Zihang Cheng

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.

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.

Removal of selenite by zero-valent iron combined with ultrasound: Se(IV) concentration changes, Se(VI) generation, and reaction mechanism

In this paper, the performance and application of zero-valent iron (ZVI) assisted by ultrasonic irradiation for the removal of selenite (Se(IV)) in wastewater was evaluated and reaction mechanism of Se(IV) with ZVI in such systems was investigated. A series of batch experiments were conducted to determine the effects of ultrasound power, pH, ZVI concentration, N2 and air on Se(IV) removal. ZVI before and after reaction with Se(IV) was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Results indicated that ultrasound can lead to a significant synergy in the removal of Se(IV) by ZVI because ultrasound can promote the generation of OH and accelerate the advanced Fenton process. The primary reaction products of ZVI and Se(IV) were Se(0), ferrihydrite, and Fe2O3.