Heavy metal leaching from coal fly ash amended container substrates during Syngonium production

Coal fly ash has been proposed to be an alternative to lime amendment and a nutrient source of container substrates for ornamental plant production. A great concern over this proposed beneficial use, however, is the potential contamination of surface and ground water by heavy metals. In this study, three fly ashes collected from Florida, Michigan, and North Carolina and a commercial dolomite were amended in a basal substrate. The formulated substrates were used to produce Syngonium podophyllum Schott 'Berry Allusion' in 15-cm diameter containers in a shaded greenhouse. Leachates from the containers were collected during the entire six months of plant production and analyzed for heavy metal concentrations. There were no detectable As, Cr, Hg, Pb, and Se in the leachates; Cd and Mo were only detected in few leachate samples. The metals constantly detected were Cu, Mn, Ni, and Zn. The total amounts of Cu, Mn, Ni, and Zn leached during the six-month production period were 95, 210, 44, and 337 microg per container, indicating that such amounts in leachates may contribute little to contamination of surface and ground water. In addition, plant growth indices and fresh and dry weights of S. podophyllum 'Berry Allusion' produced from fly ash and dolomite-amended substrates were comparable except for the plants produced from the substrate amended with fly ash collected from Michigan which had reduced growth indices and fresh and dry weights. Thus, selected fly ashes can be alternatives to commercial dolomites as amendments to container substrates for ornamental plant production. The use of fly ashes as container substrate amendments should represent a new market for the beneficial use of this coal combustion byproduct.     

Removal of PCBs from wastewater using fly ash

Liquids and sludges containing polychlorinated biphenyls (PCBs) can be treated to concentrate the PCBs in a solid residue. The latter can then be handled to destroy the PCBs. A study on sorption kinetics of PCBs on fly ash was conducted in controlled batch systems. TCB and HeCB are removed at 25 degrees C by adsorption on fly ash up to 97% at pH 7, with an adsorbent dose of 5 g/l. An examination of the thermodynamic parameters shows that the adsorption of TCB and HeCB by fly ash is a process occurring spontaneously at ambient conditions. Activation energies for the sorption process ranged between 5.6 and 49.1 kJ/mol. It was observed that the rate at which TCB and HeCB are adsorbed onto fly ash showed a diffusion limitation. The uptake rate of TCB and HeCB increases with increasing initial concentration and gradually tends to a constant value. A decrease in the adsorption of TCB and HeCB was observed when interfering ions and other PCB congeners were present. Changing the pH in the aqueous solution from 2 to 10 had no effect on the adsorption process. Overall, fly ash can be used for an efficient removal of PCBs from several aqueous solutions.     

火电灰渣场自然恢复下灰渣养分及重金属含量研究

对自然恢复下4类不同年代样地的灰渣养分含量及重金属含量进行研究,通过对比分析发现,有机质、全氮、全钾、全磷含量随着自然恢复时间的增加呈现递增的趋势,全磷含量在各恢复阶段与对照样地之间并不存在显著差异(P0.05)。pH随着恢复时间的增加呈现递减的趋势。对灰渣综合质量指数进行研究发现,自然恢复长期、中期、短期与自然恢复初期对比均有显著提高(P0.05),且随着自然恢复时间的增加灰渣综合质量指数逐渐提高。对灰渣场锌、铅、铜3种重金属研究后发现,在自然恢复下随着时间的增加,灰渣中重金属含量均呈现递减的趋势。     

不同粒径垃圾焚烧飞灰金属形态分布比较研究

研究了华南地区某垃圾焚烧厂的除尘器飞灰的化学组成和粒径分布,并采用分级提取法对不同粒径飞灰中的重金属化学形态进行了研究。同时比较了华南、华东、西南地区以及台湾地区垃圾焚烧飞灰的筛下累积分布和不同粒径飞灰中各重金属组成。结果表明,飞灰的组要成分为：CaO、SiO2和SO3等;各地区75%的飞灰粒径都主要集中在38.5～75μm。华南地区各粒径飞灰中挥发性金属（Zn和Pb）含量明显高于其他金属。除Ni和Cr外,Cu、Zn、Pb和Cd含量随粒径减小呈先减少后增大的趋势。华南地区Cu、Zn、Ni、Cr、Pb和Cd的含量均高于其他地区（台湾地区除外）。Cu、Zn和Cd的弱酸提取态和可还原态含量较高。高于40%的水溶态Pb表明其对环境有较大潜在危害;40%Ni和Cr主要以残渣态存在,对环境的潜在影响较小。     

