Advanced Oxidation Processes - Science topic

You may find the following papers useful, as they are relevant to your area of interest.

1.

2. Identifying key factors of peroxymonosulfate activation on single-atom M–N–C catalysts: a combined density functional theory and machine learning study (https://doi.org/10.1039/D3TA02371K)

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As I wrote, there is no general answer to your question. The initial reaction rate is commonly calculated at conversions less than 10%. If you want to quantitavely describe the effect of co-oxidation, you should build the kinetic model and simulate the process. This is an extremely comlicated task.

I might help you if you provide the details. You can message to me.

Oh yes, the volume of carbon dioxide is negligible and quite safe. Although depending on your choice of pollutant of interest to be treated, otherwise you may decide to sequestrate it

In general a given dye will absorb some wavelengths of light, and if they emit light (via fluorescence, phosphorescence, or in the case of LEDs a current of electricity), they do so at a longer wavelength. There are exceptions to this (e.g. upconversion processes), but generally the emission is at a longer wavelength. The difference between the maximum of absorbance (of the first excited state) and the maximum of emission is called the Stokes shift, and it can be a few nm to over 100 nm.

So you could see a dye absorb blue light in the range of say 420-500 nm. It would appear some shade of yellow to red, since those wavelengths would not be absorbed. If it subsequently emitted light, we would expect it to be maybe 490-550 nm.

You can use this tool to look at the excitation and emission spectra of many dyes. Hope that helps!

You can try with biopolymeric active materials like CNC-GO based membrane.

For better understanding you can follow this article.

Also this particular article could be beneficial.

Dear friend Alaa Al-Khalaf

Ah, the intriguing world of catalysts and contaminants! Now, pay attention because I am about to drop some knowledge.

Solid catalysts can indeed be like the superheroes of the chemical world, capable of removing both acidic and basic contaminants simultaneously. This often happens in the realm of Advanced Oxidation Processes (AOPs), Green Sustainable Materials, and Nano Organic Materials. Let me break it down:

1. **Advanced Oxidation Processes (AOPs):** These are a set of chemical treatment procedures designed to remove organic and inorganic pollutants from water and air. Solid catalysts in AOPs, like titanium dioxide (TiO2) or other metal oxides, can generate reactive oxygen species under certain conditions. These reactive species, like hydroxyl radicals, have the power to oxidize a wide range of contaminants, whether they are acidic or basic.

2. **Green Sustainable Materials:** The term "green" here suggests a more environmentally friendly approach. Solid catalysts in green materials could include various natural or sustainable substances. For example, some clays or modified natural materials can act as catalysts to neutralize both acidic and basic pollutants, providing a more sustainable solution.

3. **Nano Organic Materials:** The magic of nanotechnology! Nano-sized organic materials, such as carbon-based nanomaterials, can also be engineered to have catalytic properties. These nanomaterials might exhibit excellent catalytic activity, removing contaminants irrespective of their acidic or basic nature.

The key lies in the tailored design of these materials. Engineers and researchers can modify the surface properties, composition, and structure of solid catalysts to make them effective for a broad spectrum of contaminants. So, imagine a world where a single catalyst can handle both the Batman and Joker of contaminants simultaneously!

Remember, my friend Alaa Al-Khalaf, the world of catalysts is ever-evolving, and researchers are continuously pushing the boundaries of what these materials can achieve. It's a thrilling time in the chemistry of contaminants, and solid catalysts are at the forefront of this chemical crusade!

Bougdour Nadia and Badreddine Sellam

Fenton reaction is the reaction of 1 eq Fe(II) with 1 eq H2O2. Commonly, this reaction is fast. If H2O2 is an excess over Fe(II), the reaction mechanism includes so called Haber-Weiss cycle. The "Fenton-like reaction" is a very confusing term. Fe(III) is quickly hydrolyzed in distilled water producing insoluble iron-oxides. Contaminated water might be acidic or basic, might contain species forming stable complexes with Fe(II) and/or Fe(III). The generated HO(.) radical with contaminants affects the ratio of the steady state concentrations of Fe(II)/Fe(III).

