Prominent examples of metal/metalloids forming anionic oxyanions for which reduction is more effective than oxidation at lowering solubility are As, Se, and Cr. Because of the complex physico-chemical properties of red mud it is very challenging These spent linings represent the largest volume of solid waste associated with the smelting process. Performances of two common types of red mud, Bayer red mud and Sintering red mud, were investigated in this research. The chemical composition of Al 2O 3 and red mud particles used in this study are presented in Table 2 and Table 3, respectively. Paramguru et al., 2005; Pontikes and Angelopoulos, 2013), systematic dumping of millions of tonnes at sea, let alone within a semienclosed Gulf such as the GOC, is not only hazardous but also wasteful. Different combinations and amounts of iron by-products derived from production of TiO2, triple superphosphate (TSP), phosphoric acids, and biosolids compost were used to immobilize Pb, Zn, and Cd from smelter-contaminated soils (Brown et al., 2004). For example, sewage sludge was used to counteract effects of sulfide oxidation of copper mine tailings in northern Sweden (Forsberg and Ledin, 2006). Sodalite hematite The application of synthetic zeolite pellets to Cd-contaminated soils has been shown to significantly reduce the concentrations of Cd in the roots and shoots of a range of crop plants (Gworek, 1992). Other metals, such as Cr3+, form fairly soluble oxide/hydroxide precipitates. Because striped dolphins tend to be epi- and mesopelagic feeders and red mud dumping impacts predominantly the seafloor, avoidance would not be expected. Arsenic removal efficiency can also be improved by pretreatment of oxidized As(III) to As(V). Limitations to use of this technology include soils contaminated with mixed pollutants for which a chemical strategy to manage one of the pollutants is incompatible with the chemistry required to manage another. The sulfidized red mud is not as efficient at removing arsenic, manganese, and strontium as red mud itself, Iannicelli says. The addition of lime as ground limestone not only raises pH but also renders metal(loid)s insoluble, thus reducing their bioavailability to plants (Down, 1975). For example, an incubation study performed with biowastes (ie, manure and compost) and heavy metal contaminated soils has observed a significant degradation of OM from biowastes thereby increased Cu bioavailability through metal-OM chelation (Clemente et al., 2006). Water suspensions and highly alkaline Normally, as the pH decreases, the mobility of some metal(loid)s is elevated. The specific gravity of red mud is 2.77 gcm−3 measured by gas picnometer. One way is to cap the residue with a mixture of soil, paper mill pulp, chopped hay, and manure. In this method, an upper pitcher is used to reduce arsenate to arsenite, a middle pitcher contains charcoal for adsorption of arsenic species, and a lower pitcher collects arsenic-free water. Gray et al. Chemical Composition of Red Mud The red mud used for this study was generated in Aluminum of Greece (Boeotia, Greece) S.A. the world is presented in Tabl e 5. ABSTRACT. Red mud has greater sorption capacity than any other inorganic amendment because it has a large amount of hydroxides, which are used in the adsorption and co-precipitation mechanism for the removal of Cd from water, and has a large amount of Al and Fe oxides (Wang et al., 2008a). Hydrous manganese oxides reduced Cd or Pb transfer from soil to soil solution and their entry into the food chain via plant uptake. Cells are equipped with hoods to collect these gases and duct them to pollution control equipment. Red mud which was produced from a sintering process can contain various mineral resources, including Al 2 O 3, Fe 2 O 3, CaO, TiO 2 and SiO 2. Many metal citrates are highly mobile and not readily degraded. Particle size distribution in Red Mud showed a fine physical texture of solid sludge: > 93.80 % particles smaller than 0.125 mm size in fresh Red Mud and respectively, higher 85.64 percent of particles with lower size of 0.125 mm in aged Red Mud. Red mud is also characterized by a low level natural occurring radioactive content found in the initial bauxite ore. A chemical analysis would reveal that RM contains silica, aluminum, iron, calcium, titanium, as well as an array of minor constituents, namely: Na, K, Cr, V, Ni, Ba, Cu, Mn, Pb, Zn etc. Physical texture of Red mud classified by equilateral triangle are sandy loam (57.1% sand; limon 33.8%; clay 9.1%). Different characterizations were carried out on red mud uncalcined and samples calcined in the range of 100°C–1400°C. Wetlands designed to treat oxyanions such as arsenate therefore are dependent on the intended mechanism, and design must carefully consider that mechanism. This deficiency is confounded by a lack of knowledge on the chemical composition of red mud leachate and the changes in composition that occur as a result of interactions with sediments and freshwater organisms during transport through aquatic ecosystems. Environmental concerns caused by disposal of red mud relate to its high alkalinity and sodicity (Paramguru et al., 2005; Power et al., 2011) and its documented hazards to sea life (Blackman and Wilson, 1973; Dauvin, 2010; Dethlefsen and Rosenthal, 1973; Pagano et al., 2002). Iron is often abundant in metals-containing waters such as mine drainage and readily forms an insoluble oxide precipitate. The most logical, ecologically friendly and economically viable method is by in situ immobilization of metals using abundant, inexpensive soil amendments. As the precipitate forms, the anionic ligands may be exposed to solution and capture a different cation of similar charge, such as instead of Fe2+, Pb2+ being added into the precipitate. If the water has iron present, a FWS system, which allows coprecipitation, would be designed. Multitalia). At low pH, oxide mineral is dissolved in water and arsenic is released into the aqueous phase, with a resultant very high arsenic input to downstream water bodies. In addition, inorganic nutrients such as phosphorus and nitrate leaching have reported further, indicating issues (ie, groundwater pollution) related to the land application of biowastes. Both As and Se are generally found as the mobile oxidized form (As5+ and Se6+), and reduction (As3+, Se4+, Se0, or Se−2) results in precipitate formation as an oxide or as a sulfide depending on redox conditions. Cancrinite hematite. T he major chemical composition of red mud for selected cou ntries over. It is chemically characterized by the presence of Si, Al, Fe, Ca, Ti as well as an array of minor constituents such as Na, K, Cr, Ni, Mn, Cu, Zn and Pb. Arsenic tends to be in the arsenate form, HAsO42−, at neutral pH and behaves much like phosphate, in part, because As is the third member of group 15 in the periodic table, with P directly above. High levels of metals were found in seagrass (Posidonia oceanica) from the Bay of Antikyra (Malea et al., 1994), an area where levels of polycyclic aromatic hydrocarbons in sediments, and concentrations of polychlorinated biphenyls (PCBs) and dichlorodiphenyl trichloroethane and its metabolites (DDTs) in Mediterranean mussels (Mytilus galloprovincialis) were among the highest sampled throughout Greece (Botsou and Hatzianestis, 2012; Tsangaris et al., 2010, 2011). In order to sustain the immobility (or high Kd) of metals, the ‘counter’ processes (e.g., desorption, dissolution, high oxidation potential) should be minimized or prevented, otherwise they can impede metal immobilization processes. The ability of apatite to immobilize dissolved Pb2+ as precipitates is more commonly manifested as hydroxypyromorphite or as chloropyromorphite. Many such agents are by-products from processing industries and so are inexpensive. The addition of beringite, a modified aluminosilicate, resulted in a complete disappearance of visual and metabolic symptoms of metal(loid) phytotoxicity by metal(loid) immobilization. The Bayer process produces large quantities of bauxite residue (red mud). The chemical structure of red mud is pretty similar to produced glass-ceramics (Peng et al., 2005). Fixation–stabilization technologies aim to decrease the concentration of the aqueous and exchangeable forms of pollutants in soils through the application of nontoxic reactive agents. These factors include the availability of biowastes and their transportation cost, public acceptance and political ramifications, suitability of biowastes for the targeted spoil, and application rate (Castillejo and Castello, 2010; Larney and Angers, 2012). As the temperature and pressure increases, the solubility of red mud decreases with sodium hydroxide (Nie et al., 2016). The linings of the cell must be replaced periodically. Gadd, in Encyclopedia of Microbiology (Third Edition), 2009. Thus, a high Kd translates to low bioavailability induced by effective immobilization. Ecosystem modelling would be a valuable