Carbon-/Zeolite-Supported TiO2 for Sorption/Photocatalysis Applications in Water Treatment

The role of various carbon forms, i.e., activated carbon and carbon nanotubes/nanofibers as support for TiO2 in drinking water treatment, is discussed. Also, TiO2 supported onto zeolite that acts bifunctionally as a sorbent/photocatalyst for drinking water treatment is presented. The main contaminants of natural organic matter (NOM), arsenic species, and nitrogen compounds from drinking water sources by the type of groundwater and surface water can be removed/degraded by sorption/photocatalysis using TiO2 supported onto carbon and/or zeolite. TiO2 supported on powdered activated carbon (PAC-TiO2), granular activated carbon (GAC-TiO2), and zeolite (Z-TiO2), namely, supported TiO2, was synthesized through the sol-gel method, and TiO2 and multiwall carbon nanotubes/carbon nanofibers dispersed within epoxy matrix (CNT-TiO2-Epoxy, CNF-TiO2-Epoxy), namely, TiO2 composite, were obtained through the two-roll mill method. Kinetic study results through specific mathematic models allowed to elucidate some mechanistic aspects for sorption and photocatalysis for the application in drinking water. The intercalation of the carbon- and zeolite-supported TiO2 layers into a filtering system allows to develop a self-cleaning filtering system in drinking water

Synthesis, characterization and anticorrosive properties of pseudo-binary oxide nanomaterials

This paper presents some results of the study regarding the corrosion inhibition properties evaluated in 0.1 M NaCl environment of drop casting deposited on steel, using Zn3Ta2O8 and Zn3Nb2O8 nanomaterials. Zn3Ta2O8 and Zn3Nb2O8 nanomaterials were obtained by hydrothermal method. The starting materials used during the synthesis were: tantalum (V) oxide - Ta2O5(99.99%, Merck), niobium (V) oxide - Nb2O5 (99.99%, Merck) and zinc acetate dihydrate – (CH3COO)2Zn x 2H2O Merck, 99.5 %) while keeping the molar ratio at 1:3. The pH of the obtained mixtures was adjusted to 12 by using sodium hydroxide (NaOH) solution of 10 M concentration. The resulting suspensions were transferred into Teflon-lined stainless steel autoclaves and then these were introduced in an oven at 220 0C for 8 h long. The filling degree of the used autoclaves was set at 70%. The resulting white precipitates were filtrated, and then five times washed with distilled water and, finally, three times with ethylic alcohol. In the next stage, the precipitate was dried in an oven at 80 0C for 6 h [1-3]. The obtained materials were used for thin films depositions using the drop casting method. The depositions were realized on polished carbon steel electrode disks (10 mm diameter and 2 mm thick). The surfaces of the thin films realized using the pseudo-binary oxides nanomaterials Zn3Ta2O8 and Zn3Nb2O8 on electrode steels were morphological and topographical investigated using the scanning electron microscopy (SEM – Model Inspect S) and the atomic force microscopy (AFM - ModelNanosurf@ EasyScan 2 Advanced Research microscope) using the non-contact mode cantilever (scan size 2.3 µm x 2.3 µm). From AFM measurements, according to equations from [4], were determined the topographical parameters Sa – the average roughness and Sq – the mean square root roughness for each drop casting deposition’s surface on steel electrodes. The obtained values were calculated using the NanoSurf EasyScan 2 software. The corrosion behaviour was studied using on Voltalab potentiostat Model PGZ 402 with single compartment three-electrode cell. Platinum wire was employed as counter electrode and the saturated calomel electrode (SCE) was the reference electrode. All potentials reported in this article were referenced to the standard hydrogen electrode (SHE). Bare and coated steel substrates were used as working electrodes. The potentiodynamic polarization curves were analyzed using VoltaMaster 4, v.7.09 software. This software performed the Tafel fitting and calculated the values of the corrosion potential (Ecorr), corrosion current density (icorr) and corrosion rate (vcorr). The measurements were performed by sweeping the potential between − 700 and 100 mV, in 0.1 M NaCl electrolyte solution, at a scan rate (v) of 1 mV/s. The degree of the corrosion inhibition efficiency IE (%) has been calculated [5] for each drop casting deposition

Morphological investigation of calcium phosphates electrodeposited on Ti in the presence of tartaric acid

The electrochemical deposition method was employed to deposit calcium phosphates on Ti substrates in the presence of different concentrations of tartaric acid. Scanning electron microscopy was used to investigate the morphology of the obtained specimens. The micrographs indicate that as the tartaric acid concentration increases, the size and number of calcium phosphate irregular structures increases as well. At the highest concentration a new morphology is evidenced, represented by flat ordered structures with high aspect ratio

Electrochemical detection of pentachlorophenol from water at carbon nanofibers-epoxy composite electrodes

In this paper cyclic voltammetry (CV) and linear-sweep voltammetry (LSV) experiments were conducted in order to compare the electroactivity of three types of carbon nanofibers based composite electrodes, i.e., natural and synthetic zeolite modified electrodes and a simple carbon nanofibers electrode for pentachlorophenol (PCP) detection. The enhancement factor of electrode sensitivity for the determination of PCP at the tested electrodes was determined by applying a chemical preconcentration step prior to voltammetric quantification. Synthetic-zeolite modified electrode exhibited a larger electroactivity than the other two electrodes, due to a better ability of synthetic zeolite particles from the electrode surface to retain PCP molecules, without inactivation of electroactive sites

Capecitabine removal from water using commercial granular activated carbon

The aim of this study consisted of removal of capecitabine (CCB), a cytostatic that is often used in cancer therapy and its presence in water exhibited negative impact and risk on the human health. Granular activated carbon (GAC) was tested as sorbent in batch system for CCB removal from water, considering its common usage in water/wastewater treatment technology. Influence of operation variables, e.g, pH, GAC dose and CCB initial concentrations, was studied to optimize GAC-based sorption for CCB removal