凡口铅锌矿人工湿地重金属分布特征研究

研究了凡口铅锌矿人工湿地处理系统中水体和沉积物重金属(Pb、Zn、Cu、Cd和Mn)的含量及分布特征。结果表明:人工湿地系统对矿山重金属废水有良好的处理效果。湿地系统水体中重金属Pb、Zn、Cu和Cd都主要以悬浮态存在,Mn的存在形式比较复杂,5种重金属的总量沿流程均呈现出先增大后减小的变化趋势。沉积物中Pb、Zn、Cu、Cd和Mn的总量与水平沿程均呈极显著负相关(P0.01)。湿地沉积物中重金属的主要存在形态为残渣态,其次为铁锰氧化物态和有机结合态。沉积物pH值和有机质含量都随着沿流程而逐渐降低,沉积物pH和有机质含量与重金属含量一定的相关性。     

剩余污泥中重金属形态分布及浸出特征研究

剩余污泥具有改良土壤结构、增加土壤肥力、促进农作物生长等优点,由于含有有害的重金属等,妨碍其农用。通过对剩余污泥中重金属形态分布及浸出特征研究,结果显示,剩余污泥中Cu、Zn、Ni、Cr及Pb交换态含量都比较少,Cu、Zn、Ni主要以碳酸盐结合态、铁锰氧结合态和硫化物及有机结合态存在,Cr、Cd和Pb主要以残渣态存在;在酸性条件下,交换态、碳酸盐结合态溶出量大,并且溶出量都随浸出时间的延长而增加。     

废弃钒钛系选择性催化还原催化剂重金属浸出特性

为探讨废弃选择性催化还原（SCR）催钒钛系催化剂中重金属的浸出毒性及其浸出特性,收集了山东某电厂的废弃SCR催化剂进行实验。采用固体废弃物毒性浸出方法硫酸/硝酸法（HJ/T299-2007）进行废弃SCR催化剂毒性浸出实验,同时开展了不同溶液pH、不同浸出时间和不同液固比（L/S）下废弃SCR催化剂中重金属浸出特性的实验研究。结果表明：废弃钒钛系SCR催化剂有一定的重金属浸出毒性,其中V和Zn的浸出浓度偏高,分别为13.8mg/L和2.1mg/L;pH对重金属的浸出影响显著,强酸对Cr、Ni、Cu和Zn的浸出有促进作用,V在强酸强碱环境下（pH<3或pH>11）容易释放;V、Cr、Ni和Cu主要在浸出过程的前2h内释放,18h时释放率都已高达96%以上,18h后这4种重金属浸出基本完成,而Zn在浸出18h后仍有6%释放,浸出周期相对较长;室温下加大液固比对废弃催化剂中V的浸出仅起稀释作用;Cr、Ni、Cu和Zn的溶出在液固比（L/S）<30时受溶解度的影响,L/S>30时被稀释。     

微波-柠檬酸浸出城市污泥中重金属

采用微波辅助柠檬酸浸出城市污泥中的重金属,考察了升温速率、pH值、搅拌时间等对浸出率的影响。结果表明,升温速率为15℃/min,pH值调至3,前搅拌30 min,170 W功率下微波2.3 min,再反应3 h,污泥中Zn、Cu、Ni与Pb的浸出率分别达到了47.84%,11.05%,43.83%,25.59%,较无微波条件下,重金属浸出率平均提升了50.7%,反应时间缩短了8 h。处理后污泥中重金属含量远低于《农用污泥中污染物控制标准》(GB 4284—84)。     

