Investigation of adsorption of dyes onto modified titanium dioxide

Titanium dioxide (TiO2) nanoparticles with different sizes and crystalloid structures produced by the thermal method and doped with silver iodide (AgI), nitrogen (N), sulphur (S) and carbon (C) were applied as adsorbents. The adsorption of Methyl Violet (MV), Methylene Blue (MB), Methyl Orange (MO) and Orange II on the surface of these particles was studied. The photocatalytic activity of some particles for the destruction of MV and Orange II was evaluated under sunlight and visible light. The equilibrium adsorption data were fitted to the Langmuir, Freundlich, Langmuir-Freundlich and Temkin isotherms. The equilibrium data show that TiO2 particles with larger sizes and doped with AgI, N, S and C have the highest adsorption capacity for the dyes. The kinetic data followed the pseudo-first order and pseudo-second order models, while desorption data fitted the zero order, first order and second order models. The highest adsorption rate constant was observed for the TiO2 with the highest anatase phase percentage. Factors such as anatase crystalloid structure, particle size and doping with AgI affect the photocatalytic activity significantly. Increasing the rutile phase percentage also decreases the tendency to desorption for N-TiO2 and S-TiO2. Adsorption was not found to be important in the photocatalytic decomposition of MV in an investigation with differently sized AgI-TiO2 nanoparticles. Nevertheless C-TiO2 was found to have higher adsorption activity onto Orange II, as the adsorption role of carbon approached synchronicity with the oxidation role.

Understanding the adsorption of salmon calcitonin, antimicrobial peptide AP114 and polymyxin B onto lipid nanocapsules

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Adsorption of aromatic compound by multi-walled carbon nanotube from sea water

It is global concern that soil and water were contaminated with organic substances such as BTEX (benzene) (B), toluene (T) and xylene (x) .The presence of excessive amounts of BTEX in aqueous surroundings may have a greatly adverse impact on water quality and thus endanger public health and welfare. Carbon nanotubes (CNT) have aroused widespread attention as a new type of adsorptions due to their outstanding ability for the removal of various inorganic and organic pollutants from large volume of wastewater. Due to variety of adsorbent and their ability to adsorb pollutant, it is possible to reduce expenses and completely omit pollutant. In this CNT is used as a new adsorbent for removal pollutant such as benzene, toluene, and xylene. The result in the area of adsorbing benzene, toluene, and xylene is as follows: the changes of pH don’t affect the capacity of adsorption and the greatest amount of adsorption occurs in pH. The greatest amount of adsorption occurs when using 0.01gr CNT oxidized. Comparing CNT with CNT oxidized in term of adsorption capacity, it is proved that the adsorption capacity of CNT oxidized is much more than CNT. The result of comparing the percentage of adsorption of mentioned elements (B, X, T) is as follows; the amount of adsorption of xylene is more than toluene and toluene is more than benzene. It should be mentioned that in this research the percentage of adsorption to measure is between to 70-80.

Towards a Bourdieusian analysis of the disabled body and practice: embodying negative symbolic capitals and the uneasy experience of hysteresis

Within the last few years, disabled people have become the target of government austerity measures through drastic cuts to welfare justified through the portrayal of benefit claimants as inactive, problem citizens who are wilfully unemployed. For all that is wrong with these cuts, they are one of many aspects of exclusion that disabled people face. Attitudes towards disability are deteriorating (Scope, 2011) and disabled people are devalued and negatively positioned in a myriad of ways, meaning that an understanding of the perceptions and positioning of disability and the power of disabling practices is critical. This thesis will examine how Bourdieu’s theoretical repertoire may be applied to the area of Disability Studies in order to discern how society produces oppressive and exclusionary systems of classification which structures the social position and perceptions of disability. The composite nature of disability and multiple forms of exclusion and inequality associated with it benefits from a multipronged approach which acknowledges personal, embodied and psychological aspects of disability alongside socio-political and cultural conceptualisations. Bourdieu’s approach is one in which the micro and macro aspects of social life are brought together through their meso interplay and provides a thorough analysis of the many aspects of disability.

