电解锰渣中锰稳定化与氨氮控制的方法研究

发布时间：2018-01-25 16:35

  本文关键词： CO_2碳化 电化学氧化 磷酸铵镁沉淀 空气氧化 电动力富集　出处：《重庆大学》2016年博士论文　论文类型：学位论文

【摘要】：电解锰渣是电解锰生产过程中碳酸锰矿经酸浸、中和、压滤工序后产生的酸性废渣,其中主要污染物是可溶性锰(Mn)和氨氮(NH_4~+-N)。我国电解锰企业主要采取渣库堆存的方式处置电解锰渣,渣场产生的渗滤液中含有高浓度的Mn~(2+)和NH_4~+-N,严重污染周边环境。目前,电解锰渣的资源化利用技术不够成熟,对企业来说,安全填埋是处置电解锰渣的首选方法。然而电解锰渣的无害化处置是实现电解锰渣安全填埋的前提,电解锰渣无害化处置的关键是Mn的稳定化和NH_4~+-N的控制。当前电解锰渣无害化处置关注的重点是固定重金属离子,对氨氮处置的研究较少,并且固定重金属离子的方法易造成废渣的pH值升高。鉴于现有的研究在电解锰渣的氨氮去除、重金属离子稳定、处理量、二次污染防止等诸多方面仍存在明显的不足,本文基于CO_2碳化、空气氧化、电化学氧化和电动力富集等新思路,研究电解锰渣中污染物处置的新技术。本文选取重庆秀山某电解锰厂的电解锰渣为研究对象,通过CO_2碳化、电化学氧化、磷酸铵镁沉淀、空气氧化以及电动力富集等手段探索了电解锰渣无害化处置和资源回收的新方法,分析了电解锰渣处置过程的矿物学特征变化、化学反应原理以及动力学机制,并提出了电解锰渣无害化处置的新工艺。主要内容和结论如下:(1)研究电解锰渣的理化特性发现,渣中主要污染是可溶性Mn和NH_4~+-N,主要以MnSO_4·H_2O、(NH_4)_2SO_4、(NH_4)_2Mn(SO_4)_2·6H_2O、(NH_4)_2Mg(SO_4)_2·6H_2O、CaMn_2O_4等矿物形式存在。Mn和NH_4~+-N的可浸出量分别占渣重的1.55%和0.55%。(2)比较了碳酸盐和碱性试剂辅助作用下CO_2对电解锰渣中可溶性Mn稳定化的效果及作用机制。Na_2CO_3、NaHCO_3均能够固定可溶性Mn形成球状MnCO_3,Na_2CO_3对Mn的固定效果优于NaHCO_3。另外当Na_2CO_3:渣质量比大于0.4时,电解锰渣中柱状、条状CaSO_4·2H_2O转化为CaCO_3;与NaOH相比,CaO更适合作为CO_2固定Mn的辅助剂。在CaO和CO_2作用下,电解锰渣的矿物相(NH_4)_2Mn(SO_4)_2·6H_2O、MnSO_4·H_2O中的Mn转化为MnCO_3矿物。当CaO:渣质量比为0.05、CO_2流量为0.8 L/min时,20 min后Mn的固定率为99.99%。利用化学平衡原理分析了不同pH值下CO_2固定Mn~(2+)的效果,与实验结果吻合。(3)采用Ti/RuO_2-TiO_2-Ir O_2-Sn O_2(DSA)阳极、石墨阴极对CaO作用下CO_2稳定化Mn后的滤液中NH_4~+-N进行间接电化学去除。发现增加Cl-浓度或初始pH值,NH_4~+-N去除率和电流效率均增大。增加电流密度有利于提高NH_4~+-N的去除率,但是不利于提高电流效率。NH_4~+-N浓度越低,NH_4~+-N的去除率越高,但是电流效率下降。Mn~(2+)对NH_4~+-N去除的影响较大。采用电化学法除NH_4~+-N之前,应先去除滤液中的Mn~(2+)。探索了NH_4~+-N去除的反应机制和动力学关系;研究了在CaO作用下CO_2稳定化Mn后的电解锰渣浆液中加入镁源、磷源固定NH_4~+-N。电解锰渣浆液中NH_4~+-N与加入的镁源、磷源反应形成磷酸铵镁沉淀。比较了不同镁源、磷源对NH_4~+-N固定的效果,发现MgCl_2、Na_3PO_4作用下Mg:P:N摩尔比为1.5:1.5:1时,NH_4~+-N的固定率最大为89.1%。利用Visual MINTEQ软件模拟了电解锰渣浆液中NH_4~+-N在平衡状态下化学物质的形态、物质的溶解与平衡以及固体的溶解饱和状态等。磷酸铵镁沉淀法固定电解锰渣浆液中NH_4~+-N后。采用电化学法直接去除滤液中剩余的NH_4~+-N,取得了较好的效果。该研究证实磷酸铵镁固定+电化学氧化是一种高效的控制电解锰渣中NH_4~+-N的方法。通过小试实验,提出的CO_2-镁盐、磷酸盐-电氧化工艺处置电解锰渣,可以有效稳定化Mn和控制NH_4~+-N,避免了污染物进入水体污染环境。(4)研究了空气吹脱回收电解锰渣中NH_4~+-N和氧化固定Mn的影响条件和化学反应原理。与NaOH比较,CaO适合作为空气吹脱NH_4~+-N和氧化Mn的碱性辅助剂。增加温度和空气流量均有助于NH_4~+-N的吹脱回收。增加温度有利于Mn的固定。空气吹脱NH_4~+-N和H_2SO_4溶液吸收后主要生成了(NH_4)_2SO_4和(NH_4)_3H(SO_4)_2。空气氧化可溶性Mn形成了Mn_3O_4。通过小试实验,提出的空气-镁盐、磷酸盐-电氧化联合处置电解锰渣,能有效稳定化Mn和控制NH_4~+-N。经计算空气-镁盐、磷酸盐-电氧化工艺的费用低于CO_2-镁盐、磷酸盐-电氧化工艺。建议采用空气-镁盐、磷酸盐-电氧化工艺无害化处理电解锰渣。(5)研究了电动力富集电解锰渣中Mn的效果和反应特征。CO_2辅助电动力处理电解锰渣,CO_2与阴极区的OH-反应形成CO_3~(2-),降低了阴极板附近的pH值,且CO_3~(2-)进一步与迁移到阴极板附近的Mn~(2+)反应形成MnCO_3。比较分析,0.1mol/LH_2C2O4溶液为预处理试剂,0.2 L/min CO_2辅助电动力处理电解锰渣48 h后,在阴极板附近Mn的富集量和锰碳酸盐含量均最高,分别为7.5%和4.5%。这与酸性条件下,H_2C2O4还原渣中高价锰氧化物形成Mn~(2+)有关。
[Abstract]:Electrolytic manganese slag is manganese carbonate in electrolytic manganese production process by acid leaching, acid neutralization, filtration process waste residue, the main pollutant which is soluble manganese (Mn) and ammonia (NH_4~+-N). The electrolytic manganese enterprises in China mainly adopts the slag stockpiling disposal of electrolytic manganese slag, slag containing high permeability field the concentration in the filtrate of Mn~ (2+) and NH_4~+-N, the serious pollution of the surrounding environment. At present, electrolytic manganese slag utilization technology is not mature, to the enterprise, is the preferred method for safe landfill disposal of electrolytic manganese slag. However harmless electrolytic manganese slag is the precondition of electrolytic manganese slag landfill, key electrolytic manganese slag harmless disposal is the stable