Granular Red Mud Research Articles

A strategy-purifying wastewater with waste materials: Zn2+ modified waste red mud as recoverable adsorbents with an enhanced removal capacity of congo red

The strategy, called purifying wastewater with waste materials (PWWM), can simultaneously improve the secondary utilization of industrial waste materials and in turn, reduce environmental pollution. However, the PWWM strategy has still not been extensively used because of its low purification efficiency of organic pollutants and extremely difficult secondary utilization process. Herein, we use zinc aluminum silicate (ZAS) to modify waste granular red mud (GRM) to form a recoverable adsorbent, called ZAS/GRM adsorbent. The ZAS has been found to exhibit exceptional adsorption performance with the ability to firmly anchor onto the surface of GRM, in which heavy metal ions can effectively solidify and reduce their outflow. Furthermore, many voids have been tactfully designed in the ZAS/GRM adsorbents by using a water vapor project, which provide more active sites for congo red (CR) organic dye, thereby remarkably improving the removal efficiency of CR. From our purification of CR, we find that the CR adsorption capacity of the ZAS/GRM adsorbent is 3.509 mg g−1, which is four times higher than pure GRM (0.820 mg g−1). This study demonstrates our PWWM strategy is highly effective and can inspire more research on waste reuse.

Efficient removal of acid orange 7 using a porous adsorbent-supported zero-valent iron as a synergistic catalyst in advanced oxidation process.

This study focuses on the synthesis of granular red mud reinforced by zero-valent iron (Fe@GRM) and its application for the removal acid orange 7 (AO7) from aqueous solution. Then ZVI is employed as a catalyst for the activation of persulfate (PS) to produce sulfate radicals (SO4•-) that are produced at 900°C in an anoxic atmosphere using the direct reduction of iron oxide in the red mud with maize straw as the reductant. Furthermore, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) are used to illustrate the morphology and porous structure of the Fe@GRM. The X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) revealed that Fe@GRM was loaded with zero-valent iron. This characterization confirmed that the Fe@GRM was a porous structure material that contained zero-valent iron. The influence of conditions for AO7 elimination, including initial pH, Fe@GRM dosage, initial AO7 concentrations, and temperature, is also investigated. The removal efficiency of AO7 was 90.78% using Fe@GRM/PS, while only 18.15% was removed when Fe@GRM was used alone. The degradation kinetics were well fitted to a pseudo-first-order kinetic model, and the rate of removal increased with temperature, demonstrating an endothermic elimination process. The Arrhenius activation energy of the process was 20.77kJ/mol, which indicated that the reduction of AO7 was a diffusion-mediated reaction. Fe@GRM is a low-cost material that demonstrated outstanding performance with great potential for wastewater treatment.

Fabrication of a low-cost adsorbent supported zero-valent iron by using red mud for removing Pb(ii) and Cr(vi) from aqueous solutions.

In this study, a granular red mud supported zero-valent iron (ZVI@GRM) was successfully prepared and was used to remove Pb(ii) and Cr(vi) from aqueous solution. Zero-valent iron (ZVI) was synthesized by direct reduction of iron oxide in red mud by maize straw as a reductant at 900 °C in an anoxic atmosphere. The technical characterization (SEM, EDS, XRD, FTIR and BET) revealed that ZVI@GRM was loaded with zero-valent iron and contained different size pores. The factors of adsorption experiments include initial concentration, contact time, pH and temperature. The Pb(ii) and Cr(vi) removal by ZVI@GRM well fitted the pseudo-second-order kinetics model and the removal of heavy metals was an endothermic process. Essentially, Pb(ii) was transformed to precipitate forms (Pb0, Pb (OH)2, or 2PbCO3·Pb (OH)2) and Cr(vi) was converted to Cr (OH)3 or Cr3+/Fe3+ hydroxides. The maximum removal capacity for Pb(ii) and Cr(vi) by ZVI@GRM was 149.42 and 37.14 mg g−1. ZVI@GRM was a low-cost material and had outstanding performance and great potential in wastewater treatment.

Preparation of granular red mud supported zero-valent iron for Crystal Violet removal from aqueous solution

Preparation of granular red mud supported zero-valent iron for Crystal Violet removal from aqueous solution

Pore-forming mechanism of granular red mud by microwave activation and its application in organic dyes adsorption from aqueous solution

Red mud was mixed with starch and granulated, then roasted by microwave to form microwave-activated granular red mud (GRM) adsorbent. In this work, pore-forming mechanism of microwave-activated GRM and its effect for the removal of a cationic dye (methylene blue, MB) from aqueous solution were investigated. The results of dielectric properties of GRM and red mud in microwave field reveal that the addition of starch can effectively improve the microwave absorbing properties of the GRM sample. In addition, it is found that microwave-activated GRM adsorbent contains more pores and larger BET surface area than conventional-activated GRM adsorbent. The pore-forming mechanism of GRM by microwave activation is explained by the existence of temperature gradient and good absorbing properties of H2O vapor and starch. The adsorption experiment results show that the MB removal rate of the microwave-activated GRM can reach 82% within 15 min, while the conventional-activated GRM requires 180 min to reach the same MB removal effect when the initial MB concentration is 60 mg L−1. Langmuir model is found to represent the adsorption isotherm of MB on GRM better than Freundlich model. The adsorption capacity at 25 °C is 16.005 mg MB/1 g GRM. Thermodynamic parameters depicte spontaneous and endothermic nature of adsorption. The kinetics study shows that pseudo-second order model matches well the kinetic data.

