibrational motions ; Gas > Liquid > Solid Interparticle distance : Gas > Liquid > Solid Volume decreases as the interparticle distance decreases 3 Density (mass/cm3) of Gas, Liquid, Solids Solid Gas Liquid (g/cm3) (g/cm3) (g/cm3) Ar 1.65 1.40 0.001784 N2 1.026 0.8081 0.001251 O2 1.426 1.149 0.001429 -the density of a typical solid is about 20% larger than the corresponding liquid, -while the liquid is roughly 800 times as dense as the gas. 4 2  10/5/2024 Why density increases, while going from gas to liquid? Interparticle distance decreases, this decreases volume. Therefore, density increases while going from gas-to-liquid and liquid-to-solid. ρ = M/V 5 Different types of Solid Based on atomic/molecular arrangements, there are three type pf solids; Single crystal, polycrystal , amorphous. All of them have open surfaces. 6 3  10/5/2024 Phase Transition A phase transition is the transition from one state of matter to another Phase diagrams illustrate the variations between the states of matter of elements or compounds as they relate to pressure and temperatures. 7 Phase Transition The red line divides – Solid phase and gas phase Blue line – Liquid and gas phase Green line – divides solid and liquid phase 8 4  10/5/2024 Phase Transition Triple point – the point on a phase diagram at which the three states of matter: gas, liquid, and solid coexist Critical point – the point on a phase diagram at which the substance is indistinguishable between liquid and gaseous states Fusion(melting) (or freezing) curve – the curve on a phase diagram which represents the transition between liquid and solid states Vaporization (or condensation) curve – the curve on a phase diagram which represents the transition between gaseous and liquid states Sublimation (or deposition) curve – the curve on a phase diagram which represents the transition between gaseous and solid states 9 Plasma State 10 5  10/5/2024 Plasma Plasma is a “superheated matter” comprised of ions formed from atoms or molecules by striping of at least one electron. It comprises over 99% of the visible universe. In the night sky, plasma glows in the form of stars, nebulas, and even the auroras that sometimes ripple above the north and south poles. Plasma is often called “the fourth state of matter,” along with solid, liquid and gas. 11 https://www.nasa.gov/sites/default/files/thumbnails/image/147515main_phases_large.jpg 12 6  10/5/2024 Applications of Plasma Researchers have used the properties of plasma as a charged gas to confine it with magnetic fields and to heat it to temperatures hotter than the core of the sun. Therefore, one can use plasma for high temperature applications. Other researchers pursue plasmas for making computer chips, rocket propulsion, cleaning the environment, destroying biological hazards, healing wounds and other exciting applications. 13 Adsorption 14 7  10/5/2024 Interaction of surfaces of solid with gases The phenomena of sticking of small molecules or atoms on the surface of a solid is known as adsorption. 15 Interaction of solid surfaces with liquids On hydrophobic surface, oily water repelling surfaces, water drops curl into beads. On hydrophilic surface, water loving surfaces, water molecules adsorbs strongly and spreads flat. 16 8  10/5/2024 17 Phenomena Interaction Open of Adsorption Surfaces solid The with Gases phenomena of interaction of a gas or liquid, or ionic species with a solid surface is referred as adsorption. Adsorptive Adsorbate Adsorbent Except in special cases, adsorption is an exothermic process, releases heat to the surrounding. Enthalpy change is negative ∆Had = -Ve 18 9  10/5/2024 Thermodynamic Considerations Adsorption (or any) spontaneous process requires ∆G < 0. Because the translational freedom of the adsorbate is reduced when it is adsorbed, ∆S is negative. Therefore, in order for ∆G = ∆ H − T∆S to be negative, ∆H must be negative (that is, the process is exothermic). Exceptions may occur if the adsorbate dissociates and has high translational mobility on the surface. 19 What causes adsorption?  Each surface atom is surrounded by less number of neighbor atoms as compared to each bulk atom. Surface atoms Bulk atoms are are coordinatively coordinatively unsaturated saturated  It leads presence of unbalanced residual forces on the surface of solid known as surface force which causes adsorption.  The surface force have tendency to attract and retain the gas molecular species with which it comes in contact with the surface. 20 10  10/5/2024 What kind of bonding interaction occurs between adsorbent and adsorbate? The attractive interaction can be either long range or short range 1. Long range interaction: Physical contact, due to Van der Waals force. 2. Short range interaction: Chemical bonding, such as covalent, ionic, metallic bonding Accordingly, the first one is called physisorption (Physical adsorption) and the second one is called chemisorption (Chemical adsorption). 21 Example of Physisorption Surface of gold atoms Coronene Sticking of benzene-like molecules, for example coronene, on the surface of gold (111) is an example of physisorption. 22 11  10/5/2024 Example of Physisorption The interaction between the charcoal and nonpolar adsorbate molecules are another Example of physisorption 23 Enthalpies of Physisorption Exothermic reactions, enthalpy change is negative 24 12  10/5/2024 Example of Chemisorption Metal hydride is formed through chemical bonding, hence, chemisorption. a) Metal surface (adsorbent) b) Physisorption of H2 through van der Waals interaction c) Chemisorptions of H2 through M-H bond (metal hydrides) d) Chemisorbed H atom may slid into the bulk metal through diffusion “Chemisorption always accompanied by physisorption” http://cdn.intechopen.com/pdfs-wm/40231.pdf 25 Enthalpies of Chemisorption Enthalpies of chemisorption are greater than enthalpies of physisorption. These enthalpies are close to covalent bond enthalpies. 26 13  10/5/2024 27 28 14  10/5/2024 Application of Adsorbents Organic contaminants such as pharmaceuticals, cosmetics, pesticides can be removed from water using the method of adsorption. To speed up chemical reactions (catalysis) To remove bad odor and color in water Used as a solid support purify proteins and chemical compounds Used to remove unwanted impurities from gas 29 Uses of activated carbon as a adsorbent Uses Remove man-made organic chemicals Remove miscellaneous tastes and odor from water assuming no bacterial problems Remove radon gas from water Maintenance Carbon must be replaced routinely 30 15  10/5/2024 31 The real development of activated carbon began during World War I, when hard granular activated carbon (GAC) was developed for use in gas masks A particle of activated carbon is composed of a complex network of pores that can be divided into two distinct classes with respect to size: Macropores and Micropores The micropores have diameters in the range of 10-500 Å The macropores are arbitrarily defined as pores greater than 500 Å in diameter 32 16  10/5/2024 The pore size distribution depends on the type of starting material and the method of manufacturing the activated carbon 33 Oxidized Activated Carbons (OACs) Oxidized activated carbons (OACs) are porous carbon with surface carboxylic acids (-COOH) and –OH groups. 34 17  10/5/2024 Possible physisorption interactions between adsorbent and adsorbate Van der Waals force, Dispersion force Dipole-dipole interaction, Hydrogen bonding Dipole-induced dipole interaction Ion-dipole interaction Oxidized activated carbons (OACs) have more surface functional groups which are responsible for strong adsorptive removal of “pharmaceutical and personal care products” (PPCPs) present in contaminated water. 35 18