scholarly journals Physicochemical and Microstructural Properties of Red Muds under Acidic and Alkaline Conditions

2020 ◽  
Vol 10 (9) ◽  
pp. 2993
Author(s):  
Qingke Nie ◽  
Youdong Li ◽  
Guohui Wang ◽  
Bing Bai
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Red Mud ◽  
Ph Value ◽  
Soil Layer ◽  
Microstructural Properties ◽  
Naoh Solution ◽  
Red Muds ◽  
Hcl Solution

The main purpose of this study was to characterize the mineral and chemical composition of typical red muds in China. Changes in the physicochemical and microstructural properties of red muds collected from the Shanxi and Shandong provinces were investigated after they were immersed in an alkaline NaOH or an acidic HCl solution for 7, 28, and 120 days. The results showed that red mud has a high cation exchange capacity and active physicochemical properties, which can be closely related to its extremely high alkalinity and complex microstructure. The neutralization of red mud with the HCl solution results in the release of Na+ from the red mud particles into the leachate and can effectively decrease the pH value of the filtrate. The neutralization process can result in a significant decrease in the liquid limit, plastic limit and plasticity index, whereas the opposite was observed for the different parameters after the addition of the NaOH solution. In this sense, acid neutralization can significantly improve the cementation property of the red mud. This result will increase the water permeability of the acid-treated soil layer and improve the growth ability of plants. The specific surface area of red mud immersed in the NaOH solution decreased, whereas the specific surface area of red mud immersed in the HCl solution increased. This study contributes to our understanding of red mud properties after the red mud has been subjected to acidic and alkaline treatments, and the results can provide insights into the safe disposal of red mud.

scholarly journals Obtaining of Maghemite Containing Red Mud for Effective As(V) Adsorption

2020 ◽  
Author(s):  
Andrei A. Shoppert ◽  
Irina V. Loginova ◽  
Denis A. Rogozhnikov
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Red Mud ◽  
Large Specific Surface Area ◽  
Caustic Alkali ◽  
Arsenic Adsorption ◽  
Alkali Fusion ◽  
Different Temperatures ◽  
Red Muds

This paper describes the studies of the use of red muds as adsorbents for cleaning solutions from As(V). The 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 large specific surface area. The purpose of the experiment was to study the possibility of obtaining an effective adsorbent by direct extraction of alumina from bauxite using the caustic alkali fusion method and optimization of the process. The main iron-containing phase of the red muds obtained by fusing bauxite with caustic alkali was maghemite, which has a large specific surface area. Arsenic adsorption experiments were carried out using red muds obtained through bauxite alkali fusing at different temperatures and time of fusion, as well as the mass ratio of caustic alkali to bauxite. The red muds obtained by fusing bauxite with caustic alkali at 400∘ C and NaOH to bauxite mass ration 1.5 within 70 minutes have the highest effectiveness removing arsenic. Their As(V) uptake capacity was over than 37 mg/g. Keywords: red mud, maghemite, nanoparticles, As(V) adsorption, optimization

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

Minerals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 60 ◽  
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.

Preparation of Sands Modified by Aluminous Salt and its Adsorption Capability of CD2+

2011 ◽  
Vol 130-134 ◽  
pp. 856-859
Author(s):  
Chun Sheng Ding ◽  
Yang Ping Fu ◽  
Qian Fen Zhu ◽  
Jing Fu
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Influencing Factors ◽  
Removal Efficiency ◽  
Specific Surface Area ◽  
Quartz Sand ◽  
Ph Value ◽  
Alkaline Condition ◽  
Initial Concentration ◽  
Adsorption Capability

In this experiment quartz sand was chosen as a carrier to be coated by aluminous salt under alkaline condition, and then the specific surface area was tested, and the adsorption capability and Cd2+ removal influencing factors of modified sand were studied. The investigation results showed that the specific surface area of modified sand was 75.244m2/g which was 9.38 times of that of original sand; the removal efficiency of Cd2+ by aluminous salt modified sand reached 59% contrast to 39% of original sand with pH 7.00. It was also found that the removal efficiency of Cd2+ by the aluminous salt modified sand was reduced with the increase of initial concentration of Cd2+ solution, and was enhanced with the increase of pH value, the Cd2+ removal efficiency was almost 71% with pH 9.0.

