Swelling behaviors of superabsorbent composites based on acrylic acid/acrylamide copolymer and acid-modified attapulgite.

The swelling behaviors and water retention of superabsorbent materials prepared from acrylic acid/acrylamide copolymer and acid-modified attapulgite under ultrasonic treatment and different pH conditions were investigated. The results demonstrated that a suitable amount of attapulgite can effectively improve the absorption capacity. The superabsorbent achieved the highest absorptions of 1257.54 g g-1 and 209.45 g g-1 in distilled water and a 0.9 wt% NaCl solution, and a higher water absorbency occurred over a wide pH range of 5-9 when the ultrasonic power was 200 W, and the attapulgite content was 10%. Addition of attapulgite could significantly increase the water absorption and retention of this kind of material, which can be applied as a sand-fixing material.

Effective degradation of phenol by activating PMS with bimetallic Mo and Ni Co-doped g C3N4 composite catalyst: A Fenton-like degradation process promoted by non-free radical 1O2.

The application of bimetal supported graphite phase carbon nitride in activated peroxymonosulfate (PMS) process has become a research hotspot in recent years. In this study, 8-g C3N4/Mo/Ni composite catalyst material was successfully prepared by doping Mo and Ni in graphite phase carbon nitride. The bimetallic active sites were formed in the catalyst, and PMS was activated by the metal valence Mo6+/Mo4+ and Ni2+/Ni(0) through redox double cycle to effectively degrade phenol. When pH was neutral, the degradation rate of 20 mg/L phenol solution with 8-g C3N4/Mo/Ni (0.35 g/L) and PMS (0.6 mM) could reach 95% within 20 min. The degradation rate of 8-g C3N4/Mo/Ni/PMS catalytic system could reach more than 90% within 20min under the condition of pH range of 3-11 and different anions. Meanwhile, the degradation effects of RhB, MB and OFX on different pollutants within 30min were 99%, 100% and 82%, respectively. Electron spin resonance and quenching experiments showed that in 8-g C3N4/Mo/Ni/PMS system, the degradation mechanism was mainly non-free radicals, and the main active species in the degradation process was 1O2. This study provides a new idea for the study of bimetal supported graphite phase carbon nitride activation of PMS and the theoretical study of degradation mechanism.

Correlations among Antibiotic Resistance Genes, Mobile Genetic Elements and Microbial Communities in Municipal Sewage Treatment Plants Revealed by High-Throughput Sequencing.

Municipal sewage treatment plants (MSTPs) are environmental pools for antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs), which is cause for growing environmental-health concerns. In this study, the effects of different wastewater treatment processes on microbial antibiotic resistance in four MSTPs were investigated. PCR, q-PCR, and molecular cloning integrally indicated that the tetracycline resistance (tet) genes significantly reduced after activated-sludge treatment. Illumina high-throughput sequencing revealed that the broad-spectrum profile of ARGs and mobile element genes (MGEs) were also greatly decreased by one order of magnitude via activated sludge treatment and were closely associated with each other. Correlations between ARGs and bacterial communities showed that potential ARB, such as Acinetobacter, Bacteroides, and Cloaibacterium, were removed by the activated-sludge process. Sedimentation processes cannot significantly affect the bacterial structure, resulting in the relative abundance of ARGs, MGEs, and ARB in second-clarifier effluent water being similar to activated sludge. A comprehensive study of ARGs associated with MGEs and bacterial structure might be technologically guided for activated sludge design and operation in the MSTPs, to purposefully control ARGs carried by pathogenic hosts and mobility.

Pollution Characteristics, Source Apportionment, and Health Risk Assessment of Potentially Toxic Elements (PTEs) in Road Dust Samples in Jiayuguan, Hexi Corridor, China.

The sources of potentially toxic elements (PTEs) in road dust are complex and potentially harmful to humans, especially in industrial cities. Jiayuguan is the largest steel-producing city in Northwest China, and this study was the first to conduct a related study on PTEs in road dust in this city, including the pollution characteristics, source apportionment, and health risk assessment of PTEs in road dust. The results showed that the highest concentration of PTEs in the local road dust samples were Mn, Ba, Zn, and Cr. The enrichment factor (EF) of Se was the highest, and it was "Very high enrichment" in areas other than the background area, indicating that the local Se was more affected by human activities. The geoaccumulation index (Igeo) of Se was also the highest, and the pollution level was 5 in all areas except the background area, indicating that the local Se was more polluted and related to coal combustion. The sources of PTEs in local road dust samples mainly included geogenic-industrial sources, coal combustion, traffic sources, and oil combustion. For the non-carcinogenic risk, the hazard index (HI) of each element of children was higher than that of adults, and the sum of the HI of each element was greater than 1, indicating that there was a non-carcinogenic risk under the combined influence of multiple elements, which was especially obvious in industrial areas. For the carcinogenic risk, the cancer risk (CR) of Cr at a certain point in the industrial area exceeded 10-4, which was a carcinogenic risk, and the Cr in this area may be related to the topsoil of the local abandoned chromate plant.

