Abstract Part weakly alkaline natural uranium-containing water contains abundant Ca2+ and (bi)carbonate. Herein, two kinds of materials, namely mesoporous hydrous manganese dioxide (MHMO) and polyacrylonitrile (PAN)/dolomite composites were synthesized and characterized to evaluate their adsorption behaviors of U(VI) from Ca2+ coexisted bicarbonate solution. Characterization results showed that both samples exhibited good structural stability after U(VI) load. MHMO could coordinate U(VI) through the surface –OH sites, whereas an unfavorable U(VI) adsorption onto mineral composites was deduced. Adsorption tests indicated that increasing Ca2+ and (bi)carbonate amounts suppress U(VI) adsorption process, and ∼19.0 mg/g U adsorbed by MHMO could be obtained in solutions with 1 mmol/L [Ca2+], 5 mmol/L [CO3]T, 50 mg/L [U(VI)]initial at pH 8.0. Moreover, a heterogeneous surface chemical adsorption was verified through kinetics and isotherms study. Results from our study should be useful in exploring the adsorption behaviors and mechanisms of U(VI) on selected inorganic and mineral materials from natural uranium-containing water.

中文翻译：

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无机和矿物合成材料对Ca2+共存碳酸氢盐溶液吸附U(VI)的评价

摘要 部分弱碱性天然含铀水含有丰富的Ca2+和(重)碳酸盐。在此，合成并表征了两种材料，即介孔水合二氧化锰 (MHMO) 和聚丙烯腈 (PAN)/白云石复合材料，以评估它们对 Ca2+ 共存碳酸氢盐溶液中 U(VI) 的吸附行为。表征结果表明，两种样品在 U(VI) 载荷后都表现出良好的结构稳定性。MHMO 可以通过表面-OH 位点协调 U(VI)，而推断出不利的 U(VI) 吸附到矿物复合材料上。吸附试验表明，增加 Ca2+ 和 (bi)carbonate 的量会抑制 U(VI) 吸附过程，在 1 mmol/L [Ca2+]、5 mmol/L [CO3 ]T, 50 mg/L [U(VI)] 初始在 pH 8.0。而且，通过动力学和等温线研究验证了异质表面化学吸附。我们的研究结果应该有助于探索 U(VI) 对天然含铀水中选定的无机和矿物材料的吸附行为和机制。