Hesham Hamad

Synthesis and characterization of core–shell–shell magnetic (CoFe2O4–SiO2–TiO2) nanocomposites and TiO2 nanoparticles for the evaluation of photocatalytic activity under UV and visible irradiation

Magnetic TiO2–SiO2–CoFe2O4 (TSC) composite photocatalytic particles with a core–shell structure and a high crystalline anatase TiO2 shell were synthesized via controlled hydrolysis and condensation of titanium isopropoxide. Nano-sized TiO2 powders were synthesized by a sol–gel/hydrothermal route. The prepared TiO2 and its composites were characterized by XRD, SEM, TEM, FT-IR, VSM, and UV-Vis. The results show that the obtained TSC composite particles were composed of spherical nanoparticles, about 5–8 nm in diameter, with several CoFe2O4 fine particles as cores and silica as coatings and barrier layers between the magnetic cores and anatase titania shells. The average crystallite size of TiO2 nanoparticles with an anatase structure is 6 nm. The photocatalytic activities of the samples were evaluated by the photocatalytic degradation of dichlorophenol-indophenol (DCPIP) dye. The maximum level reached for the degradation of the dye molecule was 95.32 and 87.27% for 3 minutes under UV and visible light respectively for mesoporous TiO2 nanoparticles.

Photocatalytic parameters and kinetic study for degradation of dichlorophenol-indophenol (DCPIP) dye using highly active mesoporous TiO2 nanoparticles.

Highly active mesoporous TiO2 of about 6nm crystal size and 280.7m(2)/g specific surface areas has been successfully synthesized via controlled hydrolysis of titanium butoxide at acidic medium. It was characterized by means of XRD (X-ray diffraction), SEM (scanning electron microscopy), TEM (transmission electron microscopy), FT-IR (Fourier transform infrared spectroscopy), TGA (thermogravimetric analysis), DSC (differential scanning calorimetry) and BET (Brunauer-Emmett-Teller) surface area. The degradation of dichlorophenol-indophenol (DCPIP) under ultraviolet (UV) light was studied to evaluate the photocatalytic activity of samples. The effects of different parameters and kinetics were investigated. Accordingly, a complete degradation of DCPIP dye was achieved by applying the optimal operational conditions of 1g/L of catalyst, 10mg/L of DCPIP, pH of 3 and the temperature at 25±3°C after 3min under UV irradiation. Meanwhile, the Langmuir-Hinshelwood kinetic model described the variations in pure photocatalytic branch in consistent with a first order power law model. The results proved that the prepared TiO2 nanoparticle has a photocatalytic activity significantly better than Degussa P-25.

Comparative performance of anodic oxidation and electrocoagulation as clean processes for electrocatalytic degradation of diazo dye Acid Brown 14 in aqueous medium

In this study, a laboratory scale for the treatment of a recalcitrant and toxic synthetic wastewater containing diazo dye, acid brown 14 (AB-14) has been comparatively performed by two electro-catalytic treatment processes, namely anodic oxidation (AO) and electrocoagulation (EC) using a new batch electrochemical cell. Additionally, the influence of several operating parameters such as; current density (j), initial dye concentration (Co), NaCl concentration (CN), and pH on the color removal efficiency and chemical oxygen demand (COD) are evaluated. The powerful capability of the AO and EC of AB-14 which related to the mechanistic reaction pathway is shown. The poor degradation is ascribed to higher Co and pH, while the enhancement of j and CN is responsible for better degradation of AB-14 dye. The results indicate that the EC is more effective than AO under the same operational condition. A kinetic model is developed for evaluation of the pseudo-first-order-rate constant (kapp) as a function of various operational parameters. The results emphasize the high efficiency of AO and EC and the clean processes which are hopeful alternative for the treatment of the large volume wastewater of the textile industry.

