PHD
  1. Inorganic chemistry  1.1. Coordination chemistry  1.1.1. Ligand field theory  1.1.2. Crystal field theory  1.1.3. Molecular Orbital Theory for Coordination Compounds  1.1.4. Stability of Coordination Compounds  1.1.5. Electronic spectra of coordination compounds  1.1.6. Isomerism in Coordination Compounds  1.1.7. Kinetics and mechanism of coordination reactions  1.2. Organometallic Chemistry  1.2.1. Metal Carbonyls  1.2.2. Metal alkyl and aryl  1.2.3. Fischer and Schrock carbonaceans  1.2.4. Oxidative Addition and Reductive Elimination  1.2.5. Metal Hydrides  1.2.6. Catalysis by organometallic compounds  1.2.7. Metallocenes and Sandwich Complexes  1.2.8. CH activation  1.3. Solid state chemistry  1.3.1. Crystal structures and lattices  1.3.2. Band theory and electrical properties  1.3.3. Defects in the crystal  1.3.4. Synthesis of solid state materials  1.3.5. Magnetic and optical properties of solids  1.3.6. Superconductivity  1.3.7. Solid state ionics  1.4. Bio-inorganic chemistry  1.4.1. Metalloproteins and enzymes  1.4.2. Metal ion transport and storage  1.4.3. The role of metals in medicine  1.4.4. Bioinspired catalysis  1.4.5. Metal–DNA interactions  1.4.6. Metal Complexes in Medical Science  1.5. Lanthanides and Actinides  1.5.1. Electronic configuration and oxidation states in lanthanides and actinides  1.5.2. Spectral and Magnetic Properties in Lanthanides and Actinides  1.5.3. Separation and Extraction of Lanthanides and Actinides  1.5.4. Coordination chemistry of f-block elements  1.6. Main Group Chemistry  1.6.1. Chemistry of boron compounds  1.6.2. Chemistry of Silicon and Germanium Compounds  1.6.3. Chemistry of Phosphorus and Sulfur Compounds  1.6.4. Organosilicon chemistry  1.6.5. Noble Gas Chemistry
  2. Organic chemistry  2.1. Reaction mechanism  2.1.1. Nucleophilic substitution reactions  2.1.2. Electrophilic addition and substitution reactions  2.1.3. Elimination reactions  2.1.4. Rearrangement reactions  2.1.5. Radical reactions  2.1.6. Pericyclic Reactions  2.1.7. Photochemical reactions  2.2. Stereoscopic  2.2.1. Chirality and optical activity  2.2.2. Structural analysis  2.2.3. Stereoelectronic effects  2.2.4. Asymmetric synthesis  2.2.5. Dynamic Stereochemistry  2.3. Organometallic Chemistry in Organic Synthesis  2.3.1. Organolithium and organomagnesium reagents  2.3.2. Transition metal catalyzed coupling reactions  2.3.3. Palladium-catalyzed reactions  2.3.4. Olefin Metathesis  2.3.5. Gold and silver catalysis  2.4. Natural products chemistry  2.4.1. Alkaloids and terpenoids  2.4.2. Steroids and Flavonoids  2.4.3. Total synthesis of natural products  2.4.4. Biosynthesis of natural products  2.5. Supramolecular Chemistry  2.5.1. Host-Guest Chemistry  2.5.2. Self-assembly and molecular recognition  2.5.3. Supramolecular Catalysis  2.5.4. Molecular Machines
  3. Physical Chemistry  3.1. Thermodynamics  3.1.1. Laws of Thermodynamics  3.1.2. Chemical Potential and Equilibrium  3.1.3. Statistical thermodynamics  3.1.4. Non-equilibrium thermodynamics  3.2. Quantum Chemistry  3.2.1. Schrödinger equation and its applications  3.2.2. Molecular orbital theory  3.2.3. Density functional theory  3.2.4. Post-Hartree–Fock methods  3.3. Chemical kinetics  3.3.1. Reaction rate theory  3.3.2. Mechanism and rate laws  3.3.3. Catalysis and enzyme kinetics  3.3.4. Reaction dynamics  3.4. Spectroscopy and molecular structure  3.4.1. Infrared Spectroscopy  3.4.2. UV-visible spectroscopy  3.4.3. Nuclear Magnetic Resonance Spectroscopy  3.4.4. Mass Spectrometry  3.4.5. Raman Spectroscopy  3.5. Surface and Colloid Chemistry  3.5.1. Absorption and Catalysis  3.5.2. Surfactants and micelles  3.5.3. Colloidal Stability  3.5.4. Nanomaterials and Interfaces
  4. Analytical chemistry  4.1. Chromatography  4.1.1. Gas Chromatography  4.1.2. High Performance Liquid Chromatography  4.1.3. Thin Layer Chromatography  4.1.4. Ion Chromatography  4.2. Electroanalytical techniques  4.2.1. Voltammetry and Polarography  4.2.2. Conductometry and potentiometry  4.2.3. Colometry  4.3. Spectroscopic Methods  4.3.1. Atomic absorption spectroscopy  4.3.2. Fluorescence Spectroscopy  4.3.3. X-ray diffraction  4.3.4. Electron paramagnetic resonance spectroscopy  4.4. Chemometrics  4.4.1. Data processing and statistical methods  4.4.2. Multidisciplinary analysis  4.4.3. Machine Learning in Analytical Chemistry
  5. Theoretical and Computational Chemistry  5.1. Molecular dynamics simulation  5.2. Quantum chemistry methods  5.3. Computational drug design  5.4. Machine Learning in Chemistry  5.5. Ab initio molecular dynamics
  6. Biophysics and Medicinal Chemistry  6.1. Drug discovery and design  6.2. Enzyme kinetics and inhibition  6.3. Chemical biology approach  6.4. Protein-ligand interactions  6.5. Bioorthogonal chemistry
  7. Materials chemistry  7.1. Polymer chemistry  7.1.1. Polymerization mechanism  7.1.2. Functional Polymers  7.1.3. Biodegradable Polymer  7.1.4. Conducting and semiconducting polymers  7.2. Nano Chemistry  7.2.1. Nanoparticles and nanostructures  7.2.2. Carbon-based nanomaterials  7.2.3. Quantum dots  7.3. Energy and Environmental Chemistry  7.3.1. Battery and Fuel Cell Chemistry  7.3.2. Green chemistry and sustainable materials  7.3.3. Photocatalysis