Without having details of your experiment, your questions can't be answered. After dissolving 0.5 mM Fe(III) salt in water, the pH will drop to about 3 and some Fe(III)-oxides precipitate out. This process might be affected by contaminants.

Based exclusively on intuition, I would expect some precipitation of Fe(III), which would decrease the total amount of Fe. This amount could be affected by contaminants. The simplest experiment would be to check the initial and final pHs of solutions.

Have you ever thought how to store F2? F2 and the HF products are extremely corrosive.

Joe Tylczak thanks for the reply. Could you name some of free resources.

With such a limited infomation it is impossible even guess. More details.

Well it depends on the potential that we applied. Positive potential gives oxidation reaction and negative potential gives reduction potential. If working electrode is in oxidation state then counter/ auxiliary electrode get reduced. It also depends on chemical behaviour of the electrolyte and assays that you studied.

Hi, Magnetic stirrer and RB flask are enough to reach out TiO2-RGO composite (https://www.sciencedirect.com/science/article/abs/pii/S1004954118308759)

If you want methodology in a detail, kindly let me know.

High-pressure membranes, such as nanofiltration or reverse osmosis, have been extremely effective at removing PFAS. Reverse osmosis membranes are tighter than nanofiltration membranes.

The flow diagram

thanks for this information

Hi Federico Verdini,

For the said industrial wastewater, determine or (repeat) the COD by varying dilution factors

(1:10, 1:50, 1:100, 1: 200). After that you may get average range of COD.First confirm intial value of given sample. For more accuracy you can correlate with BOD value.

However you can more details about interference and its limitations in APHA Standard method 5220, SECTION 5-11)

Reg

Prashant. B.B

Amir Darban Loghmani i do agree with the expert comments above but I only have to say about that there are many studies available and reports various kinetic modelling of ethane oxidative dehydrogenation under an oxygen free atmosphere employing a catalyst of various percentage and sometimes it might be based on the weight and can from 5-12% wt % of VOx supported on ...... and one can see these studies in the links shared

https://pubs.acs.org/doi/abs/10.1021/ie303305c#:~:text=This%20study%20reports%20kinetic%20modeling,c%2DAl2O3.&text=On%20the%20basis%20of%20the,to%20the%20catalyst%20oxidation%20extent.

Dear Prof.

Looking forward to hear if any special issue under your editorship.

Thanks

Siddhartha

With ADF (and other codes in the Amsterdam Modeling Suite) you can define electric fields as well as multipole charges:

Try using electrodes with high OER and HER overpotentials. Such materials include MMO and Pt. This will reduce the overall gas evolution, thereby reducing the froth formation.

Thanks for your invitation. We can contribute if publication charges are waived.

In the paper, "Heterogeneous photo–Fenton treatment for degradation of indigo carmine dye ". Cosme-Torres, et al., MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.451 . 23 de febrero 2020. https://www.cambridge.org/core/terms,

you can read about this topics

For L-B-L technique you need strong binder and pH control, maybe you try with chitosan. You can also try screen printing or dip coating method with TiO2 paste. Ref:

Fabrication of screen-printing pastes from TiO2 powders for dye-sensitised solar cells

So sorry Stjepan!..in fact my answer was directed to the person who asked the question in the first place (@Michael Wierer)

Best regards

That is a really awesome question, which has troubled me for quite a long time. To be honest, we have paid too much attention to the cathodic H2O2 accumulation and unquestionably, it is crucial in the electro-Fenton process. In fact, electro-Fenton comprises two Fenton’s reagents: one is H2O2 and another is VALID Fe2+. The role of the valid Fe2+ is important as well since Fe3+/Fe2+ is the rate-limiting step in the classical Fenton reaction. We could notice as we pave our way to improve H2O2 accumulation to fabricate various cathodes, among which gas diffusion electrodes (GDEs) are regarded as one of the most efficient ones for H2O2 formation, however, hydroxyl radical generation in the GDEs-based electro-Fenton is not that promising. Because iron precipitation happened near-cathode vicinity as H+ was consumed too much by an oxygen reduction reaction (Journal of Power Sources, 2020, 466: 228342). As a result, we need to balance H2O2 formation and Fe3+ reduction to maximize the radical generation if one single cathode used for both reactions.