上海石洞口第二电厂拟建粉煤灰分选系统的技术可行性研究

上海石洞口第二电厂拟建设粉煤灰分选系统生产国标等级灰,但其粉煤灰的游离氧化钙偏高.研究表明:游离氧化钙在细灰中没有明显富集的趋势,即源灰游离氧化钙含量指标合格,那么分选所产细灰的也合格;供分选用的源灰细度和粒度分布较利于提高分选效率,生产国标Ⅱ级灰的分选产率可达70%左右;建设分选系统在技术上是可行的,且可获得较大的综合效益.     

粉煤灰对焦化废水总铬去除的影响

以1 mg/L模拟焦化废水为研究对象,采用高锰酸钾氧化-二苯基碳酰二肼分光光度法测定焦化废水中总铬,研究不同条件下粉煤灰对总铬去除率的影响.结果表明:(1)粉煤灰粒径、粉煤灰用量、搅拌时间、pH对总铬去除率都有一定的影响.最佳条件:粉煤灰粒径为150μm,粉煤灰用量为4.00 g/L,搅拌时间为40 min,pH为3.在最佳条件下,总铬去除率可达98.82%.(2)在粉煤灰处理模拟焦化废水的最佳条件下,粉煤灰处理实际焦化废水的总铬去除率达90.00%.(3)粉煤灰处理焦化废水,可以以废治废,而且处理效果好、处理费用低、原料获取方便,在实践中具有可操作性.     

垃圾焚烧飞灰的资源化处置前景

对大量数据进行统计分析,得出垃圾焚烧飞灰中主要重金属元素和二噁英类物质的含量分布特征,并根据垃圾焚烧飞灰的综合特点,结合其他领域现有技术,初步提出了3个垃圾焚烧飞灰的资源化处置方案:①烧制陶粒;②作为凝石成岩剂的原料;③作为上流式厌氧污泥床(UASB)或膨胀式颗粒污泥床(EGSB)废水处理装置的生化反应促进剂.同时回收重金属,并对其前景进行了初步分析.若将上述3个方案逐步完善,不但能节约1000～2000元/t的垃圾焚烧飞灰处置费用,还能够产生很大的附加经济效益.     

Dioxin contents in fly ash from large-scale MSW incinerators in Taiwan

In this study, fly ash samples were collected from three municipal waste incinerators (MWI) in Taiwan. These MWIs investigated are equipped with different air pollution control devices (APCDs). Preliminary results indicated that 2,3,7,8-PCDD/Fs homologue patterns of various types of fly ash were quite similar for all three MWIs. Concentrations of higher-chlorinated congeners of PCDDs and PCDFs were remarkably higher than those of lower-chlorinated congeners. In the case of MSW-A, the PCDD/PCDF ratios of ashes were found in the decreasing order for cyclone, boiler and baghouse. The PCDD/PCDF ratios in various types of fly ash of MWI-B was boiler-A < boiler-B < ESP < boiler-C. As for MSW-C, no obvious trend has been observed for PCDD/PCDF ratio. However, the ratio in boiler ash was higher than that in baghouse ash of MWI-A. The dioxin contents in fly ash would increase as the fly ash passed through APCD zones. In other words, the environmental conditions of APCD may actually cause the increase of the dioxin contents in fly ash. The trend for dioxin contents in fly ash collected from three MSW incinerators investigated was MSW-C < MSW-A < MSW-B.     

Biodiversity variability and metal accumulation strategies in plants spontaneously inhibiting fly ash lagoon,India

Environmental Science and Pollution Research - Out of 29 plant species taken into consideration for biodiversity investigations, the present study screened out Cyperus rotundus L., Calotropis...     

