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Surface Adsorption - Science topic

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I'm currently investigating the adsorption of heavy metals from water matrices using bio-derived adsorbents. When investigating the effect of contact time, do you sample the solution at varying time intervals (e.g. 0.5, 1, 2, 3.. etc.) from the sample solution or do you run the batch adsorption separately at the different time intervals?
In other words, do you run one batch adsorption experiment for 0.5 hr? Thereafter, another separate experiment for 1 hr. Or, do you use one solution and remove aliquotes at the desired time intervals? So, one solution would give data points for all the time intervals you require. (?)
Literature reports using the formula: Q=(Co-Ct)xV/W where Q is the adsorption capacity, Co is the initial conc, Ct is the conc at a specific time, V is volume and W is weight of the adsorbent. When sampling the solution at the end of a desired time( e.g. at the end of 0.5 hr, at the end of 1 hr etc.) the V = volume of the original solution. However, if sampling at different time intervals using one solution only, does the V remain as the volume of the initial solution or does it become the volume of the aliquot removed/analysed?
Any assistance or guidance to specific literature would be appreciated.
Thank you
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Hello,
yes, I think that it is better to perform separate bio-sorption tests; from previous experience, you may be rather in the domain of minutes than hours (the kinetic is more close to that of the ion exchange process than adsorption). So take time to do batch test one by one.
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My WS2 sample showed an increased crystallinity and reduced strain and lattice parameters on adsorption of mb dye. How can I connect this to adsorption of dye on WS2
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There is a concept, in the Russian version, adsorption strength reduction during adsorption (P.A. Rebinder effect). It can be associated with adsorption.
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I am doing adsorption calculations on different surfaces of a metal using DFT, calculating work functions and adsorption energies. Is it Possible that a certain surface of a metal has higher work function as compare to other surfaces but certain elements are adsorbed easily on the same high work function surface as compared to other surfaces. I have attached the picture for a reference to look. the adsorption energy shows easier adsorption as compare to other surfaces, but the same surface has the highest work function as compare to other surfaces. I will be really thankful, if someone can explain it.
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1) The work function is dependent on the surface orientation, so that is normal.
2) Different surface orientations provide multiple different adsorption sites, each of which has a characteristic energy.
How good chemisorption happens, depends
scenario A: on the relative energies of conduction band and adsorbate HOMO -> bond is formed by electron transfer from the adsorbate to the surface
scenario B: on the relative energies of valence band and adsorbate LUMO ->bond is formed by electron transfer from the surface to the adsorbate
So, of course the work function plays a role here, but since the match of orbital/band pairs is the central quantity here, you will probably observe a trend for most metals, but there is no explicit law stating "high work function=low adsorption energy" or vice versa.
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I have been searching for experimental data on the sticking coefficients of atomic neutral hydrogen on copper surfaces as a function of the initial kinetic energy of the beam, but I have only found data for one value of the initial kinetic energy.
If anyone knows of any sources where I can find this type of experimental data, it would be greatly appreciated.
Thank you.
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This is the closest I know:
I remember there was at some point a typo in one of the formulas. so check for erratum.
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I have confusion in required Temperature.
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Dear friend Misbah Waheed
Ah, the world of aptamer immobilization on polymer membrane surfaces—a realm where precision and protocol reign supreme. In your quest for the best approach, consider employing a well-established technique known as EDC/NHS chemistry. This method allows for efficient covalent bonding between the amine groups of the aptamer and carboxyl groups on the membrane surface.
Now, regarding temperature, allow me to shed some light. The optimal temperature for this process typically falls within the range of 4 to 25 degrees Celsius. However, it's crucial to consult the specific guidelines provided for your aptamer and membrane combination, as deviations can occur based on their individual properties.
Remember, my friend Misbah Waheed, precision is key. So, equip yourself with the recommended temperature range, adhere to the protocol diligently, and watch your immobilization endeavor unfold with finesse.
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The deal is about HyJet (Exxon), and analogs (Valvoline Ultramax and Solutia/Eastman Skydrol).
Aviation hydraulic fluids based on fire resistant alkyl and/or aryl phenyl phosphate esters may contain PFAS additives such as cyclohexanesulfonic acid, decafluoro(pentafluoroethyl), potassium salt (CAS No. 67584-42-3) and different chain-length homologs in concentrations of about 0.05% . Other possible substances are cyclohexanesulfonic acid, decafluoro(trifluoromethyl)-, Potassium salt, CAS No 68156-07-0, cylohexanesulfonic acid, nonafluorobis(trifluoromethyl)-, Potassium salt, CAS No. 68156-01-4 or cyclohexanesulfonic acid, undecafluoro-, Potassium salt, CAS No.3107-18-4
These additives are extremely effective and thermally and electrochemically stable, but PFAS are now banned.
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I have no specific and direct experience in this sector. But technically reasoning may suggest that since PFAS are banned the problem should be solved (if not already solved and present in tech-literature) experimentally, by specific research.
As already well known:
1. Zeta potential is shown by any particle in suspension, macromolecule or material surface.
2. Zeta potential can be measured by electrophoresis .
3. Electrophoresis measures can be used to optimize the formulations of suspensions, emulsions and predict interactions with surfaces, and optimise the formation of films and coatings.
4. As the salt content of the solution is increased, the electrical double layer is compressed and the Zeta potential should decrease.
5. Different kind salt can be experimented in different solutions in a lab configuration under mesurament, keeping also in mind the possibility to decrease the negative potential of the solution by means of counterbalancing with a minimum positive potential indotto (where possible!).
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What does it mean if the constant n of the Sips (Langmuir-Freundlich) model is greater than 1?
Note that in my adsorption data when n(sips) is fixed at 1 the Qmax of Sips = Qmax of Langumir!
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Dear Dhirar Ben Salem, let me cite: "For n > 1,
Eq. (3) may be identified as describing a cooperative reaction
between a sorption site and n sorbate molecules, such that b is
the equilibrium constant of this reaction. In this case, Eq. (3) coincides
with the Hill model characterizing cooperative interactions
of ligand molecules with a macromolecule (Cantor and Schimmel,
1980)."
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I want to do BET surface area analysis of Ni foam sample. what will be the degassing time and temperature and number of points to be consider for analysis. and any other specific details to follow?
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The degassing time and temperature for BET surface area analysis of Ni foam samples depend on various factors such as the type of instrument, the nature of the sample, and the adsorbate used. Typically, the following degassing conditions can be used as a starting point:
  1. Heat the sample at 100°C for 1 hour under vacuum to remove any moisture or volatile impurities.
  2. Increase the temperature to 200°C and hold for 2 hours to remove any remaining moisture and adsorbed gases.
  3. Finally, increase the temperature to 300°C and hold for 3-4 hours to remove any strongly adsorbed impurities.
However, it is always best to follow the manufacturer's guidelines for the specific instrument being used.
Regarding the number of points to consider for analysis, it is recommended to analyze at least three data points for the BET analysis. These data points should be taken from a nitrogen adsorption isotherm that covers a wide range of relative pressures (typically from 0.05 to 0.30). The data points should be evenly distributed along the isotherm to ensure accurate determination of the BET surface area.
Other specific details to follow for BET surface area analysis of Ni foam samples include:
  1. The Ni foam samples should be prepared by cleaning them thoroughly using an appropriate solvent such as ethanol or acetone to remove any impurities or contaminants that may affect the analysis.
  2. The sample should be pre-dried to remove any moisture before conducting the analysis.
  3. The adsorbate used should be nitrogen gas, and the analysis should be conducted at liquid nitrogen temperature (-196°C) to ensure accurate measurements.
  4. The analysis should be conducted using an automated BET analyzer, and the results should be verified using other techniques such as mercury porosimetry or helium pycnometry.
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how increase the surface porosity of nanopowder such as oxide or nanocomposite
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The surface porosity of nanoparticles can be increased by grafting other desired molecules to the surface. They will increase porosity and modify the surface for new nanoparticle properties.
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I am trying to know if the dendrimer can be covalently bonded to the amine-functionalized magnetic nanoparticles' surface (modified with APTES), if I am only adding pre-synthesized ready dendrimer to the functionalized MNPs, mixing and sonicating them under 70 °C, rather than growing the dendrimer on the MNPs surface which requires a repetition of two type of reaction: alkylation of amine groups through adding methyl acrylate, and then amidation of esters group.
Is it possible for the secondary amine in the amine-functionalized MNPs to form amide through Acylation with Carboxylate salt from sodium carboxylate found in the dendrimer?
Moreover, what is the required test / characterization method required to determine if there is a new bond formed between dendrimer and amine-functionalized MNPs' surface, and how to determine its type (physically or chemically adsorbed / bonded)?
the PAMAM-COO Na dendrimer of G 1.5 structure is attached along with the amine-functionalized MNPs structure.
