Evaluation of Factors Affecting Chemical Extraction of Co Ions from Contaminated Soil

Excessive concentrations of cobalt (Co) ions in the soil cause quality degradation and pose a significant hazard to biota. One of the options for the permanent separation of the pollutant from soil matrix is extraction by chemical reagents. In this study, response‐surface methodology (RSM) was applied to evaluate the factors affecting Co extraction from contaminated calcareous soil. Solutions of disodium ethylenediaminetetraacetate (Na2EDTA), citric acid (CA), and HCl were considered as leaching media. Reagent concentration, soil to solution ratio, and extraction time were selected as process variable, while Co extraction efficiencies and final pH values of extracts were the measured responses. The effect of factor variation between three levels was studied using Box‐Behnken experimental design. By statistical analysis, the most influential factors were determined for each reagent, and the model equations were proposed for the prediction of system responses. Overlaid contour plots were used for the analysis of the effect of process conditions on both responses simultaneously. Given that each case of contamination is unique and requires extensive research before the remediation is implemented full‐scale, it was shown that experimental design methodology is a smart approach for the assessment and comparison between the treatments

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

Sorption of Ni2+ by different synthetic hydroxyapatite

Two hydroxyapatite (HAP) samples of different crystallinity were studied as a nickel immobilization matrix. Sorption isotherms were obtained by batch equilibration method, in the concentration range 1. 10-4 – 8. 10-3 mol/dm3 . Low crystalline sample has sorption capacity of 0.212 mmol/g, and due to its higher specific surface area and lower Ca/P ratio it was found to be better sorbent for Ni2+ than crystalline HAP (0.092 mmol/g).Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200

Safe Management of Sealed Radiaoctive Sources: Possible Approaches, Handling, Conditioning and Storage

Zbog široke primene u industriji, medicini, poljoprivredi i različitim oblastima istraživanja, broj zatvorenih izvora jonizujućeg zračenja u svetu je u konstantnom porastu. Kod izvora ovog tipa radioaktivni materijal je hermetički zatvoren/zapečaćen u odgovarajuća kućišta/kapsule, kako bi se sprečio kontakt sa okolinom pri normalnim uslovima primene. U slučajevima kada se korišćenje zatvorenih izvora zamenjuje drugom tehnikom, izvor postane nedovoljne aktivnosti ili oštećen, deklariše se kao isluženi izvor jonizujućeg zračenja koji i dalje može biti visoko radioaktivan i potencijalno opasan po zdravlje ljudi i životnu sredinu. Širom sveta zabeležen je veliki broj akcidenata, pa adekvatno upravljanje predstavlja prioritet sa ciljem sprečavanje nezgoda ovog tipa. Isluženi izvor nije nužno i radioaktivni otpad, pa se pre deklarisanja kao takvog razmatraju i druge opcije. Cilj ovog rada je da predoči moguće pristupe i pruži uvid u neophodne korake u bezbednom upravljanju zatvorenim izvorima jonizujućeg zračenja.Due to their wide application in industry, medicine, agriculture, and various research fields, the number of sealed radioactive sources (SRS) in the world is constantly increasing. In SRS, the radioactive material is hermetically sealed in a suitable capsule to prevent contact with the environment under normal conditions of use. In cases where such a source is replaced by another technique, becomes obsolete, has insufficient activity or is damaged, it is declared as a disused sealed radioactive source that can still be highly radioactive and potentially dangerous for human health and the environment. A large number of accidents have been recorded worldwide, so adequate management is a priority with the aim of preventing accidents of this type. The disused sealed radioactive source is not necessarily radioactive waste, so other options are considered before declaring it as such. This work aims to present possible approaches and provide insight into the necessary steps to manage sealed radioactive sources safely.XXXII Simpozijum Društva za zaštitu od zračenja Srbije i Crne Gore, 4-6. oktobar 2023; Budva, Crna GoraProceedings: [https://vinar.vin.bg.ac.rs/handle/123456789/11602

Korelacija između fizičko-hemijskih svojstava hidroksiapatita i sorpcije jona Cu(II)

Izučavan je proces sorpcije Cu2+ jona iz vodenih rastvora sintetičkim hidroksiapatitnim (HAP) prahovima različitih fizičko-hemijskih svojstava. Određeni su maksimalni sorpcioni kapaciteti uzoraka, a stabilnost nagrađenih HAP-Cu proizvoda ispitana je u rastvorima kompetitvnog katjona i u kiseloj sredini. Uspostavljena je korelacija između sorpcionih i fizičkohemijskih svojstava HAP-a. Prahovi razvijene specifične površine i niže kristaličnosti pokazali su se kao efikasniji sorbenti, dok promena molskog Ca/P odnosa i tačke nultog naelektrisanja ispitivanih uzoraka nije bitno uticala na sorpciju jona Cu2+. Na osnovu molskih odnosa sorbovanih Cu2+ i otpuštenih Ca2+ jona, promena pH vrednosti rastvora i rezultata rendgenske difrakcione analize, diskutovani su glavni mehanizmi sorpcije Cu2+ jona HAP-om

