Radioactive Contamination of the Soil: Assessments of Pollutants Mobility with Implication to Remediation Strategies

Accidental releases, nuclear weapons testing, and inadequate practices of radioactive waste disposal are the principal human activities responsible for radioactive contamination as a new and global form of soil degradation. Understanding the radionuclide distribution, mobility and bioavailability, as well as the changes caused by the variation of environmental conditions, is essential for soil rehabilitation. This chapter aims to highlight the importance of evaluating radionuclide distribution, for the selection of proper in situ or ex situ remediation strategy. Attention was focused onto remediation methods based on radioactive pollutants redistribution, for enhanced separation (chemical extraction) or containment (in situ immobilization). When the excavation and off-site leaching treatments are uneconomic, impractical, or unnecessary, in situ stabilization by the addition of appropriate reactive materials is an alternative approach. The optimization of factors in control of chemical leaching methods, selection of cost-effective immobilization agents, especially among suitable wastes and by-products, and verification of long-term effects of remediating actions are the major challenges for future investigation in this field. Furthermore, the improvement and standardization of the methods for radionuclide speciation are necessary to enable comparison between studies and monitoring of the effects achieved by the soil treatments

Investigation of mass transfer phenomenna during sorption of Cu (II)-ions onto inorganic sorbents

Predmet rada ove doktorske disertacije je bio ispitivanje sorpcije Cu (II)- jona sintetičkim HAP-om i prirodnim sorbentima zeolitom, glinom i dijatomitom, u cilju definisanja ravnoteže i kinetike procesa pri različitim uslovima. Fizičko-hemijska karakterizacija je pokazala da se sintetički HAP sastoji od čistog nestehiometrijskog, kalcijum deficitarnog, kalcijum-hidroksiapatita, zeolit od klinoptilolita, dok je glina kompozit ilita, kaolinita i montmorilonita. Glavna faza u dijatomitu je amorfni silicijum-dioksid. Takođe, HAP i zeolit su okarakterisani kao mezoporozni sorbenti specifičnih površina 58 m2/g i 23 m2/g, redom, dok su se glina i dijatomit pokazali neporozni, nižih specifičnih površina od 8 m2/g i 5 m2/g. Definisana je pHPZC koja iznosi 6,6 za HAP, glinu i dijatomit, dok je kod zeolita nešto viša i iznosi 7,5. Dobijene vrednosti pHPZC HAP-a, gline i zeolita su u dobroj saglasnosti sa literaturom, dok pHPZC dijatomita do sada nije objavljena. Ispitivanjem uticaja inicijalne pH vrednosti rastvora na ravnotežu, pokazano je da se finalne pH vrednosti razlikuju u zavisnosti od ispitivanog sorbenta. Generalno, ravnotežne pH vrednosti najviše rastu sa porastom inicijalnih pH rastvora u oblasti 2 - 4. Oblast platoa, u kome su finalne pH vrednosti nezavisne od inicijalnih i koja ukazuje na puferska svojstva sorbenata, zavisi od vrste sorbenta i koncentracije jona metala u rastvoru. Dalje povećanje polaznih pH prouzrokuje porast i finalnih. Krive zavisnosti sorbovane količine od inicijalnih pH su istog oblika kao i krive pH finalno-pH inicijalno, što se objašnjava povećanom rastvorljivoću sorbenata ili njihovih komponenti i kompeticijom Cu(II) i H+ jona u jako kiselim rastvorima. Porast finalnih pH iznad 