Effect of Ozone on Removal of Dissolved Organic Matter and its Biodegradability and Adsorbability in Biotreated Textile Effluents

A study was conducted on the efficacy of ozonation in removing dissolved organic matter (DOM) in biotreated textile effluents and effects on its biodegradability and adsorbability. Results showed the efficient removal of color and fluorescence compounds were achieved through ozonation, due to increasing hydrophilicity and lowering molecular weight of DOM. A significant biodegradability improvement was also observed, and DOM adsorbability on activated carbon was highly dependent on ozone dosage. As the key parameter, consumed 3.8 g O₃/?g TOC₀ was the optimal dosage in the hybrid process combining ozonation with biological activated carbon (BAC) for wastewater reclamation.     

A comparison of novel ozone-based systems and photocatalysis for the removal of water pollutants

Three ozone-based systems and a photocatalytic system have been compared for the removal of a reactive dyestuff, orange RO16, and 2-chlorophenol in relation to degradation performances and ozone and energy consumptions. These systems were (1) liquid/gas–ozone (LGO): ozone was applied as it is produced in the gas phase; (2) liquid/solid–ozone (LSO): ozone was adsorbed on particulate silica-based material and then applied to water; (3) liquid/liquid–ozone (LLO): ozone was dissolved in a water-immiscible solvent and then applied to water; and (4) photocatalytic system using titanium dioxide catalyst (PHC). All four systems were capable of degrading the pollutants but presented different characteristics. The LSO system offered the possibility of using long contact times for slow ozone reactions and the LLO system is most suitable for fast ozone reactions. Both systems offer the prospect of more efficient use of ozone by extracting specific pollutants away from the water phase to the solid or the solvent phases. The PHC system presented the lowest rates and the highest energy consumptions by a factor of up to 400 times as compared to the ozone-based systems. The four systems were classified on the basis of their energy consumption as follows: for the degradation of RO16 (LLO相似文献   

New equipment for detection of polymer induced flocculation of cellulosic fibres by using image analysis — application to microparticle systems

The present investigation has shown that the use of image analysis can be a very efficient way to study the state of flocculation of cellulosic fibres. By an FFT analysis of the grey-values of the collected images, of the flowing fibres, it was possible to evaluate both a degree of flocculation of the fibres and an average diameter of the formed flocs. Calibration with model flocs correlated very well with earlier published data.Investigations regarding flocculation of unbleached cellulosic fibres caused by a microparticle based retention aid, i.e. a combined addition of a high molecular mass cationic polyacrylamide (C-PAM) and a bentonite clay, and a site blocking polymer (SBP) (a dimethylamine epichlorohydrine condensate) were also conducted. The results from these measurements show that a preadsorption of the SBP to a surface coverage of 50% of the fibres (i.e. of its saturation adsorption) resulted in a higher degree of flocculation upon addition of the C-PAM of the microparticle based flocculant. This is probably due to a more extended conformation of the C-PAM out from the surface of the cellulosic fibres. These results were also in accordance with earlier published theories. A simultaneous addition of SBP and C-PAM in the microparticle system was not as efficient, regarding flocculation, as a pre-adsorption of the SBP. This can be explained by the fact that the way that both the SBP and the C-PAM are adsorbed is affected by the way the polymers are added. In accordance with earlier publishd data the results indicate that the adsorption of SBP is strongly affected by the presence of the C-PAM.The results nevertheless show that an addition of a SBP has a positive effect on microparticle based retention aids.Finally the present results clearly demonstrate that the polymer addition levels in flocculation studies (which are relevant for practical use) are comparably low compared with saturation adsorption on the fibres and the difference in flocculating ability of differently charged C-PAM is small compared with their corresponding saturation adsorption. Further investigations in this area are strongly recommended.     

Asymptotically exact driving force approximation for intraparticle mass transfer rate in diffusion and adsorption processes: nonlinear isotherm systems with macropore diffusion control

An asymptotically exact nonlinear driving force model of intra-particle mass-transfer rate for nonlinear isotherm systems with macropore diffusion control is presented. The obtained expression is compared with the solutions of the Fickian diffusion and adsorption model and excellent accuracy over the entire time (fractional uptake) domain is demonstrated. In the case of an irreversible isotherm the model reduces to the equations resulting from the shrinking core model a fact that guarantees its accuracy for highly nonlinear systems. The high accuracy of the model is further demonstrated by comparison with experimental data under various operational conditions.     

