The effects of leaching from alkaline red mud on soil biota: modelling the conditions after the Hungarian red mud disaster

A soil column experiment was set up to investigate the effect of red mud from Ajka (Hungary) on a typical soil profile from the concerned area. The chemical changes caused by the leachate of the red mud and the effects of these changes on living organisms were assessed. Ecotoxicological tests with Vibrio fischeri, Sinapis alba and Folsomia candida were performed and the number of aerobic heterotrophic microorganisms was determined. The total, plant available, exchangeable and water soluble fractions of Na, Mo, Cu, and Cr increased in the soil mostly due to their leaching from the red mud layer and partly to the increase of the pH and DOC concentration. The chemical changes had significant effects on the test organisms only in the 0 – 30 cm soil layer except for F. candida that had a lower survival rate also in the 30 – 50 cm soil layer. There were no severe toxic effects detected on the test organisms. Furthermore in case of the aerobic heterotrophic cell number and S. alba germination a stimulating effect was revealed. However, the red mud itself was toxic, therefore the performed ecotoxicology tests have justified the removal of red mud from the soil surface after the disaster

Advances in Understanding Environmental Risks of Red Mud After the Ajka Spill, Hungary

In the 5 years since the 2010 Ajka red mud spill (Hungary), there have been 46 scientific studies assessing the key risks and impacts associated with the largest single release of bauxite-processing residue (red mud) to the environment. These studies have provided insight into the main environmental concerns, as well as the effectiveness of remedial efforts that can inform future management of red mud elsewhere. The key immediate risks after the spill were associated with the highly caustic nature of the red mud slurry and fine particle size, which once desiccated, could generate fugitive dust. Studies on affected populations showed no major hazards identified beyond caustic exposure, while red mud dust risks were considered equal to or lesser than those provided by urban dusts of similar particle size distribution. The longer-term environmental risks were related to the saline nature of the spill material (salinization of inundated soils) and the release and the potential cycling of oxyanion-forming metals and metalloids (e.g., Al, As, Cr, Mo, and V) in the soil–water environment. Of these, those that are soluble at high pH, inefficiently removed from solution during dilution and likely to be exchangeable at ambient pH are of chief concern (e.g., Mo and V). Various ecotoxicological studies have identified negative impacts of red mud-amended soils and sediments at high volumes (typically [5 %) on different test organisms, with some evidence of molecularlevel impacts at high dose (e.g., genotoxic effects on plants and mice). These data provide a valuable database to inform future toxicological studies for red mud. However, extensive management efforts in the aftermath of the spill greatly limited these exposure risks through leachate neutralization and red mud recovery from the affected land. Monitoring of affected soils, stream sediments, waters and aquatic biota (fungi, invertebrates and fish) have all shown a very rapid recovery toward prespill conditions. The accident also prompted research that has also highlighted potential benefits of red mud use for critical raw material recovery (e.g., Ga, Co, V, rare earths, inform), carbon sequestration, biofuel crop production, and use as a soil ameliorant

Influence of red mud on soil microbial communities: application and comprehensive evaluation of the Biolog EcoPlate approach as a tool in soil microbiological studies

Red mud can be applied as soil ameliorant to acidic, sandy and micronutrient deficient soils. There are still knowledge gaps regarding the effects of red mud on the soil microbial community. The Biolog EcoPlate technique is a promising tool for community level physiological profiling. This study presents a detailed evaluation of Biolog EcoPlate data from two case studies. In experiment “A” red mud from Ajka (Hungary) was mixed into acidic sandy soil in soil microcosms at 5–50 w/w%. In experiement “B” red mud soil mixture was mixed into low quality subsoil in a field experiment at 5–50 w/w%. According to average well color development, substrate average well color development and substrate richness 5–20% red mud increased the microbial activity of the acidic sandy soil over the short term, but the effect did not last for 10 months. Shannon diversity index showed that red mud at up to 20% did not change microbial diversity over the short term, but the diversity decreased by the 10th month. 30–50% red mud had deteriorating effect on the soil microflora. 5–20% red mud soil mixture in the low quality subsoil had a long lasting enhancing effect on the microbial community based on all Biolog EcoPlate parameters. However, 50% red mud soil mixture caused a decrease in diversity and substrate richness. With the Biolog EcoPlate we were able to monitor the changes of the microbial community in red mud affected soils and to assess the amount of red mud and red mud soil mixture applicable for soil treatment in these cases

Usability of clay mixed red mud in Hungarian building material production industry

The naturally occurring radionuclide (226Ra,232Th and40K) content of building Materials (NORM) contributes to the total radiation dose experienced by humans. In this survey 27 clay and 68 red mud samples were surveyed with gamma spectrometry and screened according to European Basic Safety Standards (BSS) I-index. It was found that average I-index of clays was 0.6 (0.4–0.8) less than the I-index of 1, which makes them suitable for building material production. The average I-index of red mud 2.3 (1.3–3.0). The maximal mixing ratio of red mud was calculated, varied between 12 and 39 %, with 23 % average.</p

