Adamson UniversityManila

College of EngineeringChemical Engineering Department

Experiment 6Adsorption

Group # 5Name

1. Coloma, Gillyn M 2012118462. Pascual, Ronald Patrick D. 2012102703. Sosa, Ma. Rebecah 201211508

Date of Experiment: January 27, 2015

Date of Submission: February 3, 2015

Instructor : Engr. Anabella C. Vilando

Abstract

Introduction

Adsorption is a process that occurs when a gas or liquid solute accumulates on the surface of a solid or a liquid (adsorbent), forming a molecular or atomic film (the adsorbate). It is different from absorption, in which a substance diffuses into a liquid or solid to form a solution. The term sorption encompasses both processes, while desorption is the reverse process.

Adsorption is operative in most natural physical, biological, and chemical systems, and is widely used in industrial applications such as activated charcoal, synthetic resins and water purification.

Similar to surface tension, adsorption is a consequence of surface energy. In a bulk material, all the bonding requirements (be they ionic, covalent or metallic) of the constituent atoms of the material are filled. But atoms on the (clean) surface experience a bond deficiency, because they are not wholly surrounded by other atoms. Thus it is energetically favorable for them to bond with whatever happens to be available. The exact nature of the bonding depends on the details of the species involved.

The experiment aimed to determine the saturation value of monomolecular coverage for the adsorption of acetic acid by activated charcoal. It also aimed to determine the values k and n in the Freundlich equation; and to determine the values of a and b in Langmuir’s equation

Theory

Adsorption is a surface phenomenon. It consists of an interaction between the moving molecules of a liquid or gas phase and the relatively fixed molecules comprising a surface or interface. (In this discussion the term “molecule” will be used generically to include atoms and ions as well as molecules). The moving molecules become bound to the surface more or less strongly. Adsorption processes may be classified as “physical” or “ chemical”. Another classification is “reversible” and “irreversible”, referring to the comparative ease of removal, desorption of the bound molecules. Generally, physical adsorption (physisorption) is reversible, while the chemical type (chemisorptions) is irreversible. The adsorbed molecules may come from a gas phase, a liquid or from a solution in a liquid. The adsorbing surface may be either liquid or solid.

Adsorption from solution is usually monomolecular (monolayer coverage); i.e. adsorption ceases when the surface is completely covered with a layer of one molecular thick. Adsorbed layers more than one molecular thick have been proved to exist in certain cases as yet rare. The amount of adsorption varies with the concentration of the solution. There are two equations for this relationship for monomolecular adsorption. One is the empirical Freundlich equation:

x /m = KCn or log (x /m) = log k + n log C

in which x/m is the weight of the absorbed material per gram of adsorbent and C is the concentration of the solution at equilibrium. The term k and n are constants to be evaluated from experimental data in each case.

xm

= abC1+aC

∨ C

(xm

)= 1ab

+Cb

in which x/m and C have the same significance as above, a is a constant proportional to the heat of adsorption and the temperature, and b is the amount of adsorption when the surface is covered with a monomolecular film. Langmuir’s equation is based on the assumption that the solid surface is completely uniform. Deviations from the equation indicate lack of uniformity in the surface.

Apparatus

Reagents

Procedure

Results

Discussion of results

Conclusions

Recommendations

Literature Cited

Nomenclature