Ferrihydrite: Surface Structure and Its Effects on Phase Transformation

Zhao, Jun; Huggins, Frank E.; Feng, Zhen; Huffman, G.P.

doi:10.1346/ccmn.1994.0420610

Cited by 207 publications

(20 citation statements)

References 35 publications

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“…In the presence of enough dissolved oxygen, redox reaction between HS − and dissolved oxygen occurred with the generation of sulphur 17 . The newly formed Fe oxyhydroxide had a special structure in which one Fe atom had an average coordination number of hydroxyl group of 5.4, which is higher than that of aggregated ferrihydrite and hematite 36 . Thus, the hydrolysed SP160 used enough hydroxyl groups for OTC coordination.…”

Section: Resultsmentioning

confidence: 96%

Upcycling of Fe-bearing sludge: preparation of erdite-bearing particles for treating pharmaceutical manufacture wastewater

Wang

Ning

et al. 2020

Sci Rep

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Groundwater treatment sludge is a type of solid waste with 9.0-28.9% wt.% Fe content and is precipitated in large quantity from backwash wastewater in groundwater treatment. The sludge is mainly composed of fine particles containing Fe, Si and Al oxides, such as ferrihydrite, quartz and boehmite. The Fe oxides mostly originate from the oxidation of ferrous Fe in groundwater, whilst the silicate/aluminium compounds mainly originate from the broken quartz sand filter in the backwash step. In general, the sludge is firstly coagulated, dewatered by filter pressing and finally undergoes harmless solidification before it is sent to landfills. However, this process is costly (approximately US$66.1/t) and complicated. In this study, groundwater treatment sludge was effectively recycled to prepare novel erdite-bearing particles via a one-step hydrothermal method by adding only na 2 S•9H 2 O. After hydrothermal treatment, the quartz and boehmite of the sludge were dissolved and recrystallised to sodalite, whilst ferrihydrite was converted to an erdite nanorod at 160 °C and a hematite at 240 °C. SP160 was prepared as fine nanorod particles with 200 nm diameter and 2-5 μm length at a hydrothermal temperature of 160 °C. Nearly 100% OTC and its derivatives in pharmaceutical manufacture wastewater were removed by adding 0.1 g SP160. The major mechanism for the removal was the spontaneous hydrolysis of erdite in SP160 to generate Fe oxyhydroxide and use many hydroxyl groups for coordinating OTC and its derivatives. This study presents a novel method for the resource reutilisation of waste groundwater treatment sludge and reports efficient erdite-bearing particles for pharmaceutical manufacture wastewater treatment. Fe-bearing sludge is common in the metallurgical and chemical industries 1-3. Sludge contains 6.2-33.6% Fe, in the form of ferrihydrite, hematite, magnetite and andradite, and impurity minerals, such as quartz, muscovite, albite and boehmite 1,4. In China, tons of sludge are dumped and uncovered in massive piles 2. When rain occurs, Fe may leach and contaminate the soil and nearby surface water 5. Through strict environmental regulations, sludge is commonly dewatered and solidified before it is transferred to a safety landfill, but this process is costly and complicated 2,6-8. Resource reutilisation of sludge is an alternative strategy to reduce pollution and disposal cost. Many approaches have been developed to recycle sludge as a building material 9 , catalyst 10 and adsorbent 3,4,6,11. Amongst these approaches, the conversion of sludge to adsorbent is the most effective and simple, and the produced adsorbents are widely used in the adsorption of heavy metals 4,6,12 and cationic organics 1,3,11,13,14. For instance, groundwater treatment sludge and flocculent iron mud are rich in ferrihydrite and are directly applied to adsorb heavy metals, such as Cu and Zn 15. Ferrihydrite is effectively converted to maghemite and magnetite via hydrothermal route or calcination with the addition of a reductant, such as glycol 11 an...

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Section: Resultsmentioning

confidence: 96%

Upcycling of Fe-bearing sludge: preparation of erdite-bearing particles for treating pharmaceutical manufacture wastewater

Wang

Ning

et al. 2020

Sci Rep

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“…When the structural Fe in the muscovite and andradite was reduced to Fe 2+ by ascorbic acid, dissolution of muscovite and andradite occurred, followed by a release of Al into the liquid solution. The released Al was rapidly converted into Al(OH) 4 − under alkaline conditions, and coordinated to the surface sites of residual minerals [16]. However, abundant OH − was present in the liquid solution and competed with the coordinated Al(OH) 4 − via ion exchange reaction, which led to release of Al(OH) 4 − into the liquid solution.…”

Section: Conversion Of Red Mud Into Magnetic Adsorbentmentioning

confidence: 99%

“…The pH of the solution was equilibrated to 6.3, in which Zn was predominated in the form of Zn 2+ and ZnOH + [47]. Thus, zinc adsorption on P-200 appeared to occur via exchange of Zn 2+ and ZnOH + with surface-bond Na + and H + (Equations (15) and (16)). A similar observation was reported in Zn 2+ adsorption on groundwater treatment sludge, which had the similar ≡SO − sites [23].…”