Bioleaching of metal from municipal waste incineration fly ash using a mixed culture of sulfur-oxidizing and iron-oxidizing bacteria

We investigated the behavior and characteristics of metal leaching from municipal solid waste incineration (MSWI) fly ash among pure cultures of a sulfur-oxidizing bacterium (SOB) and an iron-oxidizing bacterium (IOB) and a mixed culture. The IOB has a high metal-leaching ability, though its tolerability against the ash addition is low. The SOB might better tolerate an increase in ash addition than the IOB, though metal leaching ability of the SOB is limited. Mixed culture could compensate for these deficiencies, and high metal leachability was exhibited in the 1% ash culture, i.e., 67% and 78% of leachabilities for Cu and Zn, respectively, and 100% for Cr and Cd. Furthermore, comparably high leachabilities such as 42% and 78% for Cu and Zn were observed even in the 3% ash cultures. Characterization of metal leaching by the mixed culture revealed that the acidic and oxidizing condition had remained stable thorough the experimental period. Ferric iron remained in the mixed culture, and the metal leaching was enhanced by redox mechanisms coupling with the leaching by sulfate. An increase of ferrous iron enhanced the Cr, Cu, and As leaching. The optimum concentration of sulfur existed for As and Cr (5 gl(-1)) and Cu (2 gl(-1)). The presence of the degradable and non-degradable organic compound that must be existed in the natural environment or waste landfills made no significant change in the leachability of metals other than Zn. These results suggested that bioleaching using a mixed culture of SOB and IOB is a promising technology for recovering the valuable metals from MSWI fly ash.     

壳聚糖联合碱改性粉煤灰对重金属离子的吸附特性

采用浸渍法将壳聚糖负载在经NaOH改性的粉煤灰上,制备了联合改性的粉煤灰。随粉煤灰上壳聚糖负载量的增加,粉煤灰对Pb2+和Cd2+的吸附率均提高。当负载壳聚糖的质量分数为8%,吸附温度为30℃,吸附时间为120 min时,粉煤灰对Pb2+的吸附率最高（为98.9%）,对Cd2+的吸附率也最高（为91.5%）。其吸附行为符合Freundlich等温吸附模型,但表现为2个线性区。粉煤灰负载壳聚糖的改性机理是粉煤灰与带正电荷的壳聚糖的化学键合作用。     

熔盐法处置高熔点垃圾焚烧飞灰重金属的浸出特性

对熔盐法处置高熔点垃圾焚烧飞灰重金属离子浸出特性进行了实验研究。结果表明,熔盐物料组成、熔盐温度和热处理气氛对重金属离子的热挥发特性具有重要影响。在还原性气氛条件下,热处理温度为900～1 000 ℃,添加质量分数为10%～50%的CaCl2的氯化钠熔盐中处理2 h后,垃圾焚烧飞灰渣中Pb、Cd、Cu和Zn等重金属浸出浓度降低90%以上,可以完全达到生活垃圾填埋场填埋标准。在此过程中,灰渣较原灰可减轻50%,同时转化成具有良好胶凝性能的水泥活性混合材料,XRD测试表明其晶体矿物组成为硅酸二钙、硅酸三钙和阿里尼特以及硫酸钙等。     

火力发电厂飞灰对抗生素磺胺的吸附性能

研究了吸附时间、飞灰用量、初始溶液pH和振荡频率等因素对飞灰吸附去除水溶液中磺胺的影响,并对其吸附机理进行了初步探讨。研究结果表明,飞灰用量增大有利于提高其对磺胺的吸附去除率。在25℃、振荡频率150 r/min、飞灰用量50 g/L、磺胺浓度4 mg/L条件下吸附10 min,磺胺的吸附去除率可达到92.8%。电厂飞灰对磺胺的吸附符合二级动力学模型,属于单分子层吸附。     

粉煤灰吸附除磷的改性研究

研究了粉煤灰的最佳改性条件及其吸附理论模型.获得了粉煤灰用于吸附含磷量为5 mg P/L的模拟二级出水的3种改性的最佳条件(21℃):(1)0.25 mol/L盐酸改性的粉煤灰对磷的去除率为76.0%,出水含1.20 mg P/L;(2)300℃下煅烧的粉煤灰对磷的去除率为93.8%,出水中磷含量达到了0.31 mg P/L;(3)低火(119 W)改性的粉煤灰的磷去除率达95.4%,出水含0.23 mg P/L.试验结果表明:Langmuir方程能很好地解释两种改性粉煤灰的吸附动力学(R2=0.9188,S.E=0.0032),而Simple Elovieh方程在描述两者的吸附动力学试验数据上显示出优越性(R2=0.9427,S.E=0.029).     