Effect of superparamagnetic nanoparticles on the physicochemical properties of nano hydroxyapatite for groundwater treatment: adsorption mechanism of Fe(II) and Mn(II)

Magnetic hydroxyapatite (MHAP) was found to be an ideal adsorbent for Fe(II) and Mn(II) in ground water from the El-Kharga Oasis in Egypt. The formation of surface iron phases strongly enhances the adsorption capacity of hydroxyapatite-based materials for Fe(II) and Mn(II) ions. Batch sorption studies were implemented to investigate the effect of parameters such as the contact time, dosage of MHAP, pH, agitation speed and temperature on the adsorption process. The results revealed that a good correlation with experimental data was described well by the Langmuir model and the pseudo-second-order model, which explained well the mechanism of adsorption. It was found that the adsorption process was achieved mainly via surface complexation and ion exchange. We found various dominating adsorption mechanisms by changing the initial solution pH. The thermodynamic parameters suggested that the adsorption of Fe(II) and Mn(II) were a non-spontaneous endothermic process. Moreover, the adsorption capacities were affected by several parameters such as contact time, adsorbent dosage, and initial pH. After sorption, the MHAP composites could be effectively and easily separated from aqueous solutions by an external magnet. The results revealed that MHAP had the potential to become a promising material for in situ heavy metal-contaminating groundwater remediation in large scale.

Influence of calcination temperatures on the formation of anatase TiO2 nano rods with a polyol-mediated solvothermal method

A simple and convenient method has been demonstrated for large-scale synthesis of titanium dioxide (TiO2). Nano-rod TiO2 with anatase structure had been prepared by a polyol-mediated solvothermal process of titanium tetra-isopropoxide (TTIP) and ethylene glycol (EG) followed by powder calcination at high temperature. The growth mechanism of the TiO2 nano-rods was discussed and supported by X-ray diffraction (XRD), Fourier transform infra-red (FT-IR) spectroscopy, Raman spectroscopy, high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and scanning electron microscopy (SEM). Anatase TiO2 nano-rods (NRs) were synthesized by adjusting the preparation parameters such as precursor concentration, autoclaving temperature and time duration, and calcination temperature. SEM showed TiO2 NRs of 100 to 250 nm that were produced due to the reaction of 0.7 mL of TTIP with 25 mL EG, autoclaving temperature of 205 °C for a time duration of 12 h, and calcination in air at 600 °C for 1 h. Calcination temperature had a great effect on the production of TiO2 nano-rods, where well-defined hexagonal NRs were produced at a high calcination temperature of 600 °C for 1 h.

Study on synthesis of superparamagnetic spinel cobalt ferrite nanoparticles as layered double hydroxides by co-precipitation method

Cobalt ferrite layered double hydroxide (LDH) nanoparticles with cubic structure were synthesized by the co-precipitation method: addition of NaOH solution to a solution of Co2+ and Fe3+. Formation of nanoparticles was confirmed by XRD, SEM, TEM, PSA, FT-IR, TGA, DSC, and magnetic characteristics were measured using VSM. Crystals produced by calcination at 900°C possessed high coercivity and pronounced physical and chemical stability. Nanoparticles of CoFe2O4 formed outer layers with poor crystallization on the surface of cobalt ferrite nanocrystals.

Electrocatalytic degradation and minimization of specific energy consumption of synthetic azo dye from wastewater by anodic oxidation process with an emphasis on enhancing economic efficiency and reaction mechanism

This work focused on the knowledge-based methodology for the development of an electrochemical system, enabling simultaneous optimization of various operating parameters such as current density (j), initial dye concentration (Co), NaCl concentration (CN) for the mineralization of Reactive Violet 2 (RV-2) and Acid Brown 14 (AB-14) dye on the efficiency of removal, energy consumption (EC), Chemical Oxygen Demands (COD), apparent rate constants (kapp) and Electrical Energy per Order (EEO) all of which have been examined. The relationship between kapp and EEO is also discussed. The degradation efficiency and kapp always rising at higher j and lower Co and CN while EC, EEO, and operating cost increased at higher j, Co and CN. On the other hand, The COD increased with decrease j, Co and higher CN. Due to the strong formation of hydroxyl radicals from water discharge, the graphite electrode possesses a strong power of electro-generation rate and competitive wasting reactions of organic compounds. The results demonstrated that the relatively high dye removal, COD and low specific energy consumption are obtained simultaneously only if the various parameters are regulated to a plausible value j of 79Am-2, Co of 100mg/L and CN of 1g/L within 60min of electrolysis. The color removal efficiency is much faster for RV-2 compared to AB-14 due to the contribution of azo bond in the dye molecule. Also, the EC and kapp are higher for RV-2 than AB-14 while is lower in terms of EEO and COD. A comprehensive reaction sequence of RV-2 and AB-14 mineralization involving all oxidation products was proposed. Formation and evolution of aromatic and aliphatic (short-chain carboxylic acids) intermediates during the treatment and a mineralization pathway is proposed. The estimated cost of operation for degradation at optimum conditions is calculated as 1.54 and 1.29 USD m-3/g dye for complete degradation RV-2 and AB-14, respectively.