生活污泥焚烧灰的重金属含量及其浸出特征

为了探讨生活污泥焚烧灰中重金属的含量及其浸出特征,收集了广州沥窖污水处理厂的剩余污泥,采用火焰原子吸收光谱法测量重金属含量;应用固体废物浸出毒性的浸出方法(GB5086.2-1997),以不同p H的浸提剂,对污泥中重金属的浸出特性进行了实验研究。结果表明:污泥中Fe的含量最高,达到27378 mg/kg,其次是Mn和Cu,分别为436.5 mg/kg和315.2 mg/kg,Zn、Cr、Pb和Ni的含量较高,依次是721.5、199.2、122.2和110.8 mg/kg,Cd的含量极少,仅有0.33 mg/kg。Cr和Cd金属元素的8小时浸出量分别为62.9 mg/kg、0.96 mg/kg,其余被测的金属元素:Fe、Pb、Cu、Ni、Zn以及Mn,在任何浸提时间下,其浸出量均为0 mg/kg。本实验中重金属在酸性条件下的浸出率明显高于碱性条件下,Cr、Ni和Cd的最佳浸提剂p H值均为2。其中Cu和Zn随浸提剂p H变化的浸出特征不明显。。     

煤矸石堆存区周边土壤重金属污染特征及风险评价

为探究长期堆存煤矸石中重金属在周边盛行风向土壤里的分布特征及潜在风险,以宁夏枣泉煤矿煤矸石堆存区周边土壤为研究对象,对煤矸石堆存区周边盛行风向土壤中5种重金属(Cu、Zn、Pb、Cr、Mn)总量及重金属赋存形态特征进行深入分析,开展了土壤重金属生物活性分析及评价。结果表明:由于煤矸石的长期堆放、风力、雨水淋溶等,堆存区边缘处重金属(Zn、Pb和Mn)含量较高,且随着距离的增大呈下降趋势;相关性分析中土壤pH值与Zn、Pb含量呈极显著负相关性,与Mn含量呈显著负相关性,与Pb和Cr的可交换态呈显著负相关性,总氮(TN)与Cu的有机质结合态呈极显著负相关性,与残渣态呈极显著正相关性;RAC评价结果表明Pb在土壤中具有较高风险水平,其余重金属潜在风险水平较低。     

电渗析法分离医疗垃圾焚烧飞灰浸出液中重金属

采用电渗析法分离医疗垃圾焚烧飞灰浸出液中重金属,考察了电流密度、液固比、处理时间等参数对重金属移除的影响,并分析了电渗析处理对飞灰特性、重金属形态及其浸出毒性的影响. 结果表明,电流密度0.8 mA/cm2、液固比10(w)和处理时间14 d条件下飞灰浸出液中重金属分离效果最好,11.1% Pb, 42.3% Zn, 56.7% Cd, 38.7% Cu, 7.5% Cr被移除,飞灰中大量NaCl被移除,氯含量从20.43%降低到0.78%,热灼减率从11.1%升高到34.3%,可溶态和碳酸盐态重金属含量降低,飞灰基质减少及不可溶态重金属存在导致残灰中重金属含量增加,Pb和Cd浸出浓度仍超过生活垃圾填埋场的阈值.     

不同pH值浸取液对重金属长期浸出行为的影响

本文采用不同pH值的浸取液,研究了水泥胶砂样品中各重金属在浸取液中的长期浸出扩散行为。结果表明:Cd,Mn,As三种元素均未检出;Cu离子在水溶液中,仍然具有较强的浸出性;Cd、Pb、Cr(Ⅵ)的浸出迁移性则随着浸取液酸度的增大而增强;浸泡180d后,各重金属的固化率仍在99%以上,且表面浸出率处于10-5cm.d-1的数量级,说明水泥产品中重金属的迁移是一个长期而缓慢的过程,不会对环境产生危害。     

粒径对餐厨沼渣热解制备生物炭中磷和重金属的影响

以3种粒径餐厨沼渣为原料,在600℃下热解制备生物炭,研究粒径对沼渣（BR）及生物炭（BRC）中磷和重金属的影响,并采用TCLP浸出毒性和重金属潜在生态风险评估对其安全性进行系统研究。结果表明：BR及BRC中的磷主要以酸溶态磷（HCl-P）为主,残渣态磷（Res-P）次之,其余磷形态含量较低,总磷含量均呈现出随粒径增大而降低的趋势。热解促进H₂O-P、NaHCO₃-P和NaOH-P向HCl-P和Res-P转化。随着粒径的增大,BR中Cu、Zn总量增加,Cr减少,BRC中的Cr、As总量增加,Zn、Pb减少。并且BR中Cr、Zn、Pb和As中可氧化态和残渣态F3+F4随粒径增大而减少;BRC中Cr、Pb、As中F3+F4随粒径增大而减少,而Cu、Zn、Cd与之相反。TCLP浸出毒性和重金属潜在生态风险评估结果表明BR及BRC中重金属均属于低风险水平。     