tool to investigate trophic interactions and fisheries-related ecological perturbations (Piroddi et al., 2010, 2011b). At a very low pH range (less than 1) when nearly all arsenic species exist in neutral form, arsenic is no longer sorbed and becomes mobile again. During our study, we interviewed 104 fishers operating in the GOC, and 46 (44%) mentioned beach seiners, purse seiners, bottom trawlers, or overfishing in general as negatively influencing their catch (S. Bonizzoni and G. Bearzi, unpublished data). Fe oxide minerals are considered to be most important because of their strong binding ability to arsenic. Mean density of the representative red mud sample from the Birac Industry was 3.05 g/cm3, and the ignition loss for the temperatures of 900 and 950°C was 4.93 and 5%, respectively. The solubility of Zn and Ni in dredged sediment increased when the pH was less than 6, pH 4 for Cd, pH 6 for Co, and pH 2 for Cu and Pb (Tack et al., 1996). The decomposition or mineralization of organic fraction of biowastes and mobilization of contaminants over time leads to serious concerns in mine spoil rehabilitation. Swaran J.S. Similar reactions in SSF wetlands could lead to clogging with the precipitated iron. The oxyanion forms therefore are captured by interaction with positively charged groups, such as adsorption to the aluminum in clay or the iron in iron oxides. D.C. Adriano, ... W.W. Wenzel, in Encyclopedia of Soils in the Environment, 2005. The invention discloses a method of treating high-iron red mud by alkaline process for deep dealkalization and iron enrichment. Inorganic amendments such as quarry waste, pulverized refuse, and pulverized fuel ash have also been used to improve substrate characteristics (Wong, 2003). The variation in chemical composition between different RMs worldwide is high. A potential concern is that highly reducing conditions can lead to biologically mediated methylation, producing volatile, and highly toxic, compounds. A new twist to the definition has been proposed, that natural processes can be accelerated by adding to the soil inexpensive amendments that are cost-effective and minimally invasive. Therefore, the reduction of sulfate-containing mine waters using some source of electron donor such as decaying plant matter in a wetland will result in metal sulfide precipitation as a removal mechanism. High temperature Bayer red mud. Some potential uses are as a flux in the steel industry, a fuel in making rock wool, or as a supplemental fuel in cement production. For example, arsenic is found in water most often as arsenate or arsenite, but reduction of As compounds results in less-soluble forms. The extent of immobilization can be measured by Kd (partition coefficient), which also serves as an index for bioavailability. Here, sewage sludge combined with nitrogen fertilizer was used to establish four indigenous grass species present in the mining area. This allows for coprecipitation of other metals. The formation of the new solid phase (i.e., precipitates) occurs when the ionic product in the solution exceeds the solubility product of that phase. Ferrate [Fe(VI)] is one of the environmentally friendly reagents used in water and wastewater treatment as it can be used as both an oxidant and a coagulant. The CaO and SiO 2 contents of Sintering red mud are much higher For instance, expanded clay and N and P fertilizer increased the plant biomass of Andropogon gerardii in mine tailings (Hetrick et al., 1994). Significant reduction in arsenate and arsenite adsorption by phosphorus and sulfate on various adsorbents such as amorphous iron oxide goethite, gibbsite, kaolinite, montmorillonite, aluminum oxide, and quartz has been reported [165]. In non-specific adsorption, electrostatic attraction lies between a charged surface and an oppositely charged ion in solution in which the adsorbed ion resides at a certain distance from the mineral surface. Numerous studies have shown that organic acids such as humic substances also compete with arsenic for adsorption sites on oxide surfaces due to the anionic nature of organic acids and strong affinity of their carboxylic and phenolic groups to the oxide surface [162]. Most of mine spoil rehabilitations depend on a one-time application of large amounts of biowastes rather than multiple applications of lower amounts. The washing not only irreversibly destroys the integrity of the soil in a general sense, but also produces a secondary waste – the washing effluent, which is