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Questions tagged [adsorption]

The adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface.

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DIY method for regenerating activated carbon in air filters

I am interested in regenerating activated carbon used in general house-hold air filters. I am looking for a sufficiently efficient and easy method to do this in home setting. A little tinkering in a ...
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Proper batch adsorption mechanism for heavy metals

I'm a college student with scope on environmental science, specifically the adsorption of heavy metals in aquatic media. Currently, I suffered from serious issue of batch adsorption mechanism, which ...
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Activated charcoal for water filtration: Granules vs Pellets

NOTE: After further investigation into the producer I found out that granules are made of 100% coconut shell whereas pellets of 100% hard coal. This renders this question meaningless. Apologies for ...
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Is the line between physisorption and chemisorption species specific?

I was studying about heterogenous catalysis, and my Professor said something along the line, "When the adsorption energy is comparable to (or lower than) heat of evaporation, then it is ...
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Is BET equation applicable to only monolayer adsorption range?

One of my senior colleagues is stating that although BET adsorption isotherm equation hypothesises about multilayer adsorption, the P/P0 values (usually from 0.05 to 0.3) accountable for BET surface ...
Lishachulisha Magenta's user avatar
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Enthalpy of adsorption and adsorption rate

What I want to know is about the adsorption enthalpy change by the change of surface coverage and the adsorption rate. In general situations, adsorption would be exothermic. So in the Gibbs free ...
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How do metal hydrides behave in a non-hydrogen closed system?

I am curious about the fundamentals of metal hydrides and how adsorption/desorption works in non-hydrogen systems. My understanding is that the atom ratio M/Hx of the metal hydride is a function of ...
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What is the chemical mechanism at work during the carboxylation of graphene oxides?

The literature describes carboxylation as an efficient technique to increase the ability of graphene oxide to adsorb metals, as it increases the content of carboxylic acids in the material, while ...
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Do "pseudo Van der Waals" gases exist?

In college, when deriving the Langmuir isotherm for gas-solid adsorption, the professor proposed a modified version of the Van der Waals state equation, what he called the "pseudo Van der Waals ...
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How to minimize sample dispersion during spotting for paper electrophoresis?

I am separating highly polar amino acids and their derivatives using paper electrophoresis. This requires pre-wetting a piece of filter paper with electrophoresis buffer (in this case, carbonate-...
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Why does the coordination of alkaline earths by graphene oxides increase as a function of the increasing ionic radius of the species?

The literature describes that the affinity of graphene oxides towards alkaline earth metals presents a positive correlation with their ionic radius (for example, Klímová et al. (2016) and Sófer et al. ...
Nathan Vinicius's user avatar
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Are carboxylic anhydrides in graphene oxides considered adsorption sites for metals? If so, are they more or less reactive than carboxylic acids?

The literature abundantly addresses the fact that carboxylic acids present in graphene oxides act as efficient adsorption sites for metals in aqueous solutions (e.g., HE et al., 2021; ZHAO et al., ...
Nathan Vinicius's user avatar
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245 views

Understanding isosteric enthalpy (heat) of adsorption

I am trying to understand what is isosteric heat of adsorption. Based on van't Hoff equation: $$ \left(\frac{\partial \ln K}{\partial T}\right)_θ = \frac{ΔH^\circ}{RT^2} $$ and $ΔH^\circ$ is defined ...
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Why do silver halide crystals in suspension, develop a surface charge

This is a question related to analog photography. Photographic films have a suspension of silver halide crystals in them, and these crystals have adsorptive properties which are used in this ...
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How rate of absorption remains same throughout the process?

While reading surface chemistry, I got Rate of adsorption is high at begining and then decreases till equilibrium is attained . On the other hand , rate of absorption remains same throughout the ...
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Adsorption on solids - homogeneous/heterogeneous surface definition

How could we define homogeneous and heterogeneous surfaces (rigorously)? It is among my exam questions (but I could not find any definition in my textbook or on the internet). I would say the ...
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Why is there preferential adsorption of a common ion during preparation of colloids by peptization?

There was a similar question asked here on Chem SE, but the answer was not very satisfactory to me, so I am asking a fresh question. Peptization is the process of creating a colloid from a precipitate ...
Samardeep singh's user avatar
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A physical meaning of the Danckwerts boundary condition in terms of concentration profile (adsorption)

Can someone please explain to me in a simplified way, what exactly does a well-recognized Danckwerts boundary condition do to the concentration profile of adsorption phenomena? I just cannot find a ...
Josh E.'s user avatar
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Units conversion of Henry coefficient in adsorption on solids [closed]

In a database of solid microporous materials I have the Henry coefficient in units of $\pu{mol kg^{-1} Pa^{-1}}.$ How to convert to $\pu{Pa^{-1}}?$ I tried to multiply by the molar mass of the sorbate ...
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4 votes
2 answers
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Why is the IUPAC definition of adsorption so different from other definitions?

NB: This question has been edited. Originally, some of the confusion was caused by me not knowing that condensed phase could refer to solid phases as well. This has been removed, but the confusion ...
user110391's user avatar
2 votes
1 answer
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Is there a practical re-use value gained by grinding up activated carbon that is spent/saturated?

I want to buy bulk activated carbon for use in a DIY air-filtration set-up, like this, to improve air quality in my bedroom. From what I understand, the relatively larger sizes of carbon media on the ...
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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 ...
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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 ...
Josh E.'s user avatar
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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 ...
Josh E.'s user avatar
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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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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 ...
prata's user avatar
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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 ($\ce{CaSO4*1/2H2O}$...
PoorYorick's user avatar
1 vote
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39 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} ...
Josh E.'s user avatar
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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 /...
Josh E.'s user avatar
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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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2 answers
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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 ...
user92142's user avatar
2 votes
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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 ...
Chor's user avatar
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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 ...
cjperkie's user avatar
3 votes
3 answers
4k 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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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 ...
Straticiuc Vicu's user avatar
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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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5 votes
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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 ...
N4v's user avatar
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6 votes
1 answer
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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 ...
Mr.HiggsBoson's user avatar
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2 answers
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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 ...
Suzie Waters's user avatar
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381 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 ...
Polo Jerome Daquipil's user avatar
1 vote
2 answers
695 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 ...
MRG's user avatar
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3 votes
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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 ...
Anonymous Chemistry Student's user avatar
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290 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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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 ...
Zorg's user avatar
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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 ...
Stephen Allen's user avatar
2 votes
1 answer
727 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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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 ...
K J P Singh's user avatar
2 votes
0 answers
464 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 ...
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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 ...
Phebe Bonilla's user avatar
1 vote
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44 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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