Cesium adsorption/desorption behavior of clay minerals considering actual contamination conditions in Fukushima

Abstract

Cesium adsorption/desorption experiments for various clay minerals, considering actual contamination conditions in Fukushima, were conducted using the 137Cs radioisotope and an autoradiography using imaging plates (IPs). A 50 μl solution containing 0.185 ~ 1.85 Bq of 137Cs (10−11 ~ 10−9 molL−1 of 137Cs) was dropped onto a substrate where various mineral particles were arranged. It was found that partially-vermiculitized biotite, which is termed “weathered biotite” (WB) in this study, from Fukushima sorbed 137Cs far more than the other clay minerals (fresh biotite, illite, smectite, kaolinite, halloysite, allophane, imogolite) on the same substrate. When WB was absent on the substrate, the amount of 137Cs sorbed to the other clay minerals was considerably increased, implying that selective sorption to WB caused depletion of radiocesium in the solution and less sorption to the coexisting minerals. Cs-sorption to WB continued for about one day, whereas that to ferruginous smectite was completed within one hour. The sorbed 137Cs in WB was hardly leached with hydrochloric acid at pH 1, particularly in samples with a longer sorption time. The presence/absence of WB sorbing radiocesium is a key factor affecting the dynamics and fate of radiocesium in Fukushima.

Removal of barium, cobalt, strontium and zinc from solution by natural and synthetic allophane adsorbents

“…Furthermore, one can see that 5-10 min is enough to achieve adsorption equilibrium under the experimental conditions used in this study, which indicates that physical adsorption rather than ion exchange contributes mainly to the removal of metal ions by natural and synthetic allophane adsorbents. This finding is in line with previous experimental results, where allophane has been successfully used in the remediation of aqueous solutions that were contaminated with, for example, heavy metals cations [15,22,33,35], metal (oxy)anions [18,23,30], heterocyclic organic components [10] and anionic surfactants and organic acids [17,23]. …”

“…≡Al-OH° and ≡Si-OH°) in adsorbents are favorable to ensure a desired adsorption rate and appropriate metal ion removal efficiency [10,11]. Recently, agricultural and industrial waste products, activated carbon nanotubes, cellulose, carbonates, Feand Al-oxyhydroxides, zeolites, phosphates and clay minerals are used in the remediation of water that is severely polluted with persistent and hazardous components such as heavy metal ions, dyes, antibiotics, biocide compounds and other organic chemicals [12][13][14][15][16]. The use of clay minerals for wastewater treatment can be advantageous over other sorbents due to their worldwide occurrence, low mining and processing costs and outstanding physicochemical and surface properties, making clayey materials suitable for selective ion exchange, adsorption and catalyst uses [1,17,18].…”

Removal of Barium, Cobalt, Strontium, and Zinc from Solution by Natural and Synthetic Allophane Adsorbents

“…Furthermore, one can see that 5-10 min is enough to achieve adsorption equilibrium under the experimental conditions used in this study, which indicates that physical adsorption rather than ion exchange mainly contributes to the removal of metal ions by natural and synthetic allophane adsorbents. This finding is in line with previous experimental results, where allophane has been successfully used in the remediation of aqueous solutions that were contaminated with, for example, heavy metals cations [15,22,33,35], metal (oxy)anions [18,23,30], heterocyclic organic components [10], anionic surfactants, and organic acids [17,23]. Unfortunately, in most of these works, high reaction times (e.g., 24 h or longer) have been used and no kinetic data are provided [10,15,18,22,23,30,35], which greatly complicates the comparison of the adsorption kinetics of, for example, allophanic soils and synthetic allophanes.…”

Adsorption and Transport Behaviors of Potassium in Vermiculitic Soils

“…4,21) RADIOISOTOPES mica core and vermiculite structure in a particle of micaceous minerals. 7) Mukai et al (2016) 15) found that partially-vermiculitized biotite (weathered biotite) sorbed RCs far more than the other clay minerals such as fresh biotite, illite, smectite, kaolinite, halloysite, allophane, and imogolite, on the same substrate. In addition, the sorbed RCs in the weathered biotite was hardly leached with 0.1 mol dm −3 hydrochloric acid.…”