Comparative Analysis on Chemical Composition and Charcoal Characterization of Two Miscanthus Species

2011 ◽  
Vol 415-417 ◽  
pp. 1265-1272
Author(s):  
Wen Biao Zhang ◽  
Wen Zhu Li ◽  
Bing Song Zheng
Keyword(s):  
Chemical Composition ◽  
Specific Surface ◽  
Water Content ◽  
Surface Area ◽  
Specific Surface Area ◽  
Ph Value ◽  
Perennial Grass ◽  
Water Extract ◽  
Carbonization Temperature ◽  
Hot Water

Miscanthus is a highly productive, rhizomatous, C4 perennial grass that should be considered as an excellent active carbon precursor. This paper compares the charcoal characterization and chemical composition between M. sinensis and M. floridulus. Species differed in water content, hot water extract, 1% NaOH extract, organic solvent extract, cellulose, lignin and ash. Carbonization temperatures have effects on charcoal yields of Miscanthus, which ranged from 23.5% to 48.0% for M. sinensis and 11.3% to 37.2% for M. floridulus. Water content, charcoal density, pH value, and specific surface area of charcoal characterization varied between two species of Miscanthus. The specific surface area increased with the increase of carbonization temperature. The highest specific surface area of M. sinensis and M. floridulus was 351.74 m2g−1and 352.74 m2g−1, respectively, when the carbonization temperature was 800°C.

Preparing of Silica Aerogel and Adsorption Performance on Nitrobenzene

2012 ◽  
Vol 512-515 ◽  
pp. 1980-1985
Author(s):  
Ya Jun Luo ◽  
Xue Li ◽  
Xiao Li Hu ◽  
Deng Liang He ◽  
Peng Lin
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Ph Value ◽  
Adsorption Property ◽  
Infrared Absorption Spectrum ◽  
Nitrobenzene Solution ◽  
Silica Source ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes

SiO2aerogel is prepared under normal conditions by taking tetraethyl orthosilicate (TEOS) as the silica source, N-hexane as the displacer, trimethylchlorosilane hexane as the modifier and hydrolysis environment provided by hydrochloric acid and ammonia water. The effect of pH value, time, temperature, initial concentration on the adsorption of nitrobenzene by aerogel has been studied. The results show that the best range of the pH value for adsorption is 10.72. When adsorption time is 100 min, adsorption equilibrium can be reached. The best temperature for adsorption is 40 °C. The adsorption capacity becomes larger with the concentration increasing of the nitrobenzene solution. When the concentration reaches 500 mg/L, the adsorption reaches 32.402 mg/g. The adsorption equation matches Langmuir model. Scanning Electron Microscopes (SEM), infrared absorption spectrum and specific surface area measurements have shown that the adsorption property of SiO2aerogel for the nitrobenzene is related to cellular structure of the aerogel and large specific surface area.

scholarly journals Obtaining of transition phases of alumina starting from sodium aluminate in Bayer process

2011 ◽  
Vol 65 (3) ◽  
pp. 271-277
Author(s):  
Zoran Obrenovic ◽  
Radislav Filipovic ◽  
Marija Milanovic ◽  
Ivan Stijepovic ◽  
Ljubica Nikolic
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Ph Value ◽  
Sodium Aluminate ◽  
High Specific Surface Area ◽  
Heterogeneous Structure ◽  
Aluminate Solution ◽  
Bayer Liquor ◽  
Sodium Aluminate Solution

Transition (active) phases of alumina were synthesized starting from sodium aluminate solution prepared out of Bayer liquor. The neutralisation of sodium aluminate solution was performed by sulphuric acid. Powder X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and low-temperature nitrogen absorption studies were employed to trace the formation of the transition phases of alumina. The results show that the properties of the powders (phase composition, morphology and specific surface area) are strongly influenced by the initial pH value of the system, as well as by the duration of neutralisation step. It is possible to obtain powders with heterogeneous structure with dominant phase of bayerite, gibbsite or boehmit by tuning the pH and concentration of the starting sodium aluminate solution. The transition (active) phases of alumina (?- and ?-alumina) with high specific surface area (264-373 m2/g) are formed through the thermal dehydratation of aluminium hydroxide (bayerite and gibbsite) and aluminium oxyhydroxide (boehmite or pseudoboehmite) at the temperature of 500?C. Namely, bayerite and pseudoboehmite transforms to ?-phase of alumina upon heating, while gibbsite transforms to ?-phase, maintaining the parent morphology.

Co-Producing Active Carbons and Sodium Silicate from Pyrolyzed Rice Husk by CO2 Activation Coupled with NaOH Solution Boiling

2014 ◽  
Vol 595 ◽  
pp. 30-35
Author(s):  
Da Wei Li ◽  
Xi Feng Zhu
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Sodium Silicate ◽  
Specific Surface Area ◽  
Rice Husk ◽  
Active Carbon ◽  
Desirability Function ◽  
Active Carbons ◽  
Solid Ratio ◽  
Naoh Solution

Active carbon and sodium silicate were produced simultaneously from pyrolyzed rice husk (PRH) by CO2 activation coupled with NaOH solution boiling. Doehlert matrix and Derringer's desirability function were applied to optimizing the boiling conditions to achieve a large specific surface area, a high silica extraction and low alkali consumption. In terms of this purpose, the optimum condition was determined as boiling CO2-activated char with 1mol/L NaOH solution at a liquid/solid ratio of 9.7 mL/g. Under this condition, the modulus of the sodium silicate and the specific surface area (SSA) of the active carbon were 2.62 and 897 m2/g, respectively. The values both reached their respective commercial levels. The pretreatment of the PRH with CO2 activation can markedly increase the SSA of active carbons.