城市生活垃圾焚烧飞灰重金属在磁性作用中浸出行为

对城市生活垃圾焚烧飞灰进行了物理化学特性分析,研究了飞灰在不同浸取液pH值、不同磁场强度条件下的重金属浸出行为。实验结果表明:根据我国危险废物浸出毒性鉴别标准,飞灰属于危险废物;飞灰是晶体矿和非晶体矿的混合物;飞灰是由许多形态不规则,结构疏松的玻璃质颗粒组成的,平均粒径为22.15μm;磁场强度为0.1T,pH=4时,飞灰中被浸出的Pb含量最多;磁场强度为0.1T,pH=2时,飞灰中被浸出的Cr含量最多。因此可以通过调控磁场强度和浸取液pH值,高效回收飞灰中的重金属,实现资源化利用,减少环境污染和危害人类健康的风险。     

Investigation of stabilization/solidification for treatment of electric arc furnace dust: Dynamic leaching of monolithic specimens

Diffusion-controlled leaching of heavy metals (Cr, Ni, Pb and Zn) from electric arc furnace dust treated with ground granulated blast furnace slag (GGBFS) and with ordinary Portland cement (OPC) was evaluated. Monolithic specimens were evaluated under dynamic leaching conditions for 84 days with periodic leachant renewal. The influence of leaching time, nature of the leachant, binder type and the water/solid ratio of the monoliths were investigated. Results obtained showed both binders can immobilize heavy metals in the monoliths under dynamic leaching conditions, with cumulative quantity of leached metal under 0.138 mg (Cr). Alkaline leachant increased metal release from specimens and reducing the water/solid ratio of the monolith allowed for a decrease in the cumulative mass of metals leached. Chemical and mineralogical characterizations indicated that the metals were evenly distributed throughout the specimens for both binders. Decalcification was observed on the OPC monolith border following leaching. This decrease in Ca corresponded to an altered zone (20 μm), identified by scanning electron microscopy. The GGBFS sample did not show an altered zone.     

Waste stabilization/solidification of an electric arc furnace dust using fly ash-based geopolymers

The stabilization/solidification (S/S) of a carbon steel electric arc furnace (EAF) dust containing hazardous metals such as Pb, Cd, Cr or Zn using geopolymerization technology is described in this paper. Different reagents such as sodium hydroxide, potassium hydroxide, sodium silicate, potassium silicate, kaolinite, metakaolinite and blast furnace slag have been used. Mixtures of EAF waste with these geopolymeric materials and class F fly ash have been processed for studying the potential of geopolymers as waste immobilizing agents. Compressive strength tests and leaching tests for determining the efficiency of heavy metal immobilisation have been carried out. Comparison of fly ash-based geopolymer systems with classic Portland cement stabilization methods has also been accomplished. Compressive strength values far better than those achieved by hydraulic S/S methods were easily obtained by geopolymer solids at 28 days. Regarding leachability, the geopolymer S/S solids also manifested in general a better behaviour, showing very promising results.     

Study of the leaching behaviour of paving concretes: quantification of heavy metal content in leachates issued from tank test using demineralized water

The leaching behaviour of concretes made from porphyry aggregate, river sand and Portland cement or blast furnace slag cement has been studied by means of a tank test using demineralized water in accordance with NEN 7345. The results show that the amount of heavy metals leached is small, much lower than the parametric values specified by the European Directive defining the quality of drinking water, and becomes negligible after prolonged immersion.At the end of the tank test, the fraction of heavy metals leached by the concrete represents less than 1% of the total heavy metal content of the cement. To refer to the bulk content as a criterion of environmental quality is therefore unjustified and unduly restrictive.The results suggest that the controlled use of alternative fuels and raw materials to replace natural materials does not in any way alter the leaching behaviour. Similarly, the replacement of a defined fraction of the clinker with blast furnace slag does not compromise the environmental compatibility of the concrete in terms of the heavy metals it releases.A second finding of these experiments is that the risk of contamination due to release of heavy metals from concrete on-site appears small. The total heavy metal content of concrete is of the same order of magnitude as (or even smaller than) that of a soil considered as being unpolluted in Belgium. Moreover, the fraction of heavy metals released by the concrete as a proportion of this total heavy metal content is nonsignificant.     

