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题名: 电解锰废渣化学稳定化处理及固锰机理研究
作者: 杜兵
学位类别: 博士
答辩日期: 2015-05-01
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 栾兆坤 ; 段宁
关键词: 电解锰废渣,轻质氧化镁,包裹,长期稳定性,加速碳化 ; electrolytic manganese solid waste, light magnesium, encapsulation, long-term stability, accelerated carbonation
其他题名: Immobilization mechanism on soluble Mn from electrolytic manganese solid waste with chemical stabilization treatment
学位专业: 环境工程
中文摘要:     “无锰不成钢”,锰在国民经济中具有重要的战略意义。电解锰行业是我国特色优势战略性资源行业,我国电解锰产量占世界产量98%以上,是世界最大的电解锰生产国和消费国。电解锰行业快速发展的同时,带来了严重的环境问题,尤其电解锰废渣(锰渣)是该行业最大、最危险的污染源。
    锰渣产生的严重环境问题主要由于:(1)锰污染物含量高,锰质量分数为2%~3%;(2)锰易转移,水溶态锰含量占总锰85%以上;(3)锰浓度高,锰渣渗滤液锰浓度超地表水标准数万倍;(4)堆存量巨大;(5)活性低;(6)颗粒细,水分高,粘性大,难分散。
    针对锰渣在堆存过程中存在的环境污染问题,本文提出了“以锰渣化学稳定化处理为核心,末端资源化利用”的解决思路。由于水泥固化的稳定化处理方法存在增容量大、固化体抗渗性差、成本高等问题,本文采用化学药剂稳定化处理的方法,围绕“筛选+评价+利用”思路解决锰渣污染问题。筛选稳定剂的种类包括碱性物质、磷酸盐、碳酸盐、硅酸盐和硫化物,通过批处理实验初步确定稳定剂配方,稳定剂评价方法除批处理方法,还包括固锰体系长期稳定性研究、稳定剂固锰体系的加速老化研究,最后对稳定剂处理后锰渣进行资源化利用,取得了以下主要结论:
(1)通过批处理实验得到两种固锰稳定剂配方,一种以CaO 为主的稳定剂: CaO_9%+CaCO3_5%、CaO_9%+NaHCO3_5%、CaO_9%+Na3PO4_5%,另一种以
轻质MgO 为主的稳定剂:单独投加轻质MgO 或者再分别搭配CaCO3、NaHCO3和Na2CO3,可以实现酸性浸出条件下锰释放量低于100 mg/kg、水浸出液的pH值在6~9 范围内。
(2) 对处理前后锰价态变化、化学形态分析和矿物组分分析表明,CaO+NaHCO3/Na3PO4 固锰机理为沉淀和氧化,CaO+CaCO3 固锰机理为沉淀、吸附和氧化,CaCO3 对Mn2+产生化学吸附,为Mn2+氧化反应提供反应位点,促进Mn2+的氧化。NaHCO3、CaCO3 和Na3PO4 的加入能够促进形成锰沉淀,有利于Mn2+向Mn4+转化,促进水溶态锰和酸溶态锰向中等强度还原态锰转变。以轻质MgO 为主的稳定剂的固锰机理是吸附、沉淀和氧化。
(3)CaO 稳定剂固锰过程中存在实际投加量远超过理论投加量的问题,通过对CaO 在锰渣体系中界面行为研究,借助电子探针等微观测试手段发现,CaO在锰渣体系中被包裹的现象,主要原因是锰渣中高浓度硫酸盐与CaO 反应生成CaSO4,覆盖于CaO 表面,限制了CaO 水化,从而降低单位质量固锰效率。
(4)对稳定剂处理锰渣后固锰体系的长期稳定性研究表明,以CaO 为主的稳定剂CaO_9%+Na3PO4_5%和CaO_9%+CaCO3_5%的固锰体系有良好的长期稳定性,因为在该稳定剂条件下锰转变为地质条件下稳定的含锰矿物,如软锰矿(MnO2)。轻质MgO_10%虽然固锰高效,但是其固锰体系的长期稳定性较差,若引入CaCO3_5%可改善固锰体系的长期稳定性,这是因为CaCO3 有助于形成中等强度还原态锰,表现在形成多种含锰镁矿物,如直锰辉石(MgMnSi2O6)、硅酸锰镁(MgMn(SiO3)2)和氧化锰镁(MgMn2O4)。
(5)对以CaO 为主和轻质MgO 为主的稳定剂固锰体系的老化研究表明,加速碳化会导致稳定剂固锰体系的老化,表现在碳化后锰释放量增加。两种固锰体系老化机理相同:碳化后固锰体系的pH 值降低,一方面,部分锰沉淀溶解,另一方面,使得高价态锰容易被还原,表现在固锰体系中的黑锰矿(Mn3O4)、斜方锰矿(MnO2)碳化后转变为菱锰矿(MnCO3)。碳化使镁的移动性增强,原先稳定的硅酸镁转变为稳定性较差的碱式碳酸镁或易溶的镁盐,从而导致锰的释放。对老化控制研究表明,在CaO 固锰体系中引入Na3PO4 能有效抑制固锰体系的老化。
(6)对CaO 稳定剂处理后的锰渣进行资源化实验——锰渣制备蒸压砖,并得到了工业化应用。较优的原料配比为锰渣30~40%、水泥9%、细砂41~54%、石硝5~10%;最佳工艺参数为轮碾6~8 min、成型压力15~20 MPa。在这些条件下,生产出的蒸压砖强度达到GB11945-1999 MU15 要求,浸出毒性检测满足GB5085.3-2007 限值要求。
英文摘要:       No manganese no steel. Manganese has strategic significance in the national economy. Electrolytic manganese enterprise, which is of advantage, is the characteristic strategic-resource industry in China. As the largest electrolytic manganese producer and consumer in the world, China has a production of manganese accounting for over 98% of world production. With the development of electrolytic manganese enterprise, the environmental problem from it is more serious,especially the electrolytic manganese solid waste (EMSW) which has become the largest and most dangerous pollution source in this industry.
