Fenglian Fu

The use of zero-valent iron for groundwater remediation and wastewater treatment: A review

Recent industrial and urban activities have led to elevated concentrations of a wide range of contaminants in groundwater and wastewater, which affect the health of millions of people worldwide. In recent years, the use of zero-valent iron (ZVI) for the treatment of toxic contaminants in groundwater and wastewater has received wide attention and encouraging treatment efficiencies have been documented. This paper gives an overview of the recent advances of ZVI and progress obtained during the groundwater remediation and wastewater treatment utilizing ZVI (including nanoscale zero-valent iron (nZVI)) for the removal of: (a) chlorinated organic compounds, (b) nitroaromatic compounds, (c) arsenic, (d) heavy metals, (e) nitrate, (f) dyes, and (g) phenol. Reaction mechanisms and removal efficiencies were studied and evaluated. It was found that ZVI materials with wide availability have appreciable removal efficiency for several types of contaminants. Concerning ZVI for future research, some suggestions are proposed and conclusions have been drawn.

Effective degradation of C.I. Acid Red 73 by advanced Fenton process.

The degradation of C.I. Acid Red 73 (AR 73) was investigated by advanced Fenton process based on zero-valent iron and hydrogen peroxide. The effect of zero-valent iron dosage, hydrogen peroxide concentration, initial pH, initial dye concentration, mixing rate and temperature on the degradation of AR 73 was studied. The results showed that AR 73 removal efficiency increased with the increase of zero-valent iron addition, hydrogen peroxide concentration, mixing rate and temperature, but decreased with the increase of initial pH value. The residual concentration of AR 73 was only 6.4 mg/L after 30 min treatment at optimum conditions for 200.0mg/L AR 73 initial concentration. And advanced Fenton process can partly remove COD values of AR 73. The activation energy of the degradation reaction is 31.98 kJ/mol.

Studies on the optimum conditions using acid-washed zero-valent iron/aluminum mixtures in permeable reactive barriers for the removal of different heavy metal ions from wastewater

The method of permeable reactive barriers (PRBs) is considered as one of the most practicable approaches in treating heavy metals contaminated surface and groundwater. The mixture of acid-washed zero-valent iron (ZVI) and zero-valent aluminum (ZVAl) as reactive medium in PRBs to treat heavy metal wastewater containing Cr(VI), Cd(2+), Ni(2+), Cu(2+), and Zn(2+) was investigated. The performance of column filled with the mixture of acid-washed ZVI and ZVAl was much better than the column filled with ZVI or ZVAl alone. At initial pH 5.4 and flow rates of 1.0 mL/min, the time that the removal efficiencies of Cr(VI), Cd(2+), Ni(2+), Cu(2+), and Zn(2+) were all above 99.5% can keep about 300 h using 80 g/40 g acid-washed ZVI/ZVAl when treating wastewater containing each heavy metal ions (Cr(VI), Cd(2+), Ni(2+), Cu(2+), and Zn(2+)) concentration of 20.0 mg/L. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to characterize ZVI/ZVAl before and after reaction and the reaction mechanism of the heavy metal ions with ZVI/ZVAl was discussed.

Adsorption, oxidation, and reduction behavior of arsenic in the removal of aqueous As(III) by mesoporous Fe/Al bimetallic particles

In this study, mesoporous iron/aluminum (Fe/Al) bimetallic particles were synthesized and employed for the removal of aqueous As(III). Scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS), Brunauer-Emmett-Teller (BET) analysis method, Vibrating-sample magnetometry (VSM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR) were employed to characterize the Fe/Al bimetals before and after reaction with As(III). The physical properties, compositions, and structures of Fe/Al bimetallic particles as well as the As(III) removal mechanism were investigated. The characterization of the bimetallic particles after the reaction has revealed the removal of As(III) is a complex process including surface adsorption and oxidation, and intraparticle reduction. The good As(III) removal capability and stability of the Fe/Al bimetallic particles exhibited its great potential as an effective and environmental friendly agent for As(III) removal from water.

Fe/Al bimetallic particles for the fast and highly efficient removal of Cr(VI) over a wide pH range: Performance and mechanism.

The iron/aluminum (Fe/Al) bimetallic particles with high efficiency for the removal of Cr(VI) were prepared. Fe/Al bimetallic particles were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), SEM mapping, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). SEM mapping showed that the core of bimetal was Al, and the planting Fe was deposited on the surface of Al. In acidic and neutral conditions, Fe/Al bimetal can completely remove Cr(VI) from wastewater in 20 min. Even at pH 11.0, the Cr(VI) removal efficiency achieved was 93.5%. Galvanic cell effect and high specific surface area are the main reasons for the enhanced removal of Cr(VI) by bimetallic particles. There were no iron ions released in solutions at pH values ranging from 3.0 to 11.0. The released Al(3+) ions concentrations in acidic and neutral conditions were all less than 0.2mg/L. The bimetal can be used 4 times without losing activity at initial pH 3.0. XPS indicated that the removed Cr(VI) was immobilized via the formation of Cr(III) hydroxide and Cr(III)-Fe(III) hydroxide/oxyhydroxide on the surface of Fe/Al bimetal. The Fe/Al bimetallic particles are promising for further testing for the rapid and effective removal of contaminants from water.

