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Prepared by: Nur Balqis binti Saidam A14SC0162 Nurul Farehah binti A. Bakar A14SC0222

SSCC 4493 Surface and Colloid Chemistry. Prepared by: Nur Balqis binti Saidam A14SC0162 Nurul Farehah binti A. Bakar A14SC0222 Nur Izzati binti Zakaria A14SC0179 Noor Afina binti Noor Azman A14SC0120 Afnan Azzahra ’’ binti Ahmad Kamal A14SC0005. ABSTRACT.

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Prepared by: Nur Balqis binti Saidam A14SC0162 Nurul Farehah binti A. Bakar A14SC0222

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  1. SSCC 4493Surface and Colloid Chemistry Prepared by: NurBalqisbintiSaidam A14SC0162 NurulFarehahbinti A. Bakar A14SC0222 NurIzzatibintiZakaria A14SC0179 Noor Afinabinti Noor Azman A14SC0120 AfnanAzzahra’’ binti Ahmad Kamal A14SC0005

  2. ABSTRACT • Adsorption Isotherm BET Surface Area • Type of isotherm: Type H3 hysteresis loop = 31.5457 • Type of pores: Mesoporous BET Surface Area = 137.2563 • Pore shape: nonuniform size and/or shape forming slit-like pore.

  3. Langmuir Isotherm t-plot based on Harkins-Jura • Langmuir surface area : 186.3168 ± 6.9889 m²/g Microporepore volume (= 0.001519 /g • K : 0.055358 1/mmHg External surface area (Sext) = = 133.23 /g • Vm : 42.8061 cm³/g STP Micropore surface area (Smp) = = 4.026 /g • Correlation coefficient : 0.993728 Percentage of mesoporosity and microporosity = 0.44% • Molecular cross-sectional area : 0.1620 nm²

  4. INTRODUCTION • Thermal gravimetric analysis (TGA) is a method of thermal analysisin themass of a sample is measured over time as the temperature changes. Its provides information of physical phenomena, such as phase transition,absorption and desorption as well as chemical phenomena including chemisorption, thermal decomposition and solid-gas reactions. • In this experiment, the sample used is Zn(100). • Adsorption isotherm is between the amounts of adsorbate (x) adsorbed on the surface of adsorbent (m) and pressure at constant temperature. Different adsorption isotherms have been Freundlich, Langmuir and BET theory. • Adsorption isotherm has six types of isotherm shape depends on solid porous texture: Type I, Type II, Type III, Type IV, Type V and Type VI • Four type of pores: Ultra microporous, microporous, mesoporous and macroporous • Freundlich is typical for heterogenous surface. Equilibrium occurs if no combination or dissociation of molecule when adsorped on the surface and also no chemisorption occur • Langmuir isotherm is isotherm describe the dependent of equilibrium surface coverage of adsorbed molecule on the pressure of gas above the surface at fix temperature.. It contains three assumptions: homogenous surface, maximum monolayer only and no interaction between adsorbed molecule-adsorption is immobile. • BET (Brunauer-Emmett-Teller) Model is isotherm that dealing with multilayer adsorption. From linear equation form, can get BET surface area. • T-plot of Harkins-Jura suitable for non-porous reference solid. This isotherm is more reliable

  5. METHODOLOGYPreparation of zinc oxide

  6. RESULTS AND DISCUSSION…

  7. 1) Adsorption Isotherm.

  8. Based on graph: • Based on the isotherm obtained, the information about the sample can be obtain as below: • Type of isotherm: Type H3 hysteresis loop • Type of pores: Mesoporous • Pore shape: nonuniform size and/or shape forming slit-like pore.

  9. The adsorption isotherm, i.e. the quantity of gas (vapour) adsorbed on a solid at different pressures, at constant temperature, is a function of the surface area and the pore structure of the solid and thus can provide useful information about these two factors. • The process of adsorption is usually studied through graphs know as adsorption isotherm. It is the graph between the amounts of adsorbate (x) adsorbed on the surface of adsorbent (m) and pressure at constant temperature. Different adsorption isotherms have been Freundlich, Langmuir and BET theory. • The majority of these isotherms can be grouped into in five classes (six with the stepped isotherm) after Brunauer, Deming, Deming and Teller (3) according to the pore size of the solid and, the adsorbent-adsorbate interaction. • The analysis of adsorption data can in principle produce values for the surface area and total (or micro) pore volume of the solid under investigation, by means of well-established methods such as BET, Langrnuir or DR (Sircar, 2017).

  10. From 0 until 1.0 of relative pressure, the adsorption occurs. • When the pore is filled, total pore volume can be calculated and condensation occur. • Then, from 1.0 until 0 the desorption occur. The degas occur by removing nitrogen gas from adsorbent. When further desorption occur, all nitrogen gas will dissolve in the system. • The hysteresis loop happen because of the capillary condensation in which gas condensed to become liquid.

  11. Next, it is known that the shape of the isotherm does not depend only on the texture of the porous material, but also on the differences of the thermodynamic states between the confined fluid and the bulk fluid. • This H3 is pore blocking (slit-like pore) associated with the desorption process • Isotherms with type H3 hysteresis do not exhibit any limiting adsorption at high P/P0. This behavior can for instance be caused by the existence of non-rigid aggregates of plate-like particles or assemblages of slit-shaped pores and in principle should not be expected to provide a reliable assessment of either the pore size distribution or the total pore volume. • Types H3 hysteresis contain a characteristic step-down in the desorption branch associated with the hysteresis loop closure. • It appears that cavitation induced evaporation appears to be important for many micro/mesoporous solids and is responsible for the often observed characteristic step down in the desorption isotherms associated with hysteresis loop closure (Thommes, 2010).