Regarding Fe3+ reduction, in my view, we need to consider it from two aspects.

One is about its chemical nature before it migrates to the cathode surface, I mean, iron tend to complex with various ions (like -OH) or chelating agents with function groups (-O, -N) such as humic substances polycarboxylates, etc, commonly presented in the aqueous environment. Those ligands donate a pair of electrons to the Fe atom and then redox-properties of Fe3+/Fe2+ were modified.

Another one is what you have mentioned is the nature of the cathode itself once iron approaches to the cathode. Research about it is quite limited and as far as I knew, cathode surface modified with electron-donating moieties, like phenolic -OH, quinoid -C=O, carbon-centered persistent free radicals favors Fe3+ reduction.

Dear Djamel Ghernaout ,

The relation between these two parameters is what i m seeking indeed. During my research to chose the main parameters to study in the electrochemical reactor, the fact that i don't have an interesting idea about the stirring degree rang makes me wonder about finding the appropriate domain basing on the bulk proprieties to get an idea about the mass transfer in this later, and i ended up with the Zeta potential.

As you mentioned, i think the Zeta potential will be influenced by the hydrodynamic regime and so the mass transfer, thus, it will be interesting if we can express such relation.

Thank you for the clarification and your support.

Thanks for sharing, I appreciate your help.

Dear Noor

To understand the position of Bi in TiO2 you need to first perform Neutron scattering to get a high resolution Data, Next you should perform Rietveld refinement using the TiO2 cif file. However, you will have to perform solid state NMR to understand the coordination number of Bi in the structure.

Using these methods, you will be able to develop a model for your structure which will tell you the exact occupation of your Bi.

There is another method which is called first principle method. in this method you will be able to optimize your geometry based on your primary guess for occupation of Bi. This is an excellent method in which you can even calculate band gap energy using HUMO and LUMO difference and by density of states.

Were your experiments done with ozone generated from air or from oxygen? If from air, you may find other molecules formed in the generator, are interfering with your results.

In answer to question 1, I would guess that it is the same as why ozone is not more used in Medicine i.e. there have been lo large scale trials. The reason for the lack is the same. There is no way of protecting your investment in a trial nor large money to be made.

It certainly is a cheap biocide. Even the equipment needed is cheap.

I have had saline ozone IVs and my condition did improve although it's back to where it was prior to treatment 2yrs ago.

It depends. It might be good because the degradation rate does not decrease in the course of reaction

If it is homogeneous Fenton's process, two options could be used: (i) removing H2O2 by adding small quantity of sodium sulfite (Na2SO3) (conc. of around 30 mM) should be enough and (ii) precipitating the catalysts by adding strong base. The aim of both method is to remove one of the Fenton's reagents, which will immediately halt the reaction.

When your dyes are sulfur ones, the choice of activated carbon as an adsorbent is not too good. It is well known, that efficiency of sulfur dyes reduction by activated carbon is rather low. Please see for example Thai Anh Nguyen, Ruey-Shin Juang (2013): Treatment of waters and wastewaters containing sulfur dyes: A review, Chemical Engineering Journal 219:109–117:

"The effectiveness of the activated carbon adsorption process is different with various dyes [ O. Marmagne, C. Coste, Color removal from textile plant effluents, Am. Dyest. Rep. 85 (1996) 15–21. ]. High removal rates (over 90%) are achieved using activated carbon for cationic, mordant, and acid dyes. For direct, sulfur, dispersed, and reactive dyes, the efficiency is moderate (over 40%); it can be improved using massive dosages of activated carbon. For vat dyes, color removal is very low (under 20%). In the case of sulfur dyes, the COD removal is 45.5% and the color removal is 40.9%"

Best regards

Vit

Chemical treatment of photocatalytic degradation (semiconductor based materials like ZnO and TiO2 ), has been used extensively due to its excellent catalytic activity, eco-friendly as well as low secondary pollution.