usually a chelate solution now laden with metals. Coagulant production using red mud and waste base as raw material is described together with phase and chemical composition changes in red mud during coagulant production and usage. have been used to leach Zn, Cu, Ni, and Co from a variety of solid materials, including industrial filter dust, copper converter slag, lateritic ores, -extractable Pb concentration of the amended soil. For instance, composting is used to convert the easily degradable organic fractions into a more recalcitrant fraction through humification, thereby increasing the maturity of the organic fractions of biowastes (Bernai et al., 1998). The preferred change is a precipitation reaction with a very low solubility constant, because the other significant removal mechanism is readily reversible adsorption. Hamon, in Encyclopedia of Soils in the Environment, 2005. Beckers et al., 2015; Taylor et al., 2011). It has been suggested that arsenate adsorbs mainly through non-specific sorption (electrostatic attraction), while arsenite is adsorbed via specific sorption (inner-sphere complexation). Sales Online Elements, which are amphoteric, forming anionic oxyanions are generally lower in solubility if the oxyanion is reduced. By continuing you agree to the use of cookies. Worse offenders, however, by factors of 6500 and 9200, respectively, are the CF4 and C2F6 gases that are emitted during anode effects. Two processes for the reaction of dissolved Pb2+ with apatite are proposed: first, Pb can react with apatite through hydroxyapatite (HA, Ca10(PO4)6 (OH)2); second, Pb2+ can substitute for Ca2+ in the apatite (eqn 3). Cancrinite. These organic compounds, giving RM a distinctive odour, are derived largely from decomposed vegetation and roots. Therefore RM should be regarded as a group of materials, having particular characteristics, such: Produced during the Bayer process G.M. Red mud is a waste material derived as residual from the Bayer process by the caustic digestion of crushed bauxite at elevated temperature. For example, precipitation as metal phosphate has been shown to be a major mechanism for the immobilization of metals, such as Pb and Zn by phosphate compounds. Red mud is composed of a mixture of solid and metallic oxides. The immediate goal of the rehabilitation has to be decided at the very beginning. In the present paper, the phase composition and structural transition of red mud heated from room temperature are indicated by XRD, TG-DTA, and SEM techniques. The reader is familiar with iron oxidation, resulting in iron oxy(hydrox)ides, sometimes called rust. Red mud is the tailings generated from the production process of aluminum industry and is mainly stacked in open-air at present, so how to ensure the stability of red mud stockpile is very important. Some minerals are known to have a metal(loid) immobilizing capacity. Decreasing pH leads to increased arsenic retention because of the shift in mineral surface charges from negative to more positive; consequently, arsenic species become less mobile. Red mud is classified by EC as a non hazardous waste (Commission Decision 2000/532/EC), however its small particle size (dust-like, mean particle size 0.49μm), high alkalinity and large The reader is cautioned that metal geochemistry often involves hundreds of possible reactions, and the following descriptions are simplifications. Thus the US-EPA coined the term ‘monitored natural attenuation’ (MNA) when NA is employed within the context of a carefully controlled and monitored site cleanup strategy to be able to achieve site-specific remediation objectives within a time frame that is more reasonable than that offered by other, more invasive methods. G. Bearzi, ... O. Gimenez, in Advances in Marine Biology, 2016. (depending on the initial chemical composition of the bauxite ore) along with inclusions of unwashed sodium aluminate solution. The common organization of such treatment is that the anaerobic SSF wetland follows an anoxic limestone contact system for neutralization, which feeds an aeration step to cause iron oxy(hydrox)ide formation and precipitation. Adsorption of arsenite and arsenate on mineral surfaces can be of two types: non-specific and specific. Se shares a similar relationship with S, and selenate behaves much like sulfate. Table 1. Major soil constituents such as phosphate, silicic acid, sulfate, and natural organic matter also strongly affect arsenic adsorption. The immobilization of As, Cd, Pb, and