[Fluoride Removal Efficiency of Novel Material:Magnetite Core/Zirconia Shell Nanocomposite].

Magnetite core/zirconia shell nanocomposite (abbreviated as Fe3O4@ZrO2 hereafter) was obtained using one-step co-precipitation method and its performance for removal of fluoride ion from water was studied. The results showed that the Langmuir maximum adsorption capacity of fluoride ion by Fe3O4@ZrO2 was 35.46 mg·g-1, which was far higher than those of magnetite, activated alumina and activated carbon. Studies of adsorption kinetics indicated that the adsorption of fluoride ion by Fe3O4@ZrO2 was fast and could be well described by the pseudo-second-order model. The adsorption process of fluoride ion was an endothermic reaction. The adsorption of fluoride ion by Fe3O4@ZrO2 decreased with increasing pH. Chloride, nitrate and sulfate anions, which commonly coexist in drinking water, had little effect on F- adsorption, although the coexistence of HCO3- and CO32- reduced the adsorption significantly by increasing the pH of the solution system. The fluoride adsorbed by Fe3O4@ZrO2 could be successfully desorbed with 1 mol·L-1 NaOH solution as desorption agent. The desorption rate reached 99.5%-99.6%. The F--desorbed Fe3O4@ZrO2 could be reused for the removal of F- after regeneration via restoring the protonation status of surface hydroxyl groups on hydrous zirconia. The removal efficiency of fluoride by Fe3O4@ZrO2 from actual well water was lower than that from pure water, but concentration limit for fluoride in drinking water could still be attained by increasing the dosage to a sufficiently high level. Fe3O4@ZrO2 is a promising material for fluoride removal due to its good performance, simple preparation method and easy separation from water by providing an external magnetic field.

[Preparation of the Silane Monolayer on Magnetite Nanoparticles and Its Performance with Respect to Phosphate Removal from Water].

We studied the loading of N-(2-Aminoethyl)-3-aminopropyl trimethoxy silane from aqueous solution as a monolayer on magnetite nanoparticles and examined the phosphate removal performance of the generated adsorbent (silane monolayer on magnetite nanoparticles, abbreviated as MSMNPs). The results indicate that silane monolayer adsorption on magnetite nanoparticles occurred at low concentrations (equilibrium silane concentration <300 mg·L-1) and a~100% surface monolayer coverage by silane could be established at a temperature ≥ 90℃ or a NaCl concentration ≥ 0.1 mol·L-1. The FTIR and XPS spectra indicate that hydrolyzed silane and magnetite nanoparticles are chemically linked. The loading of silane as a monolayer did not significantly change the saturation magnetization. The adsorption isotherm of phosphate based on MSMNPs fit the Langmuir model better, with a calculated maximum adsorption capacity reaching 7.59 mg·g-1. The adsorption and desorption of phosphate by MSMNPs are very fast, exceeding 90% within 30 min and reaching an equilibrium within 1 h. In conclusion, MSMNPs are novel adsorbents with easy separability, which enables the repeated use, and rapid adsorption and desorption of pollutants.

[Modification of Diatomite by Zirconium and Its Performance in Phosphate Removal from Water].

Zirconium modified diatomite was obtained by modifying raw diatomite with zirconium and the mass fraction of zirconia was 12.39% in the obtained material, which was proved to be amorphous via XRD. SEM images showed that porous floccules covered the surface of diatomite after modification and the specific surface area of the zirconium modified diatomite was 75.22 m2·g-1, larger than that of raw diatomite (14.00 m2·g-1). XPS spectra indicated that zirconia and diatomite were bonded together through chemical linkage, rather than physical deposition. The adsorption isotherm of phosphate by zirconium modified diatomite was fitted better to the Langmuir model with a calculated maximum adsorption capacity reaching 10.56 mg·g-1. The adsorption amount of zirconium oxide component in the material was estimated to be 81.67 mg·g-1 ZrO2, which was higher than that of pure zirconium oxides reported in previous studies. The adsorption amount of phosphate by zirconium modified diatomite decreased with the increase of pH. The adsorption was proved to be a ligand exchange process, supported by the XPS spectra of Zr3d region before and after adsorption. Chloride ion, sulfate ion and nitrate ion did not inhibit the adsorption of phosphate on the material, whereas coexistence of bicarbonate ions competed with phosphate ions to a certain extent. When treating eutrophic lake water with a phosphate concentration of 2 mg·L-1, the phosphate concentration level could meet the Ⅲ rank of Surface Water Environment Quality Standard of China by adopting the dosage of zirconium modified diatomite ≥1.25 g·L-1.