PHD → Physical Chemistry → Surface and Colloid Chemistry ↓


Absorption and Catalysis


In the field of physical chemistry, the study of adsorption and catalysis is of vital importance, especially in surface and colloid chemistry. This vast subject is intertwined with various fields of chemistry, physics, and even biology, reflecting important phenomena in both natural and industrial processes. This text explains the basic principles and applications of adsorption and catalysis using simple language and illustrative examples.

Absorption

Adsorption is the process by which molecules of a gas or liquid stick to the surface of a solid or liquid. This phenomenon occurs because the surface molecules of a substance have unbalanced chemical forces. As a result, they can attract and hold particles of various substances. Adsorption is a surface-based process, unlike absorption, which involves the entire volume of the substance.

Types of absorption

Adsorption may be broadly classified into two categories:

  1. Physical adsorption (physisorption): This type involves weak van der Waals forces. There is no significant chemical change in the adsorbent, and the process is usually reversible. An example of physisorption occurs when gas molecules stick to the surface of charcoal.
  2. Chemisorption: In chemisorption, molecules are held together by chemical bonds that are stronger than van der Waals forces. The process often involves a chemical change and is irreversible. A common example is the adsorption of oxygen molecules on the surface of metals, forming metal oxides.

Absorption isotherm

Adsorption isotherms describe how the amount of adsorbent on an adsorbent changes with pressure (or concentration) at a constant temperature. Some of the well-known adsorption isotherms used to explain the behaviour are as follows:

  1. Langmuir isotherm 
                q = (q_max * b * p) / (1 + b * p)

    The Langmuir isotherm is based on the assumption that maximum adsorption corresponds to a saturated monolayer of adsorbate molecules on the adsorbent surface.

  2. Freundlich isotherm 
                q = k * c^(1/n)

    The Freundlich isotherm equation is empirical and describes adsorption on heterogeneous surfaces or surfaces supporting sites with different affinities.

Example: adsorption on activated carbon

When water is passed through activated carbon, impurities such as chlorine, odors, and volatile organic compounds are adsorbed on the surface of the activated carbon. This process is a primary method used to purify drinking water.

Catalysis

Catalysis is the increase in the rate of a chemical reaction initiated by the presence of a catalyst. Catalysts are substances that provide an alternative reaction pathway with a lower activation energy, without being consumed in the process.

Types of catalysis

Catalysis can be divided into two main types:

  1. Homogeneous catalysis: The catalyst is in the same phase as the reactants. For example, chlorine gas catalyzes the decomposition of ozone in the stratosphere, reacting in the gaseous phase.
  2. Heterogeneous catalysis: The catalyst exists in a different phase than the reactants. An example of this is the catalytic converter in automobiles, where solid catalysts help convert gaseous pollutants into less harmful substances.

Example reaction: Haber process

In the Haber process, iron serves as a catalyst for the synthesis of ammonia (NH3) from nitrogen (N2) and hydrogen (H2):

        N2 (g) + 3H2 (g) → 2NH3 (g)
This process is important for the production of ammonia needed for fertilizers.

Mechanism of catalysis

Catalysts work by providing an alternative reaction pathway. It can be visualized like this:

Reactants Products Catalyzed pathway

The pathway using a catalyst (red path) has a lower peak than the non-catalyzed reaction (not shown), reducing the required activation energy and speeding up the reaction.

Enzymatic catalysis

Enzymes are biological catalysts that enable biochemical reactions to occur under relatively mild conditions of temperature and pressure, exhibiting high specificity for their substrates. For example, the enzyme amylase helps break down complex starch into simple sugars, which the body can easily assimilate.

Importance of catalysis

Catalysts play a vital role in industrial chemistry during the manufacture of chemicals, medicines and biofuels. Catalysts help save energy and resources by increasing the efficiency of existing processes and enabling less waste production. In addition, catalysts enable reactions to be achieved that are otherwise difficult under normal conditions.

Conclusion

The concepts of adsorption and catalysis have indispensable applications in various fields of science and industry. Understanding these processes helps develop advanced materials and innovative technologies, thus addressing global challenges in energy sustainability, pollution reduction, and health. Through a fundamental understanding of adsorption and catalysis, one gains insight into the enormous potential of surface and colloid chemistry in advancing scientific progress and industrial advancement.


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Absorption and Catalysis

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