Questions tagged [adsorption]
The adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface.
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questions
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Why does chemisorption decrease with increasing temperatures?
Why is it that chemisorption decreases with higher temperatures?
The explanations I found online were quite vague and one of them cited Le Chatelier's principle, but I thought chemisorption is an ...
2
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0answers
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Porous materials: Is the expression of a mean free path $\overline{\ell}$ of the gas molecule valid for a binary mixtures?
Suppose that I have a binary gas mixture at low pressure. Can I calculate the mean free path $\overline{\ell}$ of the gas molecule in a pores of solid material by substituting a molecular weight of a ...
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43 views
Dynamic viscosity of gas mixture (appropriate estimation)
What estimation of the dynamic viscosity $\eta = f(T)$ $([\eta] = \pu{Pa·s})$ of the gas mixture components would you recommend during adsorption at a low temperature, approx. $\pu{293 K}$ to $\pu{333 ...
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1answer
159 views
Finding the Freundlich adsorption isotherm from the graph of log(x/m) v/s log(p)
The following problem was asked in JEE Mains 2020 (Sept 2, Shift 1),
The mass of gas adsorbed, $x$, per unit mass of adsorbate, $m$, was measured at various pressures, $p$. A graph between $\log\frac ...
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0answers
42 views
Adsorption of Cu2+ using banana peels for pH 2,2.5,3,3.5,4
so basically I did my experiment which is the title. This is my procedure and results:
Make 0.05M CuSO4
pipette 50ml CuSO4
change to respective pH values using HCl
Add 2g of oven-dried banana peels
...
0
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1answer
34 views
How is the hydration state of a chemical related to its adsorption of water?
I am trying to understand adsorption and hydration states better, and I was thinking about the different hydration states of calcium sulfate - anhydrous ($\ce{CaSO4}$), hemihydrate ($\ce{CaSO4*1/2H2O}$...
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0answers
36 views
Column Dispersive Mass Balance analytical / numerical solution
Is there any analytical solution for the most common expression of column mass balance:
$\dfrac{\partial C}{\partial t} + \left(\dfrac{1+\varepsilon}{\varepsilon}\right)\dfrac{\partial q} {\partial t} ...
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17 views
Energy and impurities balance for adsorption with a fixed bed (with description)?
Do you have any suggestion where to look for a source of information about energy and impurities (component) balance for adsorption of mixture CO2/H2O in fixed bed?
I have looked into many articles /...
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1answer
433 views
Why are van der Waals' forces between gas molecules strong near its critical temperature?
My textbook says
…easily liquefiable gases i.e. with higher critical temperatures are readily adsorbed as van der Waals' forces are stronger near the critical temperatures.
What I do understand is ...
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2answers
322 views
What is negative adsorption? [closed]
In adsorption, the concentration of adsorbate is greater on the surface. So, how is it possible that the solvent will be more on the surface and the solute (adsorbate) in the bulk… or does solute not ...
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25 views
Work function changes with adsorption
This is the question
Observation: (0001) is close packed structure of hcp lattice, in fact this plane has the highest work function in all planes of hcp. When O is adsorbed it donates electron ...
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How to obtain the linear form of Redlich Peterson isotherm model by algebraic transformation or any other ways? [closed]
The Redlich Peterson isotherm model is known as:
$$
\begin{aligned}
q_e=\frac{AC_e}{1+BC^g_e}
\end{aligned}
$$
Is there any way to obtain the linear form of this equation by algebraic transformation ...
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0answers
17 views
hydrodynamic thickness of polymer vs. concentration of electrolyte?
I've measured the hydrodynamic thickness of a NaPSS layer on polystyrene latex and plotted it against the concentration of the supporting electrolyte, NaCl.
My graph shows a general decrease in ...
1
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1answer
2k views
Why Freundlich adsorption isotherms fails at high pressure conditions?
Experimentally it was determined that extent of gas adsorption varies directly with pressure, and then it directly varies with pressure raised to the power 1/n until saturation pressure Ps is reached. ...
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1answer
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Is activated charcoal an air purifier?
It's well known that activated charcoal is an adsorbent and due to very big surface area per unit of mass it can adsorb a lot of particles.
Let's take as an example for my question this product on ...
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0answers
436 views
Order of reaction in adsorption process
(1) $\ce{PH3(g) <=>[W]PH3(adsorption)->[W]P(s) + 3/2 H2(g)}$
The decomposition of phosphine on tungsten surface at low pressure is a pseudo first order reaction. This is because the rate of ...
