Preparation of titanium dioxide (TiO<inf>2</inf>) from sludge produced by titanium tetrachloride (TiCl<inf>4</inf>) flocculation of wastewater

Sludge disposal is one of the most costly and environmentally problematic challenges of modern wastewater treatment worldwide. In this study, a new process was developed, which has a significant potential for lower cost of waste disposal, protection of the environment and public health, and yield of economically useful byproducts. Titanium oxide (TiO2), which is the most widely used metal oxide, was produced from the wastewater sludge generated by the flocculation of secondary wastewater with titanium tetrachloride (TiCl4). Detailed analyses were conducted to compare TiCl 4, ferric chloride (FeCl3), and aluminum sulfate (Al 2(SO4)3) flocculation. Removal of organic matter and different molecular sizes by Ti-salt flocculation was similar to that of the most widely used Fe- and Al-salt flocculation. The mean size of Ti-, Fe-, and Al-salt flocs was 47.5, 42.5, and 16.9 μm, respectively. The decantability of the settled flocs by TiCl4 coagulant was similar to that by FeCl3 coagulant and much higher than that of Al 2(SO4)3. The photocatalyst from wastewater (PFW) produced by TiCl4 flocculation was characterized by X-ray diffraction, BET surface area, scanning electron microscopy/energy dispersive X-ray, transmission electron microscopy, photocatalytic activity, and X-ray photoelectron spectroscopy. The resulting PFW was found to be superior to commercial TiO2 (P-25) in terms of photocatalytic activity and surface area. The PFW was also found to be mainly doped with C and P atoms. The atomic percentage of the PFW was TiO1.42C0.44P 0.14. © 2007 American Chemical Society

Quasimonoenergetic electron beam generation by using a pinholelike collimator in a self-modulated laser wakefield acceleration

A relativistic electron bunch with a large charge (&gt;2 nC) was produced from a self-modulated laser wakefield acceleration configuration. For this experiment, an intense laser beam with a peak power of 2 TW and a duration of 700 fs was focused in a supersonic He gas jet, and relativistic high-energy electrons were observed from the strong laser-plasma interaction. By passing the electron bunch through a small pinholelike collimator, we could generate a quasimonoenergetic high-energy electron beam, in which electrons within a cone angle of 0.25 mrad (f/70) were selected. The beam clearly showed a narrow-energy-spread behavior with a central energy of 4.3 MeV and a charge of 200 pC. The acceleration gradient was estimated to be about 30 GeV/m. Particle-in-cell simulations were performed for comparison study and the result shows that both the experimental and simulation results are in good agreement and the electron trapping is initiated by the slow beat wave of the Raman backward wave and the incident laser pulse.open181

Removal behaviors and fouling mechanisms of charged antibiotics and nanoparticles on forward osmosis membrane

© 2019 Elsevier Ltd Fouling and rejection mechanisms of both charged antibiotics (ABs) and nanoparticles (NPs) were determined using a negatively-charged polyamide thin film composite forward osmosis (FO) flat sheet membrane. Two types of ABs and NPs were selected as positively and negatively charged foulants at pH 8. The ABs did not cause significant membrane fouling, but the extent of fouling and rejection changed based on the electrostatic attraction or repulsion forces. The addition of opposite charged AB and NP resulted in a decline of the membrane flux by 11.0% but a 6.5% AB average rejection efficiency improvement. On the other hand, mixing of like-charged ABs and NPs generated repulsive forces that improved average rejection efficiency about 5.5% but made no changes in the membrane flux. In addition, NPs and ABs were mixed and tested at various concentrations and pH levels to rectify the behavior of ABs. The aggregate size and removal efficiency were observed to vary with the change in the electron double layer of the mixture. It can help to make the strategy to control the ABs in the FO process and consequently it enables the FO process to produce environmentally safe effluent

Techno-economic assessment of fertiliser drawn forward osmosis process for greenwall plants from urban wastewater

© 2019 Institution of Chemical Engineers Pressure-assisted osmosis (PAO) has been suggested to integrate with fertiliser driven forward osmosis (FDFO) to improve the overall efficiency of simultaneous wastewater reuse and fertiliser osmotic dilution. This study aims to demonstrate the techno-economic feasibility of pressure-assisted fertiliser driven forward osmosis (PAFDO) hybrid system compared to the existing ultraviolet and reverse osmosis (UV–RO) process. The results showed that coupling FDFO with PAO (i.e. PAFDO) could help fulfill the water quality required for greenwall fertigation. An economic analysis on capital and operational costs for the PAFDO showed that the PAO mode application at a lower FDFO dilution stage could significantly reduce the costs. However, when considering the different applied pressures in PAO (i.e. 2, 4, and 6 bar), the increase in the total water cost was not significant. This indicates that the dilution stage for applying PAO is more sensitive to the total water cost of the PAFDO than the applied pressure. A coupling of higher average water flux (>10 L/m2h) and lower draw solution (DS) dilution factor (DF < 60) is recommended. Therefore, this could make the PAFDO system economically viable compared to the benchmark for the UV-RO disinfection system

