摘要：
The Mg/Al layered double hydroxide (Mg/Al-LDH) intercalated with the [Formula: see text] (MoS4-LDH) impregnated into poly(acrylamide-co-sodium acrylate) (PP) was synthesized as layered double hydroxides-PP (LDHS-PP), whose characterization, adsorption properties and mechanisms were investigated. The maximum adsorption capacity (qm) for Cd(II) was approximately 2789.58 mg/g by 1% LDHS-PP, while it was approximately 1893.09 mg/g by PP, which indicated that the MoS4-LDH greatly improved the Cd(II) uptake for PP in aqueous solution. In strongly acidic conditions ( approximately pH 3.0), there was still a good removal efficiency of about 45.65% by the 1% LDHS-PP, while that of PP was almost zero. At pH 5.0 the removal efficiency increased to 85.17% by the 1% LDHS-PP. The sorption kinetics for the 1% LDHS-PP was described well by a pseudo-second-order kinetic model. X-ray photoelectron spectrometry (XPS) and elemental distribution maps further confirmed the presence of MoS4-LDH in the PP and most of the Cd(II) chemisorption based on the Cd-S bonding. Due to its high removal efficiency and acid resistance, LDHS-PP is a promising in-situ fixation agent for the remediation of agricultural soil polluted with Cd(II) at low pH.
摘要：
<jats:p>An amino-functionalized water-retaining agent (PPM40-NH<jats:sub>2</jats:sub>) and a water-retaining agent lacking functionalization (PPM40) were prepared to investigate their selective Cd(II) removal properties. The affinity for Cd(II) was increased after introducing the amino functional group.
The <jats:italic>SF<jats:sub>Cd/Ca</jats:sub></jats:italic> of PPM40-NH<jats:sub>2</jats:sub> was 3–7 fold higher than that of PPM40 although the <jats:italic>C</jats:italic><jats:sub>Ca</jats:sub> was 100–1000 times higher than that of <jats:italic>C</jats:italic><jats:sub>Cd</jats:sub>. The chelating effect of –COOH and –NH<jats:sub>2</jats:sub> in PPM40-NH<jats:sub>2</jats:sub> corresponded
well with the selective adsorption of Cd(II), as confirmed by simulations. A seed germination experiment demonstrated that PPM40-NH<jats:sub>2</jats:sub> could act as a filter of heavy metals to supply “clean” water for the roots of the <jats:italic>pakchoi</jats:italic> plant. The leaching experiment indicated
that PPM40-NH<jats:sub>2</jats:sub> is an efficient in situ fixation agent for the remediation of agricultural soil contaminated with Cd(II) in the presence of high concentrations of Ca(II) salts.</jats:p>
摘要：
Chitosan-stabilized FeS magnetic (MC-FeS) composites were successfully prepared to address the easily oxidization of FeS and enhance Cr(VI) removal from water. Results showed that the MC-FeS composites enhanced the Cr(VI) removal capacity as compared to bare FeS. Further investigation using X-ray photoelectron spectroscopy showed that FeOOH, S8, Cr2O3, Cr2S3, and a Fe(III)-Cr(III) complex were apparently introduced by Cr(VI), Fe(II), and S(-II), respectively. The sorption kinetics could be interpreted using a pseudo-second-order kinetic model, whereas the isotherms were simulated using the RedlichPeterson isotherm model indicating Cr(VI) removal by MC-FeS composites was a hybrid chemical reactionsorption process. In addition, the MC-FeS composite presented high stability against aging and performed well in a long-term reaction system and typical natural water environment. The effective performance of MC-FeS composites shows their great potential in wastewater remediation contaminated by heavy metals.
摘要：
The ecological implications of livestock production intensification have received sustained attention across the globe. Anaerobic digestion is the main process for livestock waste treatment. However, the ecological consequences of dissolved organic matter originating from anaerobic digestion (AD-DOM) in eutrophic water bodies remain elusive. In this study, the physiological responses of a bloom-forming cyanobacterium, Microcystis aeruginosa, to AD-DOM were investigated. Moreover, the composition of AD-DOM was identified by using thermochemolysis followed by gas chromatography-mass spectrometry (GC-MS) analysis. The growth of M. aeruginosa FACHB905 was not sensitive to low levels (0.625-1.25%, V/V) of AD-DOM but was inhibited by high levels (2.5-5%, V/V) of AD-DOM, resulting from photoinhibition damage to photosystem II (PSII). The main target of AD-DOM in PSII was the electron accepting side (psi(0)) or the electron donor side (phi P-0), depending on time variables. The reactive oxygen species (ROS) level showed a positive correlation with AD-DOM addition; however, it was higher than that of the control for 3.75-5% AD-DOM on the 6th day. The intracellular microcystin contents (including MC-LR and Dha(7)-MC-LR) decreased in response to AD-DOM addition, but extracellular microcystin increased after 6 days of exposure. In addition, GC-MS detection showed that AD-DOM is mainly composed of lignin-derived aromatic compounds, alkanes/alkene, nitrogencontaining compounds, and sterols. The results presented in this study suggested that AD-DOM released from the livestock industry may play a subtle role in affecting harmful algal blooms through level-dependent variables. In addition, the ecological consequences of microcystin released by toxin-producing species under AD-DOM stress are still worth considering. (C) 2019 Elsevier B.V. All rights reserved.
