Abstract:The removal of 60Co and 90Sr from the aqueous phase was tested using red mud
- the fine grained residue from bauxite ore processing. This industrial waste
represents a mixture of numerous minerals, mainly oxides and hydroxides of
Fe, Al, Si, and Ti. Experiments were conducted as a function of contact
time, pH, and pollutant concentrations. Kinetic data were well fitted with a
pseudo-second order equation. The calculated rate constants and initial
sorption rates indicated faster sorption of Sr… Show more
“…[22] The calculated constants K L were also higher for raw sample, signifying higher surface affinity towards Co 2C and Sr 2C ions. The difference was particularly pronounced for Sr 2C ions.…”
Section: Kinetics Of Co 2c and Sr 2c Sorption As A Function Of Solutimentioning
confidence: 87%
“…Blank experiments with raw red mud sample from the same deposit showed wider buffering pH range (»3.5 to »10), and considerably higher pH at the plateau (9.5) due to the residual NaOH from the Bayer process. [22] The "liming" effect of red mud was attributed to several constituents: free caustic, sodalite and calcite. [36] Free caustic was washed out from RBRM sample; thus, the major alkaline anions are identified as OH ¡ , CO 3 2¡ /HCO 3 ¡ and Al(OH) 4 ¡ /Al (OH) 3 (aq), which originated from sodalite and calcite dissolution according to the reactions: [32] …”
Section: Properties Of Rbrm Sorbentmentioning
confidence: 99%
“…Also, sorption of radionuclides from aqueous media using red mud was explored in several studies. [18][19][20][21][22][23] Red mud is a waste generated during alumina production from bauxite ore by the Bayer process. It is characterized by high alkalinity (average pH from 10 to 13) [24] and heterogeneous composition (hematite (Fe 2 O 3 ), goethite (a-FeOOH), boehmite (g-AlOOH), gibbsite (Al(OH) 3 ), anatase and rutile (TiO 2 ), quartz (SiO 2 ), sodalite (Na 4 Al 3 Si 3 O 12 Cl) or cancrinite-type sodium aluminum silicate (CAN), gypsum (CaSO 4 £ 2H 2 O), calcite (CaCO 3 ), whewellite (CaC 2 O 4 £ H 2 O), etc.)…”
Section: Introductionmentioning
confidence: 99%
“…Previously, the removal of Co 2C and Sr 2C from aqueous phase using raw red mud from "Bira c" factory deposit (Bosnia and Herzegovina) was preliminarily tested, with promising results. [22] 60 Co and 90 Sr are significant radionuclides present in the LRW. [27,28] Although they have a different origin in nuclear reactors, they contribute considerably to the overall radiation level.…”
Section: Introductionmentioning
confidence: 99%
“…Due to elevated alkalinity, significant amounts of Co 2C were precipitated in the form of insoluble hydroxide. [22] In such systems, contribution of red mud mineral matrix and the mechanisms of cation sorption by various solids remain largely unknown. High alkalinity and high sodicity, coming from free NaOH, [25] may also pose an impediment to some potential red mud applications, such as soil remediation processes or construction of barriers around radioactive waste disposal sites.…”
The prospects of rinsed red mud (alumina production residue) utilization for liquid radioactive waste treatment have been investigated, with Co(2+) and Sr(2+) as model cations of radioactive elements. To evaluate the sorption effectiveness and corresponding binding mechanisms, the process was analyzed in batch conditions, by varying experimental conditions (pH, Co(2+) and Sr(2+) concentrations in single solutions and binary mixtures, contact time, and the concentration of competing cations and ligands common in liquid radioactive waste). Comparison of the Co(2+) and Sr(2+) sorption pH edges with the red mud isoelectric point has revealed that Co(2+) removal took place at both positive and negative red mud surface, while Sr(2+) sorption abruptly increased when the surface became negatively charged. The increase of initial cation content and pH resulted in increased equilibrium times and sorption capacity and decreased rate constants. From single metal solutions and various binary mixtures, Co(2+) was sorbed more efficiently and selectively than Sr(2+). While Sr(2+) sorption was reduced by coexisting cations in the order Al(3+) ≥ Ca(2+) >Na(+) ≥Cs(+), removal of Co(2+) was affected by Al(3+) species and complexing agents (EDTA and citrate). Desorption of Co(2+) was negligible in Ca(2+) and Sr(2+) containing media and in solutions with initial pH 4-7. Sr(2+) desorption was generally more pronounced, especially at low pH and in the presence of Co(2+). Collected macroscopic data signify that Co(2+) sorption by red mud minerals occurred via strong chemical bonds, while Sr(2+) was retained mainly by weaker ion-exchange or electrostatic interactions. Results indicate that the rinsed red mud represent an efficient, low-cost sorbent for Co(2+) and Sr(2+) immobilization.
