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Acid mine drainage (AMD) remediation by red mud (RM) can benefit process sustainability and waste valorization. Though the AMD properties upon using RM have been broadly investigated, the key features and the environmental stability of spent RM are poorly defined. The current study aimed to compare the AMD neutralization and metal removal potential of the fresh (FRM) and aged (ARM) Bayer red mud and evaluate the textural, mineralogical, chemical, radiological properties of solid residues, and the stability of toxic elements. The FRM had larger particles and exhibited higher pH, iron oxide content, and radioactivity than ARM, which could be driven by ARM leaching and settling inside the tailings pond. FRM displayed marginally higher neutralization and metal removal capacity than ARM. Reaction with AMD led to partial dissolution of cancrinite minerals without significant changes in the particle size distribution. The leachability of investigated toxic elements (As, Ba, Cd, Cr, Cu, Ni, Pb, Se, Zn) from neutralization residues complied with the limits set for inert waste by the EN 12457–2 test. Owing to the RM neutralization, the leachability of Al, As, Cr, and V decreased with respect to pristine samples. While Zn and Mn sorbed from AMD were stable following SPLP and EN 12457–2 tests, the sequential extraction revealed increased environmental availability, posing a potential risk during disposal or application if accompanied by a decline in pH. The slight increase in radioactivity upon RM neutralization indicates that changes in radionuclide inventory should be monitored when using RM in neutralization.

The efficient, selective, and economical sorbents for the removal of Sr radionuclides are largely needed for the decontamination of effluents with high salinity. In this study, the removal of Sr was investigated using the zeolite produced from the Bayer process liquids. Based on the XRD, SEM/EDS analysis, the product was pure and highly crystalline zeolite 4A (Z4A). Removal of Sr was fast (5 min for 100% removal at 8.80 mg/L), with high maximum sorption capacity (252.5 mg/L), and independent on the initial pH in the range 3.5–9.0. Specific sorption of Sr by protonated groups on the Z4A surface was operating in addition to ion-exchange with Na ions. The selectivity of Z4A decreased in the order Sr > Ca > K > Mg > Na. 84% of Sr was separated from seawater within 5 min, at the Z4A dose of 5 g/L, while efficiency increased to 99% using the dose of 20 g/L. Desorption of radioisotope 89 Sr from seawater/Z4A solid residue was very low in deionized water (0.1–0.2%) and groundwater (0.7%) during 60 days of leaching. Z4A is a cost-effective, selective, and high-capacity medium for Sr removal, which provides high stability of retained radionuclides.

The objective of the present study was to determine the impact of cadmium (Cd) concentration in the soil on its uptake by tobacco plants, and to compare the ability of diverse extraction procedures for determining Cd bioavailability and predicting soil-to-plant transfer and Cd plant concentrations. The pseudo-total digestion procedure, modified Tessier sequential extraction and six standard single-extraction tests for estimation of metal mobility and bioavailability were used for the leaching of Cd from a native soil, as well as samples artificially contaminated over a wide range of Cd concentrations. The results of various leaching tests were compared between each other, as well as with the amounts of Cd taken up by tobacco plants in pot experiments. In the native soil sample, most of the Cd was found in fractions not readily available under natural conditions, but with increasing pollution level, Cd amounts in readily available forms increased. With increasing concentrations of Cd in the soil, the quantity of pollutant taken up in tobacco also increased, while the transfer factor (TF) decreased. Linear and non-linear empirical models were developed for predicting the uptake of Cd by tobacco plants based on the results of selected leaching tests. The non-linear equations for ISO 14870 (diethylenetriaminepentaacetic acid extraction - DTPA), ISO/TS 21268-2 (CaCl2 leaching procedure), US EPA 1311 (toxicity characteristic leaching procedure - TCLP) single step extractions, and the sum of the first two fractions of the sequential extraction, exhibited the best correlation with the experimentally determined concentrations of Cd in plants over the entire range of pollutant concentrations. This approach can improve and facilitate the assessment of human exposure to Cd by tobacco smoking, but may also have wider applicability in predicting soil-to-plant transfer.