Electrospun nanofibers hybrid composites membranes for highly efficient antibacterial activity

Safety of drinking-water is an urgent for human health. It is critical to promote the cheap technologies for water purification to guarantee the free-pathogens-drinking water. The present study has been investigated the antibacterial activity of polyacrylonitrile (PAN) nanofibers membranes which decorated by Ag, CuO or ZnO nanoparticles as bactericides. The hybrid nanofiber composites were fabricated by electrospinning technique and the obtained membranes were characterized using SEM, EDX and FTIR. Their antibacterial activity was evaluated against E. coli and S. aureus. The data was revealed that the functionalization was successfully obtained by the incorporation of nanoparticles as an additive into the polymer solution which associated many superior properties. Continuous PAN membrane fibers with average diameters from 170 to 250 nm without any beads of plain and its hybrid membrane composites were obtained. The antimicrobial activity was estimated using both disk diffusion tests and growth kinetic models. The antibacterial activity was improved as the concentrations of nanoparticles enhanced. This study provided the real solution for production and inactivation of bacteria which related to the impregnated the PAN nanofibers membrane with Ag, CuO or ZnO NPs. The results have significant implications for finding a safe and an inexpensive path to solve the problems of drinking water, especially in the developing countries.

Influence of calcination temperature on the physical properties of nano-titania prepared by sol-gel/hydrothermal method

Nano-sized TiO2 powders were synthesized by a modified hydrolysis reaction using titanium butoxide as a precursor, water as a solvent, acetylacetone to slowdown the hydrolysis and the condensation reactions and ammonia as a base catalyst. Phase transformation and particle size of the calcined powders were investigated as a function of the calcination temperature by room-temperature X-ray diffraction; scanning electron microscopy and Fourier transform infrared spectroscopy techniques. Thermal gravimetric analysis (TGA) was used to examine the thermal properties of the produced TiO2 nanoparticles. The XRD showed that the uncalcined sample was mostly the anatase phase with some rutile content. It was indicated that the thermal annealing resulted in increasing the average crystallite size from 8.2 to 53.5 nm. As the calcination temperature increased, the particle size, the rutile phase, the crystallization of the anatase phase, and the agglomeration were increased. The increase in the rutile content and grain growth are caused by the calcination at higher temperatures even calcination at 800°C for 2 h.

On the Interactions and Synergism between Phases of Carbon–Phosphorus–Titanium Composites Synthetized from Cellulose for the Removal of the Orange-G Dye

Carbon–phosphorus–titanium composites (CPT) were synthesized by Ti-impregnation and carbonization of cellulose. Microcrystalline cellulose used as carbon precursor was initially dissolved by phosphoric acid (H3PO4) to favor the Ti-dispersion and the simultaneous functionalization of the cellulose chains with phosphorus-containing groups, namely phosphates and polyphosphates. These groups interacted with the Ti-precursor during impregnation and determined the interface transformations during carbonization as a function of the Ti-content and carbonization temperature. Amorphous composites with high surface area and mesoporosity were obtained at low Ti-content (Ti:cellulose ratio = 1) and carbonization temperature (500 °C), while in composites with Ti:cellulose ratio = 12 and 800 °C, Ti-particles reacted with the cellulose groups leading to different Ti-crystalline polyphosphates and a marked loss of the porosity. The efficiency of composites in the removal of the Orange G dye in solution by adsorption and photocatalysis was discussed based on their physicochemical properties. These materials were more active than the benchmark TiO2 material (Degussa P25), showing a clear synergism between phases.