Tarek A. Gad-Allah

Photocatalytic oxidation of ciprofloxacin under simulated sunlight.

Ciprofloxacin (CIP) is a famous synthetic chemotherapeutic antibiotic. It is widely found either in water or wastewater. In this study ciprofloxacin was photocatalytically degraded using commercial anatase titanium dioxide (TiO(2)) under simulated sunlight. The rate of reaction was found to be affected by pH, TiO(2) concentration and antibiotic concentration. The best reaction rate was obtained in natural ciprofloxacin pH (5.8) and 1000 mg/L TiO(2). More titania concentration was found to reduce the reaction rate because of the limitation in light transmittance. From kinetic studies, the reaction was proved to proceed through adsorption step then photooxidation and obeys pseudo-first order kinetics.

Minimization of the formation of disinfection by-products

The drinking water industry is required to minimize DBPs levels while ensuring adequate disinfection. In this study, efficient and appropriate treatment scheme for the reduction of disinfection by-product (DBPs) formation in drinking water containing natural organic matter has been established. This was carried out by the investigation of different treatment schemes consisting of enhanced coagulation, sedimentation, disinfection by using chlorine dioxide/ozone, filtration by sand filter, or granular activated carbon (GAC). Bench scale treatment schemes were applied on actual samples from different selected sites to identify the best conditions for the treatment of water. Samples were collected from effluent of each step in the treatment train in order to analyze pH, UV absorbance at 254 nm (UVA(254)), specific UV absorbance at 254 nm (SUVA(254)), dissolved organic carbon (DOC), haloacetic acids (HAAs) and trihalomethanes (THMs). The obtained results indicated that using pre-ozonation/enhanced coagulation/activated carbon filtration treatment train appears to be the most effective method for reducing DBPs precursors in drinking water treatment.

Utilization of nano size TiO2 for degradation of phenol enrich water by solar photocatalytic oxidation

AbstractPhotocatalytic processes using TiO2 provides an interesting route to destroy hazardous organic contaminants in water such as phenol. Usage of TiO2 in presence of solar irradiation is considered as cost-effective technique. The solar photocatalytic degradation of phenol enrich water over prepared TiO2 has been studied. The catalyst was characterized by several techniques such as X-ray diffraction, gravimetric-differential thermal analysis, and Fourier transformation infra red spectroscopy. The results showed that the nanoparticle prepared from TiO2 can be used as an effective photocatalyst for phenol removal under solar radiation. Photocatalytic activity was mainly attributed to its size 19.6 nm and in turn large amount of surface hydroxyl species. Influence of pH, catalyst loading, and hydrogen peroxide dose were investigated during this study. At optimum dose of 0.50 g/L TiO2 and pH value of 8, phenol removal was about 72% of initial concentration of 50 ppm, which was achieved within 120 min of s...

Stable plasmonic Ag/AgCl–polyaniline photoactive composite for degradation of organic contaminants under solar light

A series of novel plasmonic photocatalysts of Ag/AgCl–polyaniline (Ag/AgCl–PANI) were successfully synthesized by deposition–precipitation reaction followed by a photo-reduction method. The prepared photocatalysts were characterized by X-ray diffraction, field emission scanning electron microscopy, ultraviolet-visible diffuse reflectance spectroscopy, photoluminescence emission spectroscopy, and thermogravimetric analysis. Ag/AgCl–PANI was used to degrade methylene blue (MB) under simulated solar light. The effects of different parameters such as PANI content, initial pH and concentration of the MB solution, and catalyst dosage on the photo-degradation efficiency were assessed. Ag/AgCl–PANI plasmonic photocatalyst displayed much higher photocatalytic efficiency than the pure PANI or Ag/AgCl. The improved photocatalytic performances of the prepared photocatalysts were attributed to the high absorbance in the visible-light region, high surface areas of catalysts and the effective synergism of hetero-junction structure formed at the interface between Ag/AgCl and PANI, leading to improved separation of the photo-generated electron–hole pairs. A possible mechanism for the photo-degradation of MB molecules under simulated solar irradiation was suggested based on trapping experiments.

Treatment of landfill leachate by Fenton process: parametric and kinetic studies

AbstractFenton treatment of leachate of municipal landfill was investigated in this study. Physical and chemical characteristics of the leachate indicated that the waste is alkaline and is characterized by extremely high concentration of organic compounds. Different reaction conditions of Fenton treatment were examined including H2O2/chemical oxygen demand (COD) and Fe2+/H2O2 ratios in the present work. COD of leachate after Fenton treatment was removed by about 77 and 83% for initial COD 6,250 and 13,300 mgO2/L, respectively. Such a maximum removal was achieved at pH 3 and using reagent dosages as high as H2O2/COD = 4.4 and H2O2/Fe2+value of 50. Complete oxidation was not achieved even at optimum conditions due to the presence of inhibitors (carbonate) in the leachate wastewater. After removal of high carbonate content, the same removal efficiency could be achieved with lower H2O2/COD ratio (i.e. H2O2/COD = 3.3). A simplified kinetic study for Fenton treatment of leachate wastewater has been performed.

