Thread by @RajendranArvind

#Adsorption #Breakthrough experiments are so ubiquitous, but there isn't a good reference/review paper that addresses this technique. We wrote this review paper keeping graduate students, new entrants in mind. We hope this will be helpful. Summary in 10 pts.:

https://twitter.com/IntAdsSoc/status/1311325825338241025

1. SET-UP: Minimize dead volume; Control inlet flow & composition; Measure outlet flow &composition;Keep col.dia/part.dia >10, col.len/col.dia>3. Measure pressure drop. Industrial column-adiabatic; Lab-scale- finite heat transfer => Measure temperature inside column.

2. OPERATION- Run expt. until both outlet composition & temperature return to inlet values. Dead volumes affect both residence time and the spread of the breakthrough curve. If dead vol. is significant, do a correction.

3. SHAPE of the breakthrough curve is intimately linked to isotherm & mass transfer resistance. Type 1 isotherm (e.g. Langmuir)- adsorption is a shock; desorption is a wave. Heat fronts also impact the shape of the breakthrough curve (spreading, formation of plateaus)

4. EQUILIBRIUM: A simple mass balance allows calculation of equilibrium loading. Always check this with results from static measurements. Tells if sorbent is homogenous; allows further interpretation of results

5.MULTICOMPONENT: Breakthrough offers a simple extension for multi-component equilibrium measurements. Obtaining competitive loading of weakly adsorbed component is more challenging than that of the strongly adsorbed one. The stronger the competition the more difficult it is.

6.STRONG COMPETITION:In expts with strong sorbates, e.g. H2O(strong)+CO2(weak), the weak comp. breakthr. will appear to be same as pure comp. expt. Could be interpreted as "no competition". NOT TRUE. H2O moves so slowly that CO2 sees a clean col. Eventually H2O will displace CO2

7. ROLL-UP: A very strong competition will show a mild "roll-up" (often undetectable) of the weak comp. This is often interpreted as a sign of weak competition. NOT true. Always run expt. until H2O breakthrough (Time-consuming but worth the effort).

8. COMPETITIVE LOADINGS: Use adsorption expt to measure strong component loading & desorption to measure weak component loading.

9. KINETICS: Kinetics can be extracted provided expts are carefully set-up /operated and data correctly interpreted. However, heat, axial dispersion will interfere and have to be accounted for in the analysis.

10. BREAKTHROUGH IS NOT PROCESS: A breakthrough expt, like volumetric, gravimetry, ZLC is a characterization tool => Provides equilibrium, kinetics, pressure-drop and dispersion info. It should NOT be used for process evaluations/screening. Always perform process simulation/expt.