6 dovodi do precipitacije bakar – hidroksida što rezultira 100% uklanjanjem jona metala iz rastvora. Maksimalni sorpcioni kapaciteti prema Cu(II)- jonima, na sobnoj temperaturi, opadaju u nizu: HAP (0,585 mmol/g) > zeolit (0,128 mmol/g) > glina (0,098 mmol/g) > dijatomit (0,047 mmol/g). U datim eksperimentima je utvrđen pad pH vrednosti rastvora u odnosu na početnu, što ukazuje na postojanje mehanizma specifične sorpcije, koji je najdominantniji tokom sorpcije na dijatomitu. Za vezivanje jona metala ispitivanim materijalima, odgovoran je i mehanizam jonske izmene, gde se Cu(II)- joni izmenjuju sa Ca2+ jonima sa površine HAP-a, odnosno sa jonima Na+, K+, Ca2+, Mg2+ sa površine prirodnih sorbenata. Stabilnost sistema sorbent/jon metala je ispitana u kiselom rastvoru za izluživanje i zavisi od vrste sorbenta, kao i prethodno sorbovane količine Cu(II)- jona. Sa porastom sorbovane količine na uzorcima HAP-a i dijatomejske zemlje, raste i procenat desorbovane količine, dok desorpcija sa zeolita i gline pokazuje suprotan trend - u kiseloj sredini su stabilniji uzorci sa većom sorbovanom količinom jona metala. Ako posmatramo desorbovanu količinu izraženu u mmol/g ili mg/g, ona je veća na uzorcima koji su više zasićeni, nezavisno od vrste sorbenta. Kinetika procesa je ispitana u različitim šaržnim sistemima. Prvi sistem su pojedinačne šarže sa mešanjem na horizontalnom šejkeru, gde je proces sorpcije ispitan u funkciji od početne koncentracije Cu(II)- jona na svim ispitanim sorbentima. Drugi šaržni sistem je sud sa mešalicom u kom je ispitana kinetika procesa sorpcije HAP-om i zeolitom u funkciji od koncentracije sorbata, mase sorbenta, brzine mešanja, a za zeolit i od granulacije sorbenta. Pokazano je da je sorpcija glinom i dijatomitom, kao neporoznim sorbentima, limitirana otporom u filmu fluida. Nasuprot tome, difuzija u filmu fluida tokom sorpcije na šejkeru HAP-om i zeolitom je značajna na početku procesa, tokom prvih 15 minuta. Vrednosti zapreminskog koeficijenta prenosa mase su izračunate Boyd-ovim modelom. Dobijene vrednosti kf·a su nezavisne od početne koncentracije Cu(II)- jona u rastvoru i variraju oko srednje vrednosti 0,046 1/min za HAP, 0,023 1/min za zeolit, 0,017 1/min za glinu i 0,031 1/min za dijatomit. Iz prethodno navedenog proizilazi da je kf·a kod neporoznih sorbenata funkcija veličine čestica, tj. najveći je za najsitnije čestice jer je i specifična površina veća. Primenom jednačina za difuziju u porama, pokazano je da efektivne difuzivnosti blago opadaju sa porastom c0 za sorpciju HAP-om, dok za sorpciju zeolitom Deff nije funkcija c0. Zavisnost Deff od c0 i nezavisnost kfa od c0 kod HAP-a može se objasniti suprotnostrujnom difuzijom odlazećih katjona sa površine sorbenta, kao i elektrostatičkim odbijanjem istoimenih naelektrisanja koji su zanemarljivi u masi fluida, ali se ne mogu zanemariti u unutrašnjosti pora. Analizom rezultata sorpcije HAP-om u sudu sa mešanjem, dobijeno je da kf·a za prvih 10 minuta procesa ne zavisi od mase sorbenta i brzine mešanja, a blago opada sa porastom početne koncentracije metala u rastvoru, što je najverovatnije uslovljeno postojanjem otpora difuzije u porama. Nasuprot tome, kf·a izračunat za zeolit ne zavisi od mase sorbenta, kao ni početne koncentracije, ali raste sa porastom brzine mešanja i padom veličine čestica sorbenta. Efektivne difuzivnosti i kod HAP-a i kod zeolita ne zavise od