[Effect of Preparation Methods on Phosphate Adsorption by Iron-Titanium Binary Oxide: Coprecipitation and Physical Mixing].

To investigate the effect of preparation methods on surface characteristics and adsorption properties of the formed metal composite oxides, two kinds of iron-titanium binary oxides were synthesized by a coprecipitation method or a physical mixing method and were denoted as CFe-Ti and MFe-Ti, respectively. The prepared CFe-Ti and MFe-Ti were systematically characterized using SEM, XRD, BET, and FTIR techniques. Their phosphate adsorption behaviors were also studied via batch adsorption experiments. Compared with pure FeOOH and TiO2, CFe-Ti exhibited a looser nanostructure with more pore and surface hydroxyls. Moreover, the CFe-Ti had a high maximal phosphorus adsorption capacity of 40.6 mg·g-1, which is about 1.5 times and 2.4 times as high as that of pure FeOOH (27.2 mg·g-1) and TiO2 (16.7 mg·g-1), respectively. This suggests that an obvious synergistic effect is present in the CFe-Ti system. However, the morphology and structure of MFe-Ti were not significantly different from those of pure FeOOH and TiO2. The maximal adsorption capacity of MFe-Ti was 22.7 mg·g-1, which is obviously lower than that of CFe-Ti and even lower than that of pure FeOOH. Evidently, there is no synergistic effect in the MFe-Ti system. In addition, phosphate adsorption mechanisms at the surface of CFe-Ti and MFe-Ti were the same as those of their component oxides, and chemical adsorption occurred at the surface of the oxides through the formation of inner-sphere complexes. Therefore, the surface characteristics and adsorption properties of the metal composite oxides were closely related to their preparation methods. The coprecipitation method was a simpler and more economical way than the physical mixing method to fabricate a highly effective iron-titanium binary oxide for phosphate adsorption.

[Fe-Mn Binary Oxide Impregnated Chitosan Bead (FMCB): An Environmental Friendly Sorbent for Phosphate Removal].

Fe-Mn binary oxide impregnated chitosan bead (FMCB), an environmental friendly sorbent for phosphate removal, was fabricated through impregnating Fe-Mn binary oxide into chitosan matrix. The FMCB was characterized by SEM and BET surface area measurement. The adsorption behavior of phosphate on the FMCB was systemically investigated. The FMCB showed a porous and fibrous structure, with a high BET specific surface area of 248 m2·g-1 and a pore volume of 0.37 m3·g-1. It had a much higher phosphate adsorption capacity than pure chitosan bead. Langmuir model was more suitable for describing the adsorption behavior and the maximal adsorption capacity was as high as 13.3 mg·g-1 at pH 7.0.The kinetic data were well fitted by the pseudo second order model. The phosphate adsorption on FMCB was pH-dependent and decreased with increasing solution pH. Coexisting Ca2+ and Mg2+ enhanced slightly the adsorption of phosphate, while the coexisting anions hindered the phosphate adsorption in the order of SiO32- > CO32- > SO42-≥Cl-. The phosphate-loaded FMCB could be effectively regenerated using NaOH solution and repeatedly used. In column tests, about 800 bed volumes of simulated groundwater containing 3 mg·L-1 were treated before breakthrough (phosphate concentration in effluent reached 0.5 mg·L-1).

[Adsorption of Cu on Core-shell Structured Magnetic Particles: Relationship Between Adsorption Performance and Surface Properties].

In order to reveal the relationship between the adsorption performance of adsorbents and their compositions, structure, and surface properties, the core-shell structured Fe3O4/MnO2 and Fe-Mn/Mn22 magnetic particles were systematically characterized using multiple techniques and their Cu adsorption behaviors as well as mechanism were also investigated in details. It was found that both Fe3O4 and Fe-Mn had spinel structure and no obvious crystalline phase change was observed after coating with MnO2. The introduction of Mn might improve the affinity between the core and the shell, and therefore enhanced the amount and distribution uniformity of the MnO2 coated. Consequently, Fe-Mn/MnO2 exhibited a higher BET specific surface area and a lower isoelectric point. The results of sorption experiments showed that Fe-Mn had a higher maximal Cu adsorption capacity of 33.7 mg · g⁻¹ at pH 5.5, compared with 17.5 mg · g⁻¹ of Fe3O4. After coating, the maximal adsorption capacity of Fe-Mn/MnO2 was increased to 58.2 mg · g⁻¹, which was 2.6 times as high as that of Fe3O4/MnO2 and outperformed the majority of magnetic adsorbents reported in literature. In addition, a specific adsorption of Cu occurred at the surface of Fe3O4/MnO2 or Fe-Mn/MnO2 through the formation of inner-sphere complexes. In conclusion, the adsorption performance of the magnetic particles was positively related to their compositions, structure, and surface properties.

[Preparation and evaluation of Fe-La composite oxide nanoadsorbent for As(III) removal from aqueous solutions].