Unfortunately metal oxide nanomaterials have no efficient absorption in the visible light region and require activation/irradiation in the UV region.

Metal nanoparticles, on the other hand exhibit strong absorption and excellent catalytic activity in the visible range and gained much attention due to its potential application in degradation and removal of organic pollutants under irradiation of visible light.

Keep in mind the energy consumption of AOPs (ozone generation, UV lamps, production of H2O2 etc)!

In the case of hospital discharges, where the contents must be of nano grams, the use is indicated even if it costs relatively expensive but the obligation to remedy renders the technique valabale

The choice of the most suitable treatment technique depends upon pollutant concentration. When free phase of products is present, the first step should be physical treatment followed by.............. It depends upon quality of pollutants present in the effluent.

Best regards

Vit

In general, you have to answer these questions in order:

1. What is the design capacity of your plant (m3 wastewater/day)?

2. How much energy is required to process 1 m3 of watstewater (J/m3)?

3. How much one solar cell can generate (J/cell)?

It depends on solar cell design capacity, efficiency, local solar data (solar isolation, air, temp.,...). You can take ready solar modules from industry, and weather data from RETScreen if not available locally.

4. How many solar cells are required (cells)?

Hope this helps,

Abdo,

Dear Saeed,

This is one of the main concerns for students who must determine their own research topic. So, please do not be frustrated. I know that you are looking for a new, yet efficient, way to refine one of the most complex sewage. But please note that your time is only one year, and this time is not enough to carry out the number of tests. My suggestion is to combine two of them, such as oxidation and biological methods, and then focus only on them and all the effective parameters. I can tell without any information and only on the basis of my experience that there are still thousands of experiments that can be done on their combination that nobody has done yet. So you do not have to create a new method, but just do experiments that others have not done. I'll give you a simple example. Changes in temperature, pH, flow rate and feed concentration! That is, even if another researcher has checked the parameter effect, you can change the parameter check range. This is also a new experiment. Please do not drown yourself in a world of papers and methods of purification. What I've done before.

Good Luck

Hi Ayushi,

Our research group found that applying pulsed current could drastically enhance the H2O2 production in EF process, especially for porous cathode materials, such like graphite felt, carbon felt, carbon foam, etc.

Below are links of our recent research, hope they are helpful to you:

Many options are available.

1. KI,

2. NaOH can be used.

3.We can use MnO2 but it may interfere with TOC analysis.

4. We can safely use inorganic scavengers- Catalase is the best as it will not interfere with the analysis.

5. Tert-butanol or tert-butyl alcohol can be used but may interfere in analysis.

6.Even Chelating agents like EDTA can also be used for the purpose.

7. One of my students had used Sodium Thiosulfate Na2S2O3 without pH adjustment successfully.

Answers given by Niels and Soliu are very right and recommended by me

Hydrogen peroxide and UV light from the sun together catalyzes the reaction  yielding two free hydroxyl radicals  which are potent oxidizing agents.

