Arsenic (III) Removal from a High-Concentration Arsenic (III) Solution by Forming Ferric Arsenite on Red Mud Surface

Arsenic (As) is considered one of the most serious inorganic pollutants, and the wastewater produced in some smelters contains a high concentration of arsenic. In this paper, we purified the high-concentration arsenic solution with red mud and Fe3+ synergistically. In this system, arsenite anions reacted with Fe(III) ions to form ferric arsenite, which attached on the surface of red mud particles. The generated red mud/Fe1−x(As)x(OH)3 showed a better sedimentation performance than the pure ferric arsenite, which is beneficial to the separation of arsenic from the solution. The red mud not only served as the carrier, but also as the alkaline agent and adsorbent for arsenic treatment. The effects of red mud dosage, dosing order, pH, and molar ratio of Fe/As on arsenic removal were investigated. The efficiency of arsenic removal increased from a pH of 2 to 6 and reached equilibrium at a pH of 7. At the Fe/As molar ratio of 3, the removal efficiency of arsenic ions with an initial concentration of 500 mg/L reached 98%. In addition, the crystal structure, chemical composition, and morphological properties of red mud and arsenic removal residues (red mud/Fe1−x(As)x(OH)3) were characterized by XRD, XPS, X-ray fluorescence (XRF), SEM-EDS, and Raman spectroscopy to study the mechanism of arsenic removal. The results indicated that most of the arsenic was removed from the solution by forming Fe1−x(As)x(OH)3 precipitates on the red mud surface, while the remaining arsenic was adsorbed by the red mud and ferric hydroxide.

Download Full-text

Effect of LiNO3 on Expansion of Alkali–Silica Reaction in Rock Prisms and Concrete Microbars Prepared by Sandstone

Materials ◽

10.3390/ma12071150 ◽

2019 ◽

Vol 12 (7) ◽

pp. 1150 ◽

Cited By ~ 2

Author(s):

Jinxin Liu ◽

Lanqing Yu ◽

Min Deng

Keyword(s):

Electron Microscope ◽

Critical Concentration ◽

Stress Test ◽

Molar Ratio ◽

Alkali Silica Reaction ◽

X Ray Diffraction ◽

High Concentration ◽

X Ray ◽

Long Period ◽

Scanning Electron

The aim of this research is to investigate the effect of LiNO3 on the alkali–silica reaction (ASR) expansion of reactive sandstone and the mechanism through which this occurs. This paper presents the results from tests carried out on rock prisms and concrete microbars prepared by sandstone and LiNO3. The findings show that LiNO3 does not decrease the expansion of these samples unless the molar ratio of [Li]/[Na + K] exceeds 1.66, and the expansion is greatly increased when its concentration is below this critical concentration. The expansion stress test proves that Li2SiO3 is obviously expansive. X-ray diffraction (XRD) and scanning electron microscope (SEM) results indicate that LiNO3 reacts with the microcrystalline quartz inside sandstone, inhibiting the formation of ASR gel, and the formation of Li2SiO3 causes larger expansion. A high concentration of LiNO3 might inhibit the ASR reaction in the early stages, and the formation of Li2SiO3 causes expansion and cracks in concrete after a long period of time.

Download Full-text

The Effect of Citric Acid Concentration on the Properties of LaMnO3 as a Catalyst for Hydrocarbon Oxidation

Catalysts ◽

10.3390/catal9030226 ◽

2019 ◽

Vol 9 (3) ◽

pp. 226 ◽

Cited By ~ 9

Author(s):

Zakaria Sihaib ◽

Fabrizio Puleo ◽

Giuseppe Pantaleo ◽

Valeria La Parola ◽

José Luis Valverde ◽

...