Fluorapatite nanopowders with different amounts of fluoride ions were prepared using the surfactant-assisted microwave method under isothermal conditions. Microwave irradiation was applied for the rapid formation of crystals. A micellar solution of polyoxyethylene (23) lauryl ether was used as a regulator of nucleation and crystal growth. Characterization studies from X-ray diffraction, field-emission scaning electron microscopy and Fourier(-)transform infrared spectra showed that crystals have an apatite structure and particles of all samples are nano size, with an average length of 50 mn and about 15-25 nm in diameter. Antimicrobial studies have demonstrated that synthesized fluorapatite nanopowders exhibit activity against tested pathogens: Eseherichia coli, Staphylococcus aureus and Candida albicans. Activity increased with the amount of fluoride ions. The synthesized fluorapatite nanomaterials are promising as materials in environmental protection and medicine for orthopedics and dental restorations.

This paper presents the results of determining the pseudo-total concentration of five heavy metals in the soil on which the destruction of ammunition, mines, and explosive devices is carried out by the method of open detonation. In the analyzed area, the concentrations of cadmium, lead, nickel, copper, and zinc were determined, while from the physical properties of the soil were determined the granulometric composition and the pH. The aim of the study is to determine the origin and total load on heavy metals and, based on that, to assess the dangers and impact of the site in terms of the soil pollution by heavy metals. In accordance with the regulations of Bosnia and Herzegovina, the results of the soil testing showed a significant load of copper (up to seven times) and cadmium (up to six times), and exceeding the allowed values for nickel and zinc in some places. Lead was the only metal whose concentration was within the maximum allowed and according to that the soil was classified as unpolluted. A sample of soil from the edge of the pit is the only sample in which all heavy metals, except Ni, were within the maximum allowable concentration. In regard to the concentration of the examined metals, the soil of the pit is classified as medium polluted from the aspect of copper, cadmium, and nickel and highly contaminated with zinc. The concentrations of copper and zinc in the examination area correspond to contaminated soil that represents ecological risk, which requires soil remediation.

Fluorapatite nanopowders with different amounts of fluoride ions were prepared using the surfactant-assisted microwave method under isothermal conditions. Microwave irradiation was applied for the rapid formation of crystals. A micellar solution of polyoxyethylene (23) lauryl ether was used as a regulator of nucleation and crystal growth. Characterization studies from X-ray diffraction, field-emission scaning electron microscopy and Fourier(-)transform infrared spectra showed that crystals have an apatite structure and particles of all samples are nano size, with an average length of 50 mn and about 15-25 nm in diameter. Antimicrobial studies have demonstrated that synthesized fluorapatite nanopowders exhibit activity against tested pathogens: Eseherichia coli, Staphylococcus aureus and Candida albicans. Activity increased with the amount of fluoride ions. The synthesized fluorapatite nanomaterials are promising as materials in environmental protection and medicine for orthopedics and dental restorations.

The objective of the present study was to determine the impact of cadmium (Cd) concentration in the soil on its uptake by tobacco plants, and to compare the ability of diverse extraction procedures for determining Cd bioavailability and predicting soil-to-plant transfer and Cd plant concentrations. The pseudo-total digestion procedure, modified Tessier sequential extraction and six standard single-extraction tests for estimation of metal mobility and bioavailability were used for the leaching of Cd from a native soil, as well as samples artificially contaminated over a wide range of Cd concentrations. The results of various leaching tests were compared between each other, as well as with the amounts of Cd taken up by tobacco plants in pot experiments. In the native soil sample, most of the Cd was found in fractions not readily available under natural conditions, but with increasing pollution level, Cd amounts in readily available forms increased. With increasing concentrations of Cd in the soil, the quantity of pollutant taken up in tobacco also increased, while the transfer factor (TF) decreased. Linear and non-linear empirical models were developed for predicting the uptake of Cd by tobacco plants based on the results of selected leaching tests. The non-linear equations for ISO 14870 (diethylenetriaminepentaacetic acid extraction - DTPA), ISO/TS 21268-2 (CaCl2 leaching procedure), US EPA 1311 (toxicity characteristic leaching procedure - TCLP) single step extractions, and the sum of the first two fractions of the sequential extraction, exhibited the best correlation with the experimentally determined concentrations of Cd in plants over the entire range of pollutant concentrations. This approach can improve and facilitate the assessment of human exposure to Cd by tobacco smoking, but may also have wider applicability in predicting soil-to-plant transfer.

