•A novel membrane was designed to couple filtration with photoelectrocatalysis.•This membrane could directly utilize visible light for water treatment.•The integrated process shows 10.1 times higher phenol removal than filtration alone.•Antifouling ability of membrane was greatly improved by photoelectrocatalysis.•The integrated process displays outstanding performance in surface water treatment.Coupling membrane filtration with photocatalysis provides a promising way to improve the membrane performance for water treatment. However, the quick recombination of photogenerated electron-holes and poor visible-light response limit the performance of photocatalytic membrane. Herein, a g-C3N4/CNTs/Al2O3 membrane was prepared through sequentially coating carbon nanotubes (CNTs) layer with high electroconductivity and g-C3N4 layer with good visible-light response on Al2O3 membrane support. When a positive voltage was applied on the CNTs layer, photogenerated electrons in the visible light irradiated g-C3N4 layer could be drawn away and separated from the holes, thus rendering membrane with photoelectrocatalytic function and largely improved performance. The membrane filtration integrated with photoelectrocatalysis (PECM) showed enhanced phenol removal with the increase of voltage supply. At 1.0 V, the PECM process displayed photoelectric synergetic effect, whose phenol removal efficiency was 2.7, 2.0 and 10.1 times higher than that of filtration with visible light irradiation (PCM), filtration with 1.0 V and filtration alone, respectively. The PECM also presented improved antifouling capability during the removal of natural organic matters. Its stable permeability (measured at 1.5 V) was 1.4 and 3.0 times higher than that of PCM and filtration alone, respectively. Significantly, the PECM also displays outstanding capability in surface water treatment.Download high-res image (259KB)Download full-size image

A three-dimensional (3D) nanostructured photocatalyst combined with g-C3N4 quantum dots (QDs) and a TiO2 nanotube array (TNA) was fabricated to form a 3D g-C3N4/TNA nanocomposite by a facile electro-deposition process. The photocatalytic ability of the 3D g-C3N4/TNA was evaluated by measuring the amount of hydrogen generated from water splitting under visible light irradiation. Benefiting from an attractive heterostructure between g-C3N4 and TiO2 leading to a unique photogenerated charge separation, as well as a distinctive 3D well-ordered nanotube structure, this 3D g-C3N4/TNA exhibited an average H2 production of approximately 243 μmol h−1 g−1, which was approximately 4.7 times higher than that of sole g-C3N4 under the same experimental conditions. Therefore, this work could offer a prospective 3D nanostructure for visible light-driven photocatalytic applications.

Graphene electrodes (Ti/Gr) were prepared by depositing Gr sheets on Ti substrate, followed by an annealing process for enhancing the adhesion strength. Electrochemical impedance spectroscopies and X-ray diffraction patterns displayed that the electrochemical behavior of Ti/Gr electrodes can be improved due to the generation of TiO2 layer at Ti-Gr interface during the annealing process. The palladized Gr electrodes (Ti/Gr/Pd) were prepared by electrochemical depositing Pd nanoparticles on Gr sheets. The debromination ability of Ti/Gr/Pd electrodes was investigated using BDE-47 as a target pollutant with various bias potentials. The results indicated that the BDE-47 degradation rates on Ti/Gr/Pd electrodes increased with the negative bias potentials from 0 V to −0.5 V (vs. SCE). Almost all of the BDE-47 was removed in the debromination reaction on the Ti/Gr/Pd electrode at −0.5 V for 3 h, and the main product was diphenyl ethers, meaning it is promising to debrominate completely using the Ti/Gr/Pd electrode. Although the debromination rate was slightly slower at −0.3 V than that under −0.5 V, the current efficiency at −0.3 V was higher, because the electrical current acted mostly on BDE-47 rather than on water.

