Addition Of Red Mud Research Articles

Novel Inorganic Products Based on Industrial Wastes

This contribution reports the use of industrial wastes, red mud and tionite, obtained upon refining and extraction of bauxite and titania ores, respectively. For red mud, two applications were explored: geopolymers and clinker/cement. According to this study, only after 14 days the effects of addition of red mud are translated into technological properties of geopolymers. Moreover, in small proportions the mechanical strength was improved at 28 days curing, certainly due to the high alkaline nature of the waste. Belitic clinkers with balanced amounts of cementitious phases were produced at 1,350 °C. Mortars cured for 10 days produced from those clinkers/cements show mechanical strength that tends to increase when high amounts of C3S are formed. The relative content of C2S is also important in the hardening process. With the addition of red mud, the technological properties of the mortars were enhanced due to the pozzolanic reactivity of this sludge. The tionite was selected to be recycled as ceramic pigment. The colorimetric parameters of tionite pigment calcined at 1,200 °C and its application in transparent glaze show a light brownish colour, due to the strong brightness (L*). This colour should be exalted by the intercalation of metal ions present in the sludge that could form a metal bearing rutile phase. In the glaze, the yellow component (+b*) doubled and responds for the final beige coloration .

Gypsum addition to soils contaminated by red mud: implications for aluminium, arsenic, molybdenum and vanadium solubility

Red mud is highly alkaline (pH 13), saline and can contain elevated concentrations of several potentially toxic elements (e.g. Al, As, Mo and V). Release of up to 1 million m(3) of bauxite residue (red mud) suspension from the Ajka repository, western Hungary, caused large-scale contamination of downstream rivers and floodplains. There is now concern about the potential leaching of toxic metal(loid)s from the red mud as some have enhanced solubility at high pH. This study investigated the impact of red mud addition to three different Hungarian soils with respect to trace element solubility and soil geochemistry. The effectiveness of gypsum amendment for the rehabilitation of red mud-contaminated soils was also examined. Red mud addition to soils caused a pH increase, proportional to red mud addition, of up to 4 pH units (e.g. pH 7→11). Increasing red mud addition also led to significant increases in salinity, dissolved organic carbon and aqueous trace element concentrations. However, the response was highly soil specific and one of the soils tested buffered pH to around pH 8.5 even with the highest red mud loading tested (33% w/w); experiments using this soil also had much lower aqueous Al, As and V concentrations. Gypsum addition to soil/red mud mixtures, even at relatively low concentrations (1% w/w), was sufficient to buffer experimental pH to 7.5-8.5. This effect was attributed to the reaction of Ca(2+) supplied by the gypsum with OH(-) and carbonate from the red mud to precipitate calcite. The lowered pH enhanced trace element sorption and largely inhibited the release of Al, As and V. Mo concentrations, however, were largely unaffected by gypsum induced pH buffering due to the greater solubility of Mo (as molybdate) at circumneutral pH. Gypsum addition also leads to significantly higher porewater salinities, and column experiments demonstrated that this increase in total dissolved solids persisted even after 25 pore volume replacements. Gypsum addition could therefore provide a cheaper alternative to recovery (dig and dump) for the treatment of red mud-affected soils. The observed inhibition of trace metal release within red mud-affected soils was relatively insensitive to either the percentage of red mud or gypsum present, making the treatment easy to apply. However, there is risk that over-application of gypsum could lead to detrimental long-term increases in soil salinity.

Development of paving blocks from synergistic use of red mud and fly ash using geopolymerization

Red mud, a residue of Bayer’s process was used synergistically with fly ash to develop geopolymer. An influence of 0–40% red mud addition on the reaction, structure and properties of fly ash geopolymer was studied using isothermal conduction calorimetry (ICC), Fourier transform infrared spectroscopy (FTIR), electron probe microanalysis (EPMA) and mechanical testing. An improvement in intensity of reaction was observed with the red mud addition at all replacement level but improvement in setting time and compressive strength was observed only in the samples containing 5–20% red mud. Structural characterization revealed that rate of reaction was dependent on the NaOH concentration but the development of mechanical properties were related to the compact microstructure which was developed due to the combined effect of NaOH concentration, solubility of silicates and the presence of iron oxides. Based on scientific understanding, paving blocks using 10% and 20% red mud was developed. These blocks were meeting IS 15658: 2006 standard and leaching of toxic metals were within permissible limits.

Effect of red mud addition on the corrosion parameters of reinforced concrete evaluated by electrochemical methods

Red mud, the main waste generated in aluminum and alumina production from bauxite ore by the Bayer process, is considered "hazardous" due to its high pH. The high pH also provides greater protection of rebars, which is reflected in the low corrosion potential and high electrical resistivity (filler effect) of concrete. The corrosion potential was monitored by electrochemical measurements and the electrical resistivity was evaluated using sensors embedded in concrete test specimens. The results showed that the addition of red mud is beneficial to concrete, reducing its corrosion potential and increasing its electrical resistivity. Red mud proved to be a promising additive for concrete to inhibit the corrosion process.