As a result of the destruction of ammunition, mines, and explosive devices by the method of open detonation, the increased concentration of heavy metals is often recorded in the soil of military polygons, which is a serious ecological problem. However, in order to determine the potential risk of such locations to the environment, it is necessary to determine, in addition to the total content, the forms in which the metals are present. In this paper, a sequential extraction method was used to analyze the six fractions of five heavy metals (cadmium, lead, nickel, copper, and zinc) in the soil of the polygon for destruction of ammunition, mines, and explosive devices. Samples were collected from the place of direct detonation (so-called pits) and from the edge of the pit. The aim of this research is determination of metal speciation in order to obtain a better insight in their mobility and risk arising from this. The results showed that heavy metals are predominantly present in the residual, oxide, and organic fractions. Cd and Cu were also significantly present in the mobile fractions due to conducted activities on the polygon. To assess the potential environmental risk of soil, the risk assessment code (RAC) and individual (ICF) and global (GCF) contamination factors were used. According to the RAC, the mobility and bioavailability of the analyzed heavy metals decreases in the following order: Cd gt Cu gt Zn gt Pb gt Ni. ICF results show low to moderate risk, while GCF results show low risk in terms of heavy metal contamination in the examined area.

Predmet istraživanja ove doktorske disertacije je izučavanje uticaja ulaznih podataka na polja koncentracija zagađujućih materija u donjem graničnom sloju atmosfere dobijenih primenom matematičkih modela kao i usložnjavanje matematičkog modela atmosferske disperzije Gausovog tipa, čiji je rezultat generalisan Gausov disperzioni model. Cilj istraživanja u ovom radu je realizacija i primena kompleksnog matematičkog difuzionog modela, koji uzima u obzir složene atmosferske procese u sloju mešanja, kao i razrađena procedura za pripremu ulaznih podataka, koji omogućavaju praćenje rasprostiranja zagađujućih materija u okolini industrijskih i nuklearnih izvora na rastojanjima do 10-20 km, gde su koncentracije zagađujućih materija iz tih izvora obično najveće i gde se dobijaju prve informacije važne za ranu najavu akcidenata i pokretanje kontramera. Pored navedenog cilj je i verifikacija matematičkog modela pisanog u FORTRAN programskom jeziku (NFS-Vinca) preko meteoroloških podataka koji su dobijeni u realnom vremenu, kao i procena rasprostiranja polutanata na osnovu idealizovane situacije sa zadatim vetrom i klasama stabilnosti.Istraživanja u okviru doktorske disertacije polaze od hipoteze da koncentracije zagađujućih materija koje se emituju u atmosferu iz veštačkih izvora zavise od karakteristika izvora, atmosferskih procesa u donjem graničnom sloju atmosfere, tzv. sloju mešanja, karakteristika tla i fizičko hemijskih karakteristka zagađujućih materija. Kod nuklearnog postrojenja modelovana je koncentracija radioaktivnosti u vazduhu sledećih radionuklida: 137Cs, 90Sr, 60Co, 154Eu. Kod industrijskog postrojenja određivan je nivo koncetracije PM10.U prvom delu rada, matematičkim modelom su dobijene prosečne godišnje koncentracije aktivnosti u vazduhu, koncentracije suve i vlažne depozicije kao i ukupna godišnja doza koju bi primio hipotetički stanovnik u blizini nuklearnog reaktora. Rezultati modelovanja su upoređeni sa vrednostima koncentracije radioaktivnosti iz IAEA (I, The subject of this doctoral dissertation was the influence of the input data on the pollutant concentration in the lower atmospheric boundary layer obtained by mathematical model, which was the result of generalized Gaussian dispersion model. The aim was implementation of complex mathematical diffusion model and development procedures which enable the monitoring of dispersion of pollutants in the environment of industrial and nuclear power plants within 10-20 km, where the concentration of pollutants from these sources is usually the highest, and also for early warning for accidents and countermeasures. In addition is the verification of the mathematical model in FORTRAN programming language (NFS-Vinca) through meteorological data obtained in real time, as well as the evaluation of dispersion of pollutants on the basis of idealized situations specified with wind classes and stability.Research in this dissertation is based on the hypothesis that the concentrations of pollutants emitted into the atmosphere from artificial sources depend on the characteristics of the sources of atmospheric processes in the lower atmospheric boundary layer, soil characteristics and the physical and chemical characteristics of pollutants. For the nuclear power plant, radioactivity concentration of the following radionuclides 137Cs, 90Sr, 60Co, 154Eu was determined. For thermal power plant the concentration level of PM10 was measured.The air pollution dispersion model is based on average annual activity concentration in the air, deposition on soil and field of total annual dose to a hypothetical resident contaminated by air in the vicinity of a nuclear reactor. The results of modeling were compared with values from an IAEA publication for a given scenario of radionuclide emission to the atmospheric boundary layer. Due to small differences in the results, compared to the IAEA recommended model, the model presented in the thesis can be used as a basis for this type of analysis. The maximum

