[Photocatalytic removal of escherichia coli and streptococcus faecalis from water using immobilized ZnO nanoparticles]

Among different water treatment methods, photocatalytic process is applied as a new efficient technology with appropriate potential to remove inorganic, organic and microbial contaminants from water. This study aimed to evaluate photocatalytic removal of Escherichia coli and Streptococcus faecalis bacteria as microbial indicators of drinking water using immobilized ZnO nanoparticles on glass plates. In this study, at first characteristics of ZnO nanoparticles were determined using scanning electron microscope [SEM] equipped with EDX system and X-ray diffraction [XRD], then ZnO nanoparticles were immobilized on glass plates using thermal method. The water samples containing the studied bacteria were irradiated by different intensities of UV-A and the effects of intensity and duration of irradiation, number of bacteria, number of immobilized ZnO nanoparticles layers, and reactor flow on the photocatalytic removal of the bacteria were evaluated. The optimal photocatalytic removal for both Escherichia coli and Streptococcus faecalis bacteria using one layer of immobilized ZnO nanoparticles, under 360 microWs/cm[2] UV-A radiation for 2-40 and 2-50 minutes was 10-1000 CFU/100 ml. Photocatalytic process efficiency was promoted by increasing the duration and intensity of radiation intensity up to 360microWs/cm[2] and was decreased by increasing the numbers of bacteria. In addition, Streptococcus faecalis bacteria were more resistant to photocatalytic process than Escherichia coli. photocatalytic removal of bacterial contaminations using immobilized ZnO nanoparticles on glass plates is a novel technology and effective process that could be considered for water disinfection

[Study of the photocatalytic effects of nitrogen-doped titanium dioxide nanoparticles on growth inhibition and apoptosis induction in K562 cell line]

Titanium dioxide [TiO[2]] nanoparticles have shown anti-tumor activity in several cancer cell lines. TiO[2] is an effective photocatalyst that needs ultraviolet [UV] light for activation. Many efforts are in progress to improve the TiO[2] photocatalytic effects by carrying out superficial alterations in its electronic structure. For this purpose, nitrogen [N] element seems to be a proper dopant to improve photocatalytic activity of this nanoparticle. In the present study, the growth inhibitory and apoptotic effects of N-doped TiO[2] nanoparticles on human K562 cells, as an experimental model of chronic myeloid leukemia [CML], were investigated and compared with those of undoped TiO[2] in both light and dark conditions. Nanocrystalline powders of N-doped TiO[2] [80 nm] were synthesized by mechanical mixing of urea with TiO[2] powders under special experimental conditions. The structure and properties of N-doped TiO[2] nanoparticles were confirmed by transmission electron microscopy [TEM], X-ray diffraction [XRD] and Brunauer-Emmett-Teller [BET] analysis. Then we investigated the growth inhibitory and apoptotic effects of these nanoparticles on leukemia K562 cells. The results showed that visible light-irradiated N-doped TiO[2] induced profound growth inhibition and apoptosis in K562 cells in a time- and dose- dependent manner. For example, N-doped TiO[2] at concentrations of 0.01 micro g/ml, 0.1microg/ml, 1 microg/ml, 5 microg/ml and 10microg/ml inhibited growth of K562 cells by 25%, 34%, 39%, 44% and 47% and viability by 11%, 22%, 30%, 35% and 38%, respectively after 48h. Furthermore, the results of DNA fragmentation assay confirmed apoptosis in treated-K562 cells after 48h. While un-doped TiO[2] did not show any inhibitory effects on the growth and viability of K562 cells. Considering the growth inhibitory and apoptotic effects of N-doped TiO[2] in human K562 cells, this nanoparticle can be a potential candidate for photocatalytic therapy in CML in the future studies.

[Investigation of E. coli removal from polluted water using electrolysis method]

The conventional chemical and physicalmethods for water disinfection include the application of ultraviolet [UV], chlorination, and ozonation. Water disinfection by electrochemical methods has been increasingly carried out recently. The goal of this applied - analytical research is to investigate the removal of E. coli bacteria, as the index of water microbial contamination, from drinking water by electrochemistry method. In this study, the contaminated water sample was prepared through adding 102 and 103 E. coli bacteria per ml of drinking water. The contaminated water entered into the electrochemical reactor and different conditions were studied, included pH [6, 7, and 8], number of bacterium [102 and 103 per milliliter], time [5, 10, 20, and 40 min], distance between electrodes [2, 2.5, 3, and 3.5 cm], and voltage [10, 20, 30, and 40 volts]. The findings indicated the indirect correlation between bacteria removal efficiency and the variable distances between two electrode. The results indicated the direct correlation between bacteria removal efficiency and the variables voltage and electrolysis times. The results showed that the best conditions for removal of 102 and 103 bacteria per milliliter obtained at pH 7, electrolysis time of 10 min, distance between electrodes 2 cm, in the voltage 20 and 30 volts, respectively. The results of this study indicate that voltage and electrolysis time have the most significant effect on electrolysis efficiency. Research findings showed that electrolysis is a promising method for removal of E. coli bacterium from drinking water

[Photocatalytic removal of hexavalent chromium and divalent nickel from aqueous solution by UV irradiation in the presence of titanium dioxide nanoparticles]

Industrial wastewater included the heavy metal is one of the important sources of environmental pollution. Hexavalent chromium and divalent nickel are founded in plating wastewater which is harmful for human health and environment. Therefore, the purpose of this research is investigation of photocatalytic removal of hexavalent chromium and divalent nickel from aqueous solution using UV/TiO[2] process in a batch system. At first, reactor was designed. Then, optimumdosage of TiO[2] was obtained equal to 1 g/L, with variation TiO[2] dosage at constant pH and initial concentrations of hexavalent chromium and divalent nickel. The effect of pH, contact time and initial concentration of hexavalent chromium was studied at the constant amount of TiO[2] [1gr/L]. The result showed that photocatalytic removal efficiency increased with increasing reaction time and TiO[2] dosage. In addition, it was found that removal efficiency of hexavalent chromium was decreased by increasing initial chromium concentration and pH. But, photocatalytic removal efficiency of nickel ion was increased and decreased by increasing of pH and initial nickel concentration, respectively. The results showed that UV/TiO[2] was an effective method in removal of hexavalent chromium and divalent nickel from aqueous solutions