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We use hard x-ray photoemission spectroscopy (HAXPES) combined with x-ray standing waves to characterize a series of Pd/Y based periodic multilayers designed to work in the 7.5-11 nm range. The samples are prepared by magnetron sputtering. For different samples thin B4C barrier layers are inserted at different locations within the stack: at the Pd-on-B4C interfaces, at the B4C-on-Pd interfaces or at both interfaces. These barrier layers are expected to improve the reflecting performance of the multilayers [1,2]. The aimed period of the samples is 4 nm. The experiments consist in obtaining the core level photoemission spectra of the various elements for a series of grazing angles. The angular scan is made in the range given by the Bragg law, considering the multilayer period and the incident photon energy, in order to generate to strong standing wave in the stack. Owing to the period of the multilayer and the presence of a 2.5 nm-thick capping layer, the photon energy is chosen to be 10 keV in order to probe the first 5-6 periods of the stack. Thus the Bragg angle is a little less than 1°. Rotating the sample enables putting the nodes of the electric field at some particular location of the stack, thus to make the excitation depth-selective, coming from one interface or another or from the center of one given layer. The changes of the chemical shift of the Pd 2p and 3d, Y 2p and 3d, N 1s, C 1s and B 1s core level peaks as a function of the angle, that is to say as a function of the location in the stack will give information about the possible interfacial processes taking place in the multilayers.

The treatment and disposal of waste activated sludge (WAS) has become one of the major challenges for the wastewater treatment plants (WWTPs) due to large output, high treatment costs and enriched substantial emerging contaminants (ECs). Therefore, reducing sludge volume, recovering energy and resource from WAS, and removing ECs and decreasing environmental risk have gained increasing attentions. Calcium peroxide (CaO2), a versatile and safe peroxide, has been widely applied in terms of WAS treatment including sludge dewatering, anaerobic sludge digestion and anaerobic sludge fermentation due to its specific properties such as generating free radicals and alkali, etc., providing supports for sludge reduction, recycling, and risk mitigation. This review outlines comprehensively the recent progresses and breakthroughs of CaO2 in the fields of sludge treatment. In particular, the relevant mechanisms of CaO2 enhancing WAS dewaterability, methane production from anaerobic digestion, short-chain fatty acids (SCFA) and hydrogen production from anaerobic fermentation, and the removal of ECs in WAS and role of experiment parameters are systematically elucidated and discussed, respectively. Finally, the knowledge gaps and opportunities in CaO2-based sludge treatment technologies that need to be focused in the future are prospected. The review presented can supply a theoretical basis and technical reference for the application of CaO2 for improving the treatment of WAS.

The negative effects of ubiquitous microplastics on wastewater treatment have attracted increasing attention. However, the potential impacts of microplastics on anaerobic granular sludge (AGS) remain unknown. To fill this knowledge gap, this paper investigated the response of AGS to the exposure of model microplastics (polyethylene terephthalate (PET-MPs)) and provided insights into the mechanisms involved. The 84 days' long-term exposure experiments demonstrated that PET-MPs, at relatively low level (15 MP L-1) did not affect AGS performance during anaerobic wastewater treatment, while 75-300 MP L-1 of PET-MPs caused the decreases of COD removal efficiency and methane yields by 17.4-30.4% and 17.2-28.4%, accompanied with the 119.4-227.8% increase in short-chain fatty acid (SCFA) accumulation and particle breakage. Extracellular polymeric substances (EPS) analysis showed that dosage-dependent tolerance of AGS to PET-MPs was attributed to the induced EPS producing protection role, but PET-MPs at higher concentrations (75-300 MP L-1) suppressed EPS generation. Correspondingly, microbial community analysis revealed that the populations of key acidogens (e.g., Levilinea sp.) and methanogens (e.g., Methanosaeta sp.) decreased after long-term exposure to PET-MPs. Assessment of the toxicity of PET-MPs revealed that the leached di-n-butyl phthalate (DBP) and the induced reactive oxygen species (ROS) by PET-MPs were causing toxicity towards AGS, confirmed by the increases in cell mortality and lactate dehydrogenase (LDH) release. These results provide novel insights into the ecological risk assessment of microplastics in anaerobic wastewater treatment system.