Keyword(s):

Citric Acid ◽

Physicochemical Properties ◽

Photoelectron Spectroscopy ◽

Catalytic Performance ◽

Morphological Properties ◽

Molar Ratio ◽

Hydrocarbon Oxidation ◽

Total Oxidation ◽

Propene Oxidation ◽

X Ray

LaMnO3 (LM) catalysts with a molar ratio of citric acid (CA) to metal (La3+ + Mn2+) nitrates ranging from 0.5 to 2 (LM0.5 to LM2) were synthesized by the citrate sol–gel method with the aim of studying the effect of the citric acid ratio on the physicochemical properties and the catalytic performance in hydrocarbon oxidation. Structural and morphological properties of these catalysts were characterized by X-ray diffraction (XRD) and specific surface area (N2 adsorption) measurements, while the chemical composition was determined by inductively coupled plasma atomic emission spectroscopy (ICP-OES). In the selected samples, additional characterizations were carried out by thermogravimetric and differential thermal analysis (TGA/DTA), Fourier Transform Infrared Spectroscopy (FT-IR), temperature-programmed reduction by hydrogen (H2-TPR), and X-ray photoelectron spectroscopy (XPS). The results showed that the amount of citric acid used significantly influenced the TGA/DTA profile of gels along with the physicochemical properties of the catalysts. The XRD patterns are consistent with the perovskite formation as the main phase. The segregation of a small amount of Mn3O4, detected for molar ratios ranging between 0.5 and 1.5, suggested the formation of a slightly nonstoichiometric LaMn1−xO3 phase with a relatively high content of Mn4+. The catalytic performance was evaluated in the total oxidation of two selected hydrocarbons, toluene and propene, which represent typical volatile organic compounds (VOCs). Typically, three consecutive catalytic cycles were performed in order to reach steady-state performance in toluene and propene oxidation. Moreover, the stability of the catalysts under reaction conditions was investigated through 24-h experiments at 17% of toluene conversion. The catalysts LM1.2, LM1.3, and LM1.5 showed the best catalytic performance in both hydrocarbon oxidations, well comparing with the Pd/Al2O3 used as a reference.

Download Full-text

Covellite (CuS) Production from a Real Acid Mine Drainage Treated with Biogenic H2S

Metals ◽

10.3390/met9020206 ◽

2019 ◽

Vol 9 (2) ◽

pp. 206 ◽

Cited By ~ 2

Author(s):

Patricia Magalhães Pereira Silva ◽

Adriano Reis Lucheta ◽

José Augusto Pires Bitencourt ◽

Andre Luiz Vilaça do Carmo ◽

Ivan Patricio Ñancucheo Cuevas ◽

...

Keyword(s):

Acid Mine Drainage ◽

Mine Drainage ◽

Raw Materials ◽

Industrial Applications ◽

Molar Ratio ◽

High Concentration ◽

Dissolved Metals ◽

X Ray ◽

Synthesis Conditions ◽

Acid Mine

Acid Mine Drainage (AMD) is an environmental problem associated with mining activities, which resulted from the exposure of sulfur bearing materials to oxygen and water. AMD is a pollution source due to its extreme acidity, high concentration of sulfate, and soluble metals. Biological AMD treatment is one alternative to couple environmental amelioration for valuable dissolved metals recovery, as a new source of raw materials. Covellite (CuS) particles were synthetized from an AMD sample collected in a Brazilian copper mine, after 48 and 96 h of exposure to hydrogen sulfide (H2S) produced in a bioreactor containing acidophilic sulfate reducing bacteria (SRB). The time of exposure affected the morphology, nucleation, and size of CuS crystals. CuS crystals synthetized after 96 h of H2S exposure showed better ordination as indicated by sharp and intense diffractograms obtained by X-ray diffraction (XRD), and the predominance of placoid sheets with hexagonal habit structure as observed by scanning electrons microscopy (SEM). Energy dispersive X-ray fluorescence (EDXRF) spectrometry indicated a Cu:S molar ratio in agreement with CuS. Granulometric analysis demonstrated that 90% of CuS particles were less than 22 µm size. AMD biological treatment is a potential economical CuS recovery option for metallurgical process chain incorporation, or new industrial applications, since the alteration of synthesis conditions can produce different crystal forms with specific characteristics.