Section: Adsorptionmentioning

confidence: 99%

“…Liu et al [12] reported that part of the Fe oxides in red mud was converted into magnetite with pyrite as exogenous ferrous and reducing regent after calcination at 600 • C. Samouhos et al [14] reported that 87% of the hematite (Fe 2 O 3 ) in red mud was transformed into magnetite after roasting at 480 • C using H 2 as reductant. However, high temperatures were applied in these methods to promote the breakdown of the Fe-O-Si or Fe-O-Al bonds into the form of Fe-O-Fe linkage [16]. The breakdown of Fe-O-Si or Fe-O-Al bonds can be achieved at low temperature [17].…”

Section: Introductionmentioning

confidence: 99%

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Hydrothermal Conversion of Red Mud into Magnetic Adsorbent for Effective Adsorption of Zn(II) in Water

et al. 2019

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Red mud, a Fe-rich waste generated from the aluminum industry, was recovered as an adsorbent for wastewater treatment. The separation process of red mud from water after adsorption, including centrifugation and filtration, was complicated. This study demonstrated an alternative option to recycle red mud for preparing magnetic adsorbent via a facile hydrothermal route using ascorbic acid as reductant. Red mud is weakly magnetized and consists of andradite, muscovite, hematite, and cancrinite. After hydrothermal treatment, andradite in red mud was reductively dissolved by ascorbic acid, and transformed into magnetite and morimotoite. With increasing hydrothermal temperature, the dissolution of andradite accelerated, and the crystallite size of magnetite increased. When the hydrothermal temperature reached 200 °C, the prepared adsorbent P-200 showed a desirable saturation magnetization of 4.1 Am2/kg, and could be easily magnetically separated from water after adsorption. The maximum adsorption capacity of P-200 for Zn2+ was 89.6 mg/g, which is eight-fold higher than that of the raw red mud. The adsorption of Zn2+ by P-200 fitted the Langmuir model, where cation exchange was the main adsorption mechanism. The average distribution coefficient of Zn2+ at low ppm level was 16.81 L/g for P-200, higher than those of the red mud (0.3 L/g) and the prepared P-120 (1.48 L/g) and P-270 (5.48 L/g), demonstrating that P-200 had the best adsorption capacity for Zn2+ and can be served as a practical adsorbent for real-world applications. To our knowledge, this is the first study to report the conversion of red mud into a magnetic adsorbent under mild conditions.

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“…The produced sludge comprised ferrihydrite, hematite and impurities such as Si/Al oxides [9,12]. The ferrihydrite in the sludge was 16.6-33.7 wt.% [13,14], and it had a special structure wherein each iron atom was covalent with six oxygen/ hydroxyl clusters [15]. Thus, hydrogen groups were abundantly available on ferrihydrite surface for chromate coordination [11,16].…”

Section: Introductionmentioning

confidence: 99%

Upcycling of groundwater treatment sludge to magnetic Fe/Mn-bearing nanorod for chromate adsorption from wastewater treatment

Dong

Chen

et al. 2020

PLoS ONE

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Groundwater treatment sludge is a Fe/Mn-bearing waste that is mass produced in groundwater treatment plant. In this study, sludge was converted to a magnetic adsorbent (MA) by adding ascorbate. The sludge was weakly magnetised in the amorphous form with Fe and Mn contents of 28.8% and 8.1%, respectively. After hydrothermal treatment, Fe/Mn oxides in the sludge was recrystallised to siderite and rhodochrosite, with jacobsite as the intermediate in the presence of ascorbate. With an increment in ascorbate dosage, the obtained magnetic adsorbent had a significant increase in chromate adsorption but a decrease in magnetisation. When the M ascorbate /M Fe molar ratio was 10, the produced MA-10 was a dumbbell-shaped nanorod with a length of 2-5 μm and a diameter of 0.5-1 μm. This MA-10 showed 183.2 mg/g of chromate adsorption capacity and 2.81 emu/g of magnetisation. The mechanism of chromate adsorption was surface coprecipitation of the generated Cr 3+ and Fe 3+ /Mn 4+ from redox reaction between chromate and siderite/rhodochrosite on MA-10, separately. This study demonstrated an efficient recycling route of waste sludge from groundwater treatment to produce MA for treating chromate-bearing wastewater.

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Ferrihydrite: Surface Structure and Its Effects on Phase Transformation

Cited by 207 publications

References 35 publications

Upcycling of Fe-bearing sludge: preparation of erdite-bearing particles for treating pharmaceutical manufacture wastewater

Upcycling of Fe-bearing sludge: preparation of erdite-bearing particles for treating pharmaceutical manufacture wastewater

Hydrothermal Conversion of Red Mud into Magnetic Adsorbent for Effective Adsorption of Zn(II) in Water

Upcycling of groundwater treatment sludge to magnetic Fe/Mn-bearing nanorod for chromate adsorption from wastewater treatment

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