Dual-Channel-Ion Conductor Membrane for Low-Energy Lithium Extraction.

The development of energy-efficient and environmentally friendly lithium extraction techniques is essential to meet the growing global demand for lithium-ion batteries. In this work, a dual-channel ion conductor membrane was designed for a concentration-driven lithium-selective ion diffusion process. The membrane was based on a porous lithium-ion conductor, and its pores were modified with an anion-exchange polymer. Thus, the sintered lithium-ion conductors provided highly selective cation transport channels, and the functionalized nanopores with positive charges enabled the complementary permeation of anions to balance the transmembrane charges. As a result, the dual-channel membrane realized an ultrahigh Li+/Na+ selectivity of ∼1389 with a competitive Li+ flux of 21.6 mmol·m-2·h-1 in a diffusion process of the LiCl/NaCl binary solution, which was capable of further maintaining the high selectivity over 7 days of testing. Therefore, this work demonstrates the great potential of the dual-channel membrane design for high-performing lithium extraction from aqueous resources with low energy consumption and minimal environmental impact.

Electrochemical oxidation disinfects urban stormwater: Major disinfection mechanisms and longevity tests.

Although electrochemical oxidation (ECO) has shown excellent potential for disinfecting wastewater and surface waters, its application on urban stormwater has been rarely tested. In order to improve stormwater ECO design, this paper explores the major inactivation processes using Boron Doped Diamond (BDD) and titanium Dimensional Stable Anodes (DSA). Both BDD and DSA showed comparable disinfection rates. The mechanism study suggested that BDD relied on hydroxyl radical and the presence of chloride ions, while DSA disinfected stormwater mainly via the production of free­chlorine. A deterioration study carried out at a catchment in Melbourne, showed a steady performance for BDD and revealed that DSA's performance degraded with time, likely linked to the high operational voltage required for specific chemistry of stormwater. Scanning Electron Microscopes and an Energy Dispersive X-ray Detector tests confirmed elemental losses occurred on the DSA surface, together with an aluminium/silicon coating layer potentially sourced from the stormwater clayish sediments. Furthermore, disinfection by-products in electrochemical disinfected stormwater using either BDD or DSA were at least one order of magnitude lower than the Australia Drinking Water Guidelines limits. The mechanism and long-term study demonstrated that careful anode selection is required as some anodes will deteriorate in stormwater matrices faster than others.

Stormwater disinfection using electrochemical oxidation: A feasibility investigation.

Electrochemical oxidation (ECO) has shown good potential for disinfection of wastewater discharges but has not been tested for stormwater. Due to far lower salinity and chloride levels present in stormwater than in wastewaters, the knowledge so far on the ECO disinfection performance cannot simply be used for stormwater applications. This paper presents the first study on the feasibility of ECO technology for disinfection of pre-treated stormwater. Disinfection performance of E. coli was tested using a dimensional stable anode (DSA) in a series of batch experiments with synthetic stormwater of 'typical' chemical and microbial composition. The results showed that effective disinfection could be achieved with very low energy consumption; e.g. the current density of 1.74 mA/cm2 achieved total disinfection in 1.3 min, using only 0.018 kWh per ton of stormwater treatment. Chlorination was found to be the key disinfection mechanism, despite the synthetic stormwater containing only 9 mg/L of chloride. Real stormwater collected from three stormwater treatment systems in Melbourne was then used to validate the findings for indigenous microbe species. Disinfection below the detection limit was achieved for stormwater from the two sites where chloride levels were 9 and 200 mg/l, respectively, but not for the third site where stormwater contained only 2 mg/L chloride. Unfortunately, deterioration of the DSA anode was observed after only 8-10 h of its cumulative operation time, very likely due to high voltage that had to be applied to low saline stormwater to achieve the required current density. In conclusion, ECO was found to be a very promising low energy disinfection technology for stormwater, but far more work is needed to optimise the technology for unique stormwater conditions.

Highly recoverable TiO2-GO nanocomposites for stormwater disinfection.

A highly recoverable titanium dioxide-graphene oxide (TiO2-GO) composite was developed by a facile method of ultrasonic treatment of GO nanosheets and TiO2 nanoparticles, which should overcome the separation problem of nanosized TiO2 from treated water. Separability of the prepared samples was systematically investigated by gravity settling experiments. The samples' photocatalytic activity for stormwater disinfection was also studied under the irradiation of a solar simulator. The results demonstrated that TiO2-GO showed high efficient separability due to its accelerated settling behaviour. Zeta-potential analysis showed that the accelerated sedimentation of the catalyst was attributed to the aggregation of TiO2-GO resulting from the electrostatic attraction between TiO2 and GO. The TiO2-GO composite with a mass ratio of 100:2 (TiO2-2%GO) achieved both higher separability and good photocatalytic activity for stormwater disinfection. Its suspension became clear (turbidity < 50 NTU) after 8 h of sedimentation, while 99.5% of E.coli were deactivated in 90 min. The TiO2-GO composite exhibited excellent durability; no apparent change in the separability of TiO2-2%GO was observed after 10 treatment cycles (15 h in total), while only slight decrease in the photocatalytic activity was noted. In conclusion, the developed TiO2-GO composite showed promising results for stormwater disinfection.

Transformation of TiOF2 cube to a hollow nanobox assembly from anatase TiO2 nanosheets with exposed {001} facets via solvothermal strategy.

Hierarchical nanostructures have attracted increasing interest due to their exceptional properties and widespread potential applications. In this paper, anatase TiO2 hollow nanoboxes (TiO2-HNBs) are formed by assembly of nanosheets with exposed {001} facets by solvothermal treatment of TiOF2 cubes in alcohols (tert-butanol and ethanol) at 180 °C. It was found that phase transformation of TiOF2 to anatase TiO2 begins at corners and edges of TiOF2 cubes due to in situ hydrolysis of TiOF2, where water was produced by dehydration of alcohol molecules. With extension the reaction time, TiO2-HNB assemblies from nanosheets with exposed high-energy {001} facets were formed due to the steady inside-outside dissolution-recrystallization process. However, the resulting hierarchical TiO2-HNBs are unstable, which can decompose to discrete high-energy TiO2 nanosheets if the reaction time is further extended. The hierarchical TiO2-HNBs show higher photocatalytic activity than discrete high-energy TiO2 nanosheets and P25 TiO2 due to the unique structures of TiO2-HNBs.