[Removal and Recycle of Phosphor from Water Using Magnetic Core/Shell Structured Fe3O4 @ SiO2Nanoparticles Functionalized with Hydrous Aluminum Oxide].

A novel magnetic core/shell structured nano-particle Fe3O4@ SiO2phosphor-removal ahsorbent functionalized with hydrous aluminum oxides (Fe3O4@ SiO2@ Al2O3· nH2O) was synthesized. Fe3O4@ SiO2@ Al2O3· nH2O was characterized by XRD, TEM, VSM and BET nitrogen adsorption experiment. The XRD and TEM results demonstrated the presence of the core/shell structure, with saturated magnetization and specific surface area of 56.00 emu · g⁻¹ and 47.27 m² · g⁻¹, respectively. In batch phosphor adsorption experiment, the Langmuir adsorption maximum capacity was 12.90 mg · g⁻¹ and nearly 96% phosphor could be rapidly removed within a contact time of 40 mm. Adsorption of phosphor on Fe3O4@ SiO2@ Al2O3 · nH2O was highly dependent on pH condition, and the favored pH range was 5-9 in which the phosphor removal rate was above 90%. In the treatment of sewage water, the recommended dosage was 1.25 kg · t⁻¹. In 5 cycles of adsorption-regeneration-desorption experiment, over 90% of the adsorbed phosphor could be desorbed with 1 mol · L⁻¹ NaOH, and Fe3O4@ SiO2@ Al2O3· nH2O could be reused after regeneration by pH adjustment with slightly decreased phosphor removal rate with increasing recycling number, which proved the recyclability of Fe3O4@ SiO2@ Al2O3· nH2O and thereby its potential in recycling of phosphor resources.

[Study on phosphate removal and recovery by activated alumina].

Activated alumina was studied for removing phosphate from water, and the recovery of adsorbed phosphate on activated aluminum oxide was also tested. Phosphate solution was prepared using distilled water, tap water and Luoshijiang River water, respectively. All the phosphate adsorption tests using activated alumina were proved to be well fitted with Langmuir isotherm and the respective maximum adsorption amount were 20.88, 32.15 and 29.85 mg x g(-1), respectively. The presence of electrolyte in water could be a positive factor for phosphate removal. As the pH value of phosphate solution became lower the Zeta potential of activated alumina increased, which could enhance the phosphate removal efficiency of activated alumina. The recovery tests indicated that NaOH (0.1 mol x L(-1)) solution could almost completely extract the phosphate adsorbed by activated alumina.

[Adsorption of phenol chemicals by surfactant-modified zeolites].

Two kinds of zeolites were prepared from fly ash and modified by surfactant subsequently. Surfactant-modified zeolites were studied for adsorption of phenol chemicals (phenol, p-chlorphenol, bisphenol A). It showed that the adsorption affinity of zeolite to phenol chemicals was significantly improved after surfactant modification. The adsorption isotherms of phenol chemicals were well fitted by the Langmuir isotherm. For the two surfactant-surfactant modified zeolites, the maximum adsorption amounts of phenol, p-chlorphenol, and bisphenol A calculated from the Langmuir equation were 37.7, 52.36, 90.9 mg x g(-1) and 10.7, 22.83, 56.8 mg x g(-1), respectively. When pH values of solutions were higher than the pK(a) values of phenol chemicals, the removal efficiencies were getting higher with the increase of pH values. The octanol/water partition coefficient (K(ow)) was also found to be an important factor affecting adsorption of phenol chemicals by the modified zeolites. Higher K(ow) value, which means the greater hydrophobicity of the chemicals, resulted in a higher removal.

Phosphate removal from source separated urine by electrocoagulation using iron plate electrodes.

