Thermodynamic study of PCB-153 passing into single walled carbon nanotube (8,8)

Polychlorinated biphenyl (PCBs) are high resistant pollutants which cause adverse health effects in recent years. The accumulation of these toxic compounds in the food chain lead to oxidative stress in various ecosystems. Detection, absorption, and elimination of them are an environmental priority. Passing of PCB-153 through the armchair single walled carbon nanotube (SWNT) (8,8) were investigated by MNDO in semi-empirical quantum method. Calculated electrical and thermodynamic properties show a sudden change in the middle of the tube which may act as a trap for the studied pollutant. The results indicated the nanotube has considerable ability to interact with PCB-153 and cause its degradation. According to calculated thermodynamic parameters through the molecular modeling, it is expected that single wall carbon nanotube is a candidate in remediation of PCBs as well as in gas sensor devices for detection of them. The median tube is a place for trapping pollutants

Investigation of Conversion CO2 to Fuel by TiN nanotube-Cu nanoparticle

The CO and CO2 effects are global warming, acid rain, limit visibility, decreases UV radiation; yellow/black color over cities and so on. In this study, convention of CO2 and H2O to CH4 and O2 near TiN- nanotube with Cu-nanoparticle calculated by Density Functional Theory (DFT) methods. We have studied the structural, total energy, thermodynamic properties of these systems at room temperature. All the geometry optimization structures were carried out using GAMESS program package under Linux. DFT optimized their intermediates and transient states. The results have shown a sensitivity enhancement in resistance and capacitance when CO2 and H2O are converted to CH4 and O2. TiN-nanotube used photo-catalytic reactivity for the reduction of CO2 with H2O to form CH4 and O2 at 298K. The calculations are done in state them between of three TiN-nanotubes near Cu-nanoparticle.The calculation shown which heat reaction formation (∆H) is endothermic for this reaction. This reaction needs to sun, photo active or other energy in the presence of visible light for doing

Simulation of Heavy Metal Removal by α-Keratin Nano-Structure of Human Hair from Environment

Abstract Including heavy metals are environmental pollutants that human exposure through some of their water and food poisoning can be acute and chronic and sometimes dangerous to establish. Lead can enter the human body and animals by entering the food chain through the feeding and breathing polluted air and they will cause poisoning. In this study, keratin fibers nano-structure is used for Pb 2+ removal from environment. The keratin fibers using are low cost related to other methods. The interaction of them is simulated and the ab intio calculations at the density function level of theory (DFT) showed energy and thermodynamic properties changing for this interaction. The cystine in α-keratin is simulated and calculated approached to Pb ions in different distances. There is disulfide bond (-SS-) in cystine, for cation ions adsorbed in hair human fibers. The results shown this method is exothermic, spontaneous and favourable for heavy metals in environment

Recycling Monoethylene Glycol (MEG) from the Recirculating Waste of an Ethylene Oxide Unit

In the ethylene glycol generation unit of petrochemical plants, first a reaction of ethylene oxide takes place which is then followed by other side reactions. These reactions include water absorption with ethylene oxide, which leads to the generation of formaldehyde and acetaldehyde. Over the lifetime of the alpha-alumina-based silver catalyst there is an increase in side reactions, increasing the amount of the formaldehyde and acetaldehyde generated by the ethylene oxide reactor which leads to reduced MEG product purity. Given the need of a petrochemical complex to further strip the aldehyde (formaldehyde and acetaldehyde) to increase the quality of the MEG and increase the lifetime of the alpha-alumina-based silver catalyst, resin beds are designed and their surface absorption capacity is investigated to optimize aldehyde (formaldehyde and acetaldehyde) removal in the recirculating water flow of the ethylene oxide unit. Experiments show that the ion exchange system based on strong anionic resin pre-treated with a sodium bisulfite solution can reduce the aldehyde level from about 300ppm to less than 5ppm. After the resin is saturated with aldehyde, the resin can be recycled using the sodium bisulfite solution which is a cheap chemical substance

