Enhanced reduction of sulfate and chromium under sulfate-reducing condition by synergism between extracellular polymeric substances and graphene oxide.

Microbial reduction of sulfate and metal were simultaneously enhanced in the presence of graphene oxide (GO)-like nanomaterials, however, the mechanism remained unclear. In this study, bio-reduction of Cr was compared between free-living bacterium BY7 and immobilized BY7 (BY-rGO) on reduced GO particles. The role of extracellular polymeric substances (EPS) and rGO material on reduction of sulfate and Cr was investigated. Cr(VI) was reduced to Cr(III) and elemental Cr by BY-rGO particles up to 51% and 28%, respectively. EPS produced by the bacterium BY7 mainly consisted of proteins, polysaccharides, nucleic acids and humic substances. Concentration of EPS was sharply increased (about 54%) with the addition of graphene oxide, while the composition of EPS components was strongly affected by the exposure to Cr. By removing surface EPS without breaking the cells, reduction activities of sulfate and chromium by both BY-rGO particles and free-living BY7 cells were decreased. In contrast, reduction of sulfate and Cr by the free-living BY7 cells was enhanced with external addition of extracted EPS. Based on electrochemical analysis, the reduction peak indicating enhanced electron transfer was lost after removing EPS. Moreover, the contribution of each EPS fractions on sulfate and Cr reduction followed an order of polysaccharides > proteins > humic substances. Therefore, microbial sulfate and Cr reduction processes in the presence of BY-rGO particles were enhanced by the increasing amounts of EPS, which likely mediated electron transfer during sulfate and Cr reduction, and relieved bacteria from metal toxicity. Nevertheless, the presence of rGO was crucially important for elemental Cr production under sulfate-reducing condition, which might contribute to lowering electric potential or reducing activation energy for Cr(III) reduction. This work provided direct evidences for enhancing sulfate and Cr reduction activities by supplement of EPS as an additive to increase treatment efficiency in environmental bioremediation.

Removal of U(VI) from nuclear mining effluent by porous hydroxyapatite: Evaluation on characteristics, mechanisms and performance.

The effluents from nuclear mining processes contain relatively high content of radionuclides (such as uranium), which may seriously threaten the environment and human health. Herein, a novel adsorbent, porous hydroxyapatite, was prepared and proven highly efficient for removal of uranyl ions (U(VI)) given its high U(VI) uptake capacity of 111.4 mg/g, fast adsorption kinetics, and the potential stabilization of adsorbed U(VI). A nearly complete removal of U(VI) was achieved by porous HAP under optimized conditions. Langmuir model could well describe the adsorption equilibrium. The data fit well with pseudo-second-order kinetic model, suggesting that U(VI) adsorption is primarily attributed to chemisorption with porous HAP. Intraparticle diffusion analysis showed that the intraparticle diffusion is the rate-limiting step for U(VI) adsorption by porous HAP. After removal by porous HAP, the adsorbed U(VI) ions were incorporated into tetragonal autunite, which has a low solubility (log Ksp: -48.36). Our findings demonstrate that the porous HAP can effectively remediate uranium contamination and holds great promise for environmental applications.

Phosphorous Retention and Release by Sludge-Derived Hydrochar for Potential Use as a Soil Amendment.

To solve both the problems of P deficiency in arable soil and excessive waste sludge disposal, we evaluated hydrothermal carbonization of sludge with the aim of recycling sludge P resources for soil amendment. In contrast with pyrochars obtained through pyrolysis, hydrochars generated from hydrothermal carbonization often feature variable properties and therefore require detailed characterization. In this study, sludge-derived hydrochars were evaluated to determine their P content and fractionation, release and availability of P, and P adsorption and desorption behavior. We also assessed changes in P availability after soil was amended with the hydrochars. Our results showed that the chars were rich in total P (up to 25,175 mg kg), but most of the free fractions were transformed to bound fractions, thereby reducing the available P concentrations. However, available P content was >417 mg kg, which was far higher than soil demand. The hydrochars shifted from releasing to adsorbing P adsorbent when the environmental P concentration increased above 20 mg L. The hydrochars showed a high phosphate adsorption capacity (up to 23,815 mg kg) and the adsorbed P could be readily released. The addition of 1% P-laden hydrochar significantly enhanced the soil available P content by 8.93 mg kg. These findings have important implications for further development of hydrochar-based P carriers as a slow-releasing fertilizer.

Complementary approaches for the evaluation of biocompatibility of 90Y-labeled superparamagnetic citric acid (Fe,Er)3O4 coated nanoparticles.