The aim of this study was to investigate the effects of current density, gap between electrodes, urine dosage, dilution and hydrolysis on phosphate removal from human urine by electrocoagulation technique using iron as electrodes. It was shown that, although a high current density and a long electrolysis time favored the removal of phosphate, an appropriate value for these two parameters can be obtained by taking into account the consumption of energy and iron in addition to P removal. In this study, current density 40 mA/cm2 and electrolysis time 20 min were shown to be optimal for 1.0 L pure urine to achieve nearly a complete removal (98%) efficiency of phosphate under the conditions of electrode area 160 cm2, the stirring speed 150 rpm, and the gap between electrodes 5 mm. Increase of gap between electrodes had little effect on phosphate removal, although it increased the energy consumption dramatically. The use of a high urine dosage reduced the efficiency of phosphate removal but increased the amount of removed phosphate. When pure urine was diluted with tap water, use of a higher tap water proportion for dilution expedited the electrolysis to achieve a nearly complete removal of phosphate in solution, but dilution caused the increase in energy consumption. It was also revealed that the hydrolysis of urine prior to electrocoagulation treatment impeded phosphate removal.

[Early-warning and prediction technology of harmful algal bloom: a review].

Harmful algal bloom (HAB) occurs frequently and causes serious damage. To study the early-warning and prediction technology of HAB is of significance for the early-warning and prediction, ecological control, and disaster prevention and mitigation of HAB. This paper reviewed the research progress in the early-warning and prediction technologies of HAB, including transport prediction, specific factors critical value prediction, data-driven model, and ecological math model, and evaluated the advantages and disadvantages of these four types of technologies. Some new ideas were brought forward about the prediction of cyanobacterial growth rate based on cell characteristics, and the early-warning of cyanobacterial bloom based on algal community characteristics.

Simultaneous removal of ammonium and phosphate by zeolite synthesized from coal fly ash as influenced by acid treatment.

Zeolite synthesized from fly ash (ZFA) without modification is not efficient for the purification of NH4+ and phosphate at low concentrations that occur in real effluents, despite the high potential removal capacity. To develop an effective technique to enhance the removal efficiency of ammonium and phosphate at low concentrations, ZFA was modified with acid treatment and the simultaneous removal of ammonium and phosphate in a wide range of concentration was investigated. It was seen that when compared with untreated ZFA, only the treatment by 0.01 mol/L of H2SO4 significantly improved the removal efficiency of ammonium at low initial concentrations. The behavior was well explained by the pH effect. Treatment by more concentrated H2SO4 led to the deterioration of the ZFA structure and a decrease in the cation exchange capacity. Treatment by 0.01 mol/L H2SO4 improved the removal efficiency of phosphate by ZFA at all initial P concentrations, while the treatment by concentrated H2SO4 (> or = 0.9 mol/L) resulted in a limited maximum phosphate immobilization capacity (PIC). It was concluded that through a previous mild acid treatment (e.g. 0.01 mol/L of H2SO4), ZFA can be used in the simultaneous removal of NH4+ and P at low concentrations in simulating real effluent.

Reproductive toxicity of dietary copper to a saltwater cladoceran, Moina monogolica Daday.

In the present study, the chronic toxicity of dietary copper to Moina monogolica Daday was investigated. Microalgal growth inhibition tests were conducted for 96 h with the green algae Chlorella pyrenoidosa exposed to copper. The 96-h median effective concentration (95% confidence interval) was 509.12 (388.68-629.56) microg/L. Then, C. pyrenoidosa was exposed for 96 h to a control and to seven dissolved copper concentrations. Cellular copper concentration accumulated in a dose-dependent manner and was plotted against cell density. These algae were used as food in a 21-d bioassay with M. monogolica in seawater to which no dissolved copper was added. Brood size was not reduced in the first brood, but significant reductions at all algal-exposure copper concentrations (44.78-817.17 microg/L) were observed in all subsequent broods, with increasing magnitude in each brood. Neither longevity nor number of broods per female was significantly affected, even at the highest copper exposure, though both endpoints did show a consistent downward trend with increasing copper exposure. Total reproduction, brood size, and net reproductive rate were decreased significantly in all dietary copper exposures (algae exposed to 44.78-817.17 microg/L). In contrast, the intrinsic rate of natural increase was reduced significantly only with algae exposed to greater than 619.27 microg/L, most likely because of the heavy influence of early reproduction on this metric. Because cell density in algal cultures decreased with increasing copper concentrations, it is possible that changes in the nutritional content of the algal diet could have played a role in causing the observed changes in reproduction of M. monogolica.