H2O2 + hv→ 2OH·

Presence of metal ions like Fe2+ or Cu+  in seawater may assist generation of hydroxyl radical .Iron(II) is oxidized by hydrogen peroxide to iron(III), forming a hydroxyl radical and a hydroxyl ion in the  Fenton's process

Fe2+ + H2O2 → Fe3+ + HO• + OH−

Also, additional source of hydroxyl radicals is the photo-Fenton  process  

H2O2 + hν → HO• + HO•

Fe3+ + H2O + hν → Fe2+ + HO• + H+

Thank you very much for the answer

Dear Pounsamy,

It is difficult to answer as long as the question is very broad. Some people define AOPs solely as processes that work through HO· reactions. In this case it is difficult to find a process that has a variable reactivity to inorganic ions. If you take the broader definition you can get more selectivity from reactions that involve sulfate radicals (UV/PS, figure 3 in Maria Antoniou paper), ClO₂, ozone and possible Cl· from UV/Cl₂. 

I think a novel and very interesting process for selective reactions is the hydrated electrons generated by UV/SO₃^2- and gamma radiation. 

You can find very fine work on both sulfate radicals and hydrated electrons in Prof. Sayeds recent publications.

pKa of BHT (Butylated hydroxytoluene) is 12.3. No ideas about pKa of phenolic group on the surface of antioxidant. BHT is an antioxidant because of the weak O-H bond. No relationship with pKa.

We have several full-scale case studies where ozone was used to removed various dyes from textile plant effluent.  Ozone is not technically an AOP and is much less expensive compared to AOP's and chemical removal using coagulants and flocculants.  I agree with Mohamed that biological is best for pretreatment prior to chemical oxidation.  If you have a vat or batch process perhaps it is possible to use SBR or MBBR.

In photo Fenton process, hydrogen  ions H+ are produced through reduction of Fe3+ ions under UV light: 

Fe3+ + H2O+ hν → Fe2++ HO•+H+

Also, some organic  dyes  show changes in   pH  of their solution under UV irradiation

Yes, I approve the answer of Patrick! time depends on many parameters. The performer needs to know about (weight) of the parameters in the experiment.

Fenton's process should be an appropriate method for the treatment of industrial wastewaters which are characterized by a high COD content, so it it is a bit strange that only a poor COD removal is experimentally observed. In the Fenton process is recommended as a typical range for

However, in your description above, nothing was mentioned about the initial pH value of your wastewater. Remind that the Fenton process is usually inefficient when the solution under treatment has a pH value higher than 5. When the pH value of the wastewater is to high, Fe³⁺ ions willl tend to precipitate as iron(III)hydroxide, and hydrogen peroxide will decompose in H₂O₂ and O₂. This will result in a significantly lower production of OH* radicals, and hence a lower process efficiency.

In the most ideal case, the pH value should be adjusted to pH = 2. You can use sulphuric for doing this pH correction. At the optimal pH value of 2, the optimal dose Fe²⁺ / H₂O₂ of is approximately 1:3.(on weight basis). When you have a very high COD concent I also would recommended you to use 5 parts of Fe²⁺ for one part of COD (also on weight basis).

One possibility could be to use electrodialysis and separate the nitrate ions (smaller) from the humic acids. It also depends on the feed you have and if you only want to separate nitrates, because in this case other anions could be separated too (like chlorides, for example).

Thank you again Mr Manohar Sehgal for your clear explication.

If your organic contaminants are known then use UV/visible spectroscopy

Yes, I converted Rutile to Anatase phase by multiple shock treatment for the first time, on subsequent shock treatment Anatase converted back to Rutile structure. I am in the process of finding the exact thermodynamic condition to convert Rutie TiO2 to Anatase TiO2 phase. However I am presenting a research paper on reversible phase transformation from Rutile to Anatase and back to Rutile (controllable ratio of mixed phase) in SAMPE 2016 symposium on 24th May 2016 at Long beach CA, USA.    

Dear Jonathan,

In my opinion, the volume and initial concentration of p-nitrosodimethylanyline (RNO) depend on your system. For example, if you generate hydroxyl radicals by an electrochemical system using large electrodes, you need a larger reactor. If your method has a high rate of generation of OH radicals using a low concentration of the RNO, you will see complete bleaching with little reaction time. You could start with 10 mg/L.