Substituent position-induced color tunability in polymer light-emitting diodes

We report substituent position-induced color tunability in polymer light-emitting diodes fabricated with poly[2-{2- or 3- or 4-[(3,7-dimethyloctyl)oxy] phenyoxy}-1,4-phenylenevinylene] (DMOPPPV). When the position of the substituent in DMOP-PPV moves to the ortho, meta, and para sites, the corresponding photo- and electroluminescence spectra shift their peaks to a longer wavelength of about 540, 560, and 585 nm, respectively. We ascribe this to the different degree of steric effect in the backbone for each substituent position. As the substituent position is closer to the main chain, the planarity of the backbone is less conserved, thereby reducing the effective conjugated length of the main chain and broadening the pi-pi(*) energy gapopen6

Hydrogen production affected by Pt concentration on TiO <inf>2</inf> produced from the incineration of dye wastewater flocculated sludge using titanium tetrachloride

TiO 2 from the incineration of dye wastewater flocculated sludge using TiCl 4 coagulant was produced. Optimal catalyst amount and Pt-loading on TiO 2 were studied for the production of H 2 by photocatalytic reforming of methanol (6% vol.). On the other hand, BTSE (biologically treated sewage effluent) was flocculated using TiCl4 and produced sludge was incinerated to generate TiO 2 . TiO 2 was loaded with optimum Pt and added to the supernatant in a photocatalytic reactor to test the efficiency of using remaining organics as a “sacrificial reagent” for photocatalytic hydrogen production. Dissolved organic carbon (DOC) and molecular weight distribution (MWD) were measured for nanofiltration (NF) and TiCl 4 flocculation followed by photocatalysis. TiO 2 (from the incineration of BTSE flocculated sludge using TiCl4) was produced and loaded with 0.5% Pt. Results showed that the optimum concentration of TiO 2 (from dye wastewater) for H 2 production was 0.3 g/L, while the optimum amount of Pt was 0.5%. DOC and MWD removal was similar for the flocculation of BTSE followed by photocatalytic reaction and the NF process. Remaining organic compounds after flocculation could not be used as sacrificial reagent to induce H 2 production. Further investigations on studying the UV intensity and/or identifying organic/inorganic scavengers to inhibit H 2 production are underway. © 2010, Taylor & Francis Group, LLC

Serially connected forward osmosis membrane elements of pressure-assisted forward osmosis-reverse osmosis hybrid system: Process performance and economic analysis

© 2018 Elsevier B.V. Due to the improved dilution of draw streams, employing pressure-assisted forward osmosis (PAFO) to the hybrid system of forward osmosis (FO) followed by reverse osmosis (RO) for seawater desalination has been expected to reduce the overall economics. However, replacing FO with PAFO causes an additional energy cost in the seawater dilution step which inevitably leads to a question that PAFO-RO hybrid is truly an economically beneficial option. More importantly, though serial connection of FO elements improves the dilution of initial draw water, this economic benefit is also compensated with the additional membrane. To rationalize its overall performance and economic benefit, thorough performance and economic evaluations were conducted based on actual pilot-scale PAFO operations for serial connection of up to three 8040 FO elements. The results showed the FO-RO hybrid is not an economically feasible option unless a significant unit FO element cost cut-down is guaranteed. Meanwhile, PAFO-RO showed benefits with regards to target RO recovery and unit FO element cost, particularly when two FO elements are serially connected (SE2). It was found that PAFO-RO, indeed, has higher economic potential than FO-RO. A graphical overlapping method suggested in this work can help determine optimal serial configuration and operating conditions of PAFO-RO

Novel membrane bioreactor (MBR) coupled with a nonwoven fabric filter for household wastewater treatment

Conventional and modified membrane bioreactors (MBRs) are increasingly used in small-scale wastewater treatment. However, their widespread applications are hindered by their relatively high cost and operational complexity. In this study, we investigate a new concept of wastewater treatment using a nonwoven fabric filter bag (NFFB) as the membrane bioreactor. Activated sludge is charged in the nonwoven fabric filter bag and membrane filtration via the fabric is achieved under gravity flow without a suction pump. This study found that the biofilm layer formed inside the NFFB achieved 10 mg/L of suspended solids in the permeate within 20 min of initial operation. The dynamic biofilter layer showed good filterability and the specific membrane resistance consisted of 0.3-1.9 × 1012 m/kg. Due to the low F/M ratio (0.04-0.10 kg BOD5/m3/d) and the resultant low sludge yield, the reactor was operated without forming excess sludge. Although the reactor provided aerobic conditions, denitrification occurred in the biofilm layer to recover the alkalinity, thereby eliminating the need to supplement the alkalinity. This study indicates that the NFFB system provides a high potential of effective wastewater treatment with simple operation at reduced cost, and hence offer an attractive solution for widespread use in rural and sparsely populated areas. Crown Copyright © 2009