Zn in smelter-contaminated soils using diammonium phosphate (DAP) is also possible. Chemolithotrophic leaching of metal sulfides is well established for industrial-scale biomining processes, but it has also been used to solubilize metals from sewage sludge as well as remediate other metal-contaminated solid materials, including soil and. Peaty, decaying plant matter surfaces have hydroxyl and carboxyl groups as well as other moieties exposed, which can adsorb metals. Many chemoorganotrophic (heterotrophic) fungi (and bacteria) can leach metals from industrial wastes, low-grade ores, and metal-bearing minerals. The inorganic RM phases which are not contained in bauxite can be divided into three groups [W. Kurdowski, F. Sorrentino, 1997]: “NAS” phases: 3(Na2O Al2O3 2SiO2)Na2X (X=CO2 2-, 2OH-, SO4 2-, 2Cl-), “CAS-CFS” phases: 3CaO(Fe2O3)x (Al2O3)1-x kSiO2 (6-2k)H2O, “NT-CT” phases: Na2Ti3O7.3H2O, kassite, perovskite, portlandite. Castaldi et al. W. Haupin, in Encyclopedia of Materials: Science and Technology, 2001. RM is a very fine material in terms of particle size distribution. Adsorption of arsenic is a complex phenomenon and depends upon properties of the solid surface, hydration, soil pH, changes in cation coordination, isomorphous substitution, crystallinity, concentration, and species of arsenic and competing ions. The main chemical constituents of red mud (%). Chemical composition of Red mud is, by weight (% w/w): Fe 2 O 3 - 30.8; SiO 2 - 31.7; Al 2 O 3 - 15.6; TiO 2 - 2.58; Na 2 O - 3.14, CaO - 3.51; K 2 O - 0.11; MgO - 0.27; MnO - 0.02; P 2 O 5 - 0.22. As a result of sulfur and iron oxidation, metal sulfides are solubilized concomitant with the pH of their immediate environment being decreased, therefore resulting in solubilization of other metal compounds, including metals sorbed to soil and mineral constituents. Chemical constituent Fe2O3 Al2O3 SiO2 CaO Na2OTiO2 K2OSc2O3 V2O5 Nb2O5 TREO Loss Red mud is mainly composed of coarse sand and fine particles of mud. While this captures the fluoride and destroys the cyanide, it increases the volume of solid waste to be land-filled. H. Wijesekara, ... A. Surapaneni, in Advances in Agronomy, 2016. Fe oxide minerals are considered to be most important because of their strong binding ability to arsenic. The oxidation methods used include ozone and oxygen, hydrogen peroxide, manganese oxides, UV/Fe, and TiO2/UV. Adsorption of arsenic in two different oxidation states, As(III) and As(V), was not identical under the same conditions such that As(V) adsorption was high under acidic conditions, while As(III) adsorbs under basic conditions. The concentration of Pb in the aerial part of plants grown in compost soil was 87% lower than in the control sample. Oxalic acid can act as a leaching agent for metals that form soluble oxalate complexes, including Al and Fe. Overall, seiners and trawlers scored as the main anthropogenic factor perceived as a threat to fish stock viability in the GOC (also see Bearzi et al., 2008a, 2010). In addition to iron, the other dominant components include silica, unleached residual alumina, and titanium oxide. Table 2 : Chemical composition and phase analysis of the Nalco red mud A. (2011b) have demonstrated the potential value of both soluble and insoluble P compounds in the immobilization of Pb, thereby reducing its bioavailability and toxicity. At a sufficient redox potential, reduced Fe2+ will lose an electron to become Fe3+, which in the presence of water forms a variety of iron oxide/hydroxides (because water activity determines the specific mix of oxide and hydroxide; these are termed iron oxy(hydrox)ides) depending on redox potential and water activity. This may be attributed to an increased efficiency of metal(loid) binding on Fe or Mn oxides due to the high pH and precipitation of Fe oxides on clay particles induced by the beringite (Ruttens et al., 2006). INTRODUCTION Red mud; a solid- waste generated at the Aluminum plants all over the world .In Western countries, about 35 million tons of red mud are produced yearly. One disposal method is to grind, mix with lime, and incinerate. The metals which form low-solubility oxides, and thus which are precipitated to mM or lower concentration in oxidizing conditions at neutral pH, include Al, Cd, Co, Cu, Fe, Pb, Hg2+, Ni, Pd, Pt, and Zn. Soil amendments that have been successfully tested in North America, Europe, and Australia include liming materials, rock phosphate (hydroxyapatite), alkaline biosolids and/or