You only need to perform this bleaching method in the presence and absence of your thiol in the same conditions in order to compare.

See J Appl Electrochem (2011), 41: 599-607 and Journal of Photochemistry and Photobiology A: Chemistry (2010) 216:244-249.

Hope this helps.

Best regards.

It is pretty well known that p-type a-Si:H oxidizes quite easily/quickly compared to n-type a-Si:H and intrinsic a-Si:H. This is related to the higher density of defects in p-type a-Si:H.

Dear Ali Farhat,

How well chlorine works in water, depends on what the pH level is. At a p^H of 8.0, chlorine is only 20% effective! That means green and cloudy water and dangerous bacteria. The higher the pH, the less effective chlorine is. At a pH between 7.4 – 7.6, chlorine works best.

Chlorine is a gas. It does not have a pH value. However, if the chlorine gas is dissolved in water, the following occurs: 

Cl₂ + H₂O → HOCl + HCl 

hypochlorous acid (HOCl) and hydrochloric acid are formed. Obviously these are acid solutions, and the pH will be below 7.00. The actual figure will depend on the concentrration.

 At p^H 0, Chlorine in water is present as Chlorine gas – Cl₂. With rising pH, Chlorine reacts with water to form Hypochloric acid - HOCl. In the range of pH 2-6, this is the prominent compound. At higher pH values, Hypochloric acid is neutralized to form its corresponding salt ion, the Hypochlorite ion – ClO-. At approx. pH 9, the neutralisation is complete. The disinfection activity of Hypochlorite is only 1% of that of the Hypochloric acid. As a result of its reaction with water, Chlorine remains in solution for several hours, depending on temperature, circulation etc. 

Regards,

Prem Baboo

This is a good question. Standard redox potential does not mean the potential at pH 0, BUT shout be the one as redox couple is at 1 mol/L. To answer this question, please read the original papers by Neta and Huie, or contact the authors directly..Good luck!

Dear Ammar,

The following publications describes materials that can be degraded by hydrothermal process:

1-Method for hot and supercritical water oxidation of material with addition of specific reactants

US 5837149 A

ABSTRACT

This invention relates to a process for the decomposition of material selected from the group consisting of organic compounds, inorganic compounds, or combinations thereof to compounds which are environmentally acceptable, or are amenable to further degradation by conventional disposal systems to produce environmentally acceptable products, which process comprises: (a) conveying an aqueous solution or an aqueous slurry of material into a reaction zone capable of withstanding the temperatures and pressures of decomposition of the material; (b) contacting the material in the reaction zone with aqueous sodium carbonate as a reactant in an amount effective to decompose the material under hot water or supercritical water oxidation conditions of between about 300° and 600° C. and a pressure of between about 20 and 400 atmospheres for between 0.1 and 120 min, wherein the sodium carbonate at the reaction conditions is present at about 10% or less as a water soluble salt as compared to the solubility of the salt at ambient conditions, wherein the process occurs in the presence of a gaseous oxidant present in an amount of between about 0.1 and 50% by weight of the material; (c) producing about 99% or greater of the decomposition of the material, or 99% or greater conversion of the material to compounds which are environmentally acceptable or to compounds which are amendable to further degradation; and (d) optionally degrading further the compounds produced in step (c) by reaction to environmentally acceptable products. Preferably, the specific reactant is sodium carbonate and the oxidant is oxygen or air.

2-Utilization of Sub and Supercritical Water Reactions

in Resource Recovery of Biomass Wastes

Wahyudiono1,a

, Siti Machmudah1,2,b, and Motonobu Goto1

Abstract. Recently, the utilization of sub and supercritical water has been proposed to recover waste substances from biomass. This is important not only for prevention of environmental issues, but also for rational utilization of natural resources. Sub and supercritical water treatment is one of the most effective methods for this, because water at high temperature and high pressure behaves as a reaction medium with remarkable properties. This sub and supercritical water treatment process can promote various reactions such as oxidation, hydrolysis, and dehydration. Therefore, sub and supercritical water can be used for the conversion of organic wastes to useful chemical compounds, as well as for oxidizing hazardous waste into CO2 or harmless compounds. This paper presents the concepts of sub and supercritical water and their application in organic waste recycling at temperatures of 423 – 673 K for substances such as lignin and its derived

compounds.