Download Full-text

Degradation of high-concentration p-nitrophenol by Fenton oxidation

Water Science & Technology ◽

10.2166/wst.2020.284 ◽

2020 ◽

Vol 81 (10) ◽

pp. 2260-2269

Author(s):

Xiao Qing Lin ◽

Wei Min Kong ◽

Xiao Lin

Keyword(s):

Degradation Rate ◽

Removal Rate ◽

Oxidative Degradation ◽

Oxygen Demand ◽

Fenton Oxidation ◽

Utilization Efficiency ◽

Molar Ratio ◽

High Concentration ◽

Initial Concentration ◽

Toc Removal

Abstract This work aimed to degrade high-concentration p-nitrophenol (PNP) by Fenton oxidation. We studied various reaction parameters during Fenton oxidation, such as the iron dosage (as Fe2+), the initial concentration and temperature of PNP, and the dosage of hydrogen peroxide (H2O2), especially the influence of temperature on the PNP degradation rate and degree. Under the addition of the same molar ratio of H2O2/Fe2+ and H2O2 dosage according to the theoretical stoichiometry, the PNP degradation rate and the removal rate of total organic carbon (TOC) increased significantly with the increase in the initial PNP concentration. Moreover, the oxidative degradation effect was significantly affected by temperature. The increased reaction temperature not only significantly reduced the Fe2+ dosage, but also greatly promoted the removal rate of chemical oxygen demand (COD) and TOC, and improved the utilization efficiency of H2O2. For example, when the initial concentration of PNP was 4,000 mg·L−1, and the dosage of Fe2+ was 109 mg·L−1 (H2O2/Fe2+ = 200), the removal rates of COD and TOC at 85 °C reached 95% and 71% respectively. Both were higher than the 93% COD removal rate and 44% TOC removal rate when the dosage of Fe2+ was 1,092 mg·L−1 (H2O2/Fe2+ = 20) at room temperature.

Download Full-text

Arsenic Immobilization by Biological Scorodite Crystallization: Effect of High Ferric Concentration and Foreign Seeds

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.71-73.629 ◽

2009 ◽

Vol 71-73 ◽

pp. 629-632 ◽

Cited By ~ 6

Author(s):

Paula González Contreras ◽

Jan Weijma ◽

Cees N.J. Buisman

Keyword(s):

Arsenic Removal ◽

Removal Rate ◽

Molar Ratio ◽

Biological Oxidation ◽

High Concentration ◽

Kinetics Of Crystallization ◽

Iron Oxidizing Bacteria ◽

Crystallization Effect ◽

Kinetics Of ◽

High Arsenic

Biological scorodite is produced at 80°C and 1g L-1 As5+, using iron oxidizing bacteria Acidianus Sulfidivorans, with a molar ratio Fe/As of 1 and without the use of seeds. We investigated the effect of high ferrous concentration, Fe/As higher than 1, and the use of foreign seeds (gypsum) on biological scorodite crystallization. The use of high ferrous concentrations resulted in a retardation of the time of crystallization due to the high concentration of ferric produced by a high biological oxidation. However, ferrous biological oxidation might be controlled to avoid this effect. The use of seeds did not improve the kinetics of crystallization. Nonetheless, a high arsenic removal rate was observed in the presence of seeds probably as a result of the formation of less stable scorodite.

Download Full-text

Fe-FeS2 adsorbent prepared with iron powder and pyrite by facile ball milling and its application for arsenic removal

Water Science & Technology ◽

10.2166/wst.2017.204 ◽

2017 ◽

Vol 76 (1) ◽

pp. 192-200 ◽

Cited By ~ 41

Author(s):

Xiaobo Min ◽

Yangwenjun Li ◽

Yong Ke ◽

Meiqing Shi ◽

Liyuan Chai ◽

...