In this study, a Fe-La composite oxide nanoadsorbent was synthesized via a facile co-precipitation process. This adsorbent was well characterized with various techniques and its As (III) adsorption performance was investigated. Scanning electron microscopy (SEM) and transmission electron microscope (TEM) analyses indicate that the Fe-La composite oxide is formed with nanoparticles (20-200 nm). X-ray powder diffraction (XRD) analysis shows that the Fe-La composite oxide is similar to the crystal structure of La (OH)3. The specific surface area of Fe-La composite oxide is 99. 3 m2 x g(-1) and the isoelectric point is 7.8. The prepared Fe-La composite oxide nanoadsorbent is effective for As(III) removal from water. The isotherm data is well fitted with the Langmuir model (R2 = 0.95) with a maximal As(III) adsorption capacity of 58.2 mg x g(-1) at pH 7.0. The adsorption of As(III) is very fast and over 80% of the equilibrium adsorption capacity is obtained within 240 min. Elovich model (R2 = 0.97) is more suitable to describe adsorption kinetic data. The As(III) adsorption is dependent on solution pH. The effect of coexisting anions on As(III) adsorption increases in the order of SO4(2-) < CO3(2-) < SiO3(2-) < PO4(3-).

[Experiment study on the metamorphic amylum production wastewater treatment by anaerobic baffled reactor].

The present study reports the start-up of treating metamorphic amylum production wastewater by anaerobic baffled reactor (ABR) and the bio-chemical features of granular sludge. The optimal conditions in treatment of the metamorphic amylum production wastewater were proposed, and the running performance in treating salt-containing wastewater was studied. Our results show that the common anaerobic activated sludge can be acclimated by increasing the organic loading and salt-concentration at the same time, and the granular sludge tolerant to low salt can be achieved by the acclimation. When chloric ion was 8,500 mg/L and salinity was 1.6%, the anaerobic activated sludge could degrade organic materials normally in the wastewater after the acclimation, and the COD removal is over 85%. When the concentration of metamorphic amylum production wastewater in the experiment was 12,640 mg/L and the optimal hydraulic retention time was 48 h, the removal efficiency of COD was 85.9%. Effect of sharp decrease of chloric ion concentration on sludge microorganism is larger than that of the sharp increase in the system. The system can endure the change of chloric ion concentration by increasing from 8,500 mg/L to 12,500 mg/L or decreasing from 8,500 mg/L to 4,500 mg/L, and it is more tolerant to the sudden increase than that of the sudden decrease of chloric ion concentration. The ABR system can treat the wastewater with chloric ion below 15,000 mg/L and salinity of about 2.5%.

Removal mechanism of As(III) by a novel Fe-Mn binary oxide adsorbent: oxidation and sorption.

A novel Fe-Mn binary oxide adsorbent was developed for effective As(III) removal, which is more difficult to remove from drinking water and much more toxic to humans than As(V). The synthetic adsorbent showed a significantly higher As(III) uptake than As(V). The mechanism study is therefore necessary for interpreting such result and understanding the As(III) removal process. A control experiment was conducted to investigate the effect of Na2SO3-treatment on arsenic removal, which can provide useful information on As(III) removal mechanism. The adsorbent was first treated by Na2SO3, which can lower its oxidizing capacity by reductive dissolution of the Mn oxide and then reacted with As(V) or As(III). The results showed that the As(V) uptake was enhanced while the As(III) removal was inhibited after the pretreatment, indicating the important role of manganese dioxide during the As(III) removal. FTIR along with XPS was used to analyze the surface change of the original Fe-Mn adsorbent and the pretreated adsorbent before and after reaction with As(V) or As(III). Change in characteristic surface hydroxyl groups (Fe-OH, 1130, 1048, and 973 cm(-1)) was observed by the FTIR. The determination of arsenic oxidation state on the solid surface after reaction with As(III) revealed that the manganese dioxide instead of the iron oxide oxidized As(III) to As(V). The iron oxide was dominant for adsorbing the formed As(V). An oxidation and sorption mechanism for As(III) removal was developed. The relatively higher As(III) uptake may be attributed to the formation of fresh adsorption sites at the solid surface during As(III) oxidation.

Plant community succession in modern Yellow River Delta, China.

Data were collected in different successional stages using a simultaneous sampling method and analyzed through quantitative classification method. Three large groups and 12 classes were made to represent the community patterns of three succession stages and 12 succession communities. The succession series of plant community in the study area was as follows: saline bare land-->community Suaeda salsa-->community Tamarix chinensis-->grassland. Succession degree and succession process of 12 succession communities were calculated. Most of these communities were in the lower succession stage, however, community Phragmites communis+Glycine soja and community Imperata cylindrica+G. soja were close to the succession stage of grassland climax. Five species diversity indices were used to study the changes in species richness, species evenness and diversity during succession of community. Heterogeneity index and richness index increased gradually during the community succession process, but species evenness tended to decrease with succession development. The relation between succession and environment was studied by ordination technique, and the results showed that the soil salt content was an important factor to halarch succession of the modern Yellow River Delta. It affected community structure, species composition and succession process.