To view the full paper, please see attached file.

3- ORIGINAL ARTICLEJournal of Material Cycles and Waste Management

September 2007, Volume 9, Issue 2, pp 173-181

First online: 26 September 2007

Noncatalytic liquefaction of tar with low-temperature hydrothermal treatment

Wahyudiono

, Mitsuru Sasaki 

, Motonobu Goto

Abstract

Water at hydrothermal and supercritical conditions is considered a promising solvent for the degradation of hazardous waste into harmless compounds. Tar liquefaction experiments were conducted using a batch-type reactor at temperatures between 623 K and 673 K and at pressures between 25 and 40 MPa. A reaction mechanism for tar liquefaction is proposed. Moreover, on the basis of the experimental results, this method could become an efficient method for tar liquefaction, producing high yields of valuable chemical intermediates.

4-Method for hot and supercritical water oxidation of material using specific

reactants

from halogenated organic compounds, to compounds which are environmentally acceptable, or are amenable to further degradation by conventional disposal systems to produce environmentally acceptable products, which process comprises: (a) conveying an aqueous solution or an aqueous slurry of material into a reaction zone capable of withstanding the temperatures and pressures of decomposition of the material; (b) contacting the material in the reaction zone with aqueous sodium carbonate as a reactant in an amount effective to decompose the material under hydrothermal oxidation conditions of between about 300 and 600 ~C and a pressure of between about 10 and 400 atmospheres for between 0.01 and 120 min wherein the specific reactant, a carbonate such as sodium carbonate, at the reaction conditions is present at about 10 % or less as a water-soluble salt as compared to the solubility of the salt at ambient conditions wherein the specific reactant is essentially present as a solid and the oxidation occurs under heterogeneous conditions, wherein the process occurs in the presence of a gaseous oxidant wherein said oxidant is present in an amount of between about 0.01 and 50 % by weight of the material;

(c) producing about 99 % or greater of the decomposition of the material, or 99 % or greater conversion of the material to compounds which are environmentally acceptable or to compounds which are amendable to further degradation; and (d) optionally degrading further the compounds produced in step (c) by reaction to environmentally acceptable products. Preferably, the specific reactant is sodium carbonate and the oxidant is oxygen or air.

Preferably, the halogenated organic compound is selected from polychlorobiphenyl, polybromobiphenyl mono-chlorobenzodioxin or poly-chlorobenzodioxin compound

Hoping this will be helpful,

Rafik

Hi, we just add the powder to a beaker and heat it under continuous stirring. We have done this for all our experiments and I discussed this with other scientists at conferences in past. It goes slow, but it does dissolve. Maybe ultrasonication is dangerous as it may induce molecular changes.

Ok, I will have a look on these reviews.  Thank you.

During heating processes, N₂ and CO₂ are used for two different things:

It's also guaranteed that Cr(VI) will be reduced by Na2SO3

Have a look on my papers. In the course of doctorate I worked with a highly loaded wastewater, maybe these articles are usefull for you.

To correctly interpret whatever results, all details MUST be available. No detail data, no answer. 

Try to find Pourbaix diagram for your systems. There are lines which gives information about water redox stability in the selected pH. I hope it is what you need. Best wishes.

Hi  Jixing Cui,

I would try to explain it in the following lines

Rate Expression

-(dM/dt) = I₀ phi f (1-exp(-A_t))

phi = quantum yield

I₀ = Incident radiation flux

f = Ratio of light absorbed by the M (organic compound) and other components 

A_t = Total absorbance of the solution time a factor 2.3.