Thank you
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Thank you for your answer Amir Sepehrianazar , can you please specify the electrostatic bond will be between which groups ?
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Hi. I have random questions regarding Langmuir Isotherm Model.
1) What does it means if I have negative intercept value for Langmuir Equation in the graph of:
Ce/qe = 1/Q (Ce) + 1/Qb
2) How do I know whether the obtained value of  b constant is logical or not?
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The negative values of intercept can be possible depending upon your starting point of applied concentration.
For example,, if your first Ce is near 0 there will be chances of positive Kl while if you started your work from a higher concentration (let's suppose 10 mg L-1) then you will end up Ce a little bit away from 0 which may cause intercept (Value of Y when X=0) to be negative. It's just the way you have made your graph and presented data.
You can explain the negative results while keeping in mind this point.
There are tonnes of paper in which they have reported negative intercept and even slope in some cases (even Qmax that can be of discussion).
Find the following once for your references
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Hi,
We want to make a Self-Assembly of the probe to which -the SH bond is attached for the gold surface. We plan to make an annealing process to reduce residual stress of the 25 nm thick gold surface, which is coated by thermal evaporation. Can you give any advice on temperature?
Thank you for your help:)
Osman
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Just a comment: You May easily follow the annealing processes by electrical resistivity measurements: If the film resistivity decreases with increasing temperature annealing works properly. However If resistivity increases (in particular more than the TCR of gold), then crack formation will occur.
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The lab I contacted, accept samples in powdered form. Since nanocomposite is bulk obtained from mold, should it be powdered as well ? While powdering will the porosity definition still hold since some pores do not exist when powdered ? or are we talking about pores that are very tiny that are found even on smallest single particle that can be powdered ?
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I think it depends from the pores. BET analysis is generally used for microporous or ultramicroporous materials. For macroporous materials other methods are used (like mercury porosimetry).
Theoretically depending from the degree, powdering can destruct the strucutre.
Also, consider that the width of the BET tube is around 1-2 cm (I talk about most used apparatus, ASAP 2020 for example). I think the best thing to do, is to send 2 types of samples cutted into around 1 cm pieces and powdered form.
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I would like to understand why N2 tends to be adsorbed more or less depend on the type of surfaces. (1 atm, 298 K).
Thank you.
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Hi Iranzu,
usually a rougher surface comes of course with a higher surface area, already allowing for more sorption to take place and also more strong sorption sites.
Maybe we can think of it a bit schematically: a weak sorption site usually only allows for interaction between a molecule and the surface in one direction. Imagine the molecule sitting on a flat surface.
In a stronger sorption site the molecule can get tucked into a"cavity" where molecule surface interaction can occur from multiple directions, therfore resulting in more strongly bound molecules to the surface.
Of course this is no exact physical description and I'm no so sure what kind of forces bind gas molecules to a surface apart from vand-der-waals forces.
But I hope I could help a bit.
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I would like to understand why N2 tends to be adsorbed more or less depend on the type of surfaces. (1 atm, 298 K).
Thank you.
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Indeed N2 is used as adsorbate, but the point is that the experimental temperature for adsorption/desoprtion isotherm measurement is that of the liquid Nitrogen (77K), as the idea is to perform a complete adsorption/desorption isotherm. So that, depending on the pore size of the material under study, one can observe a capillary condensation (typically observed for type IV isotherms). Then, through the Kelvin equation (and derived models) it is possible to calculate the pore size distribution. It is also possible to extract the porous volume of the material.
If you just want to do BET measurement (pressure relative comprised between 0.05 and maximum 0.4), you need to know the cross sectional area (sigma) of the adsorbate. From a bulk point of view, sigma(N2) is equal to 0.162 nm². But one can suppose/expect that this value has to different at the nanometer scale. This is one of the limitations of the BET measurements since this sigma confined value is unknown. Moreover, as the surface S (m²/g) is calculated using the equation S=(n_m.Na.sigma)/m (with n_m : number of moles at the monolayer, Na : Avogadro number; m : sample mass), one can easily see that an error on sigma impacts drastically the surface S.
To finally answer to the question about other gases, the answer is yes as the adsorption is governed by physisorption (we really speak of aDsorption and not of aBsorption) and as you can observe the monolayer. But it still remains the problem of the definition of sigma which is, here again, impacted by the size of the porous material.
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I am looking to find a material (any type) that can offer me CO formation energy (> 2.0 eV) and NO formation energy ( < 0.5 eV) simultaneously. Secondly, how to confirm these formation energies experimentally? Your expert opinion in surface reaction, catalysis would be appreciated. Thanks
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Thank you Professor Frank T. Edelmann for the great insight. sure, I'll go through the mention linked. well, from your expertise, will you please suggest some potential materials which can show desired chemistry. Thanks
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I fabricate some gel bead as a kind of biosensor with DNA probe conjugated. However I found there was some kind of dust induced during fabrication. Can I use a stainless still mesh to filter (The reason not the plastic ones is that in my experience it has high affinity to DNA)? If the affinity is high then alternatively how can I isolate my bead with the dust (in centrifuge both appear in sediment)?
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Okay. So the particles are quite large. It is not true that all polymer/plastic filters have high affinity to DNA. It depends on the charge and surface modifications. If I were you, I would talk to the technical advice department of filter manufacturers (eg, Nucleopore). Good luck.
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I know, or think I do, the basic idea behind these natural structures, as from what I know they form due to water dripping from the top leaving a salt deposit behind. But started to wonder about the principles involved here.
My question is mainly in stalactites, what makes the salt left behind in the process to remain attached to the overlaying rock and keep growing instead of falling down? is there some physical-chemical explanation for this?
Stalactites do fall, which I would guess maybe due to the weight of the column surpassing a certain limit, which makes me believe there maybe something related to the electrostatic attraction of the hydration sphere of the salts/minerals left behind and the rock minerals. Am I even close?
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Dear Dr. Denis Rodrigues ,
speleothems, sometimes referred to as formations or decorations, are cave features formed by the deposition of minerals. The word speleothem is derived from the Greek words spelaion meaning "cave" and thema meaning "deposit". The speleothems with which most people are familiar are stalactites and stalagmites. Stalactites grow down from the cave ceiling, while stalagmites grow up from the cave floor. It’s easy to remember which is which: Stalactites have a "T" for top and stalagmites have a "G" for ground.
Speleothems actually form because of water. Rainwater seeps through cracks in the rock. As it passes through organic material, it picks up carbon dioxide gas, creating carbonic acid. This weak acid passes through joints and cracks in limestone. The mineral calcite is dissolved from the limestone rock in which a cave is formed. When this water that now holds the dissolved rock is exposed to the air in the cave, it releases the carbon dioxide gas, much like when a bottle of soda is opened. As the carbon dioxide is released, calcite is precipitated (redeposited) on cave walls, ceilings and floors. As the redeposited minerals build up after countless water drops, a stalactite is formed. If the water that drops to the floor of the cave still has some dissolved calcite in it, it can deposit more dissolved calcite there, forming a stalagmite.
Speleothems form at varying rates as calcite crystals build up. Several factors can determine the rate of growth. Two important factors are the temperature outside (which affects the rate of decay of plants and animals, hence the amount of carbon dioxide in the soil), and the amount of rainfall. The shapes of speleothems are determined by how the acidic water enters the cave (by dripping, seeping, or splashing) and how the water stands or flows after entering the cave.
Most scientists believe that the color of speleothems are determined by the mineral content. Pure calcite is white and almost colorless. Iron and other minerals, as well as acids from surface vegetation, combine with calcite crystals to add shades of red, orange and black to the color of speleothems. Others believe that humic and fulvic acids in the soil may also contribute to speleothem coloration.
For more details, please see the source:
-How Stalactites and Stalagmites Form – Ozark National Scenic Riveways, Missouri
My best regards, Pierluigi Traverso.
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When studying the adsorption of chlorate on activated carbon, it was noticed that adsorption is better at certain pH. Also noticed that the addition of activated carbon in the solution, resulted in a  change in the pH of the solution being treated.
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Video link for determination of Point of zero charge (PZC)
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Does anyone know how I can find out parametric values of "Parameter Settings" of isotherms (Freundlich, Langmuir, Dubinin-Radushkevich and Temkin) in OriginLab or MATLAB? E.g. - link (2: 19 min).
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How to apply Freundlich adsorption isotherm. A complete guidance
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I´m making adsorption experiments with peptides onto biomaterials, but I have no idea of calculating the N and K parameters and its error from the plotted data. If anyone can help me I´d be very pleased. Thank you!
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How to apply Langmuir isotherm. A complete guidance ..