The Preparation and Characterization of the Mesoporous Poly(bisphenol-A carbonate) – Silica Nanocomposites

2014 ◽  
Vol 513-517 ◽  
pp. 82-85
Author(s):  
Rui Rui Li ◽  
Yue Shi ◽  
Lei Zu ◽  
Hui Qin Lian ◽  
Yang Liu ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Pore Volume ◽  
Pore Diameter ◽  
Ph Value ◽  
Sol Gel ◽  
Synthesis System ◽  
Silica Nanocomposites

The mesoporous polycarbonate-silica nanocomposite materials were synthesized through the modified sol-gel approach under acidic condition. The specific surface area, pore diameter and pore volume of polycarbonate-silica could be controlled by changing the acidity of the synthesis system. The polycarbonate-silica possess an irregular block morphology according to the scanning electron microscopy observations. With decreasing the pH value of the synthesis system, the specific surface area and pore diameter of polycarbonate-silica were raised but the pore volume was reduced. The maximum specific surface area of polycarbonate-silica was 701.71m2/g which presented by the results of Nitrogen adsorptiondesorption isotherms.

Influence of pH Value and Precipitant on Zn2SnO4 Formation via Co-Precipitation Method

2011 ◽  
Vol 291-294 ◽  
pp. 61-64
Author(s):  
Yu Shiang Wu ◽  
Min He Tsau
Keyword(s):  
Photocatalytic Activity ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Ph Value ◽  
Particle Morphology ◽  
Nano Particles ◽  
Precipitation Method ◽  
Strong Base ◽  
Co Precipitation

Nanorod-shaped zinc stannate Zn2SnO4 (ZTO) with great photocatalytic activity was successfully synthesized via a co-precipitation method. In this paper, a strong base (NaOH) and a weak base (Na2CO3) are adopted as precipitants in order to form the precursor precipitate. The titration endpoints are fixed at pH6, pH8, and pH10 in order to adjust the solution precipitant quantity. Dependent variables above were not seen in other research before. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results show that the powders synthesized were ZTO nano-particles. Photocatalytic activity of the powders was measured utilizing a photocatalytic degradation reaction with methylene blue (MB) solution. The smallest particles were obtained by utilizing NaOH as a precipitant and adjusting pH to 6. Based on TEM images, the ZTO had nano-rod particle morphology. However, when precipitant Na2CO3 was utilized, particles agglomerated together, reducing specific surface area. Hence, the former sample shows better photocatalytic activity than the latter one. Consequently, powders titrated to pH6 by precipitant NaOH and calcined for 1 hour will form partly nano-rod particles with slight agglomeration, increasing the specific surface area of ZTO and bringing about the best photocatalytic characteristics.

Study on Microstructural Properties of PAN/MnO2 Nanofibers via Electrospinning Method

2015 ◽  
Vol 752-753 ◽  
pp. 113-118
Author(s):  
Norhaniza Yusof ◽  
Ieqmal Emeer Affandi ◽  
Norfadhilatuladha Abdullah ◽  
Ahmad Fauzi Ismail ◽  
Juhana Jaafar
Keyword(s):  
Specific Surface ◽  
Polymer Solution ◽  
Surface Area ◽  
Specific Surface Area ◽  
Micropore Volume ◽  
Bet Surface Area ◽  
Microstructural Properties ◽  
Adsorption Performance ◽  
Electrospinning Method ◽  
Scanning Electron

This paper reported the production of precursor PAN/MnO2 nanofibers via electrospinning method and studying its microstructural properties. The nanofibers were prepared by electrospun the polymer solution of polyacrylonitrile (PAN) and Manganese Oxide (MnO2) in, N, N-Dimethylformamide as its solvent. The factors considered in this study were polymer PAN/ MnO2 concentration which will significantly affect the specific surface area, nanofibers morphology, micropore volume and diameter of the nanofibers. The nanofibers were characterized using Scanning Electron Microscopy (SEM), Brunauer Emmett and Teller (BET) surface area, and Fourier Transmission Infrared Spectroscopy (FTIR). The addition of MnO2 in polymer solution increased the specific surface area of the nanofibers up to 3.5 wt % which found to be its optimum loading. In conclusion, the precursor PAN/ MnO2 -based ACNF were successfully produced with the optimization of metal oxide loading resulting to nanofibers with higher specific surface area which will further increased its adsorption performance.

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