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：
An amino-functionalized water-retaining agent (PPM40-NH₂) 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 SF(Cd/Ca) of PPM40-NH₂ was 3-7 fold higher than that of PPM40 although the C(Ca) was 100-1000 times higher than that of C(Cd). The chelating effect of -COOH and -NH₂ in PPM40-NH₂ corresponded well with the selective adsorption of Cd(II), as confirmed by simulations. A seed germination experiment demonstrated that PPM40-NH₂ could act as a filter of heavy metals to supply "clean" water for the roots of the pakchoi plant. The leaching experiment indicated that PPM40-NH₂ 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.
摘要：
Oil spills result in severe environmental pollution and inflict serious ecological damage, which makes the development of facile, low-cost, high-capacity, and sustainable oil absorbents to be a task of high practical significance. In this study, a kaolin-modified hydrophobic melamine sponge (K-MS) was prepared via simple soaking method, which can be applied to clean up oil spills and organic solvents leaks. The properties of the K-MS were characterized by a range of instrumental techniques. The addition of fluorizated kaolin not only endowed commercially available melamine sponge hydrophobic properties and enhanced its adsorption capacity to various oils and organic solvents. The K-MS exhibited the high adsorption capacity (up to 87-194g/g) and excellent recyclability (>90%). The equilibrium adsorption time was fast within 1 s for diesel. Moreover, the as-prepared sponge adsorption performance was examined in harsh environment, which has remarkable chemical stability and compressive properties. Thus, this study presents a low-cost facile strategy to produce promising absorbent for large-scale oil and organic solvents cleanups and recovery. Furthermore, this approach can be extended to a series of clay minerals in rich source, thus could open up new prospects for design hydrophobic materials to address oil pollution. (C) 2019 Elsevier Ltd. All rights reserved.
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：
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.
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.
摘要：
A co-precipitation method has been developed to prepare the Mg/Al layered double hydroxides (Mg/Al LDHs) and La-doped Mg/Al LDHs (Mg/Al/La LDHs). The products of calcined Mg/Al LDHs (Mg/Al LDOs) and Mg/Al/La LDOs are obtained by further calcination at 450 degrees C for 24 h. Characteristics of the materials are evaluated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). Adsorption behaviors of Mg/Al LDOs and Mg/Al/La LDOs have been contrastively investigated for arsenic and fluoride. Results show that doping La3+ into Mg/Al LDOs can modify its surface and structure, resulting in enhanced adsorption capacity of anions. A pseudo-second order kinetic model describes the adsorption kinetics of As(V) and F- on the Mg/Al/La LDOs, implying the mechanism of chemisorption. Langmuir and Freundlich isotherm models are used to fit adsorption data and the maximum uptake amount of As(V) and F- are calculated as 87.30 and 62.33 mg/g, respectively. Adsorption of As(V) and F- are also investigated as a function of initial concentrations, contact time, and media pH. The influence of co-existing anions indicate that the adsorption percentage of As(V) decreased in the order Cl- approximate to SO42- > NO3- > CO32- > HPO42-, and that of F- decreased in the order NO3- approximate to Cl- > SO42- > HPO42- > CO32-. It is found that Mg/Al/La LDOs keep the sorption efficiencies over 5 cycles. These results demonstrate that the Mg/Al/La LDOs can be employed as a low-cost and efficient adsorbent for treatment of undesirable anions.
关键词：
Hammett constant;meta-position;prediction model;quantum chemical descriptor
摘要：
Quantum chemical descriptors and empirical parameters are two different types of chemical parameters that play the fundamental roles in chemical reactivity and model development. However, previous studies have lacked detail regarding the relationship between quantum chemical descriptors and empirical constants. We selected polychlorinated biphenyls (PCBs) as an object to investigate the intrinsic correlation between 16 quantum chemical descriptors and Hammett constants. The results exhibited extremely high linearity for Sigma sigma(+)(o,m,p) with Q(xx/yy/zz), alpha and E-HOMO based on the meta-position grouping. Polychlorinated dibenzodioxins (PCDDs) and polychlorinated naphthalenes (PCNs) congeners, as two independent compounds, validated the reliability of the relationship. The meta-substituent grouping method between Sigma sigma(+)(o,m,p) and alpha was successfully used to predict the rate constant (k) for (OH)-O-center dot oxidation of PCBs, as well as the octanol/water partition coefficient (logK(OW)) and aqueous solubility (-logS(W)) of PCDDs, and exhibited excellent agreement with experimental measurements. Revealing the intrinsic correlation underlying the empirical constant and quantum chemical descriptors can develop simpler and higher efficient model application in predicting the environmental behavior and chemical properties of compounds.