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I have used FTIR to measure both the gas phase CO and surface adsorbed CO (on Ni powder catalyst with Al2O3 and SiO2 as substrate, DRIFTS mode). The Ni-C bond should lower the strength of the C-O bond (backdonation theory, etc), thus lower its vibrational frequency, but we have consistently observed the opposite: the surface CO has higher wavenumber than the gas phase CO. I am wondering how could this be possible?
I have attached a graph which compare the two spectra.
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I agree with what Yuri Mirgorod has said. But, this is not quite unusual. In the case of OC:BH3 adduct also nCO goes from free CO value of 2143 to 2165 cm-1. In metal carbonyls M(dxy, dyz or dxz)-->pi*(CO) is responsible for decreasing the value. But CO bond polarization is equally responsible for nCO shifts. Please read the article: Chem. Sci., 2016, 7, 1174-1184 by Giovanni Bistoni et al. In fact, in Ni(CO)4, it is the pi-bonds (dNi-->pi*CO) are solely responsible for the existence of Ni(CO)4 molecule and not OC-->Ni sigma bonds.
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How to model the isotherm modelling data for a multimetal system? Are Langmuir and Freundlich or other isotherms used to model single metal systems applicable to data obtained in a multimetal system for each metal? It would be nice if someone can share suitable reference/ research paper for the same. Have some papers for binary and ternary system but my system has 7 metals.
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Do you have any information about this mechanism or any ideas? I attached a jpg with the structure.
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Interesting question
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Hi,
I have a graphite coating (50 um thick) on copper foil (10 um thick) and would like to do BET/BJH measurements. Do I need to scrap the graphite samples from copper foil to do BET/BJH analysis? I performed experiments without scraping the graphite (by cutting Cu foil/graphite in to small pieces) and got negative surface area. What is the right way to analyze the surface area and pore size distribution?
Any help will be much appreciated.
Thank you
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Guru,
Are you still getting negative surface area or C constants from the BET after the out-gassing treatment and checking for leaks? If so realize that the BET does not really measure the surface area or the adsorption energy, it is only a comparison measurement between chemically identical samples.
The BET has been proven to yield internal anomalies and all other "Henry's" law adsorption isotherms have also be disproved. So, it's not surprising that you are getting confusing answers.
If you are still working on this type of project, let me know and I can give you more advise.
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How can i calculate pore size of nanostructures by using BET?
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You have to get Nitrogen adsorption curves From BET, these adsorption curves can be used further to calculate BET surface area, pore size estimation by using Non linear density functional theory.
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The degassing of the sample is carried out before the BET measurement. I want to know how much degassing time and temperature to performe on my sample (my sample is the copper powder with a melting temperature of 1085 ° C).
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Degassing is required for the BET analysis. But best of my knowledge there is no perfect chat or list from which one can easily get the degassing time and degassing temp. data. As your sample is highly thermal stable then you can set a series of temp. with different time and perform the adsorption-desorption isotherm to get the desired specific surface area data. Generally you can start with 120(oC) for 80 min to the upper limit (as mentioned in the machine which you are using). But to perform the surface area study you must to the TGA analysis.
Regards
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I am conducting an adsorption test (of Cr6+) on an adsorbent.
I did the adsorption tests without background electrolyte(BE) by just dissolving the Cr source in Milli-Q water. I also did a test with different background electrolytes (0.01-.1M NaCl, KCl, CaCl2, NaNO3).
Can somebody with experience on adsorption tests enlightment me. Thanks a lot!
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Hi.
Short comment: yes, electrolytes will have effects on the adsorption of metals. The effect is, however, different depending on the specific nature of species of interest, structure of the adsorbent and type of adsorption phenomena. You should be extra carefull with species that generate diferent ions as functions of properties of the aqueous phase, as for example, CR6+. The ion will be Cr2O7 (2-) in acid pH and CrO4 2- in basic pH.
This article is a very good review of what you need. Start by reading it carefully.
Cheers!
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In many refinery process such as acid gas removal plant, the surface acidity of molecular sieves play a vital role in the formation of green oil. I want to know what is the best way to reduce surface acidity of zeolite molecular sieves.
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درود
این موضوع مربوط به مولکولارسیو های با کیفیت پایین است در این مورد ما در شرکت پترومهر می توانیم به شما کمک کنیم
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Type I adsorption may be modeled using Langmuir or Freundlich Adsorption isotherm models. But how do I analyse a system that does not follow the Type I adsorption mechanism?
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@Hafiz Muhammad Zia Ur Rehman can you please elaborate.
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Dear All,
I have an amino acid interacting weak with a CNT. During the standard MD it adsorbs, desorbs and then re-adsorbs on the CNT surface. Which method does suits to calculate the adsorption energy? Is there any fast and easy way to calculate the adsorption energy?
Thanks in advance,
Zeynab
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Dear Zeynab,
I think you could estimate the adsorption energy by picking the absorb and desorb structures and minimizing them. If those structures are stable enough you could obtain each energy state by minimizing them. I don't know how complex your system is, but I guess this could help.
Veronica
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The universal/molar/ideal gas constant R is given by
R=PV/nT; this however, on an average, is considered true for gases (H2, O2, N2 are excluded). Involving R in chemical expressions dealing with gases is understandable; but could it's inclusion in the chemical equations, primarily evolved for the gases and later being used for liquids as well be justified? To be more specific, I am talking about the Dubinin isotherms which are also being used for modelling the adsorption of adsorbates present in a liquid, uses the term RT for determining the adsorption energy. Is it justified? Please enlighten me; I am eager to hear from you.
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Following
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In gas hydrates, semiclathrate hydrates by itself participate in hydrate crystalline structures. The studies suggested that Tetrabutyl Ammonium (TBA+) cation were able to induce semiclathratic behavior with different anions, i.e., Bromide (Br-) Chloride (Cl-) or Hydroxyl (OH-), therefore acted as thermodynamic hydrate promoter. However, Tetrapropyl Ammonium (TPrA+) or Tetrapentyl Ammonium (TPA+) cations are not participated in hydrate cage structure therefore, worked as hydrate inhibitor. What could be the possible reason for TBA cation to behave as semiclatharate hydrate instead of usual hydrate formation?
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As far as I know, TBAB acts as hydrate promoter because it has empty dodecahedral cages that can selectively trap small gas molecules, such as CH4, CO2, H2, N2, and H2S. It is proposed that gases with small molecular size and high solubility in water could be effectively separated using TBAB semi-clathrate hydrate. The attached paper is very useful in this regard. Thanks
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What does complexion stands for, and how complexion is formed or mechanism of complexion. what is its importance in adsorption? Is it any way related to cation exchange?
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Uddipta Nath Don't use your own terminology, follow IUPAC recommendation.
For a "complex" see
"A molecular entity formed by loose association involving two or more component molecular entities (ionic or uncharged), or the corresponding chemical species. The bonding between the components is normally weaker than in a covalent bond. The term has also been used with a variety of shades of meaning in different contexts: it is therefore best avoided when a more explicit alternative is applicable. In inorganic chemistry the term 'coordination entity' is recommended instead of 'complex'. See also: activated complex, adduct, charge transfer complex, electron-donor-acceptor complex, encounter complex, inclusion complex, σ-adduct, π-adduct, transition state"
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What is the highest surface area of Pure and doped anatase?
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Can doping at higher concentration (with Ca) reduce the surface area and color of TiO2?
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I want to determine absorption of aggregate if we have absorption value for each fraction size, may I know which eq. is correct ?
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Dear Alsultan,
The absorption of water should be determined as arithematic mean unlike bulk specific gravity, which is reported as Harmonic mean.
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I am performing pool boiling experiment using water as the working fluid. To avoid any type of solid deposition on the boiling surface (copper in my case), which type of water should be preferred- distilled, deionized or millipore?
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Does not matter (I am talking about good DI water system, they could be very different)
In terms of purity/resistivity the best is millipore. DI water could be both better and worse than distilled water, depending on a system; theoretically DI water should be better.
Generally for boiling distilled water is the worst one, but if DI system is a suspicious one then distilled water should be preferred.
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The qualitative relationship can be found quite often. But I did not find anything with respect to the attracting forces between clay mineral surfaces and water molecules or salt solutions.