  12. 2) BET Surface Area.

  13. Based on graph, 1) Calculate • y = 0.0315x + 0.0002, R² = 0.9998 • Gradient = s = 0.0315 • y-intercept = = 0.0002 • = = = 31.5457 2) Surface area S = x x = = 1.091 = 16.2 x BET surface area: ( x x ) = ( x 16.2 x x 6.02 x ) = 137.2563

  14. While the Langmuir isotherm provides a simple picture for looking at surface adsorption, it is not an accurate representation of how nitrogen actually adsorbs to the surface. This is because more than one nitrogen molecule can adsorb to each site on the Zinc 700. A better approximation for this process is to use the BET Isotherm (named for its inventors, Brunauer, Emmett, and Teller) which allows for multiple nitrogen molecules to adsorb to each zinc site. At equilibrium the rate of adsorption is equal to the rate of desorption. • BET equation is expressed in linear form in order to predict the dissolution rate, as this rate is proportional to the specific surface area. Thus, the surface area can be used to predict bioavailability after plot a linear graph. • As the graph is in positive linear, the results from nitrogen adsorption can be taken up in a small range (0.009754225 to 0.250720534) as non-linearity is obtained at a P/Po value close to 0.3. Because non-linearity is often obtained at a P/Po value below 0.05, values in this region are not recommended. The slope and intercept are 0.0315 and 0.0002 respectively then been used to calculate the volume of nitrogen adsorbed on the surface of zinc which is 31.5457 . • The specific surface determined by BET relates to the total surface area (reactive surface) as all porous structures adsorb the small gas molecules. The surface area determined by BET is thus normally larger than the surface area determined by air permeability. The surface area of zinc 700 can be determined by measuring the volume of particular gas adsorbed on the surface with known molecular cross section area of nitrogen gas. Based on the calculation, BET surface area is 137.2563 . The value is larger than Langmuir surface because BET surface area depends on size and number of gas molecules adsorbed. Langmuir surface area depends on adsorption capacity of the adsorbent. 

  15. 3) The Langmuir Surface Area.

  16. Based on graph: • Langmuir surface area : 186.3168 ± 6.9889 m²/g • Slope : 0.023361 ± 0.000876 g/cm³ STP • Y-intercept : 0.422 ± 0.093 mmHg·g/cm³ STP • K : 0.055358 1/mmHg • Vm : 42.8061 cm³/g STP • Correlation coefficient : 0.993728 • Molecular cross-sectional area : 0.1620 nm²

  17. The Langmuir equation is more applicable to chemisorption,where a chemisorbed monolayer is formed, but is also often applied to physisorption isotherms of type I. • Although this type of isotherm is usually observed with microporous adsorbents, due to the high adsorption potential, a separation between monolayer adsorption and pore filling is not possible for many such adsorbents. • Both the Langmuir equation and the Brunauer Emmett Teller (BET) equation model are the adsorption behavior of a gas (on the surface of a solid) in terms of the monolayer capacity. Both can be used for surface area measurement based on that assumption. • However, the Langmuir equation is derived around the monolayer being the limit of adsorption and thus cannot be exceeded - which we know to be untrue in real physisorption systems with a freely accessible surface. Then, BET equation models partial and multilayer adsorption in terms of the monolayer.

  18. 4) t-plot based on Harkins-Jura Equation.

  19. Based on graph: 3) Micropore surface area (Smp) Smp = Sbet – Sext = 137.256 - 133.23 = 4.026 /g 4) Percentage of mesoporosity and microporosity 0.001519 / 0.3442 x 100 = 0.44% 1) The micropore pore volume ( Vmp = y intercept x 0.001547 = 0.9821 x 0.001547 = 0.001519 /g 2) External surface area (Sext) Sext = slope x 15.47 = 8.6122 x 15.47 = 133.23 /g

  20. CONCLUSION • In summary, the BET data can provide the information about the adsorption isotherm and graph of BET surface area, Langmuir surface area and t-plot can plotted from the data obtained. From the adsorption isotherm graph, the type of isotherm is determined which is type H3 hysteresis loop with the mesoporous pores and slit-like pore shape. From the graph plotted, BET surface area (SBET = 13.2563 m2g-1) and Langmuir surface area (Slangmuir= 186.3168 m2 g-1) can be calculated. Based on the t-plot using Harkin-Jura Equation, the micropore pore volume, VM (0.001519 cm3 g-1),external surface area, Sext (133.23 m2g-1) and percentage of mesoporosity and microporosity(0.44%) were calculated. Overall, the BET data can provide the information needed to determine the properties of pores from the sample.

  21. REFERENCE • Mikhail, R.Sh., Guindy, N.M. and Ali, I.T. (1976). Variation Of The Specific Surface Area and Porosity of Zinc Oxide Prepared in Various Atmosphere. Journal of Applied Chemistry and Biotechnology (26), 199-206. Ain Shams University, Abbasia,Cairo, Eygypt.

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