钨酸盐溶液中季铵树脂吸附除钼的应用基础研究

Removal of high-content molybdenum from tungstate solution becomes a new challenge for extractive metallurgy of tungsten. However, the adsorption method using quaternary ammonium resin (QA resin) has great potential to remove the high-content Mo without the production of residue, but the desorption of tetrathiomolybdate must be performed with the help of strong oxidant at present, which lead to oxidative degradation of the resin and shorten its service life. Aiming at such technical problem, a key measure, which is to regularize affinities of thiomolybdate and desorption reagent to the QA resin, is proposed in this project for desorbing Mo form Mo-loaded resin without the use of oxidant. Thus, it is necessary to solve an urgent scientific problem: the interaction between the QA resin and species of Mo-W-S-H2O system. For this purpose, selectivity coefficients of the QA resin to the main species of Mo-W-S-H2O system will be determined to clarify the degree of affinity of a species to the resin. Furthermore, adsorption isotherms of the main species will also determined, and then adsorption model could be established to calculate thermodynamic parameters of the adsorption reactions. On the other hand, frontal chromatography and elution chromatography performed in transparent ion-exchange column will be employed to study dynamic ion-exchange behaviors and elution behaviors, respectively. Based on such researches, regulatory mechanisms of both removing Mo with the QA resin and desorbing Mo form the Mo-loaded resin without the use of oxidant will be established. Finally, a systematic and basic theory for removing Mo by the adsorption method with the QA resin could be form. All above researches will help to through the bottleneck of the desorption of Mo without the use of oxidant, promote commercial application of the adsorption method and thus solve the problem for the removal of high-content Mo.

钨酸盐溶液中高含量钼难以高效除去是钨冶炼面临的新问题。季铵树脂吸附法处理高钼溶液潜力大，无废渣产生，但目前须用强氧化剂辅助解吸，造成树脂氧化降解，严重缩短其使用寿命。针对该技术瓶颈，本项目提出实现负钼树脂无氧化剂解吸的关键是调控硫代钼酸根和解吸剂对树脂的亲和力，并由此提炼亟需解决的科学问题：Mo-W-S-H2O体系物种与季铵树脂的相互作用规律。为此，本项目拟测定季铵树脂对Mo-W-S-H2O体系物种的选择性系数，明确其与树脂亲和力的强弱程度；测定吸附等温曲线，建立热力学模型，求得吸附反应的热力学参数；在透明离子交换柱中，采用前沿色层法和淋洗色层法分别研究物种的动态交换和洗脱行为，建立树脂吸附除钼和负钼树脂无氧化剂解吸的调控机制，最终形成系统的季铵树脂吸附除钼的基础理论。研究所得结果将有助于突破负钼季铵树脂无氧化剂解吸的技术瓶颈，推动树脂吸附法除钼的工业应用，从而解决高钼溶液除钼的难题。

本项目根据离子交换平衡的基本公式，推导出不同离子交换情形下被吸附离子及被解吸离子的等温吸附式，计算并绘制了全交换范围的等温吸附曲线。对基于离子交换平衡的等温吸附式与Langmuir模型和Freundlich模型进行了兼容性分析，揭示了离子交换反应平衡在何种情形下将“符合”这两种经典模型。通过系列实验，获得了氯型季铵树脂对钨冶炼常见阴离子静态交换的平衡浓度数据，并分别采用Langmuir模型、Freundlich模型以及本项目提出的算法对数据进行处理。结果表明新算法能通过等温吸附曲线求得平衡常数，对实验数据拟合程度较高。相比于经典吸附模型，新算法涉及的常数项均具有明确的物理意义。此外， Langmuir模型和Freundlich模型对离子交换平衡数据拟合结果的优劣，与基于新算法的理论分析结果一致。.采用离子色谱仪研究钨冶炼常见阴离子在季铵型色谱柱中的动态交换行为。分别在NaOH和Na2CO3两种淋洗体系下研究了柱温对7种离子洗脱行为的影响，并进一步通过各离子的容量因子计算其动态交换过程的热力学参数。针对硫代钼酸根负载至商用的季铵树脂后难以被NaOH直接解吸的问题，通过对离子交换树脂碱性功能团的分子设计，开发了多种新型离子交换树脂。对比商用的D201树脂，考查了新型树脂对硫代钼酸根的吸附能力，以及氢氧化钠直接碱解过程中钼的解吸能力。其中新合成的POC树脂，对硫代钼酸根的吸附能力接近于商用的D201树脂，而在钼的无氧化剂解吸方面展现出很好的效果，具有工业应用的前景。本项目结合钼酸根的硫化反应过程，研究了季铵盐对Mo-W-S-H2O系各组分在萃取和反萃过程的分配行为，尤其是明确了游离态硫离子与季铵盐的相互作用规律。在此基础上，从工业应用的角度设计了两段硫化-溶剂萃取的除钼新方法。本项目的基础研究结果对优化钨冶炼工艺具有指导意义，对丰富和完善离子交换热力学的研究方法具有一定的科学意义。