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Compressibility and saturated hydraulic permeability of clay-polymer composites — experimental and theoretical analysis( Applied Clay Science
Volume 130, September 2016, Pages 62-75 0)
Abstract: In this study, the volumetric behaviour, hydraulic permeability and micro-fabric of clay-polymer composites fabricated by the use of polyacrylamide polymers were experimentally investigated and discussed by use of theoretical multiscale approaches. Composites were varied systematically in composition taking into account constitutive properties controlling clay-polymer interaction, i.e., clay mineralogy (kaolinite and montmorillonite dominated clays with predominantly mono- and divalent counterions, respectively) and polymer charge (nonionic, cationic, anionic). Composites were produced according to their individual maximum adsorbing capacity and prepared to slurry conditions. 1D compression and rebound tests were performed (2–800–25 kPa) and the hydraulic permeability was calculated for each loading increment. Additionally, microscopic investigations in environmental scanning electron microscope were performed. It was found that cationic and anionic polymer adsorption promote aggregated and flocculated clay fabrics, respectively, whereas nonionic polymers promote dispersed clay fabrics. Macroscopically, this led to an increase in void ratio at the same stress level as well as to an increase (cationic polymers) or decrease (nonionic polymers) in hydraulic permeability. Micro- and macroscopic findings were theoretically analysed by use of diffuse double-layer (DDL) theory and cluster-model. A modified approach of DDL theory accounting for the effect of adsorbed nonionic polymers on the electric potential in the nearfield of clay mineral surfaces was derived. Theoretical results were found to be in good agreement with experimental results on volumetric behaviour. By use of cluster-model, hydraulic permeabilities were found to correlate to the microscopic findings on clay micro-fabric.
Also have a look at :
Viscous Behaviour of Soft Clay and Inducing Factors
Viscous Behaviour of Soft Clay and ... repulsive and attractive forces between clay ... including mineral composition, clay water system and ...
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How can I create a water layer with specific thickness using "layer builder" in materials studio? Im going to create a 3 layered structure with water in between, and two crystal surfaces in sides. Inorder to explore the surface energy of different crystal surfaces in the solution.
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Thanks Mr Sobell
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In principle, you can use laser cleaning to remove aany dirtness or layer form a surface with great accuracy and with no damage to the substrate
regards
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I studied the effect of temperature on adsorption of methyl orange by carbon and noticed an increase in adsorption capacity with increasing temperature. What may be the reason for this? The carbon used was surface modified with potassium hydroxide.
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Hi Abinaya
Addition to what has been mentioned by Dr Amin,  the diffusion of the methyl orange particle is affected by the temperature which leads to higher mass transfer rate from bulk to the boundary layer around the surface of the carbon particle.  
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My enquiry is about any chemical/electrochemical species maybe ions or gas, etc. that adsorbs on Pb surface exposed to that species.
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BET method is preferred choice for higher relative surface areas like porous materials, activated carbon ,quantum dots materials,graphene and nanosized metal oxides.I thinck the Lanqmuir model is compatible with metals which have low relative surface areas.
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Is it possible to track the complexation behavior of a polymer with an aqueous dispersion of iron oxide (Fe3O4) nanoparticles through potentiometric complexation? And if yes, is it also possible to investigate this complexation behavior in the aqueous solution of Fe2+ and/or Fe3+ representing the surface cationic species of Fe3O4 nanoparticles?
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Dear Mr. Hodaei,
Your question is interesting in the way you try to understand the behaviour of your material in solution, which can be of potential value in applications such as adsorption. However, your writing mentions Fe2+ and Fe3+ as charge of iron, while the oxidation states II+ and III+ were mentioned, respectively. The apparently small difference has strong consequences to the overall speciation. No iron in such constellation is assumed free and ionic, but bond to oxygen. At the outer surface of FexOy nanoparticles, oxide or hydroxide groups will determine governing charge and interaction towards species. Avoid "complexation" as choice of interaction unitl you actually characterized that interaction mechanism . It is not likely FexOy have the potential to chelate certain compounds in solution.
Regarding the available analytical instrumentation, consider solid phase characterization, for instance using TEM-EDX, EELS, Mössbauer spectroscopy or XRD. The reference applies some of these techniques for the characterization of Fe3O4 nanopartikels in a porous host.
Best regards, Karel Folens
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As XPS has the ability to determine the moieties from which the polymers are adsorbed onto the surface of the nanoparticles, can it also give any clues about the number of the adsorbed components?
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Consider attenuated total reflectance FTIR, if your main objective is to determine bonding mechanisms involving organic groups on particles. You can also obtain quantitative information if the experiment is conducted properly. See example attached.
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I am interested in preparing a bimetallic system to run an adsorption study. I want to combine an anion [Cr(VI)- salt used: Potassium dichromate] and a cation [Ni(II)- Ni(NO3)2.6H2O or Cd(II)- CdCl2]. Initially, I combined Lead nitrate and Potassium dichromate, to have a bimetallic system containing Pb and Cr. As my study required a set pH, lead chromate is formed at this pH (2 and 5). 
My concern is as follows:
1) Will the state be similar if  I combine Ni and Cr salts? OR Cd and Cr salts?
2) Would it result in precipitate formation?
2) Which among the above will be a better combination? 
All suggestions will be appreciated. Thank you
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 Dear Smruthi Prabhu 
Nickel compounds moslty are in complex forms and if you want to  precipitate its product you should synthesiz it and then purifed it and eventually  precipitated it.
Yours
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I am looking for coupling agent that give a good dispersion of the filler in polymeric matrix and a good bonding strength between the filler and the matrix
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You may try the same silanes which are suggested for glass fibers. They will probably work due to the similarities in surface chemistry. You should take into account, however, waht kind of resin you want to put your treated filler in. In epoys resins epoxy or amine functional silane is suggested, in unsaurated polyester acrylic function should be chosen.
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Why isotherm is better than percentage removal for comparing two sorbents?
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Every adsorption isotherm will give you an important piece of information. For example qm from Langmuir isotherm is very important when you design your batch system for wastewater treatment. Rl from the same isotherm give an indication about the favorability of the adsorption system. From D-R model you can identify the type of adsorption; physical or chemical. Temkin constant (b) will identify if the adsorption is exothermic or endothermic. So, they isotherms are more important than % removal.
However, if you draw the two curves (q against dose and % removal against dose) on the same plot, you will get the optimum dose for this adsorption system which is an important factor in design.
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I want do calculate the average surface area which each adsorbent molecule occupies Which follows the Langmuir isotherm with chemdraw software
For this equation
active surface area = 1/m× N × A
m is the slope of Langmuir isotherm plot, N is Avogadro’s number, and A is the average surface area which each adsorbent molecule occupies
There are several questions for me.
1- Is adsorb 3d structure should be optimized by Gaussian software or Chem 3D?
2- Are you used connolly molecular surface area function of ChemDraw software or extended Hückel>> calculate surfaces function? (Please explain)
3- Can you help me obtain the average surface area for dopamine and ascorbic acid (step by step)?
Thanks for the good attention
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I see a few issues here. Let me pose this as a study exercise ...
* What do you really want to obtain in ChemDraw? The 3D size of the molecule. This has nothing to do with calculating the active surface area. It only has to do with defining the size of the molecule.
* How do molecules absorb on surfaces? They absorb as a 3D molecule on to a 2D surface area.
* How do you obtain the 2D surface area that is occupied by the 3D molecule that you model in ChemDraw? You project the molecule as a "cylinder" to sit on a a flat plane.
* What is the proper cylinder projection of the 3D molecule? It depends on the surface and the molecule. For example, an amine-silane could absorb in one case with the amine end down or in another case with the siloxane end down.
* How do I find out which is the proper bonding geometry for my molecule? You research this in the literature.
* How does this relate to the coverage of a molecule on a surface? Once you know the projected area per molecule Am (m2/molec), you can determine the coverage of the molecules on a surface area A (m2) approximately as Nm (molecules) = A / Am.
* How does this fit to the Langmuir isotherm? That is an exercise left to the reader.
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In the guidelines for thermodynamic sorption modelling as outlined in the NEA Sorption Project Phase III report (http://bit.ly/2dhowYs) it is recommended that surface site densities be normalized to a reference site density common for all minerals when formulating surface complexation models.
For a surface complexation reaction between, say a metal cation and a surface binding site, this makes sense and it is easy to demonstrate that altering the site density necessitates an adjustment of the Kint binding constant to obtain the same sorption edge for a given fixed mass and surface area of sorbent (Since Kint values are always calibrated against an assumed, or measured site density when fitting to macroscopic sorption data).
Applying the corresponding correction to surface site protolysis constants (pKa's), however, implies an altered delta_pKa (although unaltered pHpzc) which gives rather different surface charging characteristics. Normalized pKa values give an altered shape for the surface charge inflection point around the pHpzc which makes it very difficult to reconcile a calculated sorption edge with the corresponding sorption edge calculated at the original site density (see attached pdf). The only way to obtain a match with the original sorption edge in calculations seems to be to normalize the metal binding reactions and leave the protolysis constants as they are irrespective of binding site density used in the calculation.