mase sorbenta, kao ni brzine mešanja. Deff opada sa porastom c0 usled postojanja suprotnostrujne difuzije u porama, a raste sa porastom veličine čestica. Kao krajnji zaključak, može se izvesti da je za procese sorpcije HAP-om i zeolitom na šejkeru u prvih 15 minuta limitirajući otpor u filmu fluida, a zatim difuzija u porama sorbenta, pri čemu se dešava sorpcija u mezoporama. Takođe, šejker ne obezbeđuje dovoljno efikasno mešanje, te su vrednosti kfa i Deff značajno niže od vrednosti dobijenih za sud sa mešanjem. Sorpcija HAP-om u sudu sa mešanjem je limitirana samo difuzijom u porama jer se difuzija u filmu fluida i zasićenje površine dešava skoro trenutno. Tokom sorpcije zeolitom u sudu sa mešanjem, prvih 10 minuta procesa značajan je otpor u filmu, a nakon toga otpor u porama sorbenta.The subject of the work presented in this dissertation was to investigate the sorption of Cu (II)- ions onto synthetic hydroxyapatite (HAP)-and natural sorbents: zeolite, clay and diatomite, in order to define process equilibrium and kinetics under different conditions. Physico-chemical characterization showed that synthetic HAP was consisted of pure non-stoichiometric, calcium deficient, calcium hydroxyapatite, zeolite of clinoptilolite, while clay was the composite of illite, kaolinite and montmorillonite. The main phase of diatomite was amorphous silicon dioxide. Also, HAP and zeolite were characterized as a mesoporous sorbents with specific surface areas of 58 m2 / g and 23 m2 / g, respectively, while the clay and diatomite were non-porous, with low specific surface areas of 8 m2/g and 5 m2 / g. pHPZC of 6.6 was defined for HAP, clay and diatomite, while higher value of 7.5 was obtained for zeolite. Obtained results for pHPZC for HAP, clay and zeolite are in good agrement with literature, while pHPZC of diatomite has not been published. The investigation of influence of initial solution pH in the range of 2 - 10 on equilibrium showed that the final pH values varied depending on the tested sorbent. In general, final pH values increased the most in pH range 2 – 4. Areas of the plateau, where the final pH values were independent on the initial pH indicating the buffering properties of sorbents, were dependent on the sorbent and the concentration of metal ions in solution. Further increase of initial pH caused increase of final pH values. The plots of sorbed amounts vs. initial pH were of the same shape as plots pH final vs. pH initial, which can be explained with higher solubility of sorbents and their components and competition between Cu(II) and H+ ions in the strong acidic media. The final pH increase above 6 caused copper hydroxide precipitation and 100 % removal of metal ions from solution. The maximal sorption capacities at room temperature decreased in the order: HAP (0,585 mmol/g) > zeolite (0,128 mmol/g) > clay (0,098 mmol/g) > diatomite (0,047 mmol/g). In these experiments pH drop was observed, signifying the existence of specific cation sorption mechanism which was the most dominant during the sorption onto diatomite. Also, ion-exchange mechanism between Cu(II)- ions and Ca2+ ions from HAP surface was responsible for metal bonding, as well as ion-exchange with Na+, K+, Ca2+, Mg2+ from surfaces of natural mineral sorbents. The stability of system sorbent/ metal was investigated in acidic leaching solution and it was dependant on sorbent type, as