•Designed and fabricated a photocatalytic membrane based on heterojunction structure.•The membrane exhibited efficient charge separation capacity.•Membrane filtration coupled with photocatalysis exhibited synergistic effect.•The membrane exhibited high anti-fouling capacity.Integrating a microfiltration with photocatalysis is a rising method for improving the anti-fouling capability of membrane by degradating pollutants blocked the pores of membrane via photocatalysis. However, the quick recombination of photogenerated charges in the photocatalytic layer limited the performance of this photocatalytic membrane. To inhibit the recombination of photogenerated charges, a CNTs–TiO2/Al2O3 composite membrane was designed and fabricated. Compared with TiO2/Al2O3 membranes (the typical photocatalytic membrane), the CNTs–TiO2/Al2O3 composite membrane displayed lower photoluminescence intensity and higher photocurrent density, which indicated the higher separation efficiency of its photogenerated charges. To get a good combination of membrane flux and rejection, the CNTs content and the thickness of CNTs–TiO2 layer was optimized. Under the best prepared parameters, the Polyethylene glycol (PEG) rejection and permeate flux was 70% and 980 L m−2 h−1, respectively. The optimized CNTs–TiO2/Al2O3 composite membrane under UV light irradiation exhibited 3 times higher of the stable permeate flux than filtration alone, and the humic acid removal rate of composite membrane was 10% higher than TiO2/Al2O3 membranes. This work could provide an alternative way to improve rejection and photocatalytic efficiency for conventional photocatalytic membranes and facilitate their practical application in water treatment.Graphical abstract

The competitive adsorption and desorption of Pb(II) and Cu(II) ions in the soil of three sites in North China were investigated using single and binary metal solutions with 0.01 mol·L−1 CaCl2 as background electrolyte. The desorption isotherms of Pb(II) and Cu(II) were similar to the adsorption isotherms, which can be fitted well by Freundlich equation (R2>0.96). The soil in the three sites had greater sorption capacities for Pb(II) than Cu (II), which was affected strongly by the soil characteristics. In the binary metal solution containing 1:1 molar ratio of Pb(II) and Cu(II), the total amount of Pb(II) and Cu(II) adsorption was affected by the simultaneous presence of the two metal ions, indicating the existence of adsorption competition between the two metal ions. Fourier transform infrared (FT-IR) spectroscopy was used to investigate the interaction between soil and metal ions, and the results revealed that the carboxyl and hydroxyl groups in the soil were the main binding sites of metal ions.

The nanostructured anatase film (NAF), consisted of nanoparticles or nanowires, was fabricated directly on Ti substrate by a two-step hydrothermal approach. The film obtained after the initial hydrothermal reaction was composed of titanate nanotubes or nanowires by regulating the temperature of hydrothermal treatment. Then both the precursor films were readily transformed into corresponding NAFs (nanoparticles and nanowires) via a secondary hydrothermal treatment with 0.05 M HNO3 solution at 120 °C. The NAFs exhibited remarkably high surface photovoltage (SPV) responses and photocurrent densities in UV region, suggesting the enhanced separation ability of photogenerated electrons and holes compared with the compact titania film (CTF) prepared by calcining the TiO2 sol film. The photoelectrocatalytic (PEC) activities of the NAFs were evaluated using phenol as a test substance under UV light irradiation. The kinetic constants of PEC degradation towards phenol with NAF-nanoparticles and NAF-nanowires were 2.2 and 3.4 times as great as the values with CTF, respectively. A significant PEC synergetic effect between the photocatalytic (PC) and electrochemical (EC) processes was also observed.

Sorption of perfluorooctane sulfonate (PFOS) to oil and oil-derived black carbon (BC) from solutions varying in pH and [Ca2+] was investigated. Oil is a strong sorbent for PFOS, together with the independence of oil–water distribution coefficient (Koil) on solution parameters (pH values and [Ca2+]), suggesting that hydrophobic interactions of the hydrophobic moieties of PFOS with oil played a dominant role. BC sorption for PFOS is not stronger or more nonlinear than other natural organic carbon from solution in the case of 0.5 mM [Ca2+] and pH 5.05, indicating that specific adsorption sites on BC were probably not fit for PFOS. However, both sorption capacity and nonlinearity of PFOS increased obviously with decreasing solution pH and increasing [Ca2+], resulting in the potential importance of BC at environmentally low PFOS level, from solution at high [Ca2+] or low pH. The role of BC in PFOS sorption was significantly influenced by environmental conditions and solute aqueous concentrations.