Phosphate removal from digested sludge supernatant using modified fly ash

The removal of phosphate in digested sludge supernatant by modified coal fly ash was investigated in this study. Modification of the fly ash by the addition of sulfuric acid could significantly enhance its immobilization ability. The experimental results also showed that adsorption of phosphate by the modified fly ash was rapid with the removal percentage of phosphate reaching an equilibrium of 98.62% in less than 5 minutes. The optimum pH for phosphate removal was 9 and the removal percentage increased with increasing adsorbent dosage. The effect of temperature on phosphate removal efficiency was not significant from 20 to 40 degrees C. X-ray diffraction and scanning electron microscope analyses showed that phosphate formed an amorphous precipitate with water-soluble calcium, aluminum, and iron ions in the modified fly ash.     

De novo formation of dioxins from milled model fly ash

Environmental Science and Pollution Research - Municipal solid waste incineration (MSWI) fly ash has been classified as hazardous waste and needs treatment in an environmentally safe manner....     

机械力活化固硫灰固化处理生活垃圾焚烧飞灰

为实现城市生活垃圾焚烧飞灰的安全处理,通过机械力化学法活化循环流化床燃煤固硫灰,探讨了球磨样品制备固化体的参数。并采用X射线衍射仪（XRD）和傅里叶变换红外光谱仪（FTIR）手段对垃圾焚烧飞灰中重金属的固化机制进行了研究。结果表明,当垃圾焚烧飞灰掺加比为60%,球磨转速为600 r·min-1,球磨时间为5 h,养护温度60 ℃时的固化体28 d和56 d抗压强度分别达到15.6 MPa和17.9 MPa,采用原子吸收光谱仪（AAS）测得固化体中Zn、Pb、Cu、Cd和Cr重金属浸出量均低于GB 5085.3-2007规定限值。XRD和FTIR表征结果表明,在水化过程中,该混合体系生成了水化硅酸钙（C—S—H）、斜方钙沸石和钙矾石（AFt）等水化产物,并且C—S—H凝胶可通过物理包裹的形式固化垃圾焚烧飞灰中重金属;斜方钙沸石和钙矾石以化学吸附的方式使垃圾焚烧飞灰中的重金属离子达到固化/稳定化效果,实现了垃圾焚烧飞灰中重金属的安全处理。     

Thermal behavior of PCDD/PCDF in fly ash from municipal incinerators

The effect of thermal treatment of fly ash on the behaviour of PCDD/PCDF was studied in the range between 120 and 600° C. Annealing at 300° C (2 hrs) resulted in an increase of PCDD/PCDF concentration by a factor of 10 to 15. At 600° C degradation to concentrations below 0.1 ng/g is observed.     

医疗垃圾焚烧飞灰重金属形态分析

利用原子吸收光谱仪分别对医疗垃圾焚烧飞灰重金属含量和重金属形态及其随颗粒度分布特性进行了分析,结果表明,飞灰中Cd、Zn、Pb等的浸出浓度远超标与这些重金属的可交换态和碳酸盐态含量较高有关;飞灰颗粒度主要在96 μm以下,96～150 μm的颗粒中Cd、Pb含量最高,且Zn、Cd的形态以可交换态为主.     

水泥、粉煤灰及DTCR固化/稳定化重金属污染底泥

采用水泥、粉煤灰及有机硫稳定剂DTCR固化/稳定化处理重金属污染的底泥,考察固化体的抗压强度及重金属浸出毒性,确定了底泥固化/稳定化的最佳工艺条件。结果表明:仅用水泥固化/稳定化重金属污染底泥,固化体抗压强度随水泥用量的增加而上升,重金属浸出浓度则下降,当水泥∶干底泥质量比为0.6∶1.0时,固化体7 d抗压强度能达到0.99 MPa的标准值;进一步研究发现,水泥∶粉煤灰∶干底泥质量比为0.54∶0.06∶1.0时,重金属浸出浓度有所上升,但7 d及28 d抗压强度仍能分别达到1.2 MPa和2.8 MPa;加入DTCR后,当水泥∶粉煤灰∶DTCR∶干底泥质量比为0.54∶0.06∶0.012∶1.0时,固化体7 d及28 d抗压强度分别为1.1 MPa和2.1 MPa,醋酸缓冲溶液法浸出的Cd、Pb、Zn和Cu浓度分别为0.102、0.189、0.180和0.032 mg/L。