Comparison of the fixation of heavy metals in raw material, clinker and mortar using a BCR sequential extraction procedure and NEN7341 test

The release potential and leaching behavior of five heavy metals (As, Cd, Cr, Cu and Pb) in raw material, clinker and mortar were studied by the three-step sequential extraction procedure proposed by the commission of the European Communities Bureau of Reference (BCR) and NEN7341 leaching test. The results of two experimental methods were compared to show the fixation difference of heavy metals among three kinds of samples. The results of NEN7341 leaching test show that the maximum leached concentration of cement products is low and the leached fraction of five heavy metals represents less than 15% of the total heavy metal content of the cement product. To refer to the bulk content as a criterion of environmental impact is not appropriate. The results of sequential extraction procedures show that the bonding forms of heavy metals change a lot in three samples. The contamination factor (Cf) and the leached fraction of each element in three samples indicate that all the elements are better fixed in cement products than in raw material due to calcination and hydration. To most elements, the relative metal retention is higher in mortar than in clinker. Compared within the five analyzed elements, Cd is better retained and Cu is worse retained in the same kind of sample.     

电弧炉熔融医疗垃圾焚烧灰的实验研究

利用处理量为2 kg的直流电弧炉对医疗垃圾焚烧的底灰、底灰与布袋飞灰的混合灰分别进行熔融实验研究,并比较了熔融前后灰和熔渣的化学成分、物相、微观形貌、浸出毒性及重金属残留率. 结果表明,底灰主要由复杂的硅酸盐晶体组成,布袋飞灰含有大量的硬石膏(CaSO4)、氯化钠(NaCl)晶体,熔融后两种熔渣均为无定形非晶态的玻璃熔岩. 底灰、混合灰熔融后减容率分别达到78%和80.5%;熔融前布袋飞灰浸出液中Pb, Cd, Zn浓度远超过危险废物填埋限值,熔融后的熔渣中重金属固化在Si-O网格中,渗沥液中浓度极低,完全符合环保要求. 熔融后2种熔渣中Pb, Cd, Zn的残留率较低,而且混合灰熔渣中重金属残留率均低于底灰熔渣.     

电炉精炼渣中重金属在不同溶液体系的浸出行为

采用全溶实验、短期与长期浸出实验,对电炉精炼渣中重金属元素的浸出行为进行研究,并通过SEM与XRD分析其机理. 结果表明,电炉精炼渣中Ba元素短期浸出浓度最高值为52.10 mg/L,超出国家污水重金属排放标准;Ni元素短期浸出浓度最高值为0.025 mg/L,V元素长期浸出浓度最高值为0.176 mg/L,超出生活饮用水卫生标准. 重金属元素的浸出主要是由于钢渣中Ca2SiO4×H2O (C-S-H)等结构的破坏.     

矿渣基草酸钙化学键合材料的制备及其固化重金属的研究

利用富含钙氧化物的高炉矿渣与草酸在常温进行反应制备草酸钙化学键合材料,探究了草酸(OA)和高炉矿渣(BFS)质量比对草酸钙化学键合材料力学性能的影响,以及草酸钙化学键合材料对重金属(Pb、Cd和Cu)的固化效果。结果表明,当草酸和高炉矿渣质量比为0.25时,草酸钙化学键合材料力学性能最优,其在自然养护3 d、7 d和28 d的抗压强度分别为25.70 MPa、27.86 MPa和34.79 MPa。采用XRD和SEM对草酸钙化学键合材料的物相组成和微观形貌进行分析,其主要物相为草酸钙(CaC₂O₄·H₂O),微观结构致密。在重金属(Pb和Cu)掺量为8%(质量分数)时,草酸钙化学键合材料对重金属(Pb和Cu)仍有良好的固化效果,固体浸出毒性质量浓度低于国家标准限值。研究结果为高炉矿渣制备草酸钙化学键合材料提供了参考。     