Effect of Calcined Red Mud Addition on the Hydration of Portland Cement

The red mud (RM) is a solid waste derived from the processing of bauxite ore to produce alumina and it is considered a hazardous waste due to its high pH. This paper describes the use of mud untreated and after calcination at distinct temperatures (450, 650, and 1000°C) attempting to improve its reactivity. The Portland cement was replaced up to 30 wt% red mud, and its addition changed the hydration process, evaluated by calorimetric studies of early hydration and setting time. By comparing with the reference mixture (without red mud), the obtained results confirm the potential of the red mud to be used as pozzolanic additive to cementitious materials. Temperature of hydration was monitored by a quasi-adiabatic calorimeter (Langavant). The hydration temperature increases with RM addition, particularly if calcined in the same interval (450-650°C). In this condition, the hydration process is accelerated.

Analysis of chloride diffusivity in concrete containing red mud

Red mud is a solid waste produced in the alumina production process and, due to its high pH, is classified as hazardous. Its incorporation in concrete mixtures, acting as due to the particles fineness, might be an interesting reuse alternative. The focus of this paper is to study the chloride diffusivity of concrete mixtures containing red-mud. The concentration of chlorides was monitored by measuring the conductivity of the anolyte, which was distilled water initially. In addition, the estimation of the chloride ions diffusion coefficients in steady and non-steady conditions, Ds and Dns, was obtained from the ''time-lag'' and ''equivalent time'' between diffusion and migration experiments. Due to superfine particle-size distribution and the filler effect, the red mud addition seems to assure lower chloride diffusivity.

Effect of red mud addition on the fractionation and bio-accessibility of Pb, Zn and As in combined contaminated soil

Using soil incubation experiments, the effect of red mud addition on the fractionation and bioaccessibility of Pb, Zn and As in combined contaminated soil was studied. The results showed that red mud addition could significantly decrease the concentration of HOAc-extractable Pb and Zn in soil. Compared with the control, 5% red mud addition could significantly reduce the concentrations of HOAc-extractable Pb and Zn in soil after 1, 2 and 3 months of incubation [62.5, 65.3 and 73.5% decrease (Pb), 56.7, 65.8 and 67.4% decrease (Zn)]. Whereas adding red mud could remarkably increase the concentrations of specific absorbed As and residual As in soil. The result of a simple bioavailability extraction test (SBET) indicated that all treatments with red mud addition markedly reduced the concentration of bioaccessible Zn but increased the concentration of bioaccessible As in soil, while having little effect on the concentration of bioaccessible Pb in soil. After 3 months incubation, all treatments including 1, 2 and 5% red mud addition reduced the concentration of bioaccessible Zn by 53.1–56.7% compared with the control, but increased the concentration of bioaccessible As by 1.81–6.25 times. The results suggested that red mud is an additive with potential for the remediation soil contaminated soil by combinations of heavy metals, although it should be added based on the different heavy metals in the soil. Combined use of red mud and hyperaccumulators to remediate heavy metal contaminated soil needs further study.

The Study of Red Mud Addition Influences in Metakaolinite-Based Geopolymer Characteristics

Bauxite tailing waste or commonly known as red mud is considered to be a very hazardous material. The using of red mud to make alternative building material has been widely studied for many years. Geopolymer as one of the breakthrough in the searching of ordinary portland cement/concrete substitution provides many options and possibilities of using different types of pozzolanic or alumina-silica materials. In this study, the using of red mud in metakaoline-based geopolymer paste has been studied in three different curing conditions for 7 days of sample age. Each sample then characterized both, macroscopically and microscopically including compressive strength testing, SEM photograph, XRD and FTIR spectroscopy

The Study of Red Mud Addition Influences in Metakaolinite-Based Geopolymer Characteristics

Bauxite tailing waste or commonly known as red mud is considered to be a very hazardous material. The using of red mud to make alternative building material has been widely studied for many years. Geopolymer as one of the breakthrough in the searching of ordinary portland cement/concrete substitution provides many options and possibilities of using different types of pozzolanic or alumina-silica materials. In this study, the using of red mud in metakaoline-based geopolymer paste has been studied in three different curing conditions for 7 days of sample age. Each sample then characterized both, macroscopically and microscopically including compressive strength testing, SEM photograph, XRD and FTIR spectroscopy

Effect of Red Mud on the Corrosion of Reinforced Concrete Studied by Electrochemical Impedance Spectroscopy

The corrosion of concrete reinforcement is a worldwide problem with serious consequences to humans, including accidental deaths that may occur due to the degradation of this material. Thus, techniques that can measure concrete reinforcement corrosion and provide a reliable prediction of this phenomenon are fundamental for the technological development of these materials. The corrosion of steel bars embedded in concrete containing varying amounts of red mud (up to 30% of the total binder) was tested by electrochemical impedance spectroscopy (EIS), under partial immersion in a sodium chloride solution. The addition of red mud delayed the onset of corrosion and possibly also reduced the corrosion rate.