The role of intraparticle diffusion in the sorption of Cu2+ ions onto hydroxyapatite

The Cu2+ sorption onto HAP was investigated as a function of time, in the concentration range 5·10-4 - 5·10-3 mol/dm3. The experimentally obtained kinetic data were fitted with the intraparticle diffusion model. The correlation coefficients were low considering the overall reaction period. However, q versus t0.5 plots could be divided into three segments, out of which the second linear segment can be attributed to the intraparticle diffusion. Intraparticle diffusion rate constants (ki) increased from 3.57·10-3 to 7.80·10-3 mmol/g min0.5 with the increase of the initial Cu2+ concentration. As the lines did not pass through the origin it was concluded that intrapaticle diffusion is not the only rate-controlling step.Physical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200

The evaluation of radionuclides removal using clinoptilolite, hydroxyapatite and their mixtures

The sorption properties of clinoptilolite and hydroxyapatite towards Cs1+, Co2+, and Sr2+ ions were compared, under the same experimental conditions. Cs1+ was preferably sorbed by natural clinoptilolite. Conversely, synthetic hydroxyapatite exhibited higher sorption capacities for Co2+ and Sr2+, while the sorption of Cs1+ was negligible. It was shown that, as a consequence of different affinity towards investigated cations, application of mixed clinoptilolite/hydroxyapatite sorbent represents a good strategy for the purification of effluents containing a mixture of Cs1+, Co2+ and Sr2+.Physical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200

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

Efficiency and Capacity of Ba2+ Ions Sorption by Zeolite 4A and Natural Klinoptilolite and Influence of Competing Sr2+ Ions

Radioaktivni izotop barijuma Ba-133 (t1/2 = 10,55 god.), generisan u nuklearnim reaktorima, testiranjem nuklearnog oružja, drugim nuklearnim aktivnostima i akcidentima, dospeva u životnu sredinu atmosferskom emisijom, putem kontaminiranih voda i izluživanjem iz otpada. Uzimajući u obzir da efikasnost separacije polutanta iz vodene sredine zeolitima zavisi od niza procesnih faktora, neophodni su testovi koji osiguravaju njihovu optimalnu upotrebu u specifičnim uslovima. U ovom radu je izučavano uklanjanje jona Ba prirodnim klinoptilolitom i sintetičkim zeolitom 4A iz jednokomponentnih rastvora i dvokomponentnih smeša jona Ba i Sr, u ravnotežnim uslovima. Rezultati su pokazali da se joni Ba preferentno vezuju u odnosu na Sr nezavisno od tipa zeolita, ali su kapaciteti i efikasnost sorpcije Ba, kao i oba katjona u uslovima kompeticije, značajno veći primenom Z4A. Ukupni kapacitet sorpcije jona se povećava u dvokomponentnim sistemima, što ukazuje na učešće dodatnih aktivnih centara zeolita u prisustvu jona Sr.The radioactive barium isotope Ba-133 (t1/2 = 10.55 y), generated in nuclear reactors, nuclear weapons testing, other nuclear activities, and accidents, reaches the environment through atmospheric emission, contaminated water and leaching from waste. Considering that the efficiency of pollutant separation from aqueous media using zeolites depends on many process factors, tests are necessary to ensure their optimal use in specific conditions. This work studied the removal of Ba ions by natural clinoptilolite and synthetic zeolite 4A from one-component solutions and two-component mixtures of Ba and Sr ions, under equilibrium conditions. The results showed that Ba ions bind preferentially compared to Sr regardless of zeolite type. However, the capacity and efficiency of Ba sorption and sorption of both cations under competing conditions are significantly higher with the use of Z4A. The total ion sorption capacity increases in two-component systems, indicating the participation of additional active zeolite centers in the presence of Sr ions.XXXII Simpozijum Društva za zaštitu od zračenja Srbije i Crne Gore, 4-6. oktobar 2023; Budva, Crna GoraProceedings: [https://vinar.vin.bg.ac.rs/handle/123456789/11602

Ispitivanje uticaja fizičko-hemijskih svojstava sorbenata koštanog porekla na imobilizaciju jona Co2+ i Sr2+

Cilj istraživanja predstavlja ispitivanje mogućnosti imobilizacije jona Co2+ i Sr2+ sirovim i tretiranim životinjskim kostima kao biosorbentom. Određivan je uticaj različitih tretmana (hemijske degradacije, degradacije na povišenim temperaturama) na fizičko-hemijska svojstva životinjskih kostiju. Za karakterizaciju uzoraka životinjskih kostiju korištene su standardne metode: termička analiza (TG-DTG-DTA), infracrvena spektroskopska analiza (IC), rendgenska difrakciona analiza (XRD), BET metoda određivanja specifične površine, određivanje tačke nultog naelektrisanja metodom uravnotežavanja, dok je atomska apsorpciona spektrometrija - AAS korištena za merenje koncentracije jona metala. Na osnovu fizičko-hemijskih analiza biosorbenata, kao i poređenja kapaciteta i mehanizama imobilizacije jona Co2+ i Sr2+, uspostavljene su korelacije između različitih tretmana, strukture i sorpcionih svojstava