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2answers
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Dangers of using activated carbon past its lifespan
Activated carbon (AC) is one of the most widely used media for water filtration. It's effective at removing chlorine taste and odor, and it's recognized as being safe.
However, most activated carbon ...
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1answer
165 views
Why does Freundlich adsorption isotherm not have a term for surface area?
Why does Freundlich adsorption isotherm not have a term for surface area?
The formula given by Freundlich adsorption isotherm:
$$ \frac{x}{m}= k P ^{1/n}$$
Where $x$ is the mass of gas adsorbed ...
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2answers
2k views
What are molecular species?
I am in high school learning about adsorption for the first time. My school textbook says:
"The accumulation of molecular species at the surface rather than in the bulk of a solid or liquid is ...
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0answers
59 views
Preparation of Copper (II) Sulfate Pentahydrate Solution
how would you make a solution of Copper (II) Sulfate Pentahydrate to achieve 150, 200, 250 and 300 mgL−1 concentration of copper? I do not have the anhydrous version of the solute. Also, when I ...
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2answers
414 views
Why enthalpy of adsorption is negative?
I have already read Is adsorption exothermic, and if so, why? but it didn't answered my query.
To illustrate, let's take a hypothetical vacuum space. In that space, there is a solid and a gas, the ...
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2answers
142 views
Is the adsorption of dissolved iodine onto activated carbon physical adsorption or chemical adsorption?
For an experiment, I am looking to see the effect of temperatures from 0–100 °C on the efficacy of activated carbon as an adsorbent. My adsorbate is iodine and I am confused as to whether the ...
2
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0answers
137 views
How did Zyklon hold and release HCN?
$\ce{HCN}$ is notoriously unstable: It boils at room temperature, and it tends to polymerize when concentrated in unbuffered liquid form. Yet $\ce{HCN}$ was for decades widely used as a fumigant ...
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1answer
37 views
How to quantify the adsorption affinity of gases?
Is there a term/quantity which shows how 'sticky/adsorptive' a molecule is? I am interested in gas adsorption on steel surfaces in our mass spectrometer and would like to estimate which gases have a ...
0
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1answer
2k views
Hygroscopic Substances and Drying Agents
My book says:
Most of the hygroscopic substances are drying agents
Based on what I read on several websites, I think dehydrating agents also act as drying agents. If so, all dehydrating agents ...
2
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1answer
434 views
What is 'desorption hysteresis'?
I am currently reading a paper titled "Polystyrene Nanoplastics-Enhanced Contaminant Transport: Role of Irreversible Adsorption in Glassy Polymeric Domain" (link here).
In the paper, the authors ...
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1answer
307 views
Aren't “lack of specificity” and “nature of adsorbate” contradictory factors in physisorption?
It was mentioned in my course book under "Characteristics of physisorption" that:
Lack of specificity: An adsorbent does not show any preference for a particular gas as the van der Waal's ...
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0answers
415 views
Why does physisorption change to chemisorption at high temperatures?
I read in my textbook:
In certain cases, physisorption changes to chemisorption as temperature is increased.
Could anyone explain why it is so? I know the basics of both physisorption and ...
2
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0answers
229 views
How to develop a Reactive Force Field (ReaxFF)? (Molecular simulation)
Currently, I am working on CO2 capture on Hydrotalcites as solid adsorbents. I want to run molecular simulations to analyse the behaviour of the material under different temperatures, pressures and ...
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0answers
33 views
Application of BET to micropore
'application of the BET equation should be restricted to the range where the term n(1 – p/p0) continuously increases with p/p0'see 5.2.2 in the reference
This is one of the criterias IUPAC proposes ...
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1answer
133 views
Calculating surface area from BET results
I have been trying to work out the workings of the BET method and I have come to a standstill.
The surface area of a sample is given by
$$
S_{\text{BET}} = \frac{\nu_{\text{m}}Ns}{V}
$$
where $\...
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0answers
255 views
Why does the order of adsorption of hydrated alkali metals on an ion exchange resin decrease down the group?
Why does the order of adsorption of hydrated alkali metals on an ion exchange resin decrease down the group?
I recently did a question on this topic and they say adsorption order is $$\ce{ Li+ > ...
0
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1answer
135 views
Langmuir method
I have done a biosorption study using a protein as a biosorbent and six different concentrations of $\ce{Pb}$ ions. I need to show the efficiency of the biosorbent, I was told to use the Langmuir ...