In this paper, for characteristic polytropic change of state of ideal gas is given graphical planimetric graphical representation of the most important energy values in workplace and thermal diagram, trough the appropriate area. In this paper, we used differential forms of the First and Second law of thermodynamics and basic equation which define the observed change of state, written in a suitable form. The results for the polytropic change of state, are applied to the isobaric and isochoric change of state. It is shown that any of the energy values ( q12, w12, wt12, Dh12, Du12) can be present in both workplace (p, v) as well as thermal (T-s) diagram. Graphical solutions, compared to the analytical, provide efficient theoretical explain and presentation of various thermodynamic processes of ideal gas with different aspects and greatly assist a clearer view of the problem and enhance each other living arrangement. Graphical representation of external influences or energy values shown in the diagrams, make it possible to more clearly we see connection between these effects, change of state, as well as their each other relations. This is particularly evident in the case when there are (p, v) and (T-s) diagram for a par tic u lar ideal gas, which is common in technical practices (e. g., air as an ideal gas)., U radu je za karakterističnu politropsku promenu stanja idealnog gasa dato grafičko planimetrijsko predstavljanje najvažnijih energetskih veličina u radnom i toplotnom dijagramu, preko odgovarajućih površina. Pri ovome korišćeni su diferencijalni oblici prvog i drugog zakona termodinamike, kao i osnovne relacije koje definišu posmatranu promenu stanja, napisane u pogodnom obliku. Dobijeni rezultati, za politropsku kao opštu promenu stanja, primenjeni su na izobarsku i izohorsku, kao karakteristične promene stanja. Pokazano je da bilo koju od energetskih veličina (q12, w12, wt12, Δh12, Δu12) moguće predstaviti kako u radnom (p-v), tako i u toplotnom (T-s) dijagramu. Prikazana grafička rešenja, u odnosu na analitička, omogućuju efikasnije teorijsko razmatranje i predstavljanje različitih termodinamičkih procesa idealnog gasa sa različitih aspekata i znatno pomažu jasnijem sagledavanju problema i poboljšavaju međusobno sporazumevanje. Grafički prikazi spoljnih uticaja, odnosno energetskih veličina u prikazanim dijagramima, omogućuju da se još jasnije uoči veza između tih uticaja, promena stanja, kao i njihovi međusobni odnosi. Ovo posebno dolazi do izražaja za slučaj kada postoji (p, v) i (T-s) dijagram za određeni idealni gas, što je čest slučaj u tehničkoj praksi (na primer za vazduh kao idealan gas).

Red mud, a heterogeneous mineral waste from aluminum industry, can be beneficially utilized as a sorbent. High alkalinity and the amount of water soluble ions can limit some of its applications. This study's aim was to explore and correlate physicochemical properties and sorption efficiencies of acid treated red mud. Sorbents (BRM0.05-BRM1), obtained by varying HCl concentration (0.05-1 mol/L), were characterized in terms of mineralogical composition, surface functional groups, electrical conductivity (EC) and the point of zero charge (pH(PZC)). Removal of Ni(II) ions was tested in batch conditions. Sorbents EC and pH(PZC) values decreased with the increase of acid concentration. Structural analysis revealed that sodalite and calcite phases were completely lost starting from the samples BRM0.25 and BRM0.5, respectively. Along with the sodalite dissolution, gibbsite precipitation was observed. Ni(II) sorption increased with the increase of initial pH from 2 to 4, while at pH gt 4 it depended only on sorbent material. A radical drop of maximum sorption capacities was associated with the increase of acid concentration to 0.25 mol/L, whereas additional rise to 1 mol/L caused minor fluctuations. Fully loaded sorbents BRM0.25-BRM0.1 also exhibited considerable lower stability over a range of investigated pH conditions. Dissolution of sodalite and calcite, and the consequent reduction of buffering capacities can be identified as the main reasons for decreasing sorption efficiency. Sample BRM0.05 was efficient in terms of both sorption and stability, yet environmentally more benign than the original red mud due to the lower alkalinity and content of water soluble ions.