Essential factors of an integrated moving bed biofilm reactor–membrane bioreactor: Adhesion characteristics and microbial community of the biofilm

This work aims at revealing the adhesion characteristics and microbial community of the biofilm in an integrated moving bed biofilm reactor-membrane bioreactor, and further evaluating their variations over time. With multiple methods, the adhesion characteristics and microbial community of the biofilm on the carriers were comprehensively illuminated, which showed their dynamic variation along with the operational time. Results indicated that: (1) the roughness of biofilm on the carriers increased very quickly to a maximum value at the start-up stage, then, decreased to become a flat curve, which indicated a layer of smooth biofilm formed on the surface; (2) the tightly-bound protein and polysaccharide was the most important factor influencing the stability of biofilm; (3) the development of biofilm could be divided into three stages, and Gammaproteobacteria were the most dominant microbial species in class level at the last stage, which occupied the largest ratio (51.48%) among all microbes.

Facile preparation of magnetic mesoporous MnFe2O4@SiO2−CTAB composites for Cr(VI) adsorption and reduction

Chromium-contaminated water is regarded as one of the biggest threats to human health. In this study, a novel magnetic mesoporous MnFe2O4@SiO2-CTAB composite was prepared by a facile one-step modification method and applied to remove Cr(VI). X-ray diffraction, scanning electron microscopy, transmission electron microscopy, specific surface area, and vibrating sample magnetometer were used to characterize MnFe2O4@SiO2-CTAB composites. The morphology analysis showed that the composites displayed a core-shell structure. The outer shell was mesoporous silica with CTAB and the core was MnFe2O4 nanoparticles, which ensured the easy separation by an external magnetic field. The performance of MnFe2O4@SiO2-CTAB composites in Cr(VI) removal was far better than that of bare MnFe2O4 nanoparticles. There were two reasons for the effective removal of Cr(VI) by MnFe2O4@SiO2-CTAB composites: (1) mesoporous silica shell with abundant CTA+ significantly enhanced the Cr(VI) adsorption capacity of the composites; (2) a portion of Cr(VI) was reduced to less toxic Cr(III) by MnFe2O4, followed by Cr(III) immobilized on MnFe2O4@SiO2-CTAB composites, which had been demonstrated by X-ray photoelectron spectroscopy results. The adsorption of Cr(VI) onto MnFe2O4@SiO2-CTAB followed the Freundlich isotherm model and pseudo-second-order model. Tests on the regeneration and reuse of the composites were performed. The removal efficiency of Cr(VI) still retained 92.4% in the sixth cycle. MnFe2O4@SiO2-CTAB composites exhibited a great potential for the removal of Cr(VI) from water.

Synthesis and use of bimetals and bimetal oxides in contaminants removal from water: a review

Water pollution aggravates water scarcity by contaminating large volumes of available water. There has been increasing interest in the use of bimetallic particles and bimetallic oxides for the removal of contaminants in water. This paper reviews the recent advances in the development of bimetals and bimetal oxides, and application in the treatment of environmental contaminants. 183 published studies (1999–2015) are reviewed in this paper. The synthesis methods of bimetals including chemical methods, physical methods, and biosynthesis methods and the synthesis of bimetal oxides including hydrothermal, impregnation, sol–gel, spray pyrolysis, and precipitation methods are summarized. Then the application of bimetals and bimetal oxides to remove different environmental contaminants in water including chlorinated organic compounds, heavy metal, arsenic and selenium, nitro compounds and azo dyes, anions and oxyanions are reviewed. The review focuses on experimental conditions, removal efficiency of contaminants, and reaction mechanism in the application of bimetals and bimetal oxides. Compared with monometals, bimetals have high catalytic or removal ability for contaminants. The synthesis and application of bimetals and bimetal oxides is remarked on.

Biodiversity and succession of microbial community in a multi-habitat membrane bioreactor

The present study focused on establishing a multi-habitat membrane bioreactor, as well as exploring its biodiversity and succession of microbial communities. In a long-term operational period (100 days), the dissolved oxygen level of a local zone within the bioreactor decreased consistently from the original oxic state to the final anaerobic state, which led to a continuous succession of the microbial community in the bioreactor. The results revealed that the biodiversity of the microbial community in different zones simultaneously increased, with a similar microbial composition in their final successional stage. The results also indicated that the dominant species during the whole operation were distributed among 6 major phyla. At the initial operational stages, the dominant species in the anoxic-anaerobic and the oxic zones exhibited distinguished difference, whereas at the final operational stage, both zones presented nearly the same dominant microbial species and a rather similar structure in their microbial communities.

Cr(VI) removal by mesoporous FeOOH polymorphs: performance and mechanism

The mesoporous FeOOH polymorphs, i.e., goethite (α-FeOOH), akaganeite (β-FeOOH), lepidocrocite (γ-FeOOH), and feroxyhyte (δ-FeOOH) were synthesized and characterized before and after reaction with Cr(VI) by scanning electron microscopy (SEM), N2 adsorption–desorption isotherms, X-ray diffraction (XRD), saturation magnetization measurements, and X-ray photoelectron spectroscopy (XPS). The Cr(VI) removal efficiencies by these four FeOOH polymorphs were investigated. After reaction for 120 min, the Cr(VI) removal efficiencies by α-FeOOH, β-FeOOH, γ-FeOOH, and δ-FeOOH were 94.5%, 52.0%, 100%, and 84.6%, respectively. The Cr(VI) removal efficiencies by these four FeOOH polymorphs were influenced by their specific surface area. The XPS analysis indicated that the removal of Cr(VI) by these FeOOH polymorphs was a process of electrostatic attraction and ligand exchange. The study of this paper can reveal the reaction mechanism of FeOOH with Cr(VI) and the different behaviors of the four FeOOH polymorphs in the removal of Cr(VI).