由粉煤灰合成单一的沸石及其对Cr(Ⅵ)的吸附研究

以粉煤厌为原料采用两步法合成了2种单一沸石矿物种的NaA和NaX型沸石,并对产物的结构和性能进行了详细表征.2种沸石产物的吸附性能比较结果表明,NaA型沸石优于NaX型沸石.在静态吸附条件下,研究了NaA型沸石吸附水溶液中Cr(Ⅵ)的相关参数(溶液pH值、吸附温度和吸附时间),并用Langmuir和Freundlich等温吸附线对吸附结果进行拟和.结果表明:Cr(Ⅵ)的吸附行为符合Langmuir方程;饱和吸附量为47.78 mg/g.NaA型沸石对Cr(Ⅵ)的吸附是物理和化学吸附两种行为共同作用的结果.     

粉煤灰合成NaX型分子筛的表征及其对Fe2+离子的吸附研究

以高温碱熔融处理粉煤灰合成了NaX型沸石分子筛，考察了不同水热晶化温度对产物结果的影响，用粉末XRD、XRF、SEM和FT-IR等手段对产品进行了表征，结果表明，以粉煤灰为原料用水热合成法合成微孔分子筛时，在晶化温度为90℃时能得到晶形较好的NaX型分子筛。同时考察了NaX分子筛的用量、时间和pH值等因素对Fe2+离子...     

粉煤灰合成NaX型分子筛的表征及其对Fe~（2＋）离子的吸附研究

以高温碱熔融处理粉煤灰合成了NaX型沸石分子筛,考察了不同水热晶化温度对产物结果的影响,用粉末XRD、XRF、SEM和FT-IR等手段对产品进行了表征,结果表明,以粉煤灰为原料用水热合成法合成微孔分子筛时,在晶化温度为90℃时能得到晶形较好的NaX型分子筛。同时考察了NaX分子筛的用量、时间和pH值等因素对Fe2＋离子的吸附影响,在25 mL Fe2＋离子浓度为2×103 mg/L的溶液中,当吸附剂用量为0.2 g,吸附时间为2 h,吸附效率达到最大值（36.41%）,而随着溶液pH值的升高其吸附效率显著增大。     

粉煤灰水热合成Y型沸石及其表征

针对固体废弃物粉煤灰的资源化利用问题,探索合成Y型沸石的实验方法。以燃煤锅炉产生的粉煤灰为实验对象,经过筛分、研磨、高温煅烧和酸浸等预处理方法来提高硅铝含量。将预处理后的粉煤灰加碱煅烧后与氢氧化钠水溶液混合,水热合成Y型沸石。结果表明:粉煤灰经过750℃煅烧1.5 h可以去除约15%的碳;用4 mol·L~(-1)的盐酸在90℃下处理2 h,粉煤灰中的铁、钙和硫等杂质可以分别减少约63.1%、87.3%和79.6%;粉煤灰预处理后的质量减少约51%;预处理后的粉煤灰经过加碱熔融处理,其中的石英和莫来石晶相物质被完全破坏,生成了新的晶相物质;当预处理粉末/碱的质量比为1∶1.2时,熔融产物经过水热反应(温度95~105℃、时间12~24 h)可以生成纯度良好、形貌规则的八面棱柱体Y型沸石;粉煤灰合成Y型沸石的BET等效比表面积可达389.44 m~2·g~(-1),孔容为0.348 mL·g~(-1),并具有优良的热稳定性。粉煤灰经过适当处理,可以在不外加硅、铝化学试剂以及模板剂情况下水热合成结晶度良好的Y型沸石。     

合成条件对粉煤灰合成沸石除磷特性的影响

利用不同钙含量的3种粉煤灰采用碱熔融-水热法合成沸石,研究了不用合成条件对3种粉煤灰合成沸石除磷性能的影响,并分析了除磷机理。3种粉煤灰合成沸石中沸石的种类各不相同,低钙粉煤灰合成沸石主要以Na P1型沸石为主,中钙粉煤灰合成沸石主要以一种无名沸石为主,高钙粉煤灰合成沸石则主要以加藤石为主,沸石含量几乎为零。碱灰比、熔融时间、熔融温度、固液比、结晶时间等合成因素中,对3种粉煤灰合成沸石固磷能力影响相对较大的是碱灰比和熔融时间。3种合成沸石的除磷能力顺序依次为高钙粉煤灰合成沸石中钙粉煤灰合成沸石低钙粉煤灰合成沸石,并且3种沸石的固磷能力与初始原料粉煤灰中的Ca O含量成正比。固磷机理是合成沸石溶于水后向水中释放Ca2+,释放出来的Ca2+即可与磷酸根生成磷酸钙沉淀,从而达到固磷的目的。合成的沸石最大固磷能力为92.24 mg/g。     

粉煤灰合成沸石应用风险评估研究

以粉煤灰为原料通过改良水热法合成了粉煤灰合成沸石,利用扫描电镜(SEM)、X射线衍射(XRD)、BET比表面积等技术手段对其进行了表征;对粉煤灰合成沸石浸出毒性以及出水部分重金属离子浓度进行了实验研究;将使用后的粉煤灰合成沸石与土壤混合用于玉米盆栽实验,同时设置不加粉煤灰合成沸石的对照组,研究使用后粉煤灰合成沸石农用的效果。结果表明:(1)粉煤灰合成沸石主要物相成分为P型沸石,BET比表面积比粉煤灰增加了53倍(从0.867m2/g增加到45.804m2/g)。(2)粉煤灰浸出毒性均低于《危险废物鉴别标准浸出毒性鉴别》(GB 5085.3—2007)规定的浸出毒性鉴别标准值,其中铬、铜、镍未检出;出水部分重金属离子浓度低于《城镇污水处理厂污染物排放标准》(GB 18918—2002)中相应标准值,其中镉、铅、镍均未检出。(3)粉煤灰合成沸石添加于土壤中,对土壤pH影响不大(从6.81升至6.99),但实验组玉米根茎叶长势均好于对照组。     