A convenient synthesis of NiO-CuS/molecularly imprinted polymer nanocomposites with highly enhanced adsorption activity and selectivity for removal of Letrozole

ABSTRACT

In this study, Novel NiO-CuS nanocomposites were prepared by simple chemical method. The goal of this project was to apply the Letrozole (Anti-estrogen drug) template molecularly imprinted polymer (MIP) for the selective removal of Letrozole from aqueous samples. The NiO-CuS nanocomposites and NiO-CuS/MIP nanocomposites were specified by field emission scanning electron microscopy, X-ray diffraction, photoelectron spectroscopy, N₂ adsorption-desorption, and thermogravimetric analysis. The performance of the NiO-CuS and NiO-CuS/MIP nanocomposites was analyzed by optimizing various removal factors. The optimized data for adsorption process were 0.01 g/L: MIP, contact time: 40 min and pH: 7.0. The data was evaluated best by pseudo 1st and 2nd order equation which revealed a chemical adsorption of letrozole onto NiO-CuS and NiO-CuS/MIP particles, respectively. The result of R² values indicated that the adsorption data followed the Langmuir isotherm equation which defined that the binding agent happened on the homogeneous sites of adsorbent.     

Experimental and theoretical study of the adsorption of pure molecules and binary systems containing methane, carbon monoxide, carbon dioxide and nitrogen. Application to the syngas generation

This study takes place in the context of the use of a Synthesis Gas in Gas To Liquid process, liquid hydrocarbon production by conversion based on Fischer–Tropsch synthesis. Our aim is the process improvement by a selective recycling of the tail gas. So, we measure pure component isotherms for four gases (CO₂, CH₄, CO, N₂) of the tail gas until 2000 kPa and binary mixture (CO₂–CH₄; CO₂–N₂; CH₄–N₂) equilibria at 303.15 K and 400 and 950 kPa onto a ZSM-5 zeolite. We also predict the binary mixture equilibria by the Ideal Adsorbed Solution Theory (IAST) and the Vacancy Solution Model (VSM, Flory–Huggins and Wilson forms) and we obtain very good results. So not only binary mixture equilibria but also ternary and quaternary mixture adsorption can be predicted. With these data (experimental and simulated), we can conclude that the CO₂ is the most adsorbed component while N₂ is the least one. These two components can be separated from CH₄ and CO which are sent in the Synthesis Gas production step.     

Application of immobilized titanium dioxide photocatalysts for the degradation of creatinine and phenol, model organic contaminants found in NASA''s spacecrafts wastewater streams

In this project, immobilized titanium dioxide photocatalysis was utilized as a post-treatment technology for the destruction of model organic contaminants found in wastewater streams produced on-board during space exploration. Phenol, a known human carcinogen, and creatinine, a human metabolite found in urine, were the compounds tested in this study. Phenol and creatinine have cyclic structures consisting of six and five member rings, respectively. In addition, creatinine is a methyl guanidine derivative, with almost 40% (w/w) nitrogen. The degradation and carbon mineralization efficiencies of the target contaminants were investigated at different initial concentrations. Their photocatalytic degradation appears to follow pseudo-first-order reaction with phenol giving higher organic carbon reduction rates than creatinine. The presence and position of the functional groups of creatinine (amine, imine and peptide bond) are primarily responsible for the significantly slower mineralization. The degradation of creatinine was also tested at different pH_o values. Statistical analysis showed that there is an effect of pH on the treatment of creatinine. Besides the carbon mineralization, the extent of nitrogen mineralization and the mass balance of nitrogen were conducted for three pH values (pH_o 3.0, 6.2 and 11.0). Overall, the transformation of nitrogen was low, and the total maximum conversion (<20%) occurred at basic conditions.     

New force-field parameters for molecular simulations of s-triazine and cyanurate-containing systems. 2—Application and comparison with different simulation methods

The efficiency of new force-field parameters for triazines derived from analysis of crystal data of cyanurates (described previously) is demonstrated. A comparison of the molecular mechanics results with semi-empirical and ab initio methods is presented and the molecular mechanics approach is shown to give acceptable results for a fraction of the computational effort of the molecular orbital methods.