U ovoj disertaciji proučavana je mogućnost primene crvenog mulja iz Fabrike glinice „Birač“ (Zvornik, severoistočna Bosna i Hercegovina) za izdvajanje jona nikla iz vodenih rastvora u šarčnim uslovima. U tu svrhu je ispitana efikasnost sorpcije u zavisnosti od uslova tretmana mulja i parametara sorpcije (pH, doza sorbenta, kontaktno vreme, inicijalna koncentracija jona nikla), kao i uticaja koegzistentnih jona. Stabilnost opterešenih sorbenata ispitina je u različitim ekstrakcionim rastvorima. Hemijskim i instrumentalnim metodama utvrđeno je da se ispitivani crveni mulj (BRM) odlikuje raznorodnim sastavom, malom specifičnom površinom i visokim alkalitetom. Po hemijskom sastavu, ispitivani mulj predstavlja heterogenu smešu oksida gvožđa, aluminijuma, silicijuma i titana, pri čemu je oksid gvožđa predstavljao najzastupljeniju komponentu. Glavne kristalne faze u crvenom mulju bile su: hematit (Fe2O3), gibsit i bajerit (Al(OH)3), sodalit (Na8Si6Al6O24Cl2), kvarc (SiO2), anatas i rutil (TiO2), kao i kalcit (CaCO3). Prisustvo hidroksilnih, karbonatnih, Si(Аl)–О i Fe–O grupa na površini sorbenta, igra vačnu ulogu u vezivanju jona metala. Radi dobijanja efikasnijeg i ekološki prihvatljivijeg sorbenta primenjeni su ispiranje, termički i kiselinski tretmani. Temeljnim ispiranjem polaznog uzorka dobijen je sorbent (RBRM), istog mineralnog sastava, ali niče pH vrednosti i tačke nultog naelektrisanja (pHPZC). Termički i kiselinski tretmani su, u zavisnosti od temperature tretmana i koncentracije kiseline, izazvali fizičke i hemijske promene uzorka značajne za sorpciju. Najznačajnije promene pri termičkom tretmanu su gubitak gibsita, bajerita i kalcita i strukturna destrukcija i transformacije sodalita. pHPZC ispranog uzorka čarenog na 600 °C (RBRM600) značajno je viša od vrednosti polaznog RBRM, a bliska je vrednosti sirovog mulja. Pri kiselinskom tretmanu, porast koncentracije kiseline doveo je do gubitka sodalita i kalcita, i rastvaranja kvarca. Nakon kiselinskih tretmana pHPZ, This dissertation investigated possibilities of using red mud from alumina factory “Biraţ” (Zvornik, North-East Bosnia and Herzegovina), for uptake of nickel ions from aqueous solution, in batch conditions. For this purpose, sorption efficiency was examined as a function of red mud treatment conditions and sorption parameters (pH, sorbent dose, contact time, initial sorbate concentration), as well as the presence of coexisting ions. The stability of the loaded sorbents was studied in different leaching solutions. Chemical and instrumental analyses have shown that investigated red mud (BRM) was of heterogeneous composition, with low surface area and high alkalinity. By chemical composition, investigated red mud was a mixture of oxides of iron, aluminum, silicon and titan, where the major component was iron oxide. The main crystalline phases were found to be: hematite (Fe2O3), gibbsite and bayerite (Al(OH)3), sodalite (Na8Si6Al6O24Cl2), quartz (SiO2), anatase and rutile (TiO2), as well as calcite (CaCO3). The presence of hydroxyl, carbonate, Si(Al)–O and Fe–O groups on the surface of the sorbent, play an important role in metal ion binding. In order to obtain more efficient and environmentally benign sorbents, rinsing, thermal and acid treatments were applied. By rinsing the raw red mud, a sorbent (RBRM), with the same mineral compositions, but lower pH and the point of zero charge (pHPZC), was obtained. Thermal and acid treatments, depending on heating temperature and acid concentration, caused physical and chemical changes important for the sorption. The most significant changes provoked by the thermal treatments are: decomposition of gibbsite, bayerite and calcite and structure destruction and transformations of sodalite. pHPZC of rinsed mud heated at 600 °C (RBRM600) is significantly higher than the value of starting RBRM and approaches the value of the raw sample. In acid treatments, the increase of the acid concentration led to a loss of sodalite and calcite, an

