Radium geochemistry in Na-Cl type groundwater in Niigata Prefecture, Japan

Radium isotopes in 23 Na-Cl type groundwater sampled mainly from deep wells in Niigata Prefecture, which is the site of the largest oil- and gas-fields in Japan, were measured along with U isotopes, chemical components and hydrogen and oxygen isotope ratios to elucidate the distribution and behavior of Ra in a brackish environment underground. Also analyzed were U and Th isotopes in 38 rock samples collected from outcrops at 17 locations. Ra-226 concentrations (8.86-1637 mBq kg⁻¹) of groundwater samples roughly correlated with total dissolved solid (TDS) concentrations and other alkaline earth contents. Their ²²⁸Ra/²²⁶Ra activity ratios (0.32-5.2) were similar to or higher than the ²³²Th/²³⁸U activity ratios (0.6-1.7) in the rocks. The most likely transport mechanism of Ra isotopes into groundwater was due to their α-recoil from the solid phase, probably from the water-rock interface where Th isotopes had accumulated, and adsorption/desorption reaction based on the increase in ²²⁶Ra contents with TDS.     

Characterization and adsorption capacity of modified 3D porous aerogel from grapefruit peels for removal of oils and organic solvents

With the rapid industrialization, especially offshore oil exploitation, frequent leakage incidents of oils/organic solvents have adversely affected ecological systems and environmental resources. Therefore, great interest has been shown in developing new materials to eliminate these organic pollutants, which have become worldwide problems. In this study, a cost-effective, environmentally friendly porous aerogel with three-dimensional (3D) structure was prepared from grapefruit peel by a facile hydrothermal method as the adsorbent of oils/organic solvents. The as-prepared modified grapefruit peel aerogel (M-GPA) showed mesoporous structure with high specific surface area of 36.42 m²/g and large pore volume of 0.0371 cm³/g. The excellent hydrophobicity of M-GPA with a water contact angle of 141.2° indicated a strong potential for adsorption of oils and organic solvents. The high adsorption capacity of M-GPA for a series of oils and organic solvents was 8 to 52 times as much as its own weight. Moreover, the M-GPA was easily regenerated and a high adsorption capacity recovery above 97% was maintained after five adsorption–regeneration cycles. Therefore, the M-GPA is a promising recyclable adsorbent for the removal of oils/organic solvents from polluted water.