control of NH_4~+-N and Mn. The current attention focus on the disposal of electrolytic manganese slag harmless is fixed on the disposal of heavy metal ions, ammonia nitrogen is less, and the fixed method is easy to cause heavy metal ion Waste pH value increased. In view of the existing research on nitrogen removal of electrolytic manganese residue, heavy metal ion stability, processing capacity, two times to prevent pollution and other aspects still exist obvious shortcomings, this paper based on CO_2 carbonation, air oxidation, electrochemical oxidation and electric power enrichment of new ideas, new technology of electrolytic manganese slag disposal of pollutants in the study. This article chooses an electrolytic manganese slag of electrolytic manganese plant in Chongqing mountain as the research object, through CO_2 carbonization, electrochemical oxidation, magnesium ammonium phosphate precipitation, a new method of air oxidation and enrichment of electric power to explore the electrolytic manganese slag harmless disposal and resource recovery, analyzes the change of mineralogical characteristics of electrolytic manganese slag the disposal process, the chemical reaction principle and dynamic mechanism, and puts forward a new technology of electrolytic manganese slag harmless disposal. The main contents and conclusions are as follows: (1) found that the study on the physicochemical properties of electrolytic manganese slag, slag The main pollution is mainly in the soluble Mn and NH_4~+-N, MnSO_4 - H_2O (NH_4) _2SO_4, (NH_4) _2Mn (SO_4) _2 - 6H_2O (NH_4) _2Mg (SO_4) _2, 6H_2O, CaMn_2O_4 and other mineral leaching can exist in the form of.Mn and NH_4~+-N respectively accounted for 1.55% and 0.55%. heavy slag (2) compared the carbonate and alkaline reagent under the auxiliary effect of CO_2 on soluble Mn in electrolytic manganese slag stabilization effect and mechanism of.Na_2CO_3 and NaHCO_3 were able to form soluble Mn fixed spherical MnCO_3, Na_2CO_3 on Mn NaHCO_3. Na_2CO_3: fixed effect is better than when the mass ratio of slag is higher than 0.4, electrolytic manganese slag column, strip CaSO_4 2H_2O into CaCO_3; compared with NaOH, CaO is more suitable as an auxiliary agent CO_2 fixed Mn. In CaO and CO_2 under the effect of electrolytic manganese slag mineral phase (NH_4) _2Mn (SO_4) _2 - 6H_2O, MnSO_4 - H_2O Mn into MnCO_3 CaO:. When the mineral slag mass ratio is 0.05. CO_2 flow For 0.8 L/min, 20 min after the fixed rate of Mn for 99.99%. by using the principle of chemical equilibrium analysis under different pH CO_2 Mn~ (2+) fixed effects, a good agreement with experimental results. (3) by Ti/RuO_2-TiO_2-Ir O_2-Sn O_2 (DSA) anode, graphite cathode for indirect electrochemical NH_4~+-N under CaO CO_2 stabilized Mn after the removal of leachate. It was found that the increase of Cl- concentration and initial pH value, the removal rate of NH_4~+-N and current efficiency were increased. The increase in current density can improve the removal rate of NH_4~+-N, but is not conducive to improving the current efficiency of the lower concentration of.NH_4~+-N, the removal rate of NH_4~+-N is higher, but the current efficiency decreased by.Mn~ (2+) has great influence on NH_4~+-N removal by electrochemical method. In addition to NH_4~+-N before, should first remove the filtrate in