Elemental Ag0 is well known for its remarkable catalytic and antibacterial properties, thus the regeneration of valuable Ag0 metal from Ag+ wastewater is of great significance. In this study, a novel polyethylenimine (PEI) modified potassium tungsten oxide (N-K2W4O13) adsorbent was prepared for Ag+ removal and reduction to Ag0 using glutaraldehyde as crosslinking agent. XPS and FT-IR spectra verified PEI successfully anchored on the surface O and W atoms of K2W4O13 through aldehyde bridges. The content of PEI in N-K2W4O13 was calculated as 8.74wt% by TG curve. A heterogeneous PEI coating was observed in the SEM and TEM images. The N-K2W4O13 exhibited larger Ag+ uptake (48.25mg/g) than the raw K2W4O13 (42.50mg/g) though required a longer equilibrium time. This was due to the combined results of strong chelation and weak electrostatic repulsion that meanwhile occurring on the positive-charged surface of N-K2W4O13. The maximum Ag+ uptake on N-K2W4O13 was 72.5mg/g, which was larger than many of the reported adsorbents. Furthermore, the prepared N-K2W4O13 displayed good anti-interference toward background ions (Na+, K+) and hold a stable Ag+ removal (>95%) after five runs of recycling tests. The mechanism studies elucidated that NH/N groups from the PEI modified N-K2W4O13 mainly accounted for the Ag+ adsorption and Ag0 recovery in the adsorption-reduction process. Ion-exchange between Ag+ and K+ from the N-K2W4O13 lattice also occurred. This work provided a facile method to synthesize a promising adsorbent for Ag+ wastewater remediation and valuable Ag0 recovery.

We use hard x-ray photoemission spectroscopy (HAXPES) [1] to characterize a series of Pd/Y nano-scale multilayers designed to work in the 7.5-11 nm wavelength range. The samples, prepared by magnetron sputtering, are deposited either with or without nitrogen introduced in the sputtering gas. The aimed period of the samples is 4 nm. The experiments consist in obtaining the core level spectra of the various elements under hard X-ray exposure. The interferences between the incident photons and reflected photons result in a periodic electric field that influences the photoemission intensity. Such influence depends on the grazing angle of the incident X-ray beam, thus we measure the photoemission spectra as a function of the grazing angle. The angular scan is made in the range given by the Bragg law, the multilayer period and the incident photon energy. Given the period of the multilayer and the presence of a 2.5 nm-thick B4C capping layer, the photon energy is chosen to be 10 keV in order to probe the first 5-6 periods of the stack. Thus the Bragg angle is a little less than 1°. Rotating the sample enables putting the nodes of the electric field at some particular location of the stack, thus to make the excitation depth-selective, probing one interface or another or the center of one given layer. The changes of the chemical shift in the Pd 2p and 3d, Y 2p and 3d, O 1s, N 1s, C 1s and B 1s as a function of the angle, that is to say as a function of the location in the stack will give information about the possible interfacial process taking place in the Pd/Y multilayers.

Graphene possesses a peculiar band structure and hence exhibits many fascinating properties from room temperature quantum Hall effect to massless Dirac fermions. With the understanding of graphene, topological materials with the properties similar to or even beyond graphene gradually rise and draw much attention, such as Silicene, Bi2Se3, WTe2 and most recently TaAs. Then a question arises: is it possible for another 2D carbon lattice to exhibit similar properties? If so, what are the determining factors? Here, we demonstrate that a novel two-dimensional carbon allotrope called T-graphene can possess Type-I Dirac points / loops based on the first-principles calculations [1]. T-graphene described by the plane group p4mm (See Fig. 1) can be energetically metastable and dynamically stable. The band structure of T-graphene in Fig. 1 shows the linear dispersion relation at the Fermi level. Two Dirac points are located at asymmetric positions Ξ(0.170, 0.170) between Γ and M and Λ(0, 0.249) between X and Γ, respectively. Furthermore, the linear dispersion relation near the Fermi surface exists in every direction and the cross points form a loop. Such Dirac fermions and a high υF are attributed to crossing π and π* bands and two sublattices. Under certain structure tailoring or straining, the linear dispersion relation is found to be retained. Two type of nanoribbons tailored from T graphene are predicted to have interesting magnetic properties. Besides, two possible routes to obtain T graphene are proposed: carbon deposition on certain metal substrates or electron beam irradiation on the tailored graphene growing on Ni (111). The results provide new insights to search and fabricate two-dimensional topological material.