摘要：
Iron ore tailings (FeT) and manganese ore tailings (MnT), which are abundant and inexpensive materials that contain many trace elements, were employed for the remediation of As-contaminated soil to mitigate As accumulation in rice under greenhouse conditions. Prior to the experiments, the toxicities of both amendments were assessed with the toxicity characteristic leaching procedure (TCLP) and horizontal vibration method (HVM). Based on the assessment results, both amendments were pretreated until no As was present in the leaching solution. After application of both amendments to the soil, the soil pH increased significantly (p < 0.05). The ranges of As concentrations in husk and brown rice samples were 0.13-1.54 mg kg(-1) and 0.06-0.42 mg kg(-1), respectively. The lowest concentrations of As (0.06 +/- 0.02 mg kg(-1)) in rice grains were observed with MnT treatment, which was related to the structure and composition of MnT. There was a significant negative relationship (p < 0.05) between Mn and As in rice plants, while there was a significant positive relationship (p < 0.05) between Fe and As in rice plants as well as the ratio of Fe/Mn and As in rice plants. In conclusion, MnT could potentially be useful as an amendment to remediate As-contaminated soil and control As uptake by rice plants. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
关键词：
Bacterial augmentation;Co-occurrence network analysis;Microalgae-bacteria consortia;Microbial community
摘要：
Microalgae-bacteria consortia is considered to be an efficient way to improve wastewater treatment. However, the interactions between microalgae and bacteria were not clear. In this study, commercially available bacterial inoculum were used as bio-augmentation to improve the performance of microalgae-based wastewater treatment. Co-occurrence network analysis was used to investigate the interactions between microalgae and bacteria. Results showed that bio-augmentation could increase both microalgal growth and wastewater treatment efficiency. Microalgal biomass increased by 1.2 times. Removal efficiencies of total organic carbon, ammonium nitrogen and total phosphorus increased by 5.27%, 3.41%% and 5.74%, respectively. Decreasing trends for Cyanobacteria and Salinarimonas but increasing trends for Cyclobacteriaceae were observed in the microalgal culture system with bio-augmentation. Greater variations of microbial community were found in the treatment without bio-augmentation. Co-occurrence network analysis showed that the main functions of microbial community in the treatment with bio-augmentation were both nutrient removal and organic pollutant degrading. For the treatment without bio-augmentation, main function of microbial community was nutrient removal. It indicated that bio-augmentation increased the number of organic degrading bacteria, such as Bacillus and Paenibacillaceae. The interactions between these bacteria and microalgae promoted the degradation of organic pollutants in the wastewater, providing sufficient inorganic carbon sources for the photosynthesis of microalgae and thus promoting the growth of microalgae and the removal of nitrogen and phosphorus from wastewater.
摘要：
Manganese oxides are naturally occurring powerful oxidants and scavengers, which can control the mobility and bioavailability of arsenic (As). However, the effect of synthetic nanostructured manganese oxides on the mobilization and transportation of As at actual paddy soils are poorly understood, especially in soils with low or medium background Mn concentration. In the present study, a novel nano manganese oxide with superior reactivity and surface area has been synthesized. A 90-d soil incubation experiment combined with pot and field rice cultivation trials were designed to evaluate the effectiveness of exogenous alpha-MnO2 nanorods on the mobilization and transportation of As in soil-rice systems. Our results proved that the addition of alpha-MnO2 nanorods can effectively control the soil-to-solution partitioning of As under anaerobic conditions. After treatment with different amounts of alpha-MnO2 nanorods, the content of effective As decreased, offset by an increase in residual As and insoluble binding As (Ca-As and Fe-As). Enhancing the oxidation of As(III) into As(V), the alpha-MnO2 nanorods increased the adsorption of As onto indigenous iron (hydr)oxides which greatly reduced the soil porewater As content. In addition, pot experiments and field applications revealed that the influx of As into the aerial parts of rice plants (stems, husk and leaves) was strictly prohibited after treatments with different amount of alpha-MnO2 nanorods; more interestingly, significantly negative correlations have been observed between As and Mn in rice, which indicated that as Mn is increased in soil, As in brown rice decreases. Our results demonstrated that the use of alpha-MnO2 nanorods in As polluted paddy soil containing low levels of background Mn oxides can be a promising remediation strategy.
