Qingru Zeng

Modifying Fe3O4 nanoparticles with humic acid for removal of Rhodamine B in water

Humic acid (HA) modifying Fe(3)O(4) nanoparticles (Fe(3)O(4)/HA) was developed for removal of Rhodamine B from water. Fe(3)O(4)/HA was prepared by a coprecipitation procedure with cheap and environmentally friendly iron salts and HA. TEM images revealed the Fe(3)O(4)/HA (with ≈ 10 nm Fe(3)O(4) cores) were aggregated as aqueous suspensions. With a saturation magnetization of 61.2 emu/g, the Fe(3)O(4)/HA could be simply recovered from water with magnetic separations at low magnetic field gradients within a few minutes. Sorption of the Rhodamine B to Fe(3)O(4)/HA reached equilibrium in less than 15 min, and agreed well to the Langmuir adsorption model with maximum adsorption capacities of 161.8 mg/g. The Fe(3)O(4)/HA was able to remove over 98.5% of Rhodamin B in water at optimized pH.

Synthesis of nanoscale zero-valent iron immobilized in alginate microcapsules for removal of Pb(II) from aqueous solution

Alginate microcapsules immobilized nanoscale zero-valent iron (M-NZVI), with diameters from several hundreds nanometers to several micrometers, were synthesized using ferric and calcium ions as the cross-linking cations, and then tested for removal of Pb(II) from aqueous solution. The size of NZVI particles was only a few nanometers according to transmission electron microscopy (TEM) observation. The synthesized alginate microcapsules were stable in air for as long as they were dried and contained 9.97% of iron by weight. When 0.5 g L−1 of M-NZVI were introduced into an aqueous solution containing 300.0 mg L−1 of Pb(II), 88% of Pb(II), 581.7 mg g−1 of Pb(II) uptake amount were removed from the system in 15 min. The kinetics of the removal reactions, including an initial adsorption phase and a subsequent reduction, is complicated. In addition, the synthesized M-NZVI showed a higher removal capability of Pb compared to NZVI and Ca-alginate particles. This newly synthesized material could be regenerated and reused at least 4 times when the initial concentrations of Pb(II) were ≤200.0 mg L−1. The higher reaction rates and greater removal capacity suggest that M-NZVI may be a potential material for in situ remediation of metal contaminated water and sediments.

La-EDTA coated Fe3O4 nanomaterial: Preparation and application in removal of phosphate from water

La-EDTA-Fe3O4 was prepared by a chemical co-precipitation method. The magnetic composite was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Furthermore, the adsorption properties of La-EDTA-Fe3O4 toward phosphate in water were investigated. The uptake rate of phosphate in water by La-EDTA-Fe3O4 was 3-1000 times than that of EDTA-Fe3O4, and reached 97.8% at 7 hr. The adsorption process agreed well with the Freundlich model and kinetics studies showed that the adsorption of phosphate proceeds according to pseudo second-order adsorption kinetics. The maximum removal rate was achieved at pH 6.0-7.0. The La-EDTA-Fe3O4 had good adsorption properties and could be separated well from aqueous solution by a permanent magnet. Therefore, this nanomaterial has potential application for the removal of phosphate from large water bodies.

Manganese Dioxide nanosheet suspension: A novel absorbent for Cadmium(II) contamination in waterbody

A MnO2 nanosheet (MnO2-NS) suspension was prepared from tetramethylammonium hydroxide (TMA⋅OH), H2O2, and MnCl2⋅4H2O, and its efficiency for Cd(II) removal from aqueous solutions was investigated. The maximum adsorption capacity of the MnO2-NS for Cd(II) was evaluated to be about 348 mg/g, which is thus far the highest value reported for MnO2 at pH 6.0. This high adsorption capacity is attributed to efficient ion exchange. X-ray photoelectron spectroscopy (XPS) revealed that Cd(II) was adsorbed on MnO2 as CdO and Cd(OH)2. After Cd(II) adsorption, the suspended MnO2-NS aggregated and precipitated within 5.0 min from solution. Therefore, dispersive MnO2-NS can be used to remove Cd(II) from wastewater rapidly and with high efficiency.

Carbon disulfide-modified magnetic ion-imprinted chitosan-Fe(III): A novel adsorbent for simultaneous removal of tetracycline and cadmium

A novel composite of carbon disulfide-modified magnetic ion-imprinted chitosan-Fe(III), i.e., MMIC-Fe(III) composite, was prepared as an efficient adsorbent for the simultaneous removal of tetracycline (TC) and Cd(II). This adsorbent showed excellent performance in removing TC and Cd(II) due to its rapid kinetics, high adsorption capacity, good reusability, and was well suited for use with real water samples. Kinetics studies demonstrated that the adsorption proceeded according to a pseudo-second order model. The adsorption isotherms were well described by the Langmuir model, with maximum adsorption capacity for TC and Cd(II) being 516.29 and 194.31mg/g, respectively. The synergistic effect of TC and Cd(II) adsorption might be due to the formation of TC-Cd(II) complex bridging the adsorbate and adsorbent. These properties demonstrate the potential application of MMIC-Fe(III) for the simultaneous removal of TC and Cd(II), and may provide some information for the synergistic removal of antibiotics and heavy metals from aquatic environments.