Parametric study on phenol photocatalytic degradation under pure visible and solar irradiations by Fe-doped TiO2

Abstract Fe-doped TiO2 photocatalysts of different Fe/Ti molar ratios were successfully prepared using wet impregnation method. Prepared Fe-doped TiO2 photocatalysts were characterized by X-ray diffraction, scanning electronic microscope and specific surface area analysis. All the Fe-doped TiO2 photocatalysts possess only anatase crystal structure with no peaks relevant to iron. The activity of the Fe-doped TiO2 photocatalyst for the degradation of phenol was investigated under solar and visible lights and under different reaction conditions, e.g. doping ratio, catalyst concentration and hydrogen peroxide concentration. The degradation rate under solar irradiation was much higher than that under visible light irradiation. 0.05% Fe/Ti molar ratio was the optimum doping ratio for phenol degradation under solar as well as visible light. Photocatalyst of this doping ratio showed higher activity than P25 TiO2 under solar light irradiation and visible irradiation which might be due to electron-hole separation b...

Heterogeneous Fenton process using iron-containing waste (ICW) for methyl orange degradation: process performance and modeling

AbstractThe feasibility of using iron-containing waste (ICW) as new low-cost heterogeneous Fenton catalyst for methyl orange (MO) degradation has been studied. Process modeling and simulation has been conducted using artificial neural network (ANN). Complete degradation of MO was achieved at 0.2 g/L ICW concentration, 24 mM H2O2 dose, and pH 2 in 30 min. A three-layered back-propagation neural network with tangent sigmoid transfer function (tansig) at hidden layer and linear transfer function (purelin) at output layer was used for modeling the process performance. ANN-predicted results are very close to the experimental results with a correlation coefficient (R2) of 0.961 and a mean squared error of 0.039. The sensitivity analysis showed that all studied variables (reaction time, ICW concentration, H2O2 dose, pH, and MO concentration) have strong effect on MO degradation. Among all studied variables, pH appeared to be the most influential input variable followed by ICW concentration.

Synthesis, characterization and adsorption properties of microcrystalline cellulose based nanogel for dyes and heavy metals removal

Recently, naturally occurring biopolymers have attracted the attention as potential adsorbents for the removal of water contaminants. In this work, we present the development of microcrystalline cellulose (MCC)-based nanogel grafted with acrylamide and acrylic acid in the presence of methylene bisacrylamide and potassium persulphate as a crosslinking agent and initiator, respectively. World-class facilities such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), surface analysis, field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM) and zeta sizer were used to characterize the synthesized MCC based nanogel. The prepared nanogel was applied to remove reactive red 195 (RR195) dye and Cd (II) from aqueous medium at different operational conditions. The adsorption experiments showed that the feed concentration of monomers has a significant effect on the removal of RR195 which peaked (93% removal) after 10min of contact time at pH2 and a dose of 1.5g/L. On contrary, the feed concentration has insignificant effect on the removal of Cd (II) which peaked (97% removal) after 30min of contact time at pH6 and a dose of 0.5g/L. The adsorption equilibrium data of RR195 and Cd (II) was best described by Freundlich and Langmuir, respectively. Conclusively, the prepared MCC based nanogels were proved as promising adsorbents for the removal of organic pollutants as well as heavy metals.

Solar photocatalytic activity of sol–gel prepared Ag-doped ZnO thin films

AbstractPure and silver doped ZnO thin films over glass substrate were prepared by sol–gel spin-coating method. Prepared films were calcined at different temperatures. X-ray diffraction and UV–Vis spectroscopy were used to characterize the prepared samples. The photocatalytic activity under solar irradiation of the prepared thin films was tested for the degradation of three azo reactive dyes namely Reactive Red 195, Reactive yellow 145 and Reactive orange 122 as an organic pollutant. 6 wt.% Ag doping ratio showed the highest photocatalytic activity. Various operational parameters such as pH of the solution and initial concentration of the dye have been investigated.

Transparent Nanocrystalline Glass-Ceramic System for Organic Pollutants Degradation

Because of the superior photocatalytic activities of nanocrystalline TiO2 and ZnO under UV irradiation, they were embedded into the glass system (SiO2, TiO2, ZnO, B2O3, Na2O, K2O, P2O5, Li2O and BaO) to provide easy separation from the aqueous system. Different contents of TiO2 and ZnO have been investigated. Conversion to glass-ceramic materials was carried out by heat treatment at 450 °C, which is the onset of the nucleation peak according to the differential thermal analysis (DTA) result, for different times. This heat treatment regime preserves the transparency of the prepared materials in the visible region and good absorption in the UV region. The high content of TiO2 or ZnO caused an improvement of microhardness of the prepared materials, though the presence of the two oxides with the same ratio decreased the microhardness values. Photocatalytic activity of the prepared glass-ceramic materials was investigated according to their efficiency for the degradation of humic acid (HA), the major precursor of disinfection by-products (DBPs), from water. All samples were proved to be photoactive with different extents. Four hours heat treatment at 450 °C appears to be the best conditions for the development of TiO2 and ZnO crystals leading to better photocatalytic activity.