Effect of the addition of red mud on the corrosion parameters of reinforced concrete

Red mud, the main waste generated in aluminum and alumina production by the Bayer process, is considered “hazardous” due to its high pH. The characteristic of high alkalinity associated with the presence of aluminosilicates facilitates the assimilation and formation of compounds by reaction with chloride ions. The high pH also provides greater protection of rebars, which is reflected in the low corrosion potential and high electrical resistivity (filler effect) of concrete. In this study, the chloride concentration was monitored by measuring the conductivity of the anolyte. Red mud proved to be a promising additive for concrete to inhibit the corrosion process. The corrosion potential was monitored by electrochemical measurements and the electrical resistivity was evaluated using sensors embedded in concrete test specimens. The results showed that the addition of red mud is beneficial to concrete, reducing its chloride migration rate (diffusion coefficients) and corrosion potential and increasing its electrical resistivity.

The Effect of Fly Ash and Red Mud Content on the Compressive Strength of Foam Concrete

A series of foam concrete with different content of fly ash or red mud were experimentally investigated in this study. The results indicated that the water-solids ratio of optimized material proportion and curing conditions were 0.5, and the compressive strength and density of the concrete compressive would fall with the addition of fly ash or red mud.

Red Mud as a Chemical Stabilizer for Soil Contaminated with Toxic Metals

We performed a 2-year microcosm study to assess the effectiveness of red mud, a by-product of bauxite processing, in stabilizing contaminated mine waste and agricultural soil. Our study used red mud from a long-term disposal area in Almasfuzitő, Hungary with a pH of 9.0. A 5% (by weight) red mud addition decreased the highly mobile, water-extractable amount of Cd and Zn by 57% and 87%, respectively, in the agricultural soil and by 73% and 79%, respectively, in the mine waste. In a laboratory lysimeter study, the addition of red mud reduced the concentration of Cd and Zn in the leachate by about two third of the original. The metal content of the leachate was below the Maximum Effect Based Quality Criteria for surface water as determined by a risk assessment in the metal-contaminated area of the Toka valley near Gyongyosoroszi, Hungary. The addition of red mud did not increase the toxicity of the treated mine waste and soil and decreased the Cd and Zn uptake of Sinapis alba test plants by 18–29%. These results indicate that red mud applied to agricultural soil has no negative effects on plants and soil microbes and decreases the amounts of mobile metals, thus indicating its value for soil remediation.

Enhanced Reduction of Nitrate in Groundwater by Zero-valent Iron with Activated Red Mud

ABSTRACT The objective of this study was to examine the feasibility of using red mud for enhancing the nitrate removal in groundwater by zero-valent iron (Fe(0)). Batch experiments were performed with both untreated and acid-treated red mud in conjunction with Fe(0) system to treat an actual groundwater sample containing 2.52 mM nitrate. Addition of untreated red mud into aqueous solution containing Fe(0) abruptly raised pH value to highly alkaline (11–12.5), leading to inhibition of nitrate reduction. On the other hand, the addition of acid-treated red mud significantly increased nitrate removal, resulting in 164% increase in the 1st-order rate constant (kobs) as compared to Fe(0) alone system when the red mud was dosed at 5 g/L to the solution containing 50 g/L Fe(0). Nitrate removal increased with increasing dose of acid-treated red mud, showing nearly 100% increase in removal efficiency when the dose was increased from 0 to 0.5 g in 20 mL solutions containing 0.2 g Fe(0). The enhancing effect of activated red mud was assumed to be the result from scavenging of the reaction precipitate, thereby minimizing passivation of Fe(0) surfaces, and formation of additional reactive sites (e.g. green rust) for nitrate reduction. The reactions of both untreated and acid-treated red mud in the absence of Fe(0) showed little removal of nitrate, indicating red mud alone lacks reduction or sorption capability for nitrate. Results from this study demonstrated that the potential utility of Fe(0)/activated red mud system may be developed into a viable technology for the removal of nitrate from groundwater.