“…[22] The calculated constants K L were also higher for raw sample, signifying higher surface affinity towards Co 2C and Sr 2C ions. The difference was particularly pronounced for Sr 2C ions.…”
Section: Kinetics Of Co 2c and Sr 2c Sorption As A Function Of Solutimentioning
confidence: 87%
“…Blank experiments with raw red mud sample from the same deposit showed wider buffering pH range (»3.5 to »10), and considerably higher pH at the plateau (9.5) due to the residual NaOH from the Bayer process. [22] The "liming" effect of red mud was attributed to several constituents: free caustic, sodalite and calcite. [36] Free caustic was washed out from RBRM sample; thus, the major alkaline anions are identified as OH ¡ , CO 3 2¡ /HCO 3 ¡ and Al(OH) 4 ¡ /Al (OH) 3 (aq), which originated from sodalite and calcite dissolution according to the reactions: [32] …”
Section: Properties Of Rbrm Sorbentmentioning
confidence: 99%
“…Also, sorption of radionuclides from aqueous media using red mud was explored in several studies. [18][19][20][21][22][23] Red mud is a waste generated during alumina production from bauxite ore by the Bayer process. It is characterized by high alkalinity (average pH from 10 to 13) [24] and heterogeneous composition (hematite (Fe 2 O 3 ), goethite (a-FeOOH), boehmite (g-AlOOH), gibbsite (Al(OH) 3 ), anatase and rutile (TiO 2 ), quartz (SiO 2 ), sodalite (Na 4 Al 3 Si 3 O 12 Cl) or cancrinite-type sodium aluminum silicate (CAN), gypsum (CaSO 4 £ 2H 2 O), calcite (CaCO 3 ), whewellite (CaC 2 O 4 £ H 2 O), etc.)…”
Section: Introductionmentioning
confidence: 99%
“…Previously, the removal of Co 2C and Sr 2C from aqueous phase using raw red mud from "Bira c" factory deposit (Bosnia and Herzegovina) was preliminarily tested, with promising results. [22] 60 Co and 90 Sr are significant radionuclides present in the LRW. [27,28] Although they have a different origin in nuclear reactors, they contribute considerably to the overall radiation level.…”
Section: Introductionmentioning
confidence: 99%
“…Due to elevated alkalinity, significant amounts of Co 2C were precipitated in the form of insoluble hydroxide. [22] In such systems, contribution of red mud mineral matrix and the mechanisms of cation sorption by various solids remain largely unknown. High alkalinity and high sodicity, coming from free NaOH, [25] may also pose an impediment to some potential red mud applications, such as soil remediation processes or construction of barriers around radioactive waste disposal sites.…”
The prospects of rinsed red mud (alumina production residue) utilization for liquid radioactive waste treatment have been investigated, with Co(2+) and Sr(2+) as model cations of radioactive elements. To evaluate the sorption effectiveness and corresponding binding mechanisms, the process was analyzed in batch conditions, by varying experimental conditions (pH, Co(2+) and Sr(2+) concentrations in single solutions and binary mixtures, contact time, and the concentration of competing cations and ligands common in liquid radioactive waste). Comparison of the Co(2+) and Sr(2+) sorption pH edges with the red mud isoelectric point has revealed that Co(2+) removal took place at both positive and negative red mud surface, while Sr(2+) sorption abruptly increased when the surface became negatively charged. The increase of initial cation content and pH resulted in increased equilibrium times and sorption capacity and decreased rate constants. From single metal solutions and various binary mixtures, Co(2+) was sorbed more efficiently and selectively than Sr(2+). While Sr(2+) sorption was reduced by coexisting cations in the order Al(3+) ≥ Ca(2+) >Na(+) ≥Cs(+), removal of Co(2+) was affected by Al(3+) species and complexing agents (EDTA and citrate). Desorption of Co(2+) was negligible in Ca(2+) and Sr(2+) containing media and in solutions with initial pH 4-7. Sr(2+) desorption was generally more pronounced, especially at low pH and in the presence of Co(2+). Collected macroscopic data signify that Co(2+) sorption by red mud minerals occurred via strong chemical bonds, while Sr(2+) was retained mainly by weaker ion-exchange or electrostatic interactions. Results indicate that the rinsed red mud represent an efficient, low-cost sorbent for Co(2+) and Sr(2+) immobilization.
Copper slag flotation tailings (CSFT), as the end waste from copper mining, are evaluated for radionuclide and heavy metal immobilization. Characterization of CSFT based on grain size and mineral composition, surface functional groups, pH and electrical conductivity in aqueous media, thermogravimetric analysis (TGA), determination of characteristic temperatures in sample melting process, leachability, and toxicity tests is conducted. The screening sorption of Mn(II), Co(II), Ni(II), Zn(II), Cd(II), and Pb(II) inactive isotopes from single-component solutions is performed. The Cd(II) ions show better sorption potential than other ions, with a sorption capacity of 0.08 mmol g −1 at the highest initial concentration. Sorption decreases in the sequence Cd(II) > Pb(II) > Zn(II) > Mn(II) > Ni(II) > Co(II) at all initial concentrations. Although CSFT shows lower sorption capability than synthetic sorbents based on fayalite and magnetite, its inexpensiveness and substantial accessible amount represent great advantages in wider utilization.
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