Keyword(s):

Adsorption Capacity ◽

Ball Milling ◽

Photoelectron Spectroscopy ◽

Arsenic Removal ◽

Molar Ratio ◽

Arsenic Adsorption ◽

Arsenic Uptake ◽

X Ray ◽

Before And After ◽

High Arsenic

Arsenic is one of the major pollutants and a worldwide concern because of its toxicity and chronic effects on human health. An adsorbent of Fe-FeS2 mixture for effective arsenic removal was successfully prepared by mechanical ball milling. The products before and after arsenic adsorption were characterized with scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The adsorbent shows high arsenic removal efficiency when molar ratio of iron to pyrite is 5:5. The experimental data of As(III) adsorption are fitted well with the Langmuir isotherm model with a maximal adsorption capacity of 101.123 mg/g. And As(V) data were described perfectly by the Freundlich model with a maximal adsorption capacity of 58.341 L/mg. As(III) is partial oxidized to As(V) during the adsorption process. High arsenic uptake capability and cost-effectiveness of waste make it potentially attractive for arsenic removal.

Download Full-text

Prediction of the pH effect on arsenic (V) removal by varying catalyst of magnetic xerogel monoliths based on FREN model

Water Science & Technology Water Supply ◽

10.2166/ws.2020.168 ◽

2020 ◽

Vol 20 (7) ◽

pp. 2747-2761

Author(s):

Sasirot Khamkure ◽

Chidentree Treesatayapun ◽

Sofía Esperanza Garrido-Hoyos ◽

Prócoro Gamero-Melo ◽

Audberto Reyes-Rosas

Keyword(s):

Arsenic Removal ◽

Ph Effect ◽

Total Pore Volume ◽

Textural Properties ◽

Point Of Zero Charge ◽

Molar Ratio ◽

X Ray Diffraction ◽

Alkaline Catalyst ◽

X Ray ◽

Application Range

Abstract Magnetic xerogels monoliths (MCs) were simultaneously prepared and formed by the cross-linking polymerization of resorcinol and formaldehyde using the alkaline catalyst and magnetite. The varying of molar ratio of resorcinol and catalyst (R/C) was studied and characterized by isoelectric point (IEP), point of zero charge (pHpzc), scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), N2 adsorption and Fourier transform infrared spectroscopy (FTIR). The result of XRD and EDX confirmed the presence of magnetite into the gel at 1.19% with low molar ratio of magnetite and resorcinol ratio at 0.01. The surface morphology and textural properties of MCs affect directly with SBET, total pore volume and volume of mesopore increase when molar of R/C increases. The behavior of arsenic (As(V)) adsorption by using MCs, was studied in groundwater into the ranges of pH from 2.0 to 7.0. MC50 shows the maximum As(V) uptake and removal were 72 μg/g and 73.5% at pH 5, respectively, while MC100 gave the best performance within the application range of pH both of acidic and neutral region. Furthermore, the prediction technique based on an adaptive fuzzy rules emulated network was utilized for evaluation of the arsenic removal performance.

Download Full-text

Utilization of red mud for producing a high strength binder by composition optimization and nano strengthening

Nanotechnology Reviews ◽

10.1515/ntrev-2020-0029 ◽

2020 ◽

Vol 9 (1) ◽

pp. 396-409 ◽

Cited By ~ 1

Author(s):

Sara Ahmed ◽

Tao Meng ◽

Mazahir Taha

Keyword(s):