关键词：
Crust;Heavy metal;Irrigation water;Paddy field
摘要：
The paddy-crusts (PCs) play an important pole in the transformation and transfer of heavy metal in paddy. Different PCs were collected from paddy fields whose soils contained cadmium (Cd) at four concentration levels (0.61, 0.71, 1.53, and 7.08mg/kg) in Hunan Province, China P.R. at Sep 2017. This metal's distribution among and biological community structures of PCs were both measured. Our results indicated that PCs were able to accumulate Cd from irrigation water and soil. With greater Cd levels in paddy fields, the weak EPS-binding Cd fraction decreased whereas the non-EDTA-exchangeable Cd fraction increased. The sorbed Cd fraction was initially enhanced at low-to mid-level Cd concentrations, but then gradually declined. Biomineralization was shown to function as the dominant Cd accumulation mechanism in non-EDTA-exchangeable fractions. The biological diversity of soil microbes decreased with more Cd in soil, and the Proteobacteria, Bacteroidetes, and Cyanobacteria were the dominant phyla in all the sampled PCs. Canonical correspondence analysis (CCA) between the composition of microbial communities and soil chemical variables in the PCs clustered all samples based on the Cd-contaminated level, and demonstrated that Cd, Mn, and Fe all significantly influenced the microbial communities. In particular, the Alphaproteobacteria and Chloroplast classes of bacteria may play a significant role in Cd accumulation via the bio-mineralization process. Taken together, our results provide basic empirical information to better understand the heavy metal speciation transformation mechanisms of PCs upon Cd-contaminated paddy fields.
摘要：
The effect of biological soil crust (BSC) in paddy field on the immobilization and removal of heavy metal from irrigation water is an important issue. BSC was cultured in solutions with different concentrations of manganese (Mn) salt and cadmium (Cd) sulfate for 15 days. We analyzed the Mn, Cd and Fe contents in the BSC and investigated the effects of Mn salt on the Cd distribution in different binding-forms in BSC as well. The results show that Mn salt was effective at enabling BSC to immobilize the Cd, and its removal efficiency from irrigation water improved with an increase in the Mn concentration used. The removal of 50.00mug/L of Cd from irrigation water by BSC reached as high as 95.70% in present of 20.00mg/L Mn. The highest obtained biological concentrated factor of BSC for Cd is ~2.7x10(4). The mainly Cd species (75%) in BSC is the non-EDTA extracted minerals. Based on the SEM-EDS and XPS analyses, it was reasonably inferred that the Mn ion was oxidized by Mn oxidizing bacteria (MOB), to yield the porous spongy-like birnessite with d-spacing of 2.31A, while Cd was scavenged and immobilized in the crystal lattice. The MOB was identified as Bacillus. This study provides a potentially novel method to decontaminate irrigation water polluted with Cd by using BSC in presence of Mn.
摘要：
Microcystis aeruginosa frequently forms cyanobacterial blooms in eutrophic water bodies, resulting in high concentrations of extracellular polymeric substances (EPS) in the water column. The effects of M. aeruginosa EPS (MA-EPS) on the adsorption behavior of Cu(II) onto kaolinite and the possible mechanisms were investigated in this study. The results of potentiometric titration and Fourier transform infrared (FT-IR) spectroscopy determination show that carboxyl, phosphoryl and amino/hydroxyl groups were the main adsorption groups on MA-EPS. The combination of EPS with kaolinite created new adsorption sites. MA-EPS increased the adsorption of Cu(II) by kaolinite mainly through complexation. The adsorption kinetics of Cu(II) by kaolinite or kaolinite + EPS composite (Kao + EPS) was well fitted by a pseudo-second order kinetic model. The adsorption isotherm analyses show that the incorporation of MA-EPS onto kaolinite increased its surface heterogeneity. Rather than intercalating into the kaolinite interlayers, MA-EPS and/or Cu(II) were adsorbed onto the surface of this clay.
