L3: BIG STATA CONCEPTS Getting started with Stata Angela Ambroz May 2015.
Diego Alonso Martínez Filip Ambroz Javier Marqués de Marino.
-
Upload
joy-mae-young -
Category
Documents
-
view
219 -
download
0
Transcript of Diego Alonso Martínez Filip Ambroz Javier Marqués de Marino.
RECOVERY,CONCENTRATION AND PURIFICATION
OF PHENOLICCOMPOUNDS BY
ADSORPTIONDiego Alonso Martínez
Filip AmbrozJavier Marqués de Marino
Substances who contains phenol are very dangerous to the environment at high
concentration, so therefore there are very unwanted things in nature. They are not harm in
low concentrations like 0,002 mg/L, but higher conc. can cause unpleasant taste in drinking water, they
can even adsorbed through the skin. They are also very useful, we use them in medicine, for example
as disinfectants or medical preparations, they have chemopreventive properties too, so they can be
useful in treatments of cancer.
TECHNOLOGIES Like we heard before, phenols are not environmental friendly so
therefore we need some technologies to sustained water quality. We divide these techn. to three groups. biological, chemical and physically operations.
In physically operations we have: sedimentation, flotation, filtration, flow equalization…
In chemically operations there are: adsorption, disinfection, dechlorination…
In biological operations: trickling filters, pond stabilization, anaerobic digestion, biological nutrient removal…
The most widely used treatment is biological because is the most cheapest, here is very important fact that bacteria is able to accumulate and degrade different pollutants but, these treatment is incapable to remove phenol from process. This is a big problem so therefore we have to use also chemical techniques which remove phenols, but these techniques are very expensive. They are so expensive because we need a lot of electrical energy for them and also we need a lot of chemical reagent. We have also some alternatives like oxidation processes but this is still very costly. We have also physical techniques, which are widely used but here we also have a problem. In this technique we have membrane processes but this processes don’t have a long lifetime so we have to change them a lot of times and this is costly.
Because of all this things adsorption is the most popular method for removal pollutants.
ADSORPTION
Is also very efficient. Here we use activated carbon for adsorbent, because it has very good adsorption properties for organic pollutants. Activated carbon has high-surface area, pore volume and porosity. But here we again have an economic problem. Activated carbon has high cost for an expensive regeneration system. In adsorption there is also important ionic strength and pH. At acid pH the uptake of phenolics is enhanced, but alkaline pH decreases adsorption. In adsorption is very important also the temperature, if we have high temperature then we have irreversible interactions, which favores adsorption.
Adsorption is also very important for practical operations, because of the interactions of adsorbate-adsorbent. Here we have Langmuir isotherm, this isotherm is wifely used equation. We use it when we have uniform adsorption energies at the adsorbent surface. When we have nonideal system we use the Freundlich isotherm. This isotherm is also very important, because it gives
good interpretation of concentration range.
EQUATIONSFreundlich equation:ln(q)= ln(Kf) + 1/nCe
Langmuir equation:Ce/Qe=1/Kl +(b/Kl) Ce
Dubinin-Radushkevic equation:E= R T e*(1/Ce)
These equation is very important, because information was obtained from the adsorbtion experience with p-CP and p-NP. We use connection between Freundlich and Dubinin-Radushkevic to interpret the result. Another important thing is Lewis acid-base theory, which modified clays including metal cations can be considered as Lewis acids, while phenolic compounds can be regarded as Lewis bases and Bronsted acids. Her is very tough to predict adsorption capacity, because it depends on the adsorbent property, the solution conditions and the interactions at the solid-liquid interface. We get majority informations from the experiments of adsorption.
Here we have also reversible and irreversible adsorption. Reversible adsorption we have, when we have physical adsorption, because here are important van der Waals forces, which are very weak so this thing has affect on the adsorption. If we have chemisorptions and oxidative polymerization of phenolics we have irreversible adsorption.
Imoportant method to control adsorption is electrosorption. Here
we have electrostatic field, which is applied to the surface of the electrodes and it is immersed in an electrolyte solution.
Activated Carbon
Waste materials by-products Coal Coal-iron
-nitric acid Mechanims control
Low-cost waste materials
Ozonation of activated carbons
High toxicity for human beings and aquatic life. Biological treatment not allowed.