The leachability of heavy metals in hardened fly ash cement and cement-solidified fly ash

The effect of mix proportion, leachant pH, curing age, carbonation and specimen making method etc. on the leaching of heavy metals and Cr(VI) in fly ash cement mortars and cement-solidified fly ashes has been investigated. In addition, a method for reducing the leaching of Cr(VI) from cement-solidified fly ashes is proposed. The results mainly indicate that: (1) either Portland cement or fly ash contains a certain amount of heavy and toxic metals, and the leaching of them from hardened fly ash incorporated specimens exists and is increased with fly ash addition and water to cement ratio; (2) the leachability of some heavy metals is greatly dependent on leachant pH; (3) when carbonation of cement mortars occurs the leaching of chromium ions is increased; (4) the amount of heavy metals leached from cement-solidified fly ashes depends more on the kind of fly ash than their contents in fly ash; and (5) with ground granulated blast furnace slag addition, the leaching of Cr(VI) from solidified fly ashes is decreased.     

淋溶条件下生物炭对矿区土壤中重金属迁移的影响

以玉米秸秆为原料在450℃下制备生物炭，将生物炭按5%的炭土比例施入矿区重金属污染土壤中。通过室内土柱淋溶试验，分析加入生物炭对土壤淋出液pH、重金属纵向迁移行为及重金属累积释放量的影响。结果表明：加入生物炭处理后土壤淋出液的pH显著高于对照处理，说明生物炭可以在一定程度上缓解土壤的酸性。与对照相比，添加生物炭降低了重金属向下层土壤迁移的风险，淋溶后土柱中Pb、Cu、Zn和Mn的纵向迁移量分别降低了65.93%、50.95%、49.29%和30.95%，生物炭对土壤中重金属纵向迁移抑制的顺序为Pb>Cu>Zn>Mn，生物炭对Pb的钝化效果最好。随着淋溶液体积的增加，Pb、Cu、Zn和Mn这4种重金属的淋溶累积释放量总体上呈现出前期快速溶出和后期缓慢溶出两个明显的阶段。4种重金属的累积释放量大小为Pb>Mn>Zn>Cu，添加生物炭后明显降低了重金属的累积释放量。对土壤中金属释放过程进行数学方程拟合后发现，应用Elovich方程能较好地描述重金属释放过程，说明这4种重金属元素在土壤中的淋溶和释放过程的机制不是单一反应过程，而是属于活化能变化较大的复杂反应过程。加入生物炭后各重金属的b值均低于对照组，重金属迁移速率随着生物炭的添加而降低，说明生物炭能提高土壤对重金属离子的吸附力，降低因土壤淋溶作用而引起的重金属迁移，可以实现对重金属复合污染矿区土壤的修复。     

垃圾水分对垃圾焚烧过程重金属迁移转化影响的实验研究(英文)

The effect of moisture in municipal solid waste (MSW) on partitioning of lead (Pb), zinc (Zn), copper (Cu) and cadmium (Cd) was studied in a laboratory tubular furnace by using simulated MSW. The moisture in MSW influences heavy metals in following ways, to increase the moisture in flue gas and decrease the combustion temperature, to prolong the combustion time, and to prolong the releasing time of volatiles with the furnace temperature decreased by increasing the moisture. The volatilization of Pb, Zn and Cd was enhanced by increasing the moisture in MSW because of the prolonged combustion time. For Pb and Zn, the combustion time was important at higher temperature, while for Cd, it was important at low temperature. The moisture content showed slight effect on Cu partitioning. When extra chlorine was added to MSW, such as 1%PVC + 0.5%NaCl, the volatilization of Pb, Zn and Cu was enhanced by increasing the moisture because water evaporation reduced the temperature and increased devolatilization time. At higher temperature, NaCl tends to decompose and generates more free chlorine, producing more metal chlorides. Since Cd is a strong volatile heavy metal in MSW, the effect of moisture content on its volatilization is less than that of Pb, Zn or Cu during the MSW incineration.