Investigation of the removal of chromium (VI) by Nanocomposites Chitosan-tragacanth solution from aqueous solution

Background: The aim of this study was to investigate the removal of chromium (VI) by Nanocomposites Chitosan-tragacanth solution from aqueous solution. Methods: In this study, chitosan-tragacanth nanocomposites were synthesized and analyzed by electron microscopy (SEM), (TEM) and Fourier transform spectroscopy (FT-IR) for the size and shape of the surface. The nano-composite of chitosan-tragacanth, for the adsorption of chromium (VI) in aqueous solution was used as adsorbent. Results: The optimum conditions with multiple experiments to enhance the absorption were evaluated. The highest absorption of Cr (VI) was occurred in the adsorbent dosage of 0.2 g, 8 ppm concentration of chromium ions, the pH=6 and also retention time of 50 min; in 298 ˚K temperature. After determining optimal conditions of adsorption, isotherms equations and study and thermodynamic parameters were applied. Adsorption process of chromium (VI) on nano-composite chitosan - Tragacanth was conformed with Temkin isotherm. Conclusion: The thermodynamic parameters such as standard Gibbs free energy changes, changes in enthalpy and entropy changes in the standard showed that the adsorption process of Cr (VI) is spontaneous and heating, and kinetics studies of models Lagergren, Ho , Alovich and intraparticle is used, the results show that the adsorption kinetics follows the pseudo-second order

Diameter of Single-Walled Carbon Nanotubes (SWCNTs) as an Effective Factor in the Detection and Degradation of PCBs

Polychlorinated biphenyls (PCBs) are chlorinated organic compounds and well known carcinogenic and toxic pollutants. Currently, their detection and degradation to products with less risk are among environmental and health priorities. Passing 2,2′,4,4′,5,5′-Hexachlorobiphenyl (PCB-153) through the armchair single-walled carbon nanotubes (SWCNTs) (8, 8) and (10, 10) was investigated by Modified Neglect of Diatomic Overlap in the semi-empirical method. The analysis of results suggests that there are meaningful changes in the middle of the tubes. Based on the obtained evidence, the nanotubes have substantial potential to interact with the PCB-153 molecule effectively. The results show that the increased diameter in the armchair SWCNTs improves the detection and degradation potential of the tube to PCBs. According to the calculated thermodynamic parameters, the diameter of nano-structures is an effective factor in PCBs removal efficiency, as it could be helpful to make a more sensitive PCB nano-sensor

Sensitivity Investigation of SW-B<inf>80</inf>N<inf>80</inf> Nanotube to Polychlorinated Biphenyl-153 (PCB-153): DFT Methods

Polychlorinated biphenyls (PCBs) is one of the most persistent organic pollutants that exist in the atmosphere and can be concentrated in lithosphere and hydrosphere. Because of low biodegradability and lipophilicity, PCBs accumulate in fatty tissues and through oxidative stress could lead to cancers and central nervous system disorders. Currently, degradation of these synthetic pollutants is one of the environmental issues. The aim of this study is to provide a sensor for detection of PCB-153 (PCB-153). Nano boron nitride compounds (BnNm) are magic materials with high stability that can be used as a sensor for detection of chlorinated aromatic compounds. In this study, sensitivity of B80N80 as a form of single-walled boron nitride nanotubes (SW-B80N80 nanotube (8,8)) to PCB-153 has been investigated. The PCB-153 is closed to the SW-B80N80 nanotube and electron exchanges between them have been evaluated using density functional calculations by B3LYP/6–31G* method. The calculation of the electronic properties has shown that SW-B80N80 nanotube is very sensitive to the presence of PCB-153 molecules. The HOMO/LUMO and gap energy (Eg) changes were considerable. Gap energy decreased from 4.214 eV to 2.022 eV during the formation of complex PCB-153-SW-B80N80 nanotube that leads to conversion of PCB-153 into the other products. According to thermodynamic parameter calculation through the IR-DFT method, it is expected that SW-B80N80 nanotube will be a suitable candidate in the elimination of PCB-153, as well as a gas sensor