well as on the previously loaded amounts. With increase of loaded metal amounts onto HAP and diatomite, the percentages of desorption also increased, while the opposite was observed for desorption from zeolite and clay- the samples with higher loadings were more stable in the acidic media. The desorbed amounts expressed in mmol/g or mg/g were higher for the more saturated samples, independent of sorbent type. The process kinetics was investigated as a function of initial metal concentration in batch system, on horizontal shaker. It was shown that the sorption onto non-porous sorbents, clay and diatomite was limited with diffusion film resistance. Contrary, the film diffusion was significant only during the first 15 minutes of process onto HAP and zeolite. The values of volumetric mass transfer coefficient kf·a were calculated using Boyd model. The values of kf·a were independent on initial concentration, and varied around averaged value of: 0,046 1/min for HAP, 0,023 1/min for zeolite, 0,017 1/min for clay and 0,031 1/min for diatomite. According to this it can be concluded that kf·a was a function of particle size for nonporous sorbents, i.e. it was highest for the smallest particles because specific surface area was higher. The obtained values for kf·a decreased in the order: HAP>diatomite>zeolite>clay, but probably this order would be different if the zeolite particles were smaller, where value for kf·a onto zeolite would be higher. Using pore diffusion models, it was shown that the effective diffusivities slightly decreased with c0 increase, while for sorption onto zeolite Deff was independent on c0. Dependence of Deff on c0 and independence of kfa on c0 can be explained by counter diffusion of cations released from sorbent surface, as well as with electrostatic repulsion of positive charged particles. These phenomena can be neglected in the fluid mass, but not inside the pores. From the analysis of results obtained for sorption onto HAP in the agitated vessel, it was observed that kf·a calculated for the first 10 minutes of the process was independent on sorbent mass and agitation speed, but slightly decreased with initial metal concentration increase, which was probably caused by the existence of pore diffusion resistance. Contrary, kf·a calculated for zeolite was independent on metal concentration and sorbent mass, but increased with agitation speed increase and particle size decrease. Effective diffusivities for sorption onto HAP and zeolite were independent on sorbent mass and agitation speed. Deff decreased with c0 increase because of counter diffusion inside the pores, but increased with particle size increase. Finally, it can be concluded that for the first 15 minutes of the sorption onto HAP and zeolite using shaker, the limiting step was film diffusion, and after that the pore diffusion, where sorption occurred inside the mesopores. Also, the mixing using shaker was not good enough, thus the obtained values for kfa and Deff were significantly lower than the values obtained for the sorption in the agitated vessel. The sorption onto HAP in the agitated vessel was limited only by pore diffusion because the film diffusion and surface saturation occurred almost instantaneously. The sorption onto zeolite in agitated vessel was governed by film diffusion during the first 10 minutes, whereas after that by diffusion inside the pores

