Precipitation and alteration of coffinite (USiO4nH2O) in the presence of apatite

The formation of PuSiO4under hydrothermal conditions

“…Hydrothermal synthesis of USiO 4 was also extensively studied. 3,14,53,61,[64][65][66][67][68][69][70][71][72][73] However, from a general point of view, this synthesis remained poorly reproducible. Recently, Mesbah et al 74 identified an efficient way to prepare coffinite, allowing its formation with a good repeatability.…”

Soft Hydrothermal Synthesis of Hafnon, HfSiO4

“…32 These conditions appear to be quite surprising taking into account the possibility to prepare isostructural silicates, e.g. ZrSiO 4 , 31,[33][34][35][36][37][38][39][40][41][42][43][44][45][46] CeSiO 4 , 4, 47-49 ThSiO 4 , 2,34,[50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65] USiO 4 , 2,59,60,[66][67][68][69][70][71][72][73][74][75][76] NpSiO 4 , 2 PuSiO 4 2 and AmSiO 4 2 under soft hydrothermal conditions (i.e. for T ≤ 250°C).…”

“…From a general point of view, the synthesis of HfSiO 4 was reported by high temperature solid state chemistry, ,,,,− sol–gel methods, ,, chemical transport reaction, ,, physical vapor deposition, and hydrothermal synthesis. , However, the only hydrothermal syntheses were reported by Caruba et al under acid conditions at T = 800 °C, 75 MPa, and by McNeil et al in very acid conditions, i.e., C HF = 6 mol·L –1 and C H 2 SO 4 = 0.5 mol·L –1 at T = 850 °C, 200 MPa . These conditions appear to be quite surprising, taking into account the possibility to prepare isostructural silicates, e.g., ZrSiO 4 , ,− CeSiO 4 , ,− ThSiO 4 , ,,− USiO 4 , ,,,− NpSiO 4 , PuSiO 4 , and AmSiO 4 under soft hydrothermal conditions (i.e., for T ≤ 250 °C). However, it may be also noticed that the formation of amorphous hafnon has been observed by alteration, in an aqueous solution, of Hf-bearing borosilicate glasses at 90 °C and pH = 1 .…”

Uranium Mineralization and Its Radioactive Decay-Induced Carbonization in a Black Shale-Hosted Polymetallic Sulfide Ore Layer, Southwest China

“…Organic-rich sediments containing phosphate beneath biogeochemical environments with high organic productivity are considered to be major sinks for uranium in the ocean (Veeh et al, 1974). Microscale dissolution of apatite can promote the precipitation of U(IV) and U(VI) minerals, resulting in reduced mobility of uranium under both reducing and oxidizing conditions, respectively (Deditius et al, 2010). It is believed that phosphate deposits in sedimentary rocks from the time of the Cambrian explosion had a biological origin, which might have facilitated the precipitation of phosphate (e.g., Waples, 1982;Blake et al, 1997;Hein et al, 1999;Steiner et al, 2001;Orberger et al, 2007;Li et al, 2013;Sun et al, 2014).…”