Effects of Sintering Atmosphere on the Microstructure and Surface Properties of Symmetric TiO2 Membranes

The effects of sintering atmosphere on the properties of symmetric TiO2 membranes are studied with regard to sintering behavior, porosity, mean pore size, surface comPosition. and surface charge properties. The exerimental results show that the symmetric TiO2 membranes display better sintering activity in the air than in argon, and the mean pore diameters and porosities of the membrane sintered in argon are higher than those of the membrane sintered in the air at the same temperature. The surface compositions of the symmetric TiO2 membrane sintered in the air and in argon at different temperatures, as studied by X-ray photoelectron spectroscopy, are discussed in terms of their chemical composition, with particular emphasis on the valence state of the titanium ions. The correlation between the valence state of the titanium ions at the surface and the surface charge properties is examined.It is found that the presence of Ti^3＋, introduced at the surface of the symmetric TiO2 membranes by sintering in a lower partial pressure of oxygen, is related to a significant decrease in the isoelectric point. TiO2 with Ti^4＋ at the interface has an isoelectric point of 5.1, but the non-stoichiometric TiO2-x with Ti^3＋ at the interface has a lower isoelectric point of 3.6.

TiO2-incorporated polyelectrolyte composite membrane with transformable hydrophilicity/hydrophobicity for nanofiltration separation

The wettability of the membrane surface has shown obvious influent on the separation performance of the membrane.In this work,a hydrophilic PDA-[PDDA/TiO2]+Cl-membrane was prepared by a one-step codeposition of poly(diallyldimethylammonium chloride)(PDDA)polyelectrolyte solution containing positively charged TiO2@PDDA nanoparticles with the assistance of dopamine(DA).Such positively charged membrane can be transformed into a hydrophobic membrane PDA-[PDDA/TiO2]+PFO-via the counterion exchange between Cl-and PFO-(perfluorooctanoate).The transformation between hydrophilicity and hydrophobicity is reversible.For both hydrophilic and hydrophobic membranes,the nanofiltration performances were respectively investigated by the aqueous solution and ethanol solution of dyes including methyl blue(MB),Congo red(CR)and Evans blue(EB),and as well metal salt aqueous solution.The consecutive running stability and anti-fouling performance of both hydrophilic and hydrophobic membranes were explored.The results revealed that both membranes showed high nanofiltration performances for retention of dyes in(non)aqueous solution.For the hydrophilic membrane,the rejection of salts in a sequence is MgSO4>Na2SO4>MgCl2>NaCl.Moreover,both of the hydrophilic and hydrophobic membranes showed high stability and antifouling property.

Preparation and characterization of hydrothermally engineered TiO2-fly ash composite membrane

This work targets the preparation and char-acterization of an inexpensive TiO2-fly ash composite membrane for oily wastewater treatment. The composite membrane was fabricated by depositing a hydrophilic TiO2 layer on a fly ash membrane via the hydrothermal method, and its structural, morphological and mechanical properties were evaluated. The separation potential of the composite membrane was evaluated for 100-200 mg·L^-1 synthetic oily wastewater solutions. The results show that the composite membrane has excellent separation performance and can provide permeate stream with oil concentration of only 0.26-5.83 mg·L^-1. Compared with the fly ash membrane in the average permeate flux and performance index （49.97 × 10^-4 m^3·m^2·s^-1 and 0.4620%, respectively）, the composite membrane exhibits better performance （51.63× 10^-4 m^3·m^2·s^-1 and 0.4974%）. For the composite surface methodology based ash membrane, the response analysis inferred that the optimum process parameters to achieve maximum membrane flux and rejection are 207 kPa, 200 mg·L^-1 and 0.1769 m·s^-1 for applied pressure, feed concentration and cross flow velocity, respectively. Under these conditions, predicted responses are 41.33× 10^-4 m^3·m^2·s^-1 permeate flux and 98.7% rejection, which are in good agreement with the values obtained from experimental investigations （42.84× 10^-4 m^3·m^2·s^-1 and 98.82%）. Therefore, we have demonstrated that the TiO2-fty ash composite membrane as value added product is an efficient way to recycle fly ash and thus mitigate environmental hazards associated with the disposal of oily wastewaters.

Preparation of a novel composite electrode based on N-doped TiO_2-coated Na Y zeolite membrane and its photoelectrocatalytic performance

For the first time the preparation of the N-doped TiO2-coated NaY zeolite membrane（N-doped TiO2/NaY zeolite membrane） as an electrode material for photoelectrocatalysis has been achieved and reported.The XRD, SEM, UV–vis and XPS techniques were used to characterize the structure of the N-doped TiO2/NaY zeolite membrane. The results verified that the surface of the N-doped TiO2/NaY zeolite membrane was coated by TiO2 nanoparticles of ca. 20 nm size and exhibited a distinct red-shift in the UV–vis spectra compared to N-doped TiO2. The photoelectrocatalysis performance of the N-doped TiO2/NaY zeolite membrane electrode was evaluated by phenol degradation. The results revealed it is a promising novel electrode material for application of photoelectrocatalysis in the removal of organic contaminants in waste water.

Ag–AgBr/TiO_2/RGO nanocomposite:Synthesis,characterization,photocatalytic activity and aggregation evaluation

Ag-AgBr/TiO2 supported on reduced graphene oxide （Ag-AgBr/TiO2/RGO） with different mass ratios of grapheme oxide （GO） to TiO2 were synthesized via a facile solvothermal-photo reduction method. Compared to the single-, two- and three-component nanocomposites, the four-component nanocomposite, Ag-AgBr/TiO2/RGO-1 with mass ratio of GO to TiO2 at 1%, exhibited a much higher photocatalytic activity for the degradation of penicillin G （PG） under white light-emitting diode （LED-W） irradiation. The PG degradation efficiency increased with the increase of mass ratio of GO to TiO2 from 0.2% to 1%, then it decreased with the increase of mass ratio of GO to TiO2 from 1% to 5%. The zeta potentials of RGO-nanocornposites became more negative with the presence of humic acid （HA） due to the negatively charged HA adsorption, resulting in the shift of points of zero charge to lower values of pH. The aggregations of nanocomposites were more significant due to the bridging effect of HA. Furthermore, the aggregated particle sizes were larger for ROO-nanocomposites compared to other nanoparticles, due to the bindings of the carboxylic and phenolic functional groups in HA with the oxygen-containing functional groups in the RGO-nanocomposites. The microfiltration （MF） membrane was effective for the nanocomposites separation. In the continuous flow through submerged membrane photoreactor （sMPR） system, backwashing operation could efficiently reduce membrane fouling and recover TiO2, and thus indirectly facilitate the PG removal.