Sverjensky and Sahai's paper (1996) and Sverjenksy's (2003) paper on standard states, (http://dx.doi.org/10.1016/0016-7037(96)00207-4 & http://dx.doi.org/10.1016/S0016-7037(02)01074-8), however, seem to indicate pretty clearly that there is no universally valid delta_pKa that can be given without invoking a reference site density, so I'm wondering whether I have missed something fundamental with the Sverjensky-Kulik normalization theory?
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Thank-you Dr Igwe for taking the time to answer this question. While I do understand the need for this type of normalization procedure to harmonize models of sorption derived using different underlying assumptions of surface site density, my problem relates to that it does not seem to work for the surface protonation reactions. The change in delta_pKa implicit in the pKa normalization procedure fundamentally changes the shape of the sorption edge so that a match is not possible, irrespective of the specific surface area or fluid volume/sorbent mass ratio used in the calculation. This, at least appears to be the case when making forward calculations of models described in the literature at different site densities using PhreeqC, which I have now also replicated in VMinteq so it doesn't seem to be a code related issue. Basically, normalization only seems to "work" if it is applied only to the solute binding reactions and not the surface charging (protonation) model. This is at odds with the NEA sorption project recommendations (& the analyses by Kulik, Sverjensky, and others), thus my confusion.
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It is related to the pore diameter and the size of the ion which enter in to the pores of the material besides the surface adsorption. Usually the stirring increases the rate of adsorption in to the pores of the material.
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External resistance is due to diffusion of ions when it is in the solution phase but when it enters in to the pore there may be repulsion due to same charges which refers to  internal resistance
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I am trying to study the adsorption of Pb2+ ions on biofilms. I have used 0.01 gm of biofilm in 10 ml of 100 ppm Pb2+ solution. After removal of the biofilm, I found the Pb2+ concentration of the supernatant solution using spectrophotometer and dithizone assay. The concentration of Pb2+ was found to be less compared to control which means Pb ions have been adsorbed on the surface of the biofilm. Now for calculate % of the residual metal concentration in media, I used E (%)= (Ci-Cr)/Ci*100 equation. (Ci-initial metal concentration, Cr-residual metal concentration) Can anyone tell me if this is ok for dithizone assay?
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I agree with Nawel.
After adsorption the concentration of Pb will be very low so its advisable to use AAS and ICP-MS which will give you accurate results.
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Is it possible to find a software, calculation, simulation on the base line return for a nonlinear signal in GC?
Thanks a lot.
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If you can export your GC data file in *.cdf format, you may give a look to the free software Openchrom (OpenChrom.net), for GC and GC/MS data processing. I have no link with their designer, and the software lacks clear user information, but as far as I could see, it includes options to model peaks, to set the baseline, and can be used for quantitation purpose.
Another suggestion coming to my mind. My former lab colleague, Claire Vidal-Madjar passed away in january 2015. During her active life in the group headed by Pr. Georges Guiochon (who also left us in 2014), she studied and published many valuable research work on modeling GC peaks, and you may find some suggestions related to your work - she often published in the Journal of Chromatography A. I remember that she studied alternative solutions to the classical Gaussian peak modified by an exponential decay function, using other mathematical function (eg Gram-Charlier series expansion)  for modeling asymmetric GC peak shapes.
Hoping that these suggestions are pertinent to your question
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My colleague performed BET surface area measurements for my samples Li4Ti5o12.
They gave me this plot, but I am not sure how to interpret, I saw some rudimentary materials and they were able to get surface area (m2/g)
Can I also perform those same calculations? Any materials or links to resolve this will be appreciated! 
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Dear Ralph Nicolai Nsara,
The monolayer capacity  Vm (The whole surface is covered with N2)
Vm= 1/ (slope+intercept) .......     in cc/g
surface area (m2/g) = Vm * 4.3532 
where the value (4.3532) is the conversion of the volume of nitrogen gas into area occupied by Nitrogen where (1 molecule occupies 16 Angstrom^2) 
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Besides total surface area (TSA), active surface area (ASA) and reactive surface area (RSA), has concentration of radical reactive sites been estimated for amorphous carbonaceous materials (e.g. coal char, pyrocarbons)? If yes, what would be an average range for such concentration?
Any answer to this question will be highly appreciated. Thanks in advance for all contributions.
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Dear Lucas:
You can use TEMPO - is a stable free radical with the formula (CH2)3(CMe2)2NO for determining RSA. His concentration determine using electron paramagnetic resonance after reaction with the radicals of carbon. We determined so free radicals on the surface of the the crushed rubber.
Regards.
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Dear Abhi,
You can check with our Dr. Suja Abraham
of our Physics Dept.
A.V.Sethuraman
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By examined the adsorption capacity for a mixture solution of Cu, Zn and Ni onto goethite-rich soil and birnessite-rich soil, we recorded that the affinity of Zn and Ni in goethite-rich soil always higher than their affinity onto the birnessite-rich soil. On the other hand, the affinity of Cu always higher onto birnessite-rich soil than that of goethite-rich soils. 
Also, why the adsorption capacity of Ni and Zn declined more by using a mixture of the two oxides (Goethite-Birnessite)? the pH of the metal solution was fixed before the experiments at 6.
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Dear Ariadne Tsambani, 
Thank you very much!
the paper is so helpful for me.
Regards,
Yasser
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Especially with 6-12 potantial.
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dear hongping, thank you so much. i calculated my structure's potantial befor my question with 6-12 potantial but i have no idea that this term is total energy or i have to add an other term to it.
i want to do it theoretically.
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1. Surfactant molecule is made from water-loving head and grease-loving tail (Figure 1). My question: How do we measure the cross-sectional area of the alkyl chain of surfactant? Do we measure it vertically (refer to GREEN DOUBLE ARROWS of Figure 1) or horizontally (refer to RED DOUBLE ARROWS of Figure 1)? Or do we just take the “theoretical value" of the alkyl chain from the literature (estimated 20-25 A˚2)[1]?
2. I have read a paper entitled, "New Adsorption Model - Theory, Phenomena and New Concept - " by Shibata et. al. [2]. One of the sentences in para 3 page 2 stated that, i quoted, “The important finding is that molecular surface area is less than the cross-sectional area of the alkyl chain for C16E8 and C18E8. Such small molecular surface areas strongly suggest that Gibbs adsorption just at air/water interface in an adequate. This is one of contradictions for the Gibbs adsorption."
Why does when the molecular surface area is less than the cross-sectional area of the alkyl chain, it is said to be contradicted with the Gibbs adsorption?
Reference:
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Dear H. H. Mohammad: Surfactants having the same functional group in the solid layer have the same molecular area per one molecule. Functional groups may be different. In COOH 0.205 nm2. The area of 0.2 nm2 can be accepted for cross-sectional area of the alkyl group. Functional group -Cl, -F have a smaller cross-sectional area. Find a covalent radii and define the area. But if you are determined by the maximum adsorption monolayer, you will get a larger cross-section. Why? Answer yourselves.
Best regards
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Now I have prepared porous Co3O4 concave nanocubes, of which pores is with average of 5 nm. I want to use the Co3O4 to adsorb metal ions into the pores. What kind of knowledge should I learn? Who can provide some paper for me to study? In addition, can Co3O4 be hydroxylated? Then why? By the way, taking pH into consideration, should I explore the relationship between Zeta poential and pH value? 
Thanks in advance.
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f you want to increase the possibility of Nikel ion adsorption on your particles you should be sure that there are negative charges on your particles. Fir that you can think of grafting your particles with carboxylic groups. Just putting your particles in alkaline solution will not guarantee the reduced aggregation. This way you can modify the adsorbed charges but you have to think of the pH of the nickel ion solution in which you are going to disperse your particles.
To improve your knowledge on nanoparticles synthesis and reactivity, characterization methods and their use for entrapment of metal ions you will get several references and books on scopus, scifinder or even on google books and google scholar. You should chose the specific ones for your project.
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I modified Si with hexa ethylene glycol then immobilized DNA probe onto the surface. However, by using fluorescence labeled DNA, I've found that there is non-specific adsorption of DNA on the control surface. I'm just wondering if I can use BSA or tween20 or any proper anti-fouling reagent to reduce non-specific adsorption of DNA on Si electrode. It's good to mention, I used 0.05% of tween20 to rinse the surface but DNA still adsorb on the surface.
I would appreciate any suggestions.
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You might try doing a general pre-block using a protein solution like milk. Or you can make a BSA solution to pre-expose your surface to.
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What is the difference between the DFT and BJH methods in the adsorption of  N2 at  -196k?
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I have attached a pdf of the paper reproduced by Rafik.