the Mn~ (2+). To explore the relationship between reaction kinetics and mechanism of NH_4~+-N removal; studied in the presence of CaO CO_2 stabilized after Mn electrolytic manganese slag Adding magnesium source size, source of magnesium NH_4~+-N and added phosphorus fixed NH_4~+-N. electrolytic manganese slag slurry, phosphorus source formed by reaction of magnesium ammonium phosphate precipitation. Compared with the different magnesium source, phosphorus source MgCl_2 fixed effects on NH_4~+-N, Na_3PO_4, Mg:P:N under the action of the molar ratio of 1.5:1.5:1, NH_4~+-N fixed rate is 89.1%. using Visual MINTEQ software to simulate the chemical NH_4~+-N electrolytic manganese slag slurry in the equilibrium state of the form, material balance and dissolved and solid dissolved saturation. Magnesium ammonium phosphate precipitation method NH_4~+-N fixed electrolytic manganese slag slurry. Using electrochemical method direct removal of residual NH_4~+-N in leachate, and achieved good results the study confirmed that a NH_4~+-N control method of electrolytic manganese slag is efficient in magnesium ammonium phosphate fixation and electrochemical oxidation. Through the experiment, CO_2- of magnesium salt, phosphate and oxygen The disposal process of electrolytic manganese slag, can effectively stabilized Mn and NH_4~+-N control, to avoid the pollutants into the water pollution of the environment. (4) studied the air stripping recovery condition and the principle of chemical reaction and oxidation effect of NH_4~+-N in electrolytic manganese slag fixed Mn. Compared with NaOH, CaO for air blowing agent and alkaline auxiliary NH_4~+-N and Mn were increased. The oxidation temperature and air flow to blow off the NH_4~+-N recovery. Increasing temperature is beneficial to Mn fixation. Air stripping NH_4~+-N and H_2SO_4 solution after absorption mainly generated (NH_4) and _2SO_4 (NH_4) _3H (SO_4) _2. air oxidation of soluble Mn formed by Mn_3O_4. experiments, the air - magnesium salt, phosphate - electro oxidation combined treatment of electrolytic manganese slag, can effectively control the stabilization of Mn and NH_4~+-N. calculation of air - magnesium salt, phosphate - electro oxidation process is lower than CO_2- magnesium salt, phosphate salt - chemical oxygen Art. Recommended by air - magnesium salt, phosphate - electro oxidation process of harmless treatment of electrolytic manganese slag. (5) studied the electric power enrichment in electrolytic manganese slag and the effect of Mn reaction characteristics of.CO_2 electric power assisted treatment of electrolytic manganese slag, OH- reaction of CO_2 and formation of CO_3~ cathode region (2-), reduced the cathode in nearby pH, and CO_3~ (2-) and further to migrate to the cathode plate near Mn~ (2+) comparative analysis of MnCO_3. formation reaction, 0.1mol/LH_2C2O4 was used as a pretreatment reagent, 0.2 L/min CO_2 electric power assisted treatment of electrolytic manganese residue after 48 h in cathode plate near Mn and enrichment of manganese carbonate content the highest, 7.5% and 4.5%. respectively with the acidic conditions, the reduction of H_2C2O4 in slag manganese oxide formation of Mn~ (2+).

【学位授予单位】：重庆大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：X781.1
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本文编号：1463203