Solvent extraction mechanism and precipitation stripping of bismuth(Ⅲ) in hydrochloric acid medium by tributyl phosphate

Tributyl phosphate(TBP) was employed for the Bi(Ⅲ) extraction from hydrochloric acid medium.The effects of extraction time and material concentration were examined.The replacement mechanism between the anion(Cl^-) and TBP was proposed for extraction.The results show the species extracted into the organic phase were found to be mainly BiCl_3·x TBP(x=2 or 3).Thermodynamic parameters of the extraction reaction were obtained from the thermodynamics analysis,which illustrates that higher temperatures show a negative effect on the extraction.Extraction isotherm was obtained with 2.16 mol/L TBP for a typical solution containing 0.1 mol/L of bismuth and 1.0 mol/L of hydrochloric acid.About 98.5 % of bismuth has been extracted from the leaching solution under the optimum condition.Moreover,oxalate was explored as a precipitation stripping agent for BiCl_3·x TBP(x=2 or 3) complexes,by which Bi(Ⅲ) was stripped in the form of Bi_2(C_2O_4)_3·7H_2O.A stripping efficiency of 99.3% was obtained in only one stage at the phase ratio of 1 and TBP also could be recycled.Therefore,the method is an efficient,effective and highly selective approach to extract Bi(Ⅲ) and to recover metal bismuth.

通过Bi^(3+)发光特征判定“争议”格位——以Ca_2MgSi_2O_7∶Bi^(3+)荧光粉为例（英文）

在以往的研究工作中,人们经常关注给定基质具有多个格位所对应多发光中心的光致发射。取决于所掺杂的基质,多个格位的晶体化合物应该可以提供相应的多发光中心,但某些化合物有时只会表现一个发光中心,由此产生"争议性"发光中心。据以往研究,以稀土离子掺杂而为人所知的经典镁黄长石(Ca_2MgSi_2O_7)长余辉化合物具有"争议性"Ca格位。为此,在本文中以非稀土离子(Bi^(3+))特有的发光特性从侧面来研究Ca_2MgSi_2O_7化合物中的"争议性"Ca格位问题。结果表明,在250和276 nm激发波长激发下,所有的Bi^(3+)掺杂Ca_2MgSi_2O_7样品均有峰位位于582和350 nm的两个Bi^(3+)特征发射带。结合晶体结构分析,光谱结果表明,Ca_2MgSi_2O_7∶Bi^(3+)荧光粉具有对应于六配位和八配位的两个不同Ca2+格位的两个Bi^(3+)发光中心,即,Bi^(3+)(Ⅰ)(~582 nm)和Bi^(3+)(Ⅱ)(~350 nm)发光中心。此外,光谱分析进一步表明,Bi^(3+)(Ⅰ)与Bi^(3+)(Ⅱ)具有单向的能量传递,而且,发现这两个发光中心所对应的相对发射强度是依赖于激发波长和Bi^(3+)掺杂浓度。实验证明了Ca_2MgSi_2O_7晶体化合物具有两个Ca格位,而不是有些工作中所讨论的一个Ca格位。本文工作可以为已知或未知的具有"争议性"格位的晶体化合物的验证提供新的借鉴。