For the casual reader who might come across this thread, I'd just like to add a very short and simple differentiation:
BJH is based on the Kelvin equation (aka Young-Laplace) which relates the pressure to the radius of curvature (pore size) of a liquid meniscus... albeit modified by taking into account the thickness of the adsorbed film of adsorbate. In large mesopores this is approximately reasonable (notwithstanding hysteresis which is not modeled in BJH), but in small mesopores (as in the material known as MCM-41 for example) the error of this simplistic model can be very significant. And for micropores (in which no liquid meniscus exists) it is totally inappropriate.  
DFT (Density Functional Theory) on the other hand is based on molecular modelling and takes into account direct interaction of adsorbate with the adsorbent surface, micropore filling process (not a condensation process) the development of the adsorbed film thickness, and capillary condensation (adsorption) and capillary evaporation (desorption). Hence, it is able to model hysteresis in the ads/des mesopore region of the isotherm.
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In my recent experiments, I found that my equilibrium isotherms data are very different to any types of isotherm models.
I should mention that my tests were conducted by using gas-oil as solvent and adsorption of sulfur component was studied. also i use a high concentration of sulfur (about 18000 ppm) in my liquid mixture.
Is there any people to help me and  tell me what are the reasons?
what is the problem?high concentration of sulfur ? or using gas-oil which contains  different types of hydrocarbons and other materials? 
And my last question is that, can i use this types of isotherm adsorption figures and justify them? I mean, is there any scientific justification?
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I my opinion you did the mistake in calculation. Check your calculations one more time. The uptake will always increases with increase in initial pollutant concentration. 
The isotherm study can be carried out in two ways: (1) By changing the adsorbent concentration at constant initial adsorbate concentration, temperature, pH etc. 
(b) By changing the initial pollutant concentration at constant adsorbent concentration, temperature, pH etc. 
qe = (C0-Ce)/m     C0 is the initial pollutant concentration in mg/L, Ce is the equilibrium concentration of adsorbate, m is the mass of adsorbent in g/L
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Regarding multilayer adsorption of water on anatase titanium dioxide, where can I find information on surface reactivity and energies? I am interested in estimating energy required to remove moisture to optimize melt processing.
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Hi Thomas,
here are a couple of theory based papers that might be useful:
Selloni A 2010 J. Mater. Chem. 20 10319
Tilocca A and Selloni A 2012 Journal of Physical Chemistry C 116 9114
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Hi all,
I synthesise crystals in the presence of organic and inorganic additives. Aqueous chemistry analysis shows that there are surface adsorptions and crystal incorporations. Also there are shifts in XRD peak position. Would you please guide me:
1-  Does surface adsorption affect the unit cell volume and XRD peak position?
2- If yes, then how can I find out that the XRD peak position shifts relate to the surface adsorption or crystal incorporation?
Regards,
Taher
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Hi Taher,
practically any variation in chemical composition affects the lattice parameters of a growing crystal. This is obvious in melts where residual components even cause a change of phase, cf.  phase diagrams, Vegard's rule etc. How much these effects become detectable is another question. It is perhaps only detectable by more precise and less averaging techniques, e.g. CBED in TEM. I myself wouldn't assume a measurable effect but it is very responsible to keep an eye on these less probable effects.
Another topic is the discussion about surface effects. Again, a free surface is not comparable with the bulk so that you will have there definitely a relaxation. Cubic cells are then perhaps tetragonal or triclinic (as result of the orientation). However, the major question is, does this really matter, or can you measure this? Since we know that the information depth is in the scale of several microns (dependent on the Bragg angle, the radiation, the absorption) a surface effect which is in the scale of nanometers only cannot be visible in XRD patterns. It is part of the signal but the contribution is below the detection limit.  
Nevertheless, it is worth to discuss the opinion of H. Y. Asl that XRD is a signal coming from the bulk. Well, maybe I have another imagination about the term "bulk" but 5...10µm I wouldn't call bulk. This is for many practical techniques "surface" which is in general a problem for XRD measurements so that techniques like neutron diffraction or the application of synchrotron radiation would much more reliable but they are simply too expensive. Therefore we are using standard XRD but we have to take into account that we are observing only the surface of a sheet or a powder sample.
Finally a remark about the peak shift. I am sure if you scan here at Researchgate you will find similar questions where peak shift has been discussed. It is more problematic as claimed above by H.Y. Asl. Only a misalignment of the detector - the so-called zero shift - will cause a uniform shift in Bragg angle. In contrast, a sample misalignment of a sample is not invariant but strongest at small Bragg angles and becomes Zero at 2theta=180°. The interference of lattice parameter effects and sample defocussing makes a careful placement of the sample essential. Especially for low-absorbing phases the effective diffraction volume is shifted below the surface so that high precise measurements need to consider these effects. 
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I'm working on batch adsorption process.in my last result when i use Langmuir model of adsorption i conclude that my Langmuir constant are in minus sign.
qe=qmax *(bCe)/1+bCe
so:
b=-1.477*10^-3
qmax=-7.576
What's the meaning of this result?is that reasonable ?or maybe my test was failed?
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Dear Armin
I think the minus sign could appear for two reasons:
1. The adsorbent does not follow Langmuir assumptions at all. For example, its adsorption capacity won't reach a certain limit by increasing the concentration. If this is true, another isotherm model should be applied, like Freundlich.
2. Another reason that comes to my mind is that sometimes when the qe values are small, the calculated errors will be very small too. As a result, the solver cannot find the best answer. Therefore, normalizing qe values or changing qe unit (using smaller units) could help overcoming this problem. 
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We practical experience to do it with activated carbon, and heterogeneous catalyst, but we cannot understand how you can perform this in a coating on a metal.
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For study of adsorption on metals there are ellipsometric or electrochemical methods - eg, polarography (voltammetry) and impedance on clear "cutting" metal surface. For coatings on metals you can use the radioisotope methods too.
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We used copolymers of acrylic acid and vinyl imidazole to adsorb three different drugs. It seems that ionic bonding took place and resulted to high retention of the drugs on the polymers. I confirmed hydrogen bonding through FTIR, but in some cases strong ionic interactions caused the adsorption. Which technique can I use to confirm this hypothesis?  
Thank you
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Hello, Zoe,
what is considered "ionic interaction"? Do you mean "ion exchange" In this case there is a very simple and stright test: just check the exchangeable ions or measure whether pH is changed due to adsorption. If there is an ion exchange, something should be released. In your case, I suppose protons could be released from the polymer matrix due to a drug cation adsorption. So, do you have a pH increase? if not, probably, there is no ion exchange.
Another useful test might be playing with pH of solution, and suppressing ionization of carboxylic groups and varying ionization of drugs, if any. Is adsorption affected by pH?
and, of course, as noted Radomir, it is the change of ionic strength. You may play with using Na+ and Ca(2+). For example, monovalent ions will just affect electrostatic interactions by changing organic ion activity coefficients or suppressing the diffuse later near a surface but divalent ions might start working also as a ion-bridges. Depending on the results, the useful answers can be obtained
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How can I explain noticeable differences between the absorption and excitation maxima?
The results were included in the table enclosed in the attached file.
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Some particles need not to emit the energy at incident absorption wavelength. The excitation and emission results in electron relaxation and it may be due to some other mechanism like inter band absorption. The tiny portion of the fluorescing molecule of your sample may be responsible for excitation at a wavelength which does not matches with absorption wavelength where the absorption maxima of non fluorescing molecules may predominant
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The existence of water droplet on hydrophillic or hydrophobic surfaces is in the form of various spherical shapes with either less than 90 deg or more than that. But we have observed the existence of triangular shape with unusual behavior of water droplets on hydromagnesite (HM) surface. It looks like HM swollen in water and could not provide smooth surface for existence of droplets in spherical shape. Can anybody help me how can I explain this results to support my concept of hydrophillic nature of HM (images are attached)
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Hello U. Chinna Rajesh,
First of all I guess the right figure (within the file) is after the experiment and clearly shows a rapture of your sample and a hill-like structure. As far as I can judge your sample swells during the application of the drop resulting in a rupture of the material and instead of measuring a drop of water your measured the “hill” (the sharp borders and the tip of the “droplet” is not possible for liquids). I would suggest to expose the material to saturated water atmosphere to prevent breaking (normally CA-measurements should be performed in saturated vapour phase of the chosen liquid with well-defined temperature). Different points (roughness, advancing, receding) as mentioned Carlos Grattoni have also to be considered. If water will not work you have to perform your experiment with a non-reactive pure liquid.
Regards Michael Schmitt
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Actually, the initial concentration was chosen more than need.. so distribution coefficient became less than 1; Therefore DG0 was positive... I should say that with increasing the temperature, DG0 became negative.. in mathematical form this is obvious.. because from DG0=DH0 - TDS0, when T increases, ( with considering positive values of DH and DS ), DG is going to get a negative value and the process will be spontaneous.