Assistant Professor,

Red mud is a byproduct produced in the process of extraction of alumina from bauxite. The process is called Bayers Process. It insoluble product and is generated after bauxite digestion with sodium hydroxide at elevated temperature and pressure. This paper describes the characteristic properties of Red Mud and possible use as a geotechnical material. Basics properties like Specific gravity, Particle size distribution, Atter Berg’s limit, OMC and MDD are determined. Engineering properties like shear strength, permeability and CBR values are also determined in conformity with the Indian Standard Code and test results are discussed in geotechnical point of view. It revealed that the behavior of red mud is likely as clay soil with considerably high strength compared to conventional clay soil. KEY WORDS: Red mud, Bayer’s process, Bauxite residue. I

A review of the potential for rare earth element resources from European red muds: examples from Seydişehir, Turkey and Parnassus-Giona, Greece

ArticleRare earth elements (REE) are viewed as ‘critical metals’ due to a complex array of production and political issues, most notably a near monopoly in supply from China. Red mud, the waste product of the Bayer process that produces alumina from bauxite, represents a potential secondary resource of REE. Karst-bauxite deposits represent the ideal source material for REE-enriched red mud as the conditions during formation of the bauxite allow for the retention of REE. The REE pass through the Bayer Process and are concentrated in the waste material. Millions of tonnes of red mud are currently stockpiled in onshore storage facilities across Europe, representing a potential REE resource. Red mud from two case study sites, one in Greece and the other in Turkey, has been found to contain an average of approximately 1 000 ppm total REE, with an enrichment of light over heavy REE. Although this is relatively low grade when compared with typical primary REE deposits (Mountain Pass and Mount Weld up to 80 000 ppm), it is of interest because of the large volumes available, the cost benefits of reprocessing waste, and the low proportion of contained radioactive elements. This work shows that around 12 000 tonnes of REE exist in red mud at the two case study areas alone, with much larger resources existing across Europe as a whole.The research leading to these results has received funding from the European 669 Community’s Seventh Framework Programme ([FP7/2007-2013]) under Grant 670 Agreement no. 309373

A parametric evaluation of the removal as(III) and as(V) from aqueous water by red mud

In the present study, removal of arsenide (As(III)) and arsenate As(V) ions from water/wastewater by adsorption on red mud is investigated. Laboratory experiments were carried out to analyze removal capacity of the adsorbents, to achieve adsorption isotherms and kinetic parameters. Optimum doses of adsorbents, pH dependence of solutions, and contact time have been discussed. This study proposes the potential adsorbent material for water/wastewater which is contaminated with As species

Rare earth elements in karst-bauxites: a novel untapped European resource?

Karst-bauxite deposits form as a result of the accumulation of residual clay minerals in depressions on a karst limestone surface, and their subsequent lateritic weathering. Rare earth elements (REE) become concentrated in the bauxite deposits due to crystallisation of authigenic REE-bearing minerals, accumulation of residual phases and the adsorption of ions on clays and other mineral surfaces. REE are concentrated in the red mud waste generated by alumina production from bauxite through the Bayer process. Red muds thus contain on average 900 ppm REE compared with typical values of <100 ppm to ~500 ppm REE in the bauxites. Extraction of REE from red mud has been shown to be feasible although it is challenging due to the heterogeneous spatial distribution of REE in the bauxites and the need for development of appropriate processing methods. With annual European extraction of bauxite estimated to be approximately 3.5 million tonnes per annum, resulting in approximately 1.4 million tonnes of red mud from the production of alumina, understanding the REE resource potential of bauxites is integral to the assessment of European REE resources

Study of Adsorption Equilibrium and Kinetics of direct blue 71 by activated red mud from aqueous solutions

Background: Some of dyes are toxic and even carcinogenic and require separation and advanced treatment of textile effluents before being discharged into conventional systems. The objective of this study was to remove the direct blue 71 dye from aqueous solutions using activated red mud. Methods: Red mud was activated by nitric acid and was used in the adsorption experiment. Direct blue 71 removal, using activated red mud was studied as a function of contact time, pH, and initial dye concentration. The adsorption isotherms were analyzed using the Langmuir and the Freundlich isotherms. Kinetics data were fitted with Pseudo-first-order and Pseudo-second-order models. Results: The adsorption rate increases with pH decrease, contact time increase, and increase initial dye concentrations. The Freundlich isotherm (R2=0.9737) was the best-fit adsorption isotherm model for the experiment. The adsorption data, followed a pseudo-second-order model (R2=0.9902). Conclusion: Based on the result of the study, the use of activated red mud, as an efficient low-cost adsorbent, can be considered for (pre-) treating direct blue 71 contaminated wastewater. Keywords: Direct blue 71, Textile wastewater, Activated red mud, Adsorption, Isotherm model