废铅蓄电池铅资源化回收利用新工艺

Lead recycling or recovery from waste lead storage batteries

1.铅资源化回收利用重要性废铅蓄电池的铅膏主要有PbO、PbSO_4、PbO_2等含铅化合物组成。从铅膏中回收利用铅,实现废铅蓄电池的资源化利用,不仅可以缓解铅资源日益锐减带来的问题,同时可以降低成本,减少环境污染,因此具有重要的意义。2.现有铅资源化回收利用的工艺及主要问题(1)火法:先将PbSO_4转化为较易火法处理的化合物,同时将硫酸铅中的硫酸根转化为可溶于水的硫酸盐。该方法一般采用碳酸盐为脱硫剂,过程中产生大量硫酸盐副产物,必然存在硫酸盐的回收及利用问题,而且该工艺方法的铅回收利用率低,资源浪费及能量消耗大,存在环境污染问题。(2)湿法:利用溶解在溶液中的Pb2+在阴极还原生成金属Pb实现铅的回收。该方法作为环境友好型的铅回收方法备受关注,该方法存在的主要问题是采用阴极电沉积方法制备铅,操作单元多,工艺流程长,只在阴极发生有效反应,铅回收率低、能耗大、制备成本高。(3)火法-湿法耦合技术:将湿法铅膏转化与火法制备氧化铅耦合回收利用铅的工艺技术是较理想的工艺技术。该方法存在的主要问题的化学试剂消耗量大,有副产物产生。3.研发的新工艺为了克服现有技术的缺点,研发工艺合理、过程的安全可靠、原子利用率高、成本低的废铅蓄电池的铅资源化回收利用新工艺具有重要意义。以废铅蓄电池经过预处理得到的含PbO、PbSO_4、PbO_2的铅膏为原料,采用硝酸溶解-氨法浸取-分离精制-固液分离耦合技术分离铅膏得到PbO、PbSO_4、PbO_2产品。(1)首先,利用PbO易与酸反应,生成的产物易溶解于水的特性,以HNO_3为浸取剂,PbO与HNO_3反应生成可溶于水的Pb2+盐,将铅膏混合物中的PbO浸取到酸溶液中。回收溶于水的Pb^(2+)盐,作为制备含铅化合物的原料,经过进一步处理得到PbO。(2)然后,以NH_3·H_2O-(NH4)2SO_4为浸取剂,利用PbSO_4在浸取剂中的溶解度随氨浓度和温度的升高而增加的特点,在浸取过程中,采用高浓度的浸取剂使PbSO_4从固相转移到液相中,经过分离精制的PbSO_4溶液可采用蒸发脱NH3的方法,降低浸取剂中NH3的浓度,使PbSO_4结晶析出,得到精制的PbSO_4产物。(3)铅膏经过分离除去PbO和PbSO_4的固体物料,经过进一步除杂处理得到PbO_2。

1.The importance of make good use of waste lead storage battery paste The lead paste from waste lead storage batteries,contains mainly PbO,PbSO_4 and PbO_2.It is of vital significance by recycling use of lead from the paste,not only can alleviate the shortage of lead resource,at the same time can reduce costs,reduce environmental pollution.2.Lead recycling or recovery from waste materials Either pyrometallurgical or hydro-electrometallurgical methods have been used for the treatment of waste lead pastes.While pyrometallurgical method is that to decomposition of PbSO_4 to produce PbO as a product is still the recovery technology,but the technology is under severe criticism,especially due to SO_2 emission from the decomposition of PbSO_4 at elevated temperatures,and lead emissions from fuming at these high temperatures.In order to solve these problems,the decomposition of PbCO_3 to obtain PbO by the utilization of Na_2CO_3,(NH_4)2CO_3and NH_4HCO_3 as desulfurizing agents reacting with PbSO_4 and either Na_2SO_4 or(NH_4)_2SO_4as by-products.While SO_2 gaseous emission problem is abated,water leachable hazardous waste products are produced.The hydro-electrometallurgical method is based on the electrochemical reduction of dissolved Pb2+in cathodic solution to generate metal Pb by electro-winning.The method is an environmentally friendly as a lead recycling method.The main problem of the method is high energy consumption,high preparation cost and too much unit operations required.Given the serious problems encountered in the smelting route or hydro-electrometallurgical method for recycling lead storage battery paste,several research,pilot scale and commercial methods using the coupling hydrometallurgical and pyrometallurgical approach have been developed.Hydrometallurgical methods have been used to remove Sulphur in the paste as soluble Na_2SO_4or(NH4)2SO_4(aq)using Na_2CO_3,(NH_4)_2CO_3 or NaOH solutions.Na_2SO_4or(NH4)2SO_4 is then crystallized from the remaining solution.The insoluble product PbCO_3 or Pb(OH)2collected in the form of sludge or filter cake is then routed to the smelter.The obtained PbCO_3 or Pb(OH)_2 can be treated by pyrometallurgical approach and PbO can be produced as precursors to prepare electrode active material.Despite extensive effort,it has not yet been possible to avoid the consumption of desulfurizing agents and resulting a lots of by-products and the retention of a substantial amount of sulphur in the lead bearing product and thus the smelter SO_2 problem is not fully abated.3.The developed recycling or recovery technology In order to overcome the shortcoming of the existing technology,a safe and reliable process has be developed.The waste battery paste was treated by nitrate acid leaching to convert PbO to Pb(NO_3)2,and which then reacted with H_2SO_4 to obtain PbSO_4;The leach residue containing lead sulfate and lead dioxide was leached with ammoniacal ammonium sulfate,based upon the solubility of PbSO_4 in aqueous ammoniacal ammonium sulfate solution.After solid-liquid separation the solution is then purified,PbSO_4 was obtained by removal of free ammonia and heating;The products,such as PbSO_4 and PbO_2 can be obtained,can be used as precursors to prepare e-lectrode active material and can be readily converted to PbO_2 and Pb for directly making lead storage battery pastes for achieving lead recovery simultaneously.The process can avoid smelting,desulphurization and electro-winning.The developed route is suitable for large scale operations and can be used for recovering lead from lead battery pastes.