Influence of bentonite and zeolite on Cs+ and Co2+ cement matrix leaching phenomena

The probability of Cs+ and Co2+ ions retention by immobilization processes in the cement matrix was determinate as the subject of analyses: matrix design, water/cement ratio, and structure porosity. Comparison of experimental results was accomplished by Hespe standard leaching method. Diffusion and semi-empirical models were used for the assessment of the washing rate as a function of time. The higher value of cement matrix mechanical resistance corresponds to a lower value of Co2+ and Cs+ ions leaching. The Co2+ leaching level was more than two orders of magnitude less than the leaching level of Cs+. The influence of bentonite and zeolite on Co2+ leaching reduction was significantly smaller in comparison with Cs+, while zeolite had a higher Cs+ and Co2+ sorption ability than bentonite. Under static leaching conditions, the contribution of diffusion to the total transport of ions in the matrix porous medium was dominant. The contribution of matrix dissolution was insignificant concerning the dominant contribution of diffusion and surface washing. The semi-empirical model showed a better approximation of the Co2+ and Cs+ ions laboratory leaching process

Physico-chemical characterization and tritium activity determination in spring waters

The quality of drinking water should be monitored and analyzed with the aim of determination of water pollution and to minimize health hazards. From a radiological point of view, drinking water may contain natural and artificial radionuclides. One of the radionuclides that can occur in drinking water is tritium. Tritium, as the only radioactive isotope of hydrogen, occurs naturally as a cosmogenic radioisotope in the stratosphere but also has an anthropogenic origin. This study presents the results of some physico-chemical analysis and tritium activity determination carried out for natural water sources in the vicinity of Smederevska Palanka. Water samples from eleven natural water sources were analysed: (source “Veliki Sipovac” (Azanja), source “Pinosava” (Kusadak), source “Vrelo” (Glibovac), source “Vidovača” (Vodice), source “Mineral water” (Vodice), source “Mineral water” (Cerovac), source “Sveta Trojica” (Cerovac), source “Šiljakovac” (Ratari), source “Klis” (Golobok), source “Palanački Kiseljak” (Smederevska Palanka), source “Sveta Petka” (Smederevska Palanka)), in order to determine possible contamination, because the local population is supplied with drinking water from these springs. Physico-chemical characterization was performed measuring pH, total dissolved solids (TDS) and conductivity. The pH values were measured using InoLab pH meter WTW with glass electrode SenTix 81. The conductivity of the samples was measured using Conductometer InoLab WTW Cond7110 at 20°C. TDS measurement was based on the weight of the solid residue remained after evaporation of 40 ml of sample and subsequent drying at 105°C. For tritium activity determination samples were distilled and electrolytically enriched using direct current source SORENSEN DCR60-B30. After electrolytic enrichment samples were measured by Ultra Low Level Liquid Scintillation Spectrometer Quantulus 1220. Conductivity and pH were measured before and after distillation of water samples. Some of investigated waters are naturally acidic and measured values for pH and conductivity show different results for samples before and after distillation. TDS has a higher value for natural mineral waters. In accordance with the legislation in the Republic of Serbia elevated tritium levels in water samples may indicate the presence of other artificial radionuclides. If tritium concentration exceeds allowed value, additional analysis is required. In that case it is necessary to perform gamma spectrometric analysis of the content of artificial radionuclides or analysis of 90Sr. The permissible value of tritium in drinking water is 100 Bq/l. All analyzed waters in this study meet the legal regulations and from the radiation point of view can be used for drinking. The annual effective dose was calculated based on the tritium concentration in the investigated samples for different age groups. The obtained results are in accordance with legislation.X JUBILEE International Conference on Radiation in Various Fields of Research : RAD 2022 (Spring Edition) : book of abstracts; June 13-17, 2022; Herceg Novi, Montenegr

Relationships Between Bone Treatment Conditions and Co2+ Sorption Capacities

Co-60 is an important radionuclide in spent nuclear fuel and liquid radioactive wastes. For the purification of water containing Co2+, ions sorption on hydroxyapatite (Ca-10(PO4)(6)(OH)(2)) can be applied. The process is particularly cost-effective if biological apatite from animal bones is utilized. In this study, dependence between bovine bone treatment conditions and Co2+, sorption was investigated as a function of initial metal concentration. Eight sorbents were previously prepared using fractional factorial design, by simultaneous variations of five process variables between two levels: factor A-the type of the chemical reagent (H2O2 or NaOH), factor B-reagent concentration (0.1 mol/L or 2 mol/L), factor C-reaction temperature (20(o)C or 60(o)C), factor D-contact time (1h or 3h) and factor E-sample annealing (without or at 400(o)C). At this point, the effects of treatment factors on Co2+, sorption efficiency were evaluated using statistical analysis. Amounts of Co2+ sorbed, amounts of released Ca2+ ions and final pH values were considered as system responses. The results showed that the impact of various treatment factors was different for different starting concentrations of Co2+. Consequently, no statistically important relations could be established between treatment conditions and Co2+, sorption from 10(-4) and 5*10(-4) mol/L solutions, whereas thermal treatment at 400(o)C was the only statistically significant factor influencing sorption from the most concentrated solution (5*10(-3) mol/L). Depending on initial Co2+, concentration, various factors had statistically significant effect on equilibrium pH values, whereas no relation was found between bone treatment conditions and the amounts of Ca2+, released during the sorption.3rd International Conference on Radiation and Applications in Various Fields of Research (RAD), Jun 08-12, 2015, Budva, Montenegr

Analysis of gross alpha and gross beta activity in samples around former uranium mine Gabrovnica