Preparation of Granular Red Mud Adsorbent using Different Binders by Microwave Pore – Making and Activation Method

AbstractIn this work, microwave energy is used for preparing a granular red mud (GRM) adsorbent made of red mud with different binders, such as starch, sodium silicate and cement. The effects of the preparation parameters, such as binder type, binder addition ratio, microwave heating temperature, microwave power and holding time, on the absorption property of GRM are investigated. The BET surface area, strength, pore structure, XRD and SEM of the GRM absorbent are analyzed. The results show that the microwave roasting has a good effect on pore-making of GRM, especially when using organic binder. Both the BET surface area and the strength of GRM obtained by microwave heating are significantly higher than that by conventional heating. The optimum conditions are obtained as follows: 6:100 (w/w) of starch to red mud ratio, microwave roasting with a power of 2.6 kW at 500℃ for holding time of 30 min. The BET surface area, pore volume and average pore diameter of GRM prepared at the optimum conditions are 15.58 m2/g, 0.0337 cm3/g and 3.1693 A0, respectively.

Column absorption and regeneration behavior of a granular red mud for treating wastewater containing methylene blue

This work focuses on the column absorption and regeneration behavior of a granular red mud (GRM) for absorbing methylene blue (MB) in wastewater. By investigating key parameters, such as packing column height of adsorbent, initial concentration of MB, and flow rate, on the adsorption effects of GRM, the results show that the GRM can effectively remove MB from wastewater. The breakthrough time of the absorption process can be as high as 330 min, when 20.5 cm GRM column was used, with initial concentration and flow rate of MB wastewater being 150 mg L−1 and 4 mL min−1, respectively. The Thomas model is capable of describing the adsorption kinetics. Finally, for assessing the regeneration ability of the loaded GRM, a series of experiments of eluting the MB-loaded column with dilute nitric acid solution, whose pH value is about 3.0, were conducted. The results showed that the regeneration and re-adsorption effect of the GRM column is good.

Removal of cadmium from aqueous solutions using red mud granulated with cement

A novel adsorbent was prepared from granular red mud mixed with cement and its potential to be a suitable adsorbent for the removal of cadmium ions from aqueous solutions was evaluated. The wet red mud was directly mixed up with cement at different mass fractions of 2%–8% and their properties were investigated. Based on the textural characteristics and strength, the granular red mud with 2% addition of cement maintaining for 6 d is identified to have better properties. The batch adsorption experiments for adsorption of Cd2+ ions from solution were performed at 30, 40 and 50 °C at different initial concentrations under the condition of constant pH of 6.5. The equilibrium adsorption was found to increase with the increase of temperature during the adsorption process. Langmuir adsorption isotherm model was found to match the experimental adsorption isotherm better. The kinetics of adsorption was modeled using a pseudo second order kinetic model and the model parameters were estimated.

The Application of Red Mud on Restoring Heavy Metal Contaminated Water and Soil

Red mud as environmental restoration materials has the characteristics of low cost, simple process and controlling waste by waste. The paper introduced the application of red mud on heavy metal contaminated water and soil in details. Powdered or granular red mud both has good adsorption efficiency of Cu , Zn, Pb, Ni, Ca, Cd, As and other heavy metal ions in wastewater. Langmiur or Frendlich model can express the adsorption isotherm of red mud on heavy metal ions. Red mud can not only solidify the heavy metals in soils, but also increase the soil microbial activity and population types. At the same time, de-alkali treatment can not be ignored in the process of using red mud avoiding the second pollution to environment, and achieve the zero pollution release of red mud.

Removal of fluoride from water by using granular red mud: Batch and column studies

This paper describes the removal of fluoride from water using granular red mud (GRM) according to batch and column adsorption techniques. For the batch technique, the experiments demonstrated that maximum fluoride removal was obtained at a pH of 4.7 and it took 6 h to attain equilibrium and equilibrium time did not depend upon the initial fluoride concentration. Kinetics data were fitted with pseudo-second-order model. The Redlich–Peterson and Freundlich isotherm models better represented the adsorption data in comparison to the Langmuir model. Column experiments were carried out under a constant influent concentration and bed depth, and different flow rates. The capacities of the breakthrough and exhaustion points decreased with increase of the flow rate. Thomas model was applied to the experimental results. The modelled breakthrough curves were obtained, and they were in agreement with the corresponding experimental data. The column adsorption was reversal and the regeneration operation was accomplished by pumping 0.2 M of NaOH through the loaded GRM-column.

Removal of cadmium from aqueous solutions by adsorption on granular red mud (GRM)

This study puts forward a novel method to prepare granular red mud (GRM) and evaluates its potential use to remove cadmium ions from aqueous solutions as a low-cost adsorbent. The properties of the novel adsorbent were examined and then used for cadmium adsorption experiments. Batch experiments were conducted and equilibrium isotherms at different temperatures (20 °C, 30 °C, 40 °C) have been determined and analyzed with a Freundlich model. Kinetics data at initial pH 6.0 and 3.0 were fitted with Pseudo-second-order model and external mass transfer coefficients, effective particle diffusion coefficients were subsequently calculated for cadmium–GRM system at initial pH 6.0. Column breakthrough curves were depicted and the data were analyzed with a Thomas model. The column adsorption was reversal and the regeneration operation was accomplished by pumping 0.1 mol/L hydrochloric acid through the adsorbed column.