Molecular diversity of arbuscular mycorrhizal fungi at a large-scale antimony mining area in southern China

Arbuscular mycorrhizal fungi (AMF) have great potential for assisting heavy metal hyperaccumulators in the remediation of contaminated soils. However, little information is available about the community composition of AMF under natural conditions in soils contaminated by antimony (Sb). The objective of this study was to investigate the characteristics of AMF molecular diversity, and to explore the effects of Sb content and soil properties on the AMF community structure in an Sb mining area. Four Sb mine spoils and one adjacent reference area were selected from around the Xikuangshan mine in southern China. The association of AMF molecular diversity and community composition with the rhizosphere soils of the dominant plant species was studied by Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE). Results from all five studied sites showed that the diversity of AMF decreased with increasing Sb concentration. Principal component analysis (PCA) indicated that the AMF community structure was markedly different among these groups. Further redundancy analysis (RDA) showed that Sb contamination was the dominating factor influencing the AMF community structure in the Sb mine area. However, the multivariate analysis showed that, apart from the soil Sb content, extractable nitrogen content and organic matter content also attributed to AMF sequence distribution type. Some AMF sequences were only found in the highly contaminated area and these might be ideal candidates for improving phytoremediation efficiency in Sb mining regions. Gene sequencing analysis revealed that most species were affiliated with Glomus, suggesting that Glomus was the dominant AMF genus in the studied Sb mining area.

Assessment of Pb and Cd in seed oils and meals and methodology of their extraction.

Oil seed, which is a secondary product in phytoremediation, contaminated with heavy metals should be disposed of in an appropriate fashion. In this study, heavy metal concentrations found in oilseed rape and peanut oils were below 0.1 mg kg(-1) after extractions, being found most of the heavy metals in meals rather in oils. Extraction experiments were carried out to determine the optimum methodology for the removal of Pb and Cd from seed meals using K3C6H5O7, K2C4H4O6 and (NH4)2EDTA. The highest extraction of the Pb and Cd in the seed meals was achieved using 30 mM extractant solutions at 30°C for 24 h and a three-step extraction procedure. K3C6H5O7 and K2C4H4O6 had less impact on the removal of nutrients than (NH4)2EDTA.

Phytoextraction of cadmium-contaminated soil and potential of regenerated tobacco biomass for recovery of cadmium

The aim of this study was to estimate the influence of regenerated tobacco on the extraction of Cd from two acidic soils as well as to address the problem of how to deal with contaminated leaves following phytoextraction. Results showed that a coppicing tobacco led to a decline in Cd concentration in regenerated leaves and stalks when plants were grown in pots, but increased concentrations in regenerated lower and middle leaves when plants were grown under field conditions. The highest recorded bioconcentration factors in Chaling and Guanxi soil were 37.53 and 19.21 in lower leaves in the field, respectively. Total Cd extraction efficiency in practice (9.43% for Chaling soil and 6.24% for Guanxi soil) under field conditions confirmed our theoretical calculations (10.0% for Chaling soil and 6.73% for Guanxi soil). Use of a 0.5% hydrochloric acid(HCl) solution was sufficient to reduce Cd (98.4%) in tobacco leaves to permissible levels as required by the Hygienic Standard for Feeds in China (≤0.5 mg kg−1). Regenerated tobacco has the potential to allow cultivation of Cd contaminated farmland to produce animal feed, assist in lowering total Cd content of soil, and allow income generation for farmers.

Highly efficient degradation of thidiazuron with Ag/AgCl- activated carbon composites under LED light irradiation

Thidiazuron (TDZ; 1-phenyl-3-(1,2,3-thiadiazol-5-yl)urea) is one of the most widely used defoliant and easy to dissolve in surface water. Risk associated with the pesticide is not clearly defined, so it is important to remove/degrade TDZ with an efficient and environment friendly technology. Here, we investigated the use of Ag/AgCl-activated carbon (Ag/AgCl-AC) composites in photocatalytic degradation of TDZ under LED light. By the synergic effect of Ag/AgCl and AC, the optimum Ag/carbon weight ratio of 2:1 exhibited superior visible-light photocatalytic activity, the highest removal efficiency was close to 91% in pH 7 matrix. Different types of Ag/AgCl-AC composites were tested, all showed much faster photodegradation kinetics than bare Ag/AgCl in 210min. The degradation products as identified by HPLC-MS revealed that the hydroxylation by hydroxyl radicals and that of oxidation by superoxide radicals as well as holes were the two main pathways for TDZ degradation. Results revealed that the adsorption concentrated TDZ molecules and the photocatalytically generated radicals rapidly degradated TDZ, the two contributions functioned together for removal of the pollutant from water.

Inhibitory effects of sanguinarine against the cyanobacterium Microcystis aeruginosa NIES-843 and possible mechanisms of action

Sanguinarine showed strong inhibitory effect against Microcystis aeruginosa, a typical water bloom-forming and microcystins-producing cyanobacterium. The EC50 of sanguinarine against the growth of M. aeruginosa NIES-843 was 34.54±1.17 μg/L. Results of chlorophyll fluorescence transient analysis indicated that all the electron donating side, accepting side, and the reaction center of the Photosystem II (PS II) were the targets of sanguinarine against M. aeruginosa NIES-843. The elevation of reactive oxygen species (ROS) level in the cells of M. aeruginosa NIES-843 upon exposure indicated that sanguinarine induced oxidative stress in the active growing cells of M. aeruginosa NIES-843. Further results of gene expression analysis indicated that DNA damage and cell division inhibition were also involved in the inhibitory action mechanism of sanguinarine against M. aeruginosa NIES-843. The inhibitory characteristics of sanguinarine against M. aeruginosa suggest that the ecological- and public health-risks need to be evaluated before its application in cyanobacterial bloom control to avoid devastating events irreversibly.