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1answer
1k views
“Nitrogen (gas) is physisorbed over iron (metal) at room temperature”: Is this for real? [closed]
My copy (PDF) of Levine's Physical Chemistry (6th ed.), page 570-571, section: "Adsorption of Gases on Solids", states:
Physical adsorption is nonspecific. For example, $\ce{N2}$ will be physically ...
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Pd-catalysed hydrogenation of imines
Hydrogenation of imines to amines by $\ce{H2}$ on $\ce{Pd/C}$ has been used e.g. in the synthesis of Pumiliotoxin. By contrast, carbonyl groups are rarely reduced in this way, which I though was due ...
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2answers
316 views
Is there a direct relationship between the adsorption energy and the catalytic activty
I have seen in several papers, where people correlate adsorption energy with the catalytic activity; the greater the adsorption energy, the greater would be the catalytic activity.
I understand that ...
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2answers
270 views
What is the physical state of the gas adsorbed on a solid adsorbent?
I am studying surface chemistry in high school I have this doubt and I am unable to find a answer your help is appreciated
I searched for the answer on google I asked my chemistry teacher he said the ...
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0answers
47 views
Langmuir parameters for fixed bed continous column
I have prepared a model of fixed bed adsorption column in MATLAB. I have to insert Langmuir parameter value there, so how can I calculate them in case of continuous fixed bed column. I have calculated ...
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0answers
63 views
Equations Used in Isothermal Titration Calorimetry
I have been attempting to understand and derive the formulas used for ITC which can be found here starting on page 310. I am particularly interested in the single set of identical sites. To first ...
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2answers
3k views
Freundlich Equation's dimensions
So, we have the Freundlich's Isotherm equation as $\frac{x}{m} = kp^{\frac{1}n}$, where the LHS measures the extent of adsorption with the corresponding pressure $p$ in the RHS with the two constants, ...
3
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2answers
7k views
What is the difference between BET and Langmuir model for calculating the specific surface area?
Brunauer–Emmett–Teller (BET) surface area is measured by specific surface area of the adsorbent. BET surface area is measured by using non-corrosive gases like $\ce{N2}$, $\ce{CO2}$, $\ce{Ar}$ etc. ...
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0answers
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Can negative adsorption be considered equal to sorption?
In my book it was written sorption is basically when the substance gets uniformly distributed into the bulk of the solid but at the same time its concentration is higher at the surface then in the ...
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1answer
541 views
How does activated carbon trap impurities?
I've tried and I've tried to find an answer to this all over the web, but I can't seem to find an in depth explanation.
To the best of my knowledge, activated carbon has a very microporous structure ...
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Selective sorption of toxins by polymethylsiloxane polyhydrate
Polymethylsiloxane polyhydrate (PMSPH) is used as enterosorbent for a couple of decades (nowadays under the trademark "Enterosgel"), intended for binding in the gastrointestinal tract and excretion of ...
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1answer
152 views
How does water freeze and crystallize on a cold superhydrophobic surface?
Superhydrophobic surfaces are nano-structured to "repel" liquid water and there has been a lot of work done to understand the microscopics of wetting of these nanostructures.
What I currently am ...
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Why increase in enthalpy leads to increase in entropy? [closed]
Given statement: Enthalpy of adsorption is the strength at which molecule (say $\ce{H2}$) is bound to the adsorbent (say some metal center). For a free $\ce{H2}$ molecule, the entropy contribution is ...
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2answers
124 views
How does physical adsorption of mixed gas occur on solid? (eg I mean how the gas molecules of compete each other for a slot on solid surface)
I am working on sorption phenomenon of gases (including inert gas) on coal seam surface.
For a mixture of 2 gases at a certain pressure, carbon dioxide and methane, for instance, $\ce{CO2}$ is ...
0
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1answer
960 views
Surface area: what is the difference?
What are the differences between:
van der waals surface area
solvent accessible surface area
topographical polar surface area
What is the significance of these differences, and what are the ...
7
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1answer
940 views
Interaction between a pencil and rubber (eraser)
Is there a interaction between a graphite pencil and and a eraser. For example, if I drew a line on a piece of paper and then erased that, what interaction is occurring?
Is it a Van der Waals ...
3
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4answers
7k views
Why does physisorption (physical adsorption) increase with ease of liquefaction?
This is what my textbook says about physisorption
The amount of gas adsorbed by a solid depends on the nature of gas. In general easily liquefiable gases (i.e. with higher critical temperature) ...
