离子色谱法研究钨冶金体系阴离子动态交换的热力学

Study on thermodynamics of anions′ dynamic exchange of tungsten metallurgy system by ion chromatography

针对钨冶金中阴离子与季铵树脂亲和力的争议,选用季铵型色谱柱,利用离子色谱仪研究了不同柱温下NaOH、Na2CO3和NaHCO3对阴离子的洗脱行为,由此获得阴离子与季铵型色谱柱的亲和力顺序,以及动态交换的热力学参数.结果表明:NaOH淋洗时离子对季铵型色谱柱的亲和力顺序为:MoO4^2->WO4^2->AsO4^3->PO4^3->SO4^2->Cl^->F^-,而用Na2CO3或NaHCO3淋洗时,磷和砷分别转化为HPO2-4和HAsO2-4形态,导致其与色谱柱的亲和力减弱;淋洗剂对阴离子洗脱能力的顺序为:NaOH>Na2CO3>NaHCO3;NaOH淋洗时温度对各离子出峰时间影响显著;NaOH和Na2CO3淋洗时可通过范特霍夫曲线计算出相应的热力学参数,并且算得的相对吉布斯自由能变化顺序与离子对季铵型色谱柱的亲和力顺序一致.

Aiming at the controversy over affinity between anions and quaternary ammonium resin in tungsten metallurgy,the study investigated into the influences of NaOH,Na2CO3 and NaHCO3 on anions elution in quaternary ammonium type column at different temperatures by ion chromatograph.Thus,order of affinity between the anions and the column,and the thermodynamic parameters of dynamic exchange were obtained.The results showed that with NaOH as eluent,the affinity order between anions and quaternary ammonium column was:MoO4^2->WO4^2->AsO4^3->PO4^3->SO4^2->Cl^->F^-.When Na2CO3 or NaHCO3 was used as eluent,phosphorus and arsenic were converted into the form of HPO2-4 and HAsO2-4,respectively,resulting in a decrease of their affinity for the chromatographic column.Furthermore,the capability to elute anions ranked:NaOH>Na2CO3>NaHCO3.When NaOH was used as eluent,temperature had a significant effect on the peak time of each anion.Besides,when NaOH and Na2CO3 were used as eluents,the corresponding thermodynamic parameters could be calculated by Van′t Hoff equation,and the order of relative Gibbs free energy changes was consistent with that of affinity between anions and quaternary ammonium column.