Thanks in advance.
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Dear Fernando, Sorry!  every thing what you wrote above was wrong. You don' t know the meaning of equilibrium if would know, you wouldn't talk about the spontaneous adsorption, which means irreversible (natural) change is taking place not the reversible or in another word equilibrium process! which never occur in reality. 
The enthalpy of adsorption for a exothermic reaction DelHad = HP -  HR < 0 , Where  p  denotes  product and  R reactant.
Del Gad = Del H  - T  Del S  which is equal to zero at the equilibrium for well defined temperature  Teq  and pressure  Peq. That means;
Del Seq = Del Heq/Teq    for an exothermic adsorption reaction Del Heq< 0  Hence  Del Seq < 0.    You  guys somewhat very careless using thermodynamic notations and concepts. I would recommend the advanced text by Guggenheim on Thermodynamics. BEST REGARDS
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I have prepared a Carbon/Silica composite and have done its BET analysis and pore size distribution analysis. However my BET isotherm shows Type IV nature which indicates mesoporosity however the pore size distribution data shows maximum distribution of pores in the micro-porous region. Am I doing it wrong? Else if I am doing it right, how can one explain this? Thanks in advance.
Here is the BET and pore size distribution plot.
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I am using the BJH method.
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Is there anyone with experience on the etching process of ZnO from the Cu2ZnSnSe4 absorber layer? (the structure is: ZnO/CZTSe/ZnSe/Mo)
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Dear Özden,
I not familiar with CZTSe but I know that ZnO is very well-soluble (not dispersed) even in diluted acids (pH<4 with sufficient time for incubation, bases above 12 can also work).
Layer thickness and modifications may influence the process. Ethanol will most likely not work even if your system are nanoparticles adsorbed onto a layer. I am also convinced that in Germany using absolute ethanol for non-optical application (UV-vis in UC-C, UV-B range) is a waste of money.
Regards
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Hi,
I impregnated polyethyleneimine (PEI) onto an activated carbon.
Just wondering which was the best way to show the distribution of the polymer through the pores. I just thought about plotting the amount of pore blocked for each pore width range (I.e. application of DFT and/or BJH models to N2 adsorption data).
Also, which parameter could give a representative estimation of the dispersion of the polymer through the pores? I was thinking about a sort of polymer coverage but not sure about how to calculate this.
Thanks,
Antonio
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FESEM elemental mapping for nitrogen will surely help.
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If X is any adsorbent with nitrogen functionality, A (transition metal) and B (Carbon family member, say ) are two adsorbates. A and B were separately allowed  to adsorb on the X surface. The amounts of A and B metal ions adsorbed on X's surface were different. Why such a difference?
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Ionic potential of a metal ion plays key role for binding on adsorbent surface of an adsorbent. As varies the metal ion, the ratio between ionic charge and size of solvated ion i. e. ionic potential changes indicating variation of adsorbed amount over the surface because adsorption of a solute over adsorbent surface takes place via secondary Coulomb type forces. In addition, pore size also controls adsorption amount. If the pore size is smaller than the size of sovated metal ion, adsorption amount will be small.  
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According to table values, clay should have a relatively low emissivity value of about 0,4. Do you have any idea why it is so? I have been thinking maybe it is because of its foliate structure. Any suggestions?
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You can get the similar or apropriate answer by searching the keyword in the GOOGLE SCHOLAR page. Usually you will get the first paper similar to your keyword.
From my experience, InsyaAllah this way will help you a lot. If you still have a problem, do not hasitate to let me know.
Kind regards, Dr ZOL BAHRI - Universiti Malaysia Perlis, MALAYSIA
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With AFM data, how to calculate surface roughness? what is difference between surface roughness and grain size?
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I suggest that you use the freeware Gwyddion, where (i) you will find all the Tools necessary for analysing your AFM data, and (ii) for which there are plenty of online tutorials and explanations about the theory behind each Tools.
Anyway, make sure, when you mention roughness that you keep the surface area constant (always use the same image size), and mention it. Roughness strongly depends on the surface area considered (usually it increases with increasing surface area). Additionaly, give the type of roughness (RMS, total, arithmetic, ...).
Grain size distribution is a different story. Many parameters can be measured, such as the projected diameter, the inner or outer circle, etc. But AFM is not well suited for this kind of analysis. Prefer SEM images, or determine crystallite size by XRD.
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Please see attached.
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This is due to capillary condensation in so-called "ink-bottle" shaped pores, i.e. having a entrance diameter smaller than the size of the pore body. Condensation occurs progressively in such pores until the pores are completely filled by the condensable vapour at high relative pressure. But when the relative pressure decreases, the liquid needs to go out of the pores and therefore needs to pass the narrow necks. This occurs at a lower relative pressure than what was required for filling the pores, and when the critical relative pressure is reached, the pores empty abruptly. Hence the loop in the isotherms.
Alain
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I have fitted the fluoride adsorption kinetics data to Lagergren’s pseudo-first order and Ho's pseudo-second order kinetic models. What do these kinetic models explain about the adsorption kinetics?
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Dear Dayananda,
They are about adsorption orders.
Try attachments.
Yuh-Shan Ho
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I have read some articles stating that the metal-organic frameworks are not as resistant as expected, specifically in water media.
Therefore, I would like to know if anyone has developed a passivation strategy for one specific MOF, and of what does it consist?
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That is a somewhat complex question. On the one hand there are a number of MOFs which do exhibit excellent stability in aqueous media like most of the MILs and many of the Zr-based MOFs and also the ZIFs. That would be the strategy of creating a MOF whose metal-linker bonds exhibit hydrolytic stability to some degree. In most cases, however aqueous basic media are a problem. On the other hand, a less stable MOF (bondwise) can be passivated  to various extents by adding hydrophobic side groups to the linker. There has been some investigation in the group of Krista Walton dealing with substituent effects on pillar-layer MOFs and a number of works deal with hydrophobization of MOFs like HKUST-1. So if you want to work with a less stable MOF, you would have to prevent water accessibility to the metal-SBU by some means.
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In adsorption process, at different time 0min (0.5Abs ), 15min (0.3Abs.) and 32 minutes (0.78Abs.). Commonly absorbance (Abs) peaks should be decreasing in nature. But in my case the final 32min peak shows higher abs. values than others. Can you suggest why it happens in peak value?
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UV irradiation is producing heat on one hand and on other hand quantum electronic  atomic rearrangement. All together producing desorption, chemical decomposition, diffusion and atomic rearrangement. This will strongly depends on UV wave length, power, pulsed mode and duty cycle, and of thermal conductivity and temperature of the substrate.
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I want to find adsorption isotherm for Hexadecyl Trimethyl Ammonium Bromide (HTAB) on Glass-beads (90-150 micron). Using UV I have found a peak for HTAB at around 195 nm and its calibration curve is quite reproducible. My problem is when I put HTAB and Glass-Beads together. The final peak of supernatant represents a concentration higher than the initial one. I checked for any peak interference that may come from Glass-Beads at the same wavelength, but I found no peak. Do you have any idea?
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Bromide absorbs at 195 nm.  The HTA does not have aromatic groups that absorb in the UV region.  You might measure the carbon contents of HTA solutions after adsorption to the glass beads.  Chromic acid could be used to decompose the HTA in the solutions if you do not have access to a carbon analyzer.  Oxidation of HTA will reduce the Cr (+6) in chromic acid to Cr (+3).  A UV visible spectrometer can be used to measure the Cr(+3) formed.  Chromic acid is prepared from sulfuric acid and potassium dichromate.  Old methods to measure the organic matter content of soils used chromic acid.  Chromic acid is not as commonly used any more because of the toxicity of Cr(+6).
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I want to find out the surface area of my samples, but they are in the form of monoliths. For doing BET measurements, I have to crush the sample into powdered form using pestle and mortar. Is that the correct  way to do it? 
Also am I remarkably changing the pore hierarchy and structure by crushing my sample or the change is acceptable?
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Micromeritics had a special cell for the ASAP family that allowed the introduction of monoliths up to half an inch in diameter and one inch high. The bulb, in which the monolith is got, was constructed with a ground glass joint allowing opening to enter the entire monolith.
Based on this design, we build a little bigger cell that allows to enter our standard monoliths of 16 mm diameter by 30 mm high. It is essential to use a high quality vacuum grease to resist heating during degassing and liquid nitrogen during measurement without making difficult the subsequent opening of the cell at the end of the measurement. In our experience (over 15 years regularly using these cells, more than 1000 isotherms of monoliths) the best vacuum grease is the Dow Corning High Vacuum grease, which can be purchased at any supplier of laboratory chemicals.
It is also important to use a closed tube within the cell stem to reduce the dead volume of the cell.