Gabrovnica, uranium mine near Kalna in the Eastern Serbia was a natural ore with uranium content. Exploitation of the uranium ore in this region was started in the 1960s and it was terminated in 1996. The aim of this work was to analyze radiological characterization of environmental samples around uranium mine Gabrovnica. Soil samples were taken in the autumn of 2022 and spring 2023, while surface soil samples (Gabrovnička River) were taken continuously for six month (July-December 2022 and January-June 2023). All samples were analyzed in order to determine gross alpha and gross beta activities and measured on ultra low level gas proportional counter Thermo-Eberline FHT 770T.54th International October Conference on Mining and Metallurgy : October 18-21, Bor Lake, Serbia, 2023

Mobility of Co2+ and Sr2+ ions in the contaminated soil: column study

The mobility of pollutants in the soil is closely related to their toxicity, and thus very important information for the selection of remediation strategies. In this study, leaching of Sr2+ and Co2+ ions from contaminated soil was investigated and compared under dynamic conditions. As a model soil, a sample from the “Vinča” Institute was tested. The soil artificially contaminated with inactive Sr2+ and Co2+ ions was packed in the columns, while acidic rain water was used as a leaching solution. Desorption of both cations was the most pronounced at the beginning, reaching the peak after the second day for Co2+ and after the seventh day for Sr2+. During the course of experiment (37 days), cumulative percentages of desorbed Co2+ and Sr2+ were 0.7% and 19.8 %, respectively. The results indicated significantly higher soil affinity towards Co2+ ions. In spite of its higher total concentration in the soil, Co2+ mobility was much lower compared to Sr2+

E-Waste Glass in Radionuclide Immobilization

Comprehensive needs for environmental protection are imposed by the prerogative of preserving natural resources, i.e. efficient usage of materials and energy. Therefore, there is an urgent need for different waste materials recycling or reusing. However, advances in new technologies in the electronics industry are leading to the problem of disposing of different types of E-waste, often discarded even before its usual time. This research represents an overview of E-waste glass utilization, like cathode ray tubes (CRT) from old computer monitors and TV screens, in mortar matrices for radionuclide immobilization. Due to its properties, mortar is used for liquid radioactive waste (LRW) solidification. Large quantities of cement, aggregates, and water are used annually for mortar and concrete manufacture. Also, cement production requires the consumption of large amounts of energy, i.e. the use of non-renewable fossil fuels. Nevertheless, mixing waste materials with mortar effectively reduces the amount of cement consumption. Aspects of this paper relate to a review of recent developments regarding the use of E-waste in cementitious materials. Emphasis was placed on their physico-mechanical properties to evaluate the possibility of CRT usage in mortar matrix for LRW immobilization

Development of C&DD-Based Geopolymer Products – A Practical Approach

Construction and demolition debris (C&DD) is among the fastest-growing waste streams due to accelerated urbanization processes and overall economic development. Accordingly, developing attractive and cost-effective methods and creating more valuable technologies that could use this waste type more efficiently and solve possible environmental problems is one of the main challenges in research nowadays. The C&DD-based materials design has attracted the attention of researchers, offering to reduce the impact of production on the environment. The benefits arising from this concept include the reduction of C&DD in municipal landfills and the preservation of large quantities of natural raw materials, e.g. cement, aggregates, and water. Hence, the production costs, energy consumption, and carbon footprint could be reduced simultaneously. However, the results of this promising technology are not sufficiently integrated into actual practice. This new material development concept proposes a four-step approach. The first phase involves designing a mixture for the geopolymer material. The second phase consists of basic physico-mechanical properties determination: density, absorption, and compressive strength. The next stage implies durability testing. The fourth step, often omitted in basic research, suggests the best geopolymer formulations for the delivery and investigation of eco-friendly and marketable prefabricated building product prototypes, for various applications, e.g. pavements or wall blocks

Analysis of factors influencing Cu(II) sorption by clinoptiolite

The effects of initial metal concentration and pH, as well as the sorbent mass and particle size, on Cu(II) sorption by natural clinoptilolite were evaluated and compared. Full factorial experimental design at two levels was applied. Statistically significant factors were determined considering residual Cu(II) concentrations as a system response.Physical chemistry 2012 : 11th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 201