Activated carbons (GAC) adsorb phenols.
Ozone treatments: used to fix SOG.
Description: phenolic compounds
SOG refers to Surface Oxygen Groups on the GAC.
Improvement on the phenol adsorption: - Bonds between carbonyl groups and OH groups of phenols.
Ozone produce SOG on the GAC surface.
What is SOG?
Two different GAC (F400, AQ40) at two temperatures (25 and 100 ºC).
Four experiments with ozonation, four without it.
Compounds : phenol (P), chlorophenol (PCP) and nitrophenol (PNP).
Experimentation
Enlarging of micropores: gasification.
Microporosity blockage: SOG fixed.
Temperature as an important factor: - 25ºC: only C=0 SOG. - 100ºC : different kinds of SOG.
RESULTS AFTER OZONATION
Adsorption of P, PNP and PCP depends on: - Chemistry of adsorbates. - Porosity and surface of adsorbent. - Temperature
Ozonation decrease the adsorption capacity:
- Create more bonds with water. - This blocks the access for the phenols.
Conclusions
Carbon Nanotubes Materials Results
◦ diameter◦ Effects
Aromaticy -OH hydrogen bonds
Polymeric adsorbents
GAC capacity is higher than the polymeric one : its hydrophobic surface produces low contact with aqueous solutions.
1990: “Hypercrosslinking Technique”:
- More easily wetted. - Higher adsorption
Comparison GAC- Polymeric
Two resins:
- XAD-4: polystyrene-based. - NJ-8: hypercrossed.
Four adsorbates:
- Phenol -P-chlorophenol. - P-cresol -P-nitrophenol.
Experiment
Four steps: 1. Synthesis of macroporous polymer. 2. Chlorometylation. 3. Crosslinking. 4. Filtration and drying.
Elaboration of NJ-8
Adsorption capacity - Two times higher for NJ-8 than for XAD-4.
Physical adsorption in all the experiments. - Negative values of isosteric enthalpies.
NJ8 does not trap phenol molecules - The amount of desorbant remains
constant.
RESULTS
Natural Materials
Clay Classes Price Physical properties Improvements Clarion vs vlinoptylolite
Ciliceous, Zeolite & Biadsorbents Ciliceous
◦ Physics properties◦ Improvements
Zeolite◦ Physics properties◦ Improvements
Biadsorbents◦ Physics properties◦ improvements
Peat & biomass Peat
◦ Limitations◦ Pre-treatments
Biomass◦ Affinity with microbial species◦ Working Specifics conditions
Wastes materials Agricultural
◦ Sawdust◦ Bark
Industrial◦ Fly ash◦ Sludge◦ Red mud
(1)Ahmaruzzaman, md. «elsevier.» 22 de julio de 2008. www.elsevier.com/locate/cis (último acceso: 5 de 10 de 2011).
(2) Aimi Li, Quanxing Zhang, Gencheng Zhan, Jinlong Chen, Zhenghao Fei, Fuqiang Liu. «chemosphere.» 25 de septiembre de 2001. www.elsevier.com/locate/chemosphere (último acceso: 5 de 10 de 2011).
(3) Daohui lin, Baoshan xing. «environ. sci. technol.» 24 de julio de 2008. http://pubs.acs.org/doi/abs/10.1021/es801297u (último acceso: 5 de 10 de 2011).
Bibliography
(4) Maria Luisa Soto, Andres Moure, Herminia Dominguez, Juan Carlos Parajó. «journal of food engineering.» 5 de febrero de 2011. www.elsevier.com/locate/jfoodeng (último acceso: 5 de 10 de 2011).
(5) Mehmet Akçay, Gülten Akçay. «journal of hazardous materials.» 21 de agosto de 2004. www.elservier.com/locate/jhazmat (último acceso: 5 de 10 de 2011).
(6) P.M.alvarez, J.F.Garcia-Araya, F.J.Beltran, F.J.Masa, F.Medina. «journal of colloid and interface science.» 16 de diciembre de 2004. www.elsevier.com/locate/jcis (último acceso: 5 de 10 de 2011).
Bibliography