Porosity in ion-exchanged and acid activated clays evaluated using n-nonane pre-adsorption

The applicability of the n-nonane pre-adsorption method for characterising the porosity in clays is presented. Na-SD, a Na+-exchanged purified bentonite, and materials obtained by Al3+-exchange and acid treatments of Na-SD and SAz-1 were used. Nitrogen adsorption isotherms, at -196 ºC, were determined before and after n-nonane pre-adsorption on each of the samples. In all materials, n-nonane remained adsorbed in ultramicropores after outgassing at 25 ºC. Outgassing at higher temperatures (50, 75 and 200 ºC) removed nonane and ultramicropores became available for nitrogen adsorption. All treatments on Na-SD led to increase in micropore volume. Larger ultramicropore and supermicropore volumes were obtained for Na-SD acid activated with HCl at 95 ºC than for treatments at 25 ºC with HCl or following Al3+-exchange (Al-SD), and increased with increasing acid concentration to 3 M. Activation with 4 M HCl led to the largest pore volume with contribution from mesopores. However, the specific external surface area was the same as that obtained for Na-SD, Al-SD and for most of the other acid activated samples. Treatments at 95 ºC with 1 M and 6 M HCl promoted increase in specific external surface area. The micropore volumes and specific external surface area for SAz-1 treated with 1 M HCl at 95 ºC were larger than those of Al-SAz-1, but lower than those obtained for corresponding materials derived from Na-SD. The n-nonane pre-adsorption method enabled micropore volumes and specific external surface areas to be obtained for all samples.

CO2 capture by adsorption in post combustion processes

Global concentration of CO2 in the atmosphere is increasing rapidly. CO2 emissions have huge impact on global climate change. Therefore, efficient CO2 emission abatement strategies such as Carbon Capture and Storage (CCS) are required to combat this phenomenon. There are three major approaches for CCS: - Post-combustion capture; - Pre-combustion capture; - Oxyfuel process. Post-combustion capture offers some advantages in terms of cost as existing combustion technologies can still be used without radical changes on them. This makes post-combustion capture easier to implement as a retrofit option compared to the other two approaches. Therefore, post-combustion capture is probably the first technology that will be deployed on a large scale. The aim of this work is to study the adsorption equilibrium of CO2, CH4 and N2 in zeolite 5A at 40ºC. For this, experiments were performed to determine the isotherms of adsorption of CO2, CH4 and N2 near 40ºC with the conditions of the post-combustion capture processes. It has been found that the 5A zeolite adsorbs a significant quantity of CO2 values of about 5 mol/kg at a pressure of 5 bar.

An electroanalytical application of 2-aminothiazole-modified silica gel after adsorption and separation of Hg(II) from heavy metals in aqueous solution

2-Aminothiazole covalently attached to a silica gel surface was prepared in order to obtain an adsorbent for Hg(II) ions having the following characteristics: good sorption capacity, chemical stability under conditions of use, and, especially, high selectivity. The accumulation voltammetry of mercury(II) was investigated at a carbon paste electrode chemically modified with silica gel functionalized with 2-aminothiazole (SIAMT-CPE). The repetitive cyclic voltammogram of mercury(II) solution in the potential range -0.2 to + 0.6 V versus Ag/AgCl (0.02 mol L-1 KNO3; V = 20 mV s(-1)) show two peaks one at about 0.1 V and other at 0.205 V. The anodic wave peak at 0.205 V is well defined and does not change during the cycles and it was therefore further investigated for analytical purposes using differential pulse anodic stripping voltammetry in differents supporting electrolytes. The mercury response was evaluated with respect to pH, electrode composition, preconcentration time, mercury concentration, cleaning solution, possible interferences and other variables. The precision for six determinations (n = 6) of 0.02 and 0.20 mg L-1 Hg(II) was 4.1 and 3.5% (relative standard deviation), respectively. The detection limit was estimated as 0.10 mu g L-1 mercury(II) by means of 3:1 current-to-noise ratio in connection with the optimization of the various parameters involved and using the highest-possible analyser sensitivity. (c) 2006 Elsevier Ltd. All rights reserved.

