摘要
含金属离子的废水是钴回收的重要二次来源。由于废水中金属离子浓度低,钴回收面临着高效和选择性分离的问题。近年来,一些学者通过螯合沉淀—浮选法解决了低离子浓度废水中钴的分离问题,但并未对其反应的内在规律深入研究。提出了一种数值模拟方法来研究离子螯合沉淀过程的微观机制,即通过改变反应物浓度和反应温度,分析组分的传质过程和沉淀形成过程的转化规律,研究螯合反应与沉淀参数(形态变化、沉淀速率、沉淀半径等)之间的内在关系。当反应物在液滴中的体积分数为5%时,在300 K下反应30 s,沉淀的最大体积分数约为0.00315%;在300 K的反应温度下,当反应物的体积分数为10%并持续30 s时,沉淀物的最大体积分数约为0.00388%。研究结果验证了提高反应物浓度和降低反应温度对金属离子螯合反应的影响,为含钴沉淀颗粒的浮选分离过程奠定了理论基础。
Cobalt is a crucial element in modern industries,playing an irreplaceable role in manufacturing heatresistant alloys,magnetic alloys,and cobalt-based salts.Its applications in high-tech,military,aerospace,and newenergy battery fields are extensive.In China,the scarcity of cobalt reserves and the surge in consumption have made the exploration of cobalt secondary resources a top-priority task.Wastewater containing metal ions represents a valuable source for cobalt recovery.However,the low concentration of metal ions in this wastewater presents a significant hurdle to the efficient and selective separation of cobalt.Although the chelation-sedimentation flotation method has been used to address cobalt separation in low-ion-concentration wastewater,the in-depth understanding of its reaction mechanisms remains incomplete.This research was designed to deeply explore the micromechanism of the ion chelation precipitation process.A numerical simulation method was implemented,leveraging Fluent software to simulate the intricate processes of particle formation,growth,aggregation,and stabilization within a cobalt-containing solution.These processes can be divided into two main stages:particle nucleation and growth,both of which involve mass and heat transfer under chemical reaction conditions.An established cobalt-ion chelation precipitation model incorporated key elements such as nucleation and growth formulas,saturated solutions,latent heat of condensation,and other essential thermodynamic parameters.The classic nucleation theory(CNT)was applied to describe the homogeneous nucleation process.According to CNT,in a supersaturated solution,the formation of new nuclei depends on the supersaturation level.Supersaturation(S)is defined as the ratio of the actual concentration(C0)to the equilibrium(saturated)concentration(C),i.e.,S=C0/C.When S exceeds a certain critical value,nucleation can occur.The Gibbs free energy change(ΔG)during the formation of a cluster with n moles of monomers is calculated based on the chemical potential difference between the liquid and solid phases and the energy cost of interface formation.This model posits that crystal growth involves two consecutive steps:the diffusion of solute molecules through the boundary layer and the subsequent integration of particles onto the crystal surface.To customize the simulation and display relevant parameters,user-defined functions(UDF)and user-defined memory(UDM)were utilized.UDF,programmed in C-language,enabled the definition of boundary conditions,physical models,mass-transfer processes,and material properties.By integrating the classic nucleation formula and the crystal growth rate equation into the mass-transfer mechanism via UDF and using UDM to display parameters like the nucleation rate,droplet number,growth rate,precipitation radius,and critical radius,a more in-depth analysis of the particle growth and nucleation processes was achieved.The simulation results are as follows.When the volume fraction of reactants in droplets is 5% and the reaction occurred at 300 K for 30 seconds,the maximum volume fraction of precipitation is approximately 0.00315%.When the reactant volume fraction increases to 10% at 300 K for 30 seconds,it reaches about 0.00388%.Precipitation initially formed at the center of the solution.Under the influence of gravity and mass transfer,it grows outward and gradually transforms into an elongated ellipsoid,with a higher concentration at the center.During the nucleation-growth process,regardless of whether the mass-transfer rate is controlled by the classic nucleation formula or the crystal growth rate equation,the precipitation-formation rate drops over time and eventually stops due to reactant depletion.There is a significant increase in the rate during the transition from nucleation to growth.As the reaction progressed,the reactant concentration and solution supersaturation decreased,increasing the critical radius and making the nucleation-growth process more difficult.However,the number of droplets remains relatively stable.With an increase in temperature,the molecular kinetic energy of the solution increases,reducing the energy threshold for cluster formation.This allows smaller nucleation clusters to form,and the radius of precipitation particles decrease.For Co2+,the chelation-precipitation rate drops as the temperature increases,indicating that low temperature favores the reaction.In summary,this study comprehensively investigates the mass-transfer behavior of components in the solution and systematically analyzes the transformation process of precipitation particles.It clearly elucidates the influence of reaction parameters on the chelation reaction and particle size.The findings provide a solid theoretical basis for the flotation-separation of cobalt-containing precipitation particles.The established numerical simulation method can be further extended to study chelation-precipitation processes of other metal ions,which is conducive to the development of more efficient separation technologies for metal-ion-containing wastewater.Future research can consider more complex factors,such as the co-existence of multiple metal ions and the impact of impurities,to enhance the practical significance of the research results.
作者
吕超
杨涛
殷进轩
黄宇坤
LU Chao;YANG Tao;YIN Jinxuan;HUANG Yukun(School of Mechanical Engineering and Automation,Northeastern University,Shenyang 110819,China;Zhongyuan Critical Metals Laboratory,Zhengzhou University,Zhengzhou 450001,China)
出处
《有色金属(冶炼部分)》
北大核心
2025年第7期1-10,共10页
Nonferrous Metals(Extractive Metallurgy)
基金
2023年度河南省级科技研发计划联合基金资助项目(优势学科培育类)(232301420043)
2021年广西科技重大专项(桂科AA22068078)
中原关键金属实验室优秀青年科学家项目(GJJSGFYQ202328)。
关键词
钴回收
数值模拟
成核生长理论
螯合沉淀
沉淀参数
cobalt recovery
numerical simulation
nucleation-growth theory
chelating precipitation
precipitation parameters