The removal of Ni(II) from aqueous solutions by raw red mud powder was studied in the absence and in the presence of citrate ligand, as a function of process parameters. Using lower initial Ni(II) concentration (10(-3) mol/L) detectable amounts were found only at initial pH 3, whereas for higher concentration (2 x 10(-3) mol/L) removal increased simultaneously with pH in the range 3-4 and at pH gt 8. Process efficiency was suppressed in the presence of citrate. However, at Ni/Citrate molar ratios 1:0.25 and 1:0.5, 10-20% decrease was noticed in acidic media, while the negative influence diminished with the rise of pH. At higher ligand rates, formation of stable aqueous complex between Ni(II) and citrate significantly reduced metal removal in the whole tested initial pH range (3-10). Due to instantaneous pH rise above 8, removal of Ni(II) from 10(-3) mol/L solution was completed in 5 min. Kinetic data demonstrated slower Ni(II) uptake using both solutions of higher initial Ni(II) concentrations and Ni/Citrate solutions. At initial pH 5, estimated capacity towards Ni(II) was found to be 27.4 mg/g, without citrate. For Ni/Citrate molar ratios 1:0.25 and 1:0.5, capacities decreased slightly to 25 mg/g and 21 mg/g, whereas at equimolar and higher concentrations, citrate significantly inhibited Ni(II) immobilization (7.6 mg/g and 2.5 mg/g, respectively for Ni/Citrate ratios 1:1 and 1:2). The results demonstrated beneficial effect of red mud high alkalinity on Ni(II) removal. The sorbent satisfactorily immobilize nickel from solutions having initial Ni/Citrate molar ratios lower than 1:1, and neutral to alkaline initial pH. FUR analysis confirmed that red mud can act as a removal agent for Ni(II), Ni/Citrate complex and free citrate ligand.

The waste red mud, remaining in remarkable quantities after the digestion of bauxite ores following the Bayer process, contains number of voluble minerals with excellent sorption properties towards aqueous heavy metals. Heating at 600 degrees C was found to be a favorable treatment for revalorization of rinsed red mud into an efficient Ni2+ sorbent (RBRM600). As potential practical application of RBRM600 for Ni2+ accumulation greatly depends on the solution composition and pH, the influence of these vital process variables was considered in this study. The initial pH rise from 2 to 3.5 caused the most evident increase in the amounts of Ni2+ removed: furthermore, the effect was more obvious for lower initial sorbate concentrations. Conversely, changes of the solution pH between 3.5 and 8 did not have a significant influence on the sorption. The increase of initial cation concentration caused the increase of the sorbed amount. following Langmuir isotherm model. The calculated maximum sorption capacity of 27.54 mg/g demonstrated capacity increase of approximately 20% in respect to inactivated rinsed red mud. Coexisting cations inhibited Ni2+ removal in the following order: Cu2+ gt Pb2+ gt = Zn2+ gt Cd2+ gt gt Ca2+, whereas the presence of Na+ and K+ did not affect the process. The investigated anions caused decrease of Ni2+ removal efficiency in the order: EDTA gt chromate gt acetate gt sulphate, however, fluoride slightly improved sorption. Low desorption of Ni2+ in various media showed that the heavy metal cations are tightly bound to RBRM600 surface, thus disposal or reuse of spent sorbent should be considered.

Red mud, an abundant industrial waste from alumina industry, represents a rich source of various metal oxides, mainly of Fe2O3 Al2O3 and SiO2. In this study, the rinsed Bosnian red mud (RBRM) was evaluated as an economical, composite sorbent for aqueous Ni2+ ions. The process was investigated as a function of pH, contact time and initial metal concentration. The investigated mineral mixture exhibited a high acid neutralising capacity, and its most important role in cation immobilization was observed in the initial pH range 2-8. The initial metal ion concentration strongly influenced the sorption kinetics and equilibrium times. Addition of 5 g/L of RBRM caused 100% removal from the solutions of 10(-4) to 5 x 10(-4) mol/L, whereas with the further increase of Ni2+ concentration to 8 x 10(-3) mol/L, the removal efficiency decreased to 26%. The maximum sorption capacity of 0.372 mmol/g, at initial pH 5, was determined using Langmuir theoretical model. The possibility of sorption efficiency improvement by annealing RBRM powder was investigated in the range 200-900 degrees C and the relationships between temperature, red mud physicochemical and sorption properties were established. The optimum heating temperature was found to be 600 degrees C, due to water exclusion from gibbsite and bayerite phases, leading to improved porosity and surface area, as well as increased pH value and sorption efficiency. The stability of the sorbed cation was assessed by leaching experiments in distilled water and acidic TCLP2 solution.