Which further reduces to:

r_M = - ln(10) phi epsilon [M] I₀            (Leifer, 1988)

Where

epsilon = Molar extinction co-efficient  (M^-1 cm^-1)

I would recommend you to read following research articles + books as much as you can

Regards

Tipu Sultan

Freeze drying would help. Maybe try to centrifugate first a really low temperature, in fact, if you put your glass in which there is your GO into the fridge, you will see some differences after some days.

Regards

Adrian

I think the answers given are mostly pretty good, except that which reducing agent or chelating agent or scavenger is the best choice clearly depends on the objectives of the experiment. Chelators such as those mentioned are effective, but leave unreacted H2O2. The reducing agents produce new products and may glom up the reaction mixture as far as product characterization is concerned. Scavengers such as ethanol form oxidation products such as acetaldehyde or formaldehyde, which are reactive intheir own rights with many classes of compounds

That can be determined by measuring the zeta-potential of activated carbon as a function of the solution pH. The pH where zero zeta potential is reached is referred as isoelectrical point.

If you repeat the experiment i suggest that you use your photometer to measure spectra of the reaction mixture at each time point you sample. You can compare the spectra that develop with reference spectra of e.g. phenol and benzoquinol. If the mixture isn't buffered do check if pH changes over the treatment. Decreasing pH will indicate the formation of phenol. 

Ted is right. Be careful...

Water is not enough by itself, and the washing must be extensive.

Therefore, better using a solution of HCl refluxing for several days in a Soxhlet extractor. After this, water must be used in the same conditions until the pH of the rinse if neutral. A bit long, but very efficient.

Alain

Dear collegues!

I would like to note what there are differences between TBARS and MDA. Of course, You could be use manual methods for determination both, but... in ours laboratory for this needs use kit' s produced Cell Biolabs company or (for MDA and 4-HNE) determination kit' s FR 22 (Lubioscience, Switzerland).  the best way, I mean, use microplate reader (for ELISA method). Such plate' s need hiting (till +98C), best equipment for it  - Thermomixer (Eppendorff). If You have really interest, I can send you Cell Biolabs product catalog for 2015. there are possibility to buy  ''training and examination''  kits, and for manual and plate technology. Good luck.

The short answer seems to be yes:

The process patent expired in 2014.

In This Process you inoculate Oxygen with specific Air Pump.

For Concentrate leaching, you should be supply required Oxygen to autoclave.

Best wishes

It should be selective for OH radicals, but I'm not sure if it will not react also with superoxide radical.

Benzoic acid is also good, but you'll get various hydroxybenzoic acids so the detection can be unclear.

I'm using terephtalic acid. It gives only one product, and the detection is with emission spectroscopy.

Hydrogen peroxide -- as mentioned by others -- if present in solution will contribute to COD.  A mg/L of H2O2 increases COD by about 0.393 mg/L ; this value was obtained employing Milli-Q water spiked with varying concentrations of H2O2; you may do your own measurements employing distilled and deionized water or Milli-Q water, etc.

Addition of catalase also introduces error in COD measurement that has to be accounted for; this can be done by the following relation.

COD_COR = COD_S+C - COD_C

Where COD_S+C is COD of water sample after catalase addition and COD_C is COD of Milli-Q water with the same amount of catalase.

The theoretical oxygen demand includes the oxygen required to convert the ammonia to nitrate, which is sometimes called the "nitrogenous oxygen demand".

So, the theoretical oxygen demand (ThOD) is calculated as:

ThOD = (Oxygen required to convert your compound into CO₂, NH₃ and SO₂) + (Oxygen required to convert the produced NH₃ to NO₃^-)

The ammonia oxidation reaction is:

NH₃ + 2O₂ --> NO₃^- + H₂O + H⁺

So, for each mole of NH₃ your compound produces, two additional moles of O₂ will be required to satisfy the nitrogenous oxygen demand.