Synthesis of Double-Shell Hollow TiO2@ZIF-8 Nanoparticles With Enhanced Photocatalytic Activities.

Synthesis of semiconductor-MOF heterostructure photocatalysts has attracted considerable attention for their thermal stability, controllable crystallinity, and enhanced photocatalytic activity. In this work, the hollow nanostructure of anatase TiO2 was prepared by etching SiO2 from core-shell SiO2@TiO2 nanoparticles. ZIF-8, one of the metal-organic frameworks (MOFs), was hybrid synthesized on the surface of hollow TiO2 and formed double-shell hollow nanoparticles. The photocatalytic activity of the double-shell hollow TiO2@ZIF-8 nanoparticles toward methylene blue (MB) under UV light irradiation was processed, and the highest photocatalytic efficiency of 99.1% was shown compared with TiO2 and SiO2@TiO2 nanoparticles. This study suggests a promising approach to achieve an advanced photocatalytic performance toward dye degradation using MOFs for the surface engineering of semiconductors.

Spatial frequency doubling with two-step technique.

The phenomenon of spatial frequency doubling generated by a two-step technique with the collimated beam at normal incidence in the second exposure is presented. Theoretical analysis demonstrates that the phenomenon is induced by the Talbot effect in photoresist and the superposition of two exposures, and the minimum achievable period of the grating with double spatial frequency can be close to one half of the exposure wavelength in vacuum, divided by the refractive index of photoresist λ/2n. The two-step technique has the potential to be a simpler and more practical resolution-improving technique for the Talbot-effect-based approach of spatial frequency doubling.

[Low-temperature preparation of TiO2/PS/Fe3O4, and its photocatalytic activity and magnetic recovery].

This study reports the fabrication of magnetically responsive titania catalyst, which consisted of a magnetic core surrounded by a titania shell. The magnetic core (oleic acid-modified Fe3O4 nanoparticles) was modified with polystyrene as inert isolating layer. The magnetic photocatalyst was prepared at low temperature (90 degrees C) and a neutral pH (about 7). The phase composition, morphology, surface properties and magnetic properties of the composite particles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), fourier infrared photometer (FT-IR) and vibrating sample magnetometer (VSM). The photocatalytic activity of the samples were determined by degradation of phenol and their recovery characteristics were determined by a self-regulating magnetic recycling equipment. The results illustrated that the mean diameter of anatase titanium dioxide synthesized at low temperature was 2-5 nm, the catalyst TiO2/PS/Fe3O4 [the molar ratio of the magnetic photocatalyst was n(TiO2): n(St): n(Fe3O4) = 60:2.5:1] had the structural integrity of shell/shell/core, and titanium dioxide was loaded firmly on the PS/FeO4 surface. The photocatalytic degradation of phenol followed first-order reaction kinetics and the reaction rate constant K of the TiO2/PS/Fe3O4 [n(TiO2): n(St): n (Fe3O4) = 60:2.5:1] was 0.0258, which was close to that of pure TiO2 (K = 0.0262). After 5 times recycling, the K value reduced only by 0.0034. The catalyst had a strong magnetic induction, and the average recovery rate reached 92%. The magnetic TiO2 photocatalyst prepared by this low-temperature hydrolysis method has a good application prospect.

Adaptive watermarking scheme using a gray-level computer generated hologram.

We present a new adaptive blind watermarking scheme using a gray-level computer generated hologram in the discrete wavelet transform domain. By utilizing an improved fuzzy clustering technique and human visual system , the watermark can be adaptively embedded according to block classification. To keep imperceptibility and robustness, a novel iterative embedding algorithm is adopted to change the to-be-embedded coefficients. Compared with the standard Fuzzy c-means (FCM) clustering, the suggested improved FCM (IFCM) converges more quickly and can avoid local optimum effectively. The experimental results demonstrate that the proposed scheme provides good robustness to withstand different kinds of common attack. Compared with other methods, the proposed method has the distinct advantage of better robustness to a JPEG compression attack.