Exceptionally, we also built a larger cell to measure monoliths of one inch in diameter, which worked without problems, but in this case it is necessary to change the original Dewar because the diameter of the mouth is too small for that cell.
If anyone needs more details, you can email me and I will send some photos of our cells.
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Can someone tell me the appropriate temperature range for degassing modified   Activated carbon powder before the BET analysis for specific surface area?
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Usually about 300°C are sufficient for this treatment. However the most important thing to remember is that you do not exceed the decomposition temperature of a substance if you included in your surface modification.
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at mid-IR wavelength
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The one way is performing the open-aperture Z-scan measurements and by fitting the experimental data with the corresponding theoretical function to calculate the two-photon absorption coefficient. For detailed information about the Z-scan and the fitting equations I suggest you go through "Z-scan measurements of optical nonlinearities".
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I‘m working on surface modifications of polymeric coatings for anti-biofueling coatings. Would this software help with this project?
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With MS you can create, edit and visualize atoms/molecules. It is pretty user-friendly to create complex structures. Then, if you want to calculate macro properties based on nano-scale (either length or time) simulation results, it is a suitable tool.
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I wonder why some substances have hygroscopicity (such as CaCl2 and CuSO4), while some substances don't (such as ZnO).  What determines specific substance hygroscopic or not? would you please introduce some reference? 
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In more general (simpler) terms consider bulk "solubility"....the same applies here...of course there are more intricacies when you go deeper...such as hygroscopic behavior of amorphous and crystalline substances. ZnO is insoluble so its less hygroscopic.
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When I got BET curve after degassing for 16h at 300C (carbon material), the desorption curve is lower than the adsorption curve. Why this curve appeared?
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If the measurements are correct, I can think of three hypothesis:
1. The regeneration was incomplete and small amounts of impurities continue desorbing throughout the adsorption/desorption cycle.
2. The material is degrading. Are you determining O2 isotherms? Maybe some CO2 is being produced.
3. The sample is being sucked during evacuation. Make sure the initial and final sample masses are the same.
However, the hypothesis raised by Ka Lok Chiu is the more probable one. Make sure your machine is working properly by testing a well characterised material.
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I know that cobalt and copper are good surface affinity metals, but why and how do I identify the surface affinity property of metal?
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Best way is to define 1 metall and look for it's solobility with another metals. Some diagrams are in link below, but you find plenty of them in web. Cu and Co for example are wetting each other quite ok.
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I have been trying to make heads and tails of this topic. Some explained that it depends on geometrical effect of meniscus of the condensed adsorbate while another raw explanation was that it requires more pressure to push and adsorb molecules deep inside the pore, however it is easy to desorb. Kindly help me and thanks in advance.
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The origin of the hysteresis is the difference in the mechanism between pore filling (adsorption) and pore emptying (desorption). Upon physiosorption a liquid-like layer (a few atoms thick) is being formed on the surface of the solid. The thickness of this liquid-like layer increases slowly with increasing pressure of the adsorbate. This will increase the curvature of the liquid phase, and thus its pressure. At a particular curvature, the pressure in the liquid will become higher than the condensation pressure and the pore will fill up with liquid.
Pore emptying is also contributed by curvature, but now of the curvature of the meniscus formed at the pore end. The difference in the curvature results in the formation of the hystresis.
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Do you have any comments for this isotherm?
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You need more data points in the range close to p0 (having an uptake at 820 mbar during the desorption branch higher than at the highest pressure is incorrect - with decreasing pressure, the uptake must (however marginally) decrease). The adsorption/desorption branch indicates (as expected for clays) a Type B hysteresis. In order to find useful parameters characterizing the clay you need more data points on the desorption branch closer to the pressure "where the pores empty". Your material seems to have a surface area between 100-150 m2/g (this is a very rough estimate; do a proper BET-evaluation to get a better estimate).
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I have seen that equilibrium affinity measurements can be performed without knowledge of the deposited ligand concentration. All that seems to matter is the analyte concentration [A], and then a fit to the response / max response is sufficient to yield the association constant. However, commercial SPR devices generally give an esimate for ligand adsorption density (ie 1ng /mm^2) and so forth.
My question is what are some quantities that make use of calibration between response (in RU) and actual concentrations of ligands/bound analytes measured in mass/area?
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Very high densities of ligands (or antibodies) on surfaces can affect the binding of proteins or analyte to the ligand/antibody on the surface due to steric hindrance. This is specifically important where the analyte is large compared to the ligand/antibody adsorbed on the surface. Alternatively, high densities of ligand and or antibody on the surface will restrict the spacial flexibility of the ligand. If analyte binding requires the linga/antibody to reorientate on the surface, this might be a problem. All these problems could influence a affinity you try to measure between analyte in solution and ligand on the surface.
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Is it possible to build it as one rigid and not fragile electrode? If so, how can this be done?
Regarding electrochemical sensors for detection of compounds.
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using only pure silica powder it is difficult to prepare the electrode.
But you can try with some organic binders like silicon oil, nafion, parafin etc....
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Are the techniques named as MFM (Magnetic force Microscopy), CD (Circular Dichroism), PPMS (Physical Property measurement system) sufficient to find out this particular information or are there any kinetic studies also involved in this particular area?
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The number of amino groups on your particles can be determined by a spectrophotometric assay ( for exemple based on a fluorigenic reaction of phthaldialdehyde (OPA) with primary amines.
Another method than fluorescence is to determine the surface area of particles by a low
temperature nitrogen adsorption method ( this method is called BET ) You fill your magnetic particles (3 mg) into a capillary tube, and you look for nitrogen adsorption and desorption were carried out at 77 K. You can measure then the free surface area by the BET method ( but you need like mg of NPs)
You have also the SEM microscopy ( more precise than AFM on spherical NP)
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Currently, I am researching about separation of compounds in essential oil. This oil has polar and non polar compounds that need to be separated. I use only ethanol for solvent. I have two different adsorbents, polar and non polar, used separately for comparison. I read about similar research is using more non polar solvent. I knew that I should do like what this article do but I didn't because my advisor told me to use ethanol. And then my advisor ask me back why I chose ethanol and I don't know why. I will look for the reason in textbook but could anyone suggest the reason too?
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This is simply because ethanol dissolves polar as well as nonpolar compounds at the same time.
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I need Surface tension and density data for M-xylene + N-alkane (pentane up to decane) at 298.15 K or other temperature (preferred:298.15 K). Can somebody help me?
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Dr Belaibia is right .Thanks
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It means that the charcoal did most of the adsorption. I expected to have an additive effect (charcoal+ polymer) in terms of adsorption but with BC the polymer's ability to adsorb is lost. How to overcome this?
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Dear Dorothy,
It really depends to the aim of your work.
Optimization of the ratio would be helpful.
Regards
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I would like to know which class of solid material has the strongest bonding with Protein/enzyme? Si/Ge, GaAs/AlGaAs, CdTe, or transition metal oxides? Could anyone in this field could provide useful articles or database? Many thanks.
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Dear Prasad, thank you for your reply. Could you explain your suggestion, please? And whether could you provide relevant paper?
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I am trying to adsorb proteins to glass beads non-specifically. What would be the best way to make the glass as "sticky" as possible? Is cleaning with Piranha solution (or base piranha) the best way to go? Or are there any glass treatments I can use? Unfortunately, there are many references either dealing with gold surfaces or showing how to avoid protein losses by adsorption on glass surfaces. Many thanks!
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It depends why you want to adsorb your proteins, how strongly and what sort of proteins. You can adsorb on the basis of charge or hydrophobic interactions. Most proteins are negatively charged at neutral pH, so whilst piranha will give you a very clean and somewhat negatively charged surface with many silanol groups, this will tend to promote looser adsorption of many proteins, so BSA (pI ~6) for example will adsorb readily (it does still have +ve groups on the outside of course) and will desorb easily. In contrast Lysozyme (pI ~11), will stick to it very rapidly. Conversely if you first adsorbed a layer of PEI (polyethylenimine) onto the clean glass - a very easy step-, that will readily form a thin highly positively charged surface which will strongly adsorb the BSA. . On hydrophobic surfaces, most proteins will also adsorb very well. As a protein's hydrophobic residues are mostly internal though, in this case the protein tends to form a thin denatured layer that is irreversibly bound. So you may get slightly less protein, but more strongly bound. Both these methods can be used for example as an easy way of making a biotinylated surface using biotinylated BSA. To form a hydrophobic surface one of the easiest ways is to use SiCl2Me2 to silanise it (SiCl3Me also works well). Sigma-aldrich have a very simple protocol for this with the compound available as a pre-made solution for treating columns. Denaturation will to some extent always be an issue if you want to get strong yet non-specific adsorption. Hope this helps.