Search

Recalcitrant pollutants in water with high resistance to natural degradation such as per/polyfluoroalkyl substances (PFAS) highlight the need for sustainable, cheap, and effective treatment approaches. Although photocatalysis under direct sunlight can be beneficial due to the usage of ambient conditions for the reaction, air as the oxidant, and sunlight as the energy source, identifying sustainable and sunlight photoactive materials and a process that is both scalable and industrially feasible are challenging. Herein, we report the use of ZnO/cellulose nanofiber (CNF) composites for the photodegradation of PFOA and PFOS upon irradiation by sunlight in a continuous flow photoreactor. HPLC/MS/MS and fluoride quantification using the SPADNS method were used to track the degradation of PFAS and by-product formation. Aqueous solutions of three different standard PFAS samples containing 1200 µg/L of PFOA, 800 µg/L PFOS, and a mixture of 900 µg/L of PFOA and 900 µg/L of PFOS, and a wastewater treatment plant sample with 2.5 µg/L of an environmental mixture of PFAS compounds present in urban wastewater were used for the photocatalytic degradation tests. The concentration of these pollutants and their by-products in these samples was reduced to 0.5 µg/L, 0.07 µg/L, 0.15 µg/L, and 0.3 µg/L with an EE/O figure of merit of 0.19, 0.28, 0.43, 0.88 kWh/m3 per order, respectively. It was observed that the standard mixture and the wastewater treatment plant samples were harder to degrade as compared to the standards containing one PFAS compound. Reusing the catalyst for three cycles showed less than 4% reduction in photodegradation over irradiation time. These findings emphasize the importance of location-specific design as the choice of photocatalyst is enabled by the UVA/B solar radiance characteristics present in Australia. [Display omitted] • Sun-flow photocatalytic PFASs degradation was investigated. • photodegradation of real wastewater containing PFASs was studied. • For the photodegradation process, zinc oxide/cellulose nanofiber catalyst was used. • The concentration of pollutants was reduced to below advised limits. [ABSTRACT FROM AUTHOR]

The zinc (Zn) requirements of subterranean clover (Trifolium subteraneaum L.) are well known for the predominantly marginally acidic to neutral sandy soils of southwestern Australia, but the Zn requirements of French serradella (Ornithopus sativus Brot.) and biserrula (Biserrula pelecinus L.), now also grown on these soils, is not known and were investigated in a glasshouse pot experiment. Soil was collected from field plots never treated with Zn or treated once only with 0.5 and 1.0 kg Zn/ha as Zn oxide either in 1983, 1984, 1986, 1990, 1992, 1996, 1997, or 2000. In the pot experiment, six levels of Zn were freshly-applied to samples of soil collected from each Zn treatment of the field experiment, and pots were sown either with subterranean clover cv. 'Dalkeith', French serradella cv. 'Margurita', or biserrula cv. 'Casbah'. The pasture species were defoliated by cutting pasture herbage 3 cm above the soil surface for up to 4 consecutive defoliations. The approximate linear relationship between the level of freshly-applied Zn in the pot experiment required to produce 90% of the maximum yield of dried defoliated herbage (y-axis) and the number of years since Zn was applied in the field (x-axis) was used to project the number of years it took for the 0.5 or 1.0 kg Zn/ha treatments applied in the field to require the same level of freshly-applied Zn to produce 90% of the maximum yield of the nil-Zn treatment in the field. This was 18-19 years for the 0.5 kg Zn/ha treatment and 32-35 years for the 1.0 kg Zn/ha treatment. The range in values was due to differences between legume species and the defoliation treatments, which were not significant. When yields were measured, samples of young growth (YG) were separated from the rest of the defoliated herbage (ROH) and the concentration of Zn in YG and ROH was measured. The concentration of Zn in YG that was related to 90% of the maximum yield of defoliated dried herbage (critical tissue test value) was (mg/kg) 13 for subterranean clover, 17 for French serradella, and 19 for biserrula; respective critical tissue test values for ROH were 19, 24, and 21 mg/kg. The approximate linear relationship between critical Zn concentration in YG (y-axis) and the number of years since Zn was applied in the field (x-axis) was used to project the number of years it took for the 0.5 and 1.0 kg Zn/ha levels applied in the field to reach the same critical tissue test value as the nil-Zn treatment of the field experiment. This was 17-20 years for the 0.5 kg Zn/ha treatment and 31-37 years for the 1.0 kg/ha treatment, which was similar to the 18-19 and 32-35 years projected using yield data. Before sowing the legumes in the pot study soil samples were collected to measure soil test Zn using the DTPA procedure. The critical DTPA soil test Zn, the soil test value that was related to 90% of the maximum yield of defoliated dried herbage, was about 0.20 mg Zn/kg for the 3 pasture legume species and all Zn treatments in the field and pot studies. [ABSTRACT FROM AUTHOR]

• Zn/ZnO (99.5%pure, 3-11μm) can be recovered carbothermically from the black mass. • The yield and quality of Zn/ZnO make significant impact to the economic. • Plant that processed at least 100 tonnes/year black mass is economically viable. • The minimum annual income and IRR value is AU$509,742 and 19.1%, respectively. • Use of concentrated solar energy shift the limit of viability to 15 t/year capacity. • This open up opportunity to the small to medium size industry in recycling process. While alkaline battery is the one that dominates portable battery market in Australia, its recycling rate is far from sufficient. In the current work, small-scale carbothermic process to recover high value zinc/zinc oxide (Zn/ZnO) powder from spent alkaline black mass is studied. The study involved experimental investigation, process modelling that includes thermodynamics and mass and energy balance calculations, and techno-economic analyses. Continuous and batch-type process plants; as well as adoption of solar energy were considered in the study. It was found that Zn/ZnO recovery process is economically viable at the current Australian annual black mass production (200 tonnes/year) with a minimum annual income and IRR value over 20 years plant lifetime of AU$509,742 and 19.1%, respectively. A minimum capacity of 100 tonnes/year is expected to ensure that the process is economically favourable. The application of concentrated solar energy, however, enables the batch process to be carried out at a much lower capacity of 15 tonnes/year. The results of this study can be extended to better inform the feasibility of a small-scale process in countries other than Australia. [ABSTRACT FROM AUTHOR]

This section offers news briefs on nanotechnology research. U.S. researchers have managed to isolate and crystallize a gold-thiolate cluster, which allowed them to determine the X-ray structure of gold nanoparticles. Scientists in Australia have studied the behavior of zinc oxide nanoparticles in freshwater systems to better understand their potential toxicity. Researchers in Spain have used a carbon nanotube to build a transistor that detects single electrons.