【作者】 沈妮；

【导师】 郭奋；

【作者基本信息】 北京化工大学 ， 化学工程， 2009， 硕士

【摘要】 磷化工和冶金行业产生大量含钒铬废渣,这类废渣中通常含有钒、铬、磷等元素,若直接排放到环境中会造成水资源污染,及有价金属的浪费和水体富营养化。针对这一现象,本文通过对国内某企业的磷铁矿焙烧后产生的含钒、铬的磷酸钠废渣的综合利用研究,探索了一种利用离子交换树脂脱除并回收其中的钒、铬有价金属的方法,同时净化了磷酸钠。本文首先通过对多种型号树脂的交换容量和吸附效果比较,筛选出D301R大孔弱碱性阴离子交换树脂作为吸附材料,并对其吸附、解吸过程进行了系统研究。通过静态吸附行为的研究,主要考察了pH值、温度、固液比、转速等因素对钒铬吸附的影响,并从热力学和动力学方面对D301R树脂吸附钒、铬的过程进行深入分析。动态实验主要研究了实际料液在交换柱中的吸附工艺,在料液浓度、温度、停留时间、树脂床层高等因素的优化实验基础上设计了离子交换柱参数,并确定了两步解吸的工艺路线。另外,通过多轮的吸附-解吸-再生循环实验验证树脂的重复使用性能。静态实验研究结果表明:D301R树脂在pH=6.5,最佳固液比(即树脂质量:料液体积)为1:10,转速180 r/min条件下,钒(Ⅴ)、铬(Ⅵ)的去除效率分别可达60%、85%。热力学研究表明:D301R树脂对高浓度磷酸钠溶液中钒(Ⅴ)的吸附行为可用Langmiur和Freundlich等温方程描述,相关系数分别为0.9803和0.9761。吸附钒(Ⅴ)、铬(Ⅵ)的过程是自发过程(ΔG＜0),熵变为负值(ΔS＜0),均为放热过程(ΔH＜0)。动力学研究表明D301R树脂对钒(Ⅴ)、铬(Ⅵ)的吸附交换在室温下是瞬时反应,符合二级吸附交换动力学过程。通过表观速率常数的拟合得到钒(Ⅴ)、铬(Ⅵ)的吸附交换过程的表观活化能分别为59.84J/mol,1183.33J/mol。动边界模型模拟和搅拌速度实验表明钒(Ⅴ)在D301R树脂上的吸附受颗粒扩散和化学反应联合控制,其中以化学反应控制为主;铬(Ⅵ)的吸附过程主要受颗粒扩散控制。动态的工艺实验表明:最佳工艺条件为,废渣料液浓度120 g/L、HRT=15 min,室温25℃,树脂床层体积为20mL(L/D=13)。解吸操作采用3mol/L的NaOH作为解吸剂,两步解吸的方式。经过十轮循环实验,钒和铬的吸附率分别基本稳定在90%、80%以上,解吸效率也分别保持在95%、90%左右,吸附和解吸性能没有明显改变。该工艺不仅可有效脱除并回收了钒(Ⅴ)、铬(Ⅵ)有价金属,成功净化了磷酸钠,提高了磷酸钠废渣的综合利用率及经济效益,最终达到清洁生产、环境保护和实现循环经济三者的统一。更多还原

【Abstract】 Waste residue containing vanadium(Ⅴ) and chromium(Ⅵ) from phosphorus chemical and metallurgical industries, which usually contain vanadium, chromium, phosphorus and other elements. If directly discharged into the environment will cause water pollution, waste of valuable metals and entrophication. This paper deals with an economical, effective ion exchange method to removal and recover vanadium(Ⅴ) and chromium(Ⅵ), provides process parameters for comprehensive ultilization of sodium phosphate residue.In this paper, D301R macroporous weak base anion exchange resin was selected as a suitable adsorptive material based on study of ion exchange capacities, adsorptive effects, and elution processes systematically, focusing on the influential factors of adsorption temperature, pH value, solid-liquid ratio and stirring rate. The kinetics and thermodynamics behaviors of ion exchange were studied by static method. The adsorptive process in ion exchange column was studied by dynamic method with the practical, and then the optimal parameters of ion exchange column were determined on the basis of experiments on factors such as initial concentration of solution, temperature, contact time and resin bed volume, including two-step elution process. Furthermore, the repeatability of resin was also verified through ten cycles of dynamic experiments.The statics experiment results showed that with D301R resin at pH=6.5, room temperature, and ratio of resin to solution of 1:10, stirring rate of 180 r/min, removal rates of vanadium(Ⅴ) and chromium(Ⅵ) were 90% and 80% respectively. The thermodynamics research suggested that adsorption isotherms of Vanadium(Ⅴ) approximately fitted the Langmiur or Freundlich equation with the experimental range of concentration, the correlative coefficients were 0.9803 and 0.9761. The thermodynamic study showed that the adsorption of vanadium(Ⅴ) and chromium(Ⅵ) were spontaneous, and the entropy were negative. The adsorption of vanadium(Ⅴ) and chromium(Ⅵ) were exothermic process.Dynamic data from the static experiment indicate that adsorption of vanadium( V) and chromium(Ⅵ) were instantaneous reaction under the room temperature conditions. A second-order adsorption-ion exchange kinetic equation was developed for the process. The apparent activation energy of vanadium(Ⅴ) and chromium(Ⅵ) were 59.84J/mol and 1183.33J/mol respectively, according to fitting the apparent sorption rate constant. The moving boundary model and stirring rate indicated that the adsorption of vanadium(Ⅴ) was controlled by particle diffusion and chemical reaction and chrommm(Ⅵ) was controlled by particle diffusion.The optimal conditions were obtained by dynamic process tests which showed that residue concentration of 120g/L, HRT=15min, room temperature(25℃), resin bed volume of 20 mL(L/D=13). 3 mol/L NaOH was chosen as desorption agent by means of two-steps elution process. Ten cycles of dynamic experiments showed that, removal rates of vanadium(Ⅴ) and chromium(Ⅵ) were 90% and 80% respectively, and the desorptive rates were 95% and 90%,which showed the performance of vanadium(Ⅴ) and chromium(Ⅵ) were stable.This process not only removed and recovered the valuable metallic elements effectively, meanwhile, purified sodium phosphate, but also improved the ratio of resource comprehensive utilization. If this process widely used, it will improve on the technical process in phosphorus industry, result in great economic efficiency, as well as social and environment benefit, which is good to realize circulate economy.更多还原