[Study on characteristics of simultaneous removal of ammonium and phosphate from waste water by zeolitized fly ash].

Characteristics of simultaneous removal of ammonium and phosphate from wastewater by zeolite synthesized from fly ash was investigated. The amount of ammonium and phosphate removed by zeolitized fly ash changed with time, and approached to a constant value after adsorption time of 24h was reached. The amount of ammonium and phosphate removed also increased with the rise in the amount of zeolite added, but slackened above the solid/liquid ratio of 8 g x L(-1). The removal rate of ammonium by zeolitized fly ash could rise to the maximum value of 60% when pH was between 7 and 9, and declined out of the pH range. For phosphate, minimum removal rate of about 85% was obtained within pH 7-9, and the removal rate increased to about 100% out of the pH range. The adsorption of ammonium on zeolitized fly ash was an exothermic reaction; the removal rate of ammonium could decrease with the rise in temperature. On the contrary, the adsorption of phosphate was an endothermic reaction, and the rise in temperature favored the removal of phosphate by zeolitized fly ash. The adsorptive ability of ammonium on zeolitized fly ash was: Al-Z > Mg-Z > Ca-Z > Na-Z > Fe-Z. The order for phosphate was: Al-Z > Fe-Z > Ca-Z > Mg-Z > Na-Z. It was proposed that the mechanism for the removal of ammonium from wastewater by zeolitized fly ash was cation exchange process, while the mechanism for phosphate was not only the precipitation reaction of phosphate with cation in solution, but also adsorption mechanism.

Removal of PCDD/Fs and PCBS from sediment by oxygen free pyrolysis.

Abstract: Few studies have dealt on the evaluation of volatilization and decomposition reactions of dioxins from sediment by oxygen free pyrolysis. In this study, the performance of pyrolysis on the removal of dioxins from sediment was investigated. Dioxin concentrations of the raw sediment and the solid residues after pyrolysis were analyzed at different conditions. Results showed a removal efficiency of 99.9999% for total dioxins at 800 degrees C and retention time of 30 min. All the polychlorinated dibenzo-furans (PCDFs) have been removed and were not formed in the solid residues at the retention time range of 30-90 min at 800 degrees C. Close to 100% removal of polychlorinated dibenzo-p-dioxins (PCDDs) was also achieved. Only trace PCDDs were detected in the solid yields at a retention time of 60 min. The highest removal efficiency of polychlorinated biphenyls (PCBs) was more than 99.9994% at a retention time of 30 min. During cooling period following pyrolysis, however, the concentration of total dioxins in solid residues increased 130 times as compared to that of the raw sediment under air atmosphere. This confirmed that some complex reactions do occur to form PCDD/Fs and PCBs from 800 to 400 degrees C in the presence of oxygen. Oxygen-free atmosphere therefore can prevent formation of dioxin during thermal process thus generating clean solid residues.

Sorption of a triazol derivative by soils: importance of surface acidity.

The sorption of a triazol derivative, 1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl)penten-3-ol with a common name of S3307D, on fifteen soils and three H2O2-treated soils was investigated. The sorption isotherm for each untreated and treated soil was non-linear, and was best fitted to Freundlich sorption equation. Soils containing high amount of clay content or organic matter or both sorbed much higher amounts of the chemical than soils that had low contents of these soil constituents. H2O2-treated soils showed considerable sorptive affinity for S3307D. It was concluded that both organic matter and mineral fraction in natural soils contributed to the sorption of the basic compound. Sorption by the H2O2 treated soils increased as suspension pH decreased, but all suspension pHs exceeded the pKa of the compound by more than two units. This implies that organic base protonation can occur on surfaces of soil components, and surface acidity (exchangeable acidity) is important in sorption process of the organic base rather than suspension pH.