compost, Fe-rich by-products (steel shot, Arsenic adsorption on different minerals has been reported. Soluble Cd, Cu, and Zn concentrations in soils are often found to be negatively correlated with pH values (Burgos et al., 2006). The treated soil may be returned to the site or landfilled. High salt and nutrient content of biowastes has a great influence on plant establishment at mine spoils. Composition. Despite the best efforts of medieval alchemists, metals cannot be chemically transformed to some other element. We examined the physical and chemical properties of red mud in terms of environmental effects especially for the subsurface environment. The mineralogy of the original red muh and the various sub‐fractions produced was studied by chemical assay, selective leaching, XRD and SEM techniques. Hydroxides of iron are considered to be most commonly involved minerals in adsorption of arsenic under both acidic and alkaline conditions, while other adsorbents perform the function under acidic conditions only. 30-60. In addition to iron, the other dominant components include silica, unleached residual alumina, titanium oxide, and caustic. Lime is effective in reducing the phytoavailability of Cd and Cr3+ (Bolan and Duraisamy, 2003). The specific gravity of red mud is 2.77 gcm −3 measured by gas picnometer. Its pH ranging from 10.67 measured by Italian standard soil analysis 1:2.5 ratio and also has greater ionic strength (Hua et al., 2017). However, indirect effects such as contamination up the food web are possible (Jepson et al., 2016). 1 Alumina production and Red mud. Iron oxides act as adsorbents as well as coprecipitants of other metals. The nature of metal adsorption behavior to the soils has been identified to differ among types of biowastes. | Powered by, Site dedicated on the valorisation and best practices on bauxite residue, Bauxite Residue accident from Norwegian Hydro in Brazil, Rio Tinto investing $250 million to extend life of Vaudreuil alumina refinery, Rio Tinto and GMR partner to explore potential use for bauxite residue, RUSAL produces first output of scandium oxide, BRAVO – Bauxite Residue and Aluminium Valorisation Operations, Postdoc position on red mud research at the University of Guelph. Hind et al, 1999]: Polybasic and polyhydroxy acids, alcohols and phenols, humic and fulvic acids, carbohydrates, sodium salts of succinic, acetic and oxalic acids When combined with compost, inorganic metal(loid) immobilizing amendments resulted in better plant responses when compared to the addition of inorganic amendments alone. Their compositions, mechanical properties and microstructure characterization were measured through XRD, TG and SEM analysis. Although no casualties were reported, the red mud buried many farm and domestic animals. Its composition, property and phase vary with the origin of the bauxite and the alumina production process, and will change over time when stocked . Thus, when metal precipitate forms from a solution of metals, the precipitate contains a mixture of the metals. 290-308, Edited by Satish Chandra, William Andrew Publishing/Noyes, 1997, A. R. Hind, S. K. Bhargava, Stephen C. Grocott, “The surface chemistry of Bayer process solids: a review”, Colloids and Surfaces A : Physicochem. At low pH, red mud performs well in removing Cd from soil (Liu et al., 2011). red mud soda alumina alumina values Prior art date 1996-02-15 Legal status (The legal status is an assumption and is not a legal conclusion. The following compounds have been reported [A.R. The chemical composition of the mixture varies depending on the parent ore (i.e. Most studies of wetland plants have shown exclusion of metals from tissues. (Wang and Liu, 2012) measured by using X-ray diffractometer. The amendments increased the residual fraction of heavy metal(loid)s in the soils and decreased the Pb uptake by white lupin (Lupinus albus L., cv. bauxite) used and the processing conditions during the Bayer process ... the latter constitute red mud). However, in most contexts, the term refers to siliciclastic mudstone, composed mostly of silicate minerals. The residue contains numerous potentially valuable ingredients such as soda, iron oxide, and titania. Fe 2O 3 accounting for red mud color (red brown) is evaluated to be 22.8% of the weight. Lopez-Anton et al. The capacity for metal adsorption is dependent on the metal and chemistry of the surface, with adsorption ranging from negligible to the tens of mg of metal per kg organic mass.