Effect of competing anions on pertechnetate adsorption by activated carbon

Abstract

Activated carbon (AC) has a relatively high efficiency for retaining TcO 4 -compared to other materials. AC is used on a vast scale in gas and water purification, metal extraction, medicine and many other applications. The TcO 4 -adsorption mechanism on AC is not fully known, however there are assumptions of ion-exchange reaction between AC surface and TcO 4 -anions. Adsorption and anion competitive investigation have shown that perchlorate anions have most influence on TcO 4 -adsorption. Adsorption properties depend on standard absolute molar enthalpies of hydration. Anion competitiveness was investigated with five samples that were prepared in different ways (this was already published in previous article), we used several anions Cl -, Br -, ClO 4 -, CH 3 COO -, NO 3 -, HCOO -and SO 4 2-at different concentrations. In general, the adsorption of TcO 4 -is influenced mostly by ClO 4 -, what is explained by its similar structure with TcO 4 -; however the co-existence of Fe 3? cations in the AC structure decreases TcO 4 -adsorption.

Pyrolysis Products as Soil Fertilizers: Screening of Potentially Hazardous Aromatic Compounds

“…However, repeated and excess application of these wastes to limited acreage of land has occasionally resulted in excessive nutrient accumulation in soils with subsequent runoff and leaching losses to water bodies, causing water eutrophication and quality deterioration (MORENO-JIMENEZ et al, 2016). Pyrolysis as a carbonization technique that converts organic materials thermo-chemically into recalcitrant aromatic carbon compounds represents a highly effective and reliable treatment method to avoid nutrient losses and create a more stable material for fertilization (GALAMBOŠ et al, 2015;LEHMANN and JOSEPH, 2015;VÍGLAŠOVÁ et al, 2016). The process requires an inert atmosphere with low or no oxygen and temperatures usually in the range 300-1000°C.…”

Sb-doped zirconium dioxide submicron fibers for separation of pertechnetate (TcO4–) from aqueous solutions

“…by activated carbon was significantly reduced in the presence of ClO 4 as the ions have similar tetrahedral structure and probably high affinity to the same adsorption sites. [15] Additionally, our experiment showed that H 3 BO 3 decreased the K d value of TcO 4 only slightly. This is an extremely important result since H 3 BO 3 is used in nuclear industry as a neutron absorber to regulate the power of reactors.…”

“…[14] In addition, universal nonselective sorbent materials including activated carbon have been utilized in TcO 4 removal. [15,16,17] Li et al [18] observed that after TcO 4 was remediated by porous iron, Tc(VII) was mainly reduced to Tc(IV) and co-precipitated with FeO(OH) and Fe 3 O 4 or incorporated into their structure. Even though the ZVI materials show good potential for TcO 4 uptake, these materials have their limitations such as low surface area and susceptibility for leaching.…”

Fusion-Based Neutron Generator Production of Tc-99m and Tc-101: A Prospective Avenue to Technetium Theranostics

“…Adsorption values greater than 99% [TcO 4 ] − (~1 MBq 99m Tc) onto AC within 1-min have been reported in the pH range 2-3 where maximum distribution coefficient (K d ) values were measured [51]. The primary contributing surface species are said to be carboxylic, carbonyl, laconic, and phenolic groups, where R-C=O and R-C-OH moieties serve as potential binding sites for [TcO 4 ] − [47,49,50] Measured K d greater than~10 5 for Tc uptake onto AC under acidic pHs have been reported [41,47,51] on AC [49,50]. For comparison, the change in free energy of adsorption of different anions onto activated carbon was determined to be:…”