Compressive Strength ◽

Red Mud ◽

Fourier Transformation ◽

Considerable Increase ◽

High Strength ◽

Molar Ratio ◽

X Ray Diffraction ◽

Microstructure Change ◽

X Ray ◽

Composition Optimization

AbstractRecycling of red mud (RM) has attracted more attention in recent years due to severe environmental problems caused by landfilling. The effect of composition optimization and Nano-strengthening on the properties of a binder based on RM was studied in this paper. Results showed that modifying ratios of main oxides and adding Nano-SiO2 could obviously affect the mechanical properties and microstructure of the binder. Specimens with high SiO2/Al2O3 molar ratio (S/A) displayed considerable increase in compressive strength, while decreasing Na2O/Al2O3 molar ratio (N/A) improved the workability of the fresh mix. The compressive strength was developed significantly to be 45 MPa at 28 days by adding Nano-SiO2 with 0.4 wt.% of RM. Phase transformation and microstructure change at different stages of RM decomposition and binder geopolyerization were investigated by X-ray diffraction (XRD), Fourier transformation infrared (FTIR) and Scanning electron microscopy (SEM). The results of this study may provide a prospective method to use RM more widely in construction applications.

Download Full-text

Preparation and Photocatalytic Mechanism of Ag3PO4/SnO2 Composite Photocatalyst

NANO ◽

10.1142/s1793292019500929 ◽

2019 ◽

Vol 14 (07) ◽

pp. 1950092 ◽

Cited By ~ 1

Author(s):

Fei Li ◽

Guang Zhang ◽

Yinghua Song

Keyword(s):

Degradation Rate ◽

Hydrothermal Reaction ◽

Energy Dispersive Spectrometer ◽

Volume Ratio ◽

Morphological Properties ◽

Molar Ratio ◽

Hydrothermal Conversion ◽

Composite Photocatalyst ◽

X Ray ◽

Transmission Electron

A simple hydrothermal conversion method for the preparation of Ag3PO4/SnO2 composite photocatalyst has been developed. The morphological properties of the nanocomposites are studied using transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), X-ray powder diffraction (XRD) and other methods. Different properties of catalysts are prepared by adjusting the temperature of hydrothermal reaction and the volume ratio. The prepared photocatalyst is tested by degradation of tetracycline solution under visible light show that the degradation rate of tetracycline can reach 74% when the initial [Ag3PO4]/[SnO2] molar ratio is 15 and the temperature is 140∘C. Moreover, by constructing Ag3PO4/SnO2 composite structure, the impedance and photocurrent of material are enhanced significantly according to the electrochemical characterization.

Download Full-text

Increased As Adsorption on Maghemite-Containing Red Mud Prepared by the Alkali Fusion-Leaching Method

Minerals ◽

10.3390/min9010060 ◽

2019 ◽

Vol 9 (1) ◽

pp. 60 ◽

Cited By ~ 8

Author(s):

Andrei Shoppert ◽

Irina Loginova ◽

Denis Rogozhnikov ◽

Kirill Karimov ◽

Leonid Chaikin

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Red Mud ◽

Arsenic Removal ◽

Large Specific Surface Area ◽

Caustic Alkali ◽

X Ray ◽

Alkali Fusion ◽

Red Muds

This study investigates the use of red muds as adsorbents for As (V) removal. Red mud is a waste that contains a large amount of iron oxides and hydroxides, which are excellent adsorbents of arsenic, especially those possessing magnetic properties and a large specific surface area. The purpose of the experiments was to study the possibility of obtaining an effective adsorbent by the direct extraction of alumina from bauxite using the caustic alkali fusion method and to compare the arsenic removal effectiveness and other properties of these red muds with industrial samples. Red muds were described using methods such as X-ray diffraction spectrometry (XRD), X-ray fluorescence spectrometry (XRF), SEM, vibrating sample magnetometry (VSM), and the Brunauer–Emmett–Teller (BET) method. The main iron-containing phase of the red muds obtained by fusing bauxite with caustic alkali is maghemite, which has a large specific surface area. The specific surface area of the obtained samples varied in the range of 6.1–54.9 m2/g. Arsenic adsorption experiments were carried out using five different types of red muds: industrial Bayer, industrial sintering, and red mud obtained through bauxite alkali fusion at 300, 500, and 700 °C. The red muds obtained by fusing bauxite with caustic alkali at 300 and 500 °C had the highest effectiveness removing arsenic; their As(V) uptake capacity was over 30 mg/g.

Download Full-text