Chloride diffusivity in red mud-ordinary portland cement concrete determined by migration tests

Red mud, which is a solid waste produced in the alumina production process, is classified as dangerous due to its high pH. In this work, the concentration of chlorides was monitored by measuring the conductivity of the anolyte, which initially was distilled water. The steady and nonsteady-state chloride diffusion coefficients were estimated from the "time lag"� and "equivalent time" between diffusion and migration experiments. The capillary water absorption, apparent porosity and pore size distribution of concretes were also analyzed. The addition of red mud apparently ensured lower chloride diffusion in the tested mixtures due to its superfine particle-size distribution and its "filler"� effect. Red mud lengthened the service life of the concrete to 35 years (double that of the reference concrete). This finding is very positive since it indicates a delay in the onset of the rebar corrosion process caused by the migration of chloride ions.

석탄바닥재가 포함된 인공골재의 경량화에 미치는 적니 영향

The artificial aggregates (AAs) composing of 2 wastes, coal bottom ash and dredged soil (7 : 3, weight ratio) were fabricated as a function of red mud contents,0~30 wt% using direct sintering method at for 10 min, and those physical properties were evaluated. Especially, in order to analyze the red mud addition effect on the bloating phenomenon of AAs manufactured, the specific gravity and water absorption were measured and studied linked with the microstructural observation results. The lightening of AAs was enhanced due to increased bloating with increasing temperature and red mud contents. The AAS sintered at showed well-developed black-coring structure, but for the specimens containing red mud sintered over generated excessive liquid and gas caused by reduction of , thus the black-coring part was gradually burst open out of shell of AAs. Particularly, all specimens containing 30 wt% red mud was burst up when sintered over . The AAs containing no red mud sintered at had a specific gravity of about 1.2 and those containing 20 wt% had below 1.0 which are characters of lightweight aggregate.

ИсслЕдованиЕ каталитическоЙ актИвностИ краснОгО шлАмА В реакцИИ рАспАдА монооксидА углеродА

The process of iron carburization using СО-contaning gas as a catalyst red mud is investigated. Determined the catalytic activity of red mud in the decomposition reaction of CO. The effect of red mud addition to iron ore materials to improve their recoverability and carburization

Effect of red mud addition on the rheological behaviour and on hardened state characteristics of cement mortars

This paper reports on the use of red mud (RM) in mortars, applying design of experiments. Portland cement was replaced up to 50 wt.% RM, adjusting the relative amount of water (34–38 wt.%) in order to get mortars with suitable workability as defined by rheometry and flow table measurements. Temperature of hydration, compressive strength and water absorption were also determined. RM decreases the workability and increases the torque, but causes lower impact than water variation. The effect on initial yield stress depends on water content. Mortars with similar spread on table show different behaviour along the rheology test. Values of spread on table follow a quadratic model and RM exhibited an interactive effect with water. RM did not change the hydration process, but above 20% the maximum temperature decreases. The reduction of compressive strength is not constant and depends on the water added. Its variation also follows a quadratic model.

In situ stabilization of cadmium-, lead-, and zinc-contaminated soil using various amendments

Chemical stabilization is an in situ remediation method that uses inexpensive amendments to reduce contaminant availability in polluted soil. We tested the effects of several amendments (limestone, red-mud, and furnace slag) on the extractability of heavy metals, microbial activities, phytoavailability of soil metals (assessed using lettuce, Lactuca sativa L.), and availability of heavy metals in ingested soil to the human gastrointestinal system (assessed using the physiologically based extraction test). The application of soil amendments significantly decreased the amount of soluble and extractable heavy metals in the soil ( p < 0.05). The decreased extractable metal content of soil was accompanied by increased microbial activity and decreased plant uptake of heavy metals. Soil microbial activities (soil respiration, urease, and dehydrogenase activity) significantly increased in limestone and red-mud-amended soils. Red-mud was the most effective treatment in decreasing heavy-metal concentrations in lettuce. Compared to non-amended control soil, lettuce uptake of Cd, Pb, and Zn was reduced 86%, 58%, and 73%, respectively, by the addition of red-mud.

Use of fly ash, phosphogypsum and red mud as a liner material for the disposal of hazardous zinc leach residue waste

Increasing amounts of residues and waste materials coming from industrial activities in different processes have become an increasingly urgent problem for the future. The release of large quantities of heavy metals into the environment has resulted in a number of environmental problems. The present study investigated the safe disposal of the zinc leach residue waste using industrial residues such as fly ash, phosphogypsum and red mud. In the study, leachability of heavy metals from the zinc leach residue has been evaluated by mine water leaching procedure (MWLP) and toxicity characteristic leaching procedure (TCLP). Zinc removal from leachate was studied using fly ash, phosphogypsum and red mud. The adsorption capacities and adsorption efficiencies were determined. The adsorption rate data was analyzed according to the pseudo-second-order kinetic, Elovich kinetic and intra-particle diffusion kinetic models. The pseudo-second-order kinetic was the best fit kinetic model for the experimental data. The results show that addition of fly ash, phosphogypsum and red mud to the zinc leach residue drastically reduces the heavy metal content in the leachate and could be used as liner materials.