Kinetics and Adsorption Isotherms of Bisphenol A, Estrone, 17 beta-Estradiol, and 17 alpha-Ethinylestradiol in Tropical Sediment Samples

The sorption of four endocrine disruptors, bisphenol A (BPA), estrone (E1), 17 beta-estradiol (E2), and 17 alpha-ethinylestradiol (EE2) in tropical sediment samples was studied in batch mode under different conditions of pH, time, and sediment amount. Data obtained from sorption experiments using the endocrine disruptors (EDs) and sediments containing different amounts of organic matter showed that there was a greater interaction between the EDs and organic matter (OM) present in the sediment, particularly at lower pH values. The pseudosecond order kinetics model successfully explained the interaction between the EDs and the sediment samples. The theoretical and experimentally obtained q (e) values were similar, and k values were smaller for higher SOM contents. The k (F) values, obtained from the Freundlich isotherms, varied in the ranges 4.2-7.4 x 10(-2) (higher OM sediment sample, S(2)) and 1.7 x 10(-3)-3.1 x 10(-2) (lower OM sediment sample, S(1)), the latter case indicating an interaction with the sediment that increased in the order: EE2 > > E2 > E1 > BPA. These results demonstrate that the availability of endocrine disruptors may be directly related to the presence of organic material in sediment samples. Studies of this kind provide an important means of understanding the mobility, transport, and/or reactivity of this type of emergent contaminant in aquatic systems.

Pore size distributions derived from adsorption isotherms, immersion calorimetry, and isosteric heats: A comparative study

We compare the pore size distribution of a well-characterized activated carbon derived from model-dependent, adsorption integral equation (AIE) methods with those from model-independent, immersion calorimetry and isosteric heat analyses. The AIE approach applied to nitrogen gave a mean pore width of 0.57 nm; the CO2 distribution exhibited wider dispersion. Spherical model application to CO2 and diffusion limitations for nitrogen and argon were proposed as primary reasons for inconsistency. Immersion enthalpy revealed a sharp decrease in available area equivalent to a cut-off due to molecular exclusion when the accessible surface was assessed against probe kinetic diameter. Mean pore width was identified as 0.58 ± 0.02 nm, endorsing the underlying assumptions for the nitrogen-based AIE approach. A comparison of the zero-coverage isosteric heat of adsorption for various non-polar adsorptives by the porous test sample was compared with the same adsorptives in contact with a non-porous reference adsorbent, leading to an energy ratio or adsorption enhancement factor. A linear relationship between the energy ratio and probe kinetic diameter indicated a primary pore size at 0.59 nm. The advantage of this enthalpy, model-independent methods over AIE were due to no assumptions regarding probe molecular shape, and no assumptions for pore shape and/or connectivity.

Post-combustion CO2 adsorption on activated carbons with different textural properties

Fixed bed CO2 adsorption tests were carried out in model flue-gas streams onto two commercial activated carbons, namely Filtrasorb 400 and Nuchar RGC30, at 303 K, 323 K and 353 K. Thermodynamic adsorption results highlighted that the presence of a narrower micropore size distribution with a prevailing contribution of very small pore diameters, observed for Filtrasorb 400, is a key factor in determining a higher CO2 capture capacity, mostly at low temperature. These experimental evidences were also corroborated by the higher value of the isosteric heat derived for Filtrasorb 400, testifying stronger interactions with CO2 molecules with respect to Nuchar RGC30. Dynamic adsorption results on the investigated sorbents highlighted the important role played by both a greater contribution of mesopores and the presence of wider micropores for Nuchar RGC30 in establishing faster capture kinetics with respect to Filtrasorb 400, in particular at 303 K. Furthermore, the modeling analysis of 15% CO2 breakthrough curves allowed identifying intraparticle diffusion as the rate-determining step of the process.