Magnetic nanoparticles (MNPs) are of immense interest for diagnostic and therapeutic applications in medicine. Design and development of new iron oxide-based MNPs for such applications is of rather limited breadth without reliable and sensitive methods to determine their levels in body tissues. Commonly used methods, such as ICP, are quite problematic, due to the inability to decipher the origin of the detected iron, i.e. whether it originates from the MNPs or endogenous from tissues and bodily fluids. One of the approaches to overcome this problem and to increase reliability of tracing MNPs is to partially substitute iron ions in the MNPs with Er. Here, we report on the development of citric acid coated (Fe,Er)3O4 nanoparticles and characterization of their physico-chemical and biological properties by utilization of various complementary approaches. The synthesized MNPs had a narrow (6-7nm) size distribution, as consistently seen in atomic pair distribution function, transmission electron microscopy, and DC magnetization measurements. The particles were found to be superparamagnetic, with a pronounced maximum in measured zero-field cooled magnetization at around 90K. Reduction in saturation magnetization due to incorporation of 1.7% Er3+ into the Fe3O4 matrix was clearly observed. From the biological standpoint, citric acid coated (Fe,Er)3O4 NPs were found to induce low toxicity both in human cell fibroblasts and in zebrafish (Danio rerio) embryos. Biodistribution pattern of the MNPs after intravenous administration in healthy Wistar rats was followed by the radiotracer method, revealing that 90Y-labeled MNPs were predominantly found in liver (75.33% ID), followed by lungs (16.70% ID) and spleen (2.83% ID). Quantitative agreement with these observations was obtained by ICP-MS elemental analysis using Er as the detected tracer. Based on the favorable physical, chemical and biological characteristics, citric acid coated (Fe,Er)3O4 MNPs could be further considered for the potential application as a diagnostic and/or therapeutic agent. This work also demonstrates that combined application of these techniques is a promising tool for studies of pharmacokinetics of the new MNPs in complex biological systems.

[Effect of moxibustion on motility, absorption and content of ATP in small intestine of spleen-deficiency rats].

OBJECTIVE: To explore the mechanism of reinforcing function of moxibustion to spleen-stomach. METHODS: Forty healthy Sprague Dawley rats were randomly divided into 4 groups: group A (blank group), group B (model group), group C (moxibustion group) and group D (herbs group). The rat model of spleen-deficiency was established by intragastric administration with 200% Dahuang (Rhubarb) infusion. The rats in group A and B, and D served as the blank control, model, and Sijunzi decoction group respectively, while those in group C received moxibustion at "Zusanli" (ST 36), "Zhongwan" (CV 12), "Guanyuan" (CV 4), "Pishu" (BL 20) and "Weishu" (BL 21), etc. The common symptoms and intestinal propulsive rate were observed. The content of I-xylose in serum was detected by phloroglucinol method. Colorimetry method was used to detected content of ATP in jejunum tissues. RESULTS: Compared with group A, the symptom score in group B was increased significantly (both P < 0.01), while the intestinal propulsive rates, the content of D-xylose in serum and ATP in jejunum tissues were decreased significantly (P < 0.05, P < 0.01). Compared with group B, the symptom score in group C and D was decreased significantly (both P < 0.01), while the intestinal propulsive rates, the content of D-xylose in serum and ATP in jejunum tissues were increased significantly (P < 0.05, P < 0.01). There were no significant difference between group C and D (P > 0.05). CONCLUSION: Moxibustion at "Zusanli" (ST 36) etc. could relieve symptoms of spleen-deficiency, enhance motility and absorption functions of small intestine and improve metabolism of small intestine. The efficacy is equal to administration of Sijunzi decoction.

[Effects of cigarette, alcohol consumption and sauna on sperm morphology].

OBJECTIVE: To investigate effects of cigarette, alcohol consumption and sauna on sperm morphology. METHODS: 602 cases of male infertility were selected from our case database, who were divided into three subgroups: smoking (243) , drinking(224), sauna(135) and those without any of the above habits were taken as the corresponding controls. The sperm morphology were analyzed by automated sperm morphology analyzer(ASMA). A questionnaire was voluntarily filled out by patients in order to investigate cigarette, alcohol consumption and sauna frequency. RESULTS: The normal morphologic sperm rates in cigarette, alcohol consumption and sauna groups were lower than those in the corresponding control groups, respectively(P <0.05, P <0.001). Percentages of irregularity head sperm were higher than those in normal controls, respectively(P <0.05). CONCLUSION: Cigarette, alcohol consumption and sauna could affect sperm morphology, especially caused increasing of irregularity head sperm.

Fabrication of a one-dimensional array of nanopores horizontally aligned on a Si substrate.

A one-dimensional array of nanopores horizontally aligned on a silicon substrate was successfully fabricated by anodic aluminum oxidation (AAO) using a modified two-step procedure. SEM pictures show clear nanostructures of well-aligned one-dimensional nanopore arrays without cracks at the interfaces of the sandwiched structures. The processes are compatible with the planar silicon integrated circuit processing technology, promising for applications in nanoelectronics. The formation mechanism of a single nanopore array on Si substrates was also discussed.