      There were mainly six problems in the disposal process of EMSW: (1) There was high level of manganese pollutants with the manganese mass fraction of 2% to 3%; (2) manganese was easy to transfer, and the content of water-soluble manganese accounts for more than 85% of the total manganese; (3)In EMSW leachate, manganese was of high concentration which was ten thousand times the water environment quality standard; (4) The stock of EMSW was of great amount; (5) EMSW had low activity; (6) EMSW was difficult to disperse due to its fine particles, high moisture and viscosity.
    In terms of the existing problems, this paper put forward the methods and thoughts that relied mainly on chemical stabilization of EMSW with resource utilization subsidiary in the end of pipe. Since the stabilization with cement had shortcomings such as the large volume increase, poor impermeability, high costs and so on, in this paper chemical stabilization was used around the thought of "screening→assessment→resource" to solve the problem of EMSW disposal. Species of stabilizers including alkaline substances, phosphates, carbonates, silicates and sulfides were screened. Apart from the batch method, researches on long-term stability of the manganese-immobilization system and the accelerated aging of the system with stabilizers were also used to assess stabilizers. Finally, resource utilization of EMSW after treatment with stabilizers was studied. Main conclusions obtained were summarized as follow.
    (1) Two stabilizer formulas were determined by batch experiments, the one was CaO-dominated stabilizers: CaO_9%+CaCO3_5%, CaO_9%+NaHCO3_5%, CaO_9%+ Na3PO4_5% and the other was light MgO-dominated stabilizers. Dosing light MgO alone or MgO mixed with CaCO3, NaHCO3 and Na2CO3 can achieve the manganese emissions less than 100 mg / kg under the acidic leaching conditions and the pH of the leaching solution in the range of 6 to 9.
    (2) Through analyses on the valence state, chemical speciation and mineral composition of manganese before and after treatment, it showed that immobilization mechanism on manganese with CaO-dominated stabilizers was precipitation and oxidation: NaHCO3, CaCO3 and Na3PO4 can form precipitate of manganese, make Mn2+ oxidized to Mn4+, and promote water soluble manganese and acid soluble manganese transforming into moderately reducible manganese. The manganese-immobilization mechanism of light MgO-dominated stabilizers was adsorption, precipitation and oxidation.
    (3) The problem in the manganese-immobilization process was that actual dosage of CaO-dominated stabilizer was far more than the theoretical comsumption. By studying the interface behavior of CaO in EMSW system using the electron probe micro analysis technique, it was found that CaO was encapsulated in this system,mainly because the sulfate with a high concentration reacted with CaO into CaSO4,covering the surface of CaO , limiting its hydration, thus reducing the efficiency of unit mass of manganese-immobilization.
    (4) After EMSW treated by stabilizers, the research on long-term stability of manganese-immobilization system suggested that the system with CaO-dominated stabilizers, CaO_9%+Na3PO4_5% and CaO_9%+CaCO3_5% had good long-term stability, because in the role of these stabilizers manganese transformed into stable manganese minerals in geological conditions, such as pyrolusite (MnO2). Although light MgO_10% was efficient in manganese-immobilization, the long-term stability of the system was poor. Introducing CaCO3_5%, the long-term stability of the manganese-immobilization system can be improved, which can be attributed to the formation of moderately reducible manganese with the help of CaCO3 in the form of a variety of minerals, such as straight pyroxene (MgMnSi2O6), manganese and magnesium silicate (MgMn(SiO3)2) and magnesium oxide, manganese (MgMn2O4).
    (5) Research on the ageing of manganese-immobilization system with the two stabilizer formulas, CaO-dominated and MgO-dominated stabilizers showed that accelerated carbonation would lead to the aging of the system, which can be seen from the increase of manganese release after carbonation. The aging mechanisms of the two manganese-immobilization systems were the same: the pH of the system decreased after carbonation. On the one hand, it made part of the manganese precipitate dissolved, on the other hand, it made it easy for high valent manganese to reduce, which can be seen from the transformaion of hausmannite (Mn3O4),ramsdellite (MnO2) into rhodochrosite (MnCO3) after carbonation in the system.Carbonation enhanced the mobility of magnesium, which made original stable magnesium silicate transform into less-stable hydromagnesite or soluble magnesium salt, resulting in the release of manganese. And research on the control of angeing also showed that Na3PO4 introduced in manganese-immobilization system can reduce the release of manganese and effectively inhibit the aging of the system.
    (6) After treated by CaO-dominated stabilizer, EMSW was used to conduct resources experiments, the autoclaved brick preparation with EMSW, and has been applied in industry production. For the production of autoclaved brick, the suitable cementitious material is cement, and the best raw materials consist of 30 to 40% of EMSW, 9% of cement, 31%-46% of river sand, 5%-10% of coarse sand and 10% of furnace slag. The optimum parameters include grinding 6-8 min with rounds and 15-20 MPa of forming pressure. Under conventional system, autoclaved brick produced in this way meets the grade requirements in GB 11945-1999 MU15 and has a leaching toxicity within the standard limits in GB 5085.3- 2007.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/34111
Appears in Collections:环境水质学国家重点实验室_学位论文

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Recommended Citation:
杜兵. 电解锰废渣化学稳定化处理及固锰机理研究[D]. 北京. 中国科学院研究生院. 2015.
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