改性粉煤灰合成沸石对甲基橙的吸附动力学

以粉煤灰(FA)为原料,采用水热晶化一步法制备了Na P1型沸石(ZFA),对合成产物的结构进行了表征,并采用阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)对其进行改性。通过静态吸附实验,研究了改性后Na P1型沸石(MZFA)对水溶液中甲基橙的吸附特性,从动力学角度探讨了吸附机理。结果表明,在所研究的浓度条件下,改性Na P1型沸石对甲基橙的吸附符合Langmuir等温吸附方程,在25℃时,静态饱和吸附量(Qm)为64.76 mg/g。动力学分析表明,改性Na P1型沸石对溶液中甲基橙的吸附符合准二级动力学模型。     

粉煤灰合成沸石去除城市暴雨径流中氨氮

采用粉煤灰为原料,通过耦合碱熔-两步合成法制得3种合成沸石产品,并以合成沸石制备大粒径的功能填料。通过氨氮吸附速率实验和等温吸附实验探讨了合成沸石及功能填料的氨氮吸附速率和最大吸附容量(Qm),以功能填料构建模拟人工快速渗滤系统,研究其对城市暴雨径流中氨氮的去除效果。结果表明,合成沸石对氨氮的吸附速率极快,5min去除率约达到75%,氨氮最大吸附容量为11.36～16.13 mg/g;功能填料对氨氮的最大吸附容量有所下降,但氨氮吸附速率仍较快,应用于模拟人工快速渗滤系统时能在较高的水力负荷下快速去除城市暴雨径流中的氨氮。碱处理再生法更适于进行合成沸石功能填料原位再生,氨氮吸附容量一次再生率达到67%～87%。     

粉煤灰基沸石对亚甲基蓝和Cr(Ⅲ)的共吸附行为——Ⅰ. 吸附动力学和吸附热力学

以粉煤灰为原料,采用优化改进的水热晶化一步法合成沸石。借助FTIR、XRD和SEM对沸石理化特性进行表征,分析水中双组分污染物亚甲基蓝（MB）和Cr（Ⅲ）的共吸附去除特性。结果表明,合成沸石产物呈菱形或多面体形,在XRD图谱中可见NaP1型沸石特征峰。共吸附过程为准二级反应,以化学吸附为速率控制步骤。Langmuir和Freundlich等温线方程都能有效地描述反应过程,298 K条件下,沸石对MB和Cr（Ⅲ）的理论最大吸附量分别为7.8186 mg/g和8.8889 mg/g。吸附过程自发、吸热,反应后体系自由度降低,推测吸附位点的直接竞争为MB和Cr（Ⅲ）去除的主导机制之一。     

不同沸石材料对沼液中磷素静态吸附去除

集中型沼液磷含量较高,处理不当极易造成二次污染。为了寻找高效磷吸附基质,以天然斜发沸石(TRF)、微波与氯化钠联合改性沸石(WLF)、CPB改性沸石(CPBF)、微米级(WF)及亚微米级(YWF)2种粉煤灰合成沸石为研究对象,对磷的热力学吸附解吸以及动力学进行研究,并对影响沼液中磷吸附的温度,沸石投加量、pH等因素进行探讨。结果表明,在投加量为10 g/100 mL时,TRF、WLF、CPBF、YWF、WF 5种沸石材料对实际沼液磷去除率分别达到24.24%、22.45%、28.56%、48.63%、40.22%;在15～35℃范围内,温度的升高有利于除CPBF以外的其他4种沸石材料对沼液磷的吸附;在pH从3.5～10.5的变化范围内,YWF、WF对沼液磷的吸附量变化幅度要大于其他沸石材料。与其他3种沸石材料相比,2种粉煤灰合成沸石具有更高的磷吸附量和吸附速率以及更低的解吸率,因此具有较大的沼液除磷优势,是优良的吸附材料。     

Seizure modeling of Pb(II) and Cd(II) from aqueous solution by chemically modified sugarcane bagasse fly ash: isotherms, kinetics, and column study

Heavy metal pollution is a common environmental problem all over the world. The purpose of the research is to examine the applicability of bagasse fly ash (BFA)—an agricultural waste of sugar industry used for the synthesis of zeolitic material. The zeolitic material are used for the uptake of Pb(II) and Cd(II) heavy metal. Bagasse fly ash is used as a native material for the synthesis of zeolitic materials by conventional hydrothermal treatment without (conventional zeolitic bagasse fly ash (CZBFA)) and with electrolyte (conventional zeolitic bagasse fly ash in electrolyte media (ECZBFA)) media. Heavy metal ions Pb(II) and Cd(II) were successfully seized from aqueous media using these synthesized zeolitic materials. In this study, the zeolitic materials were well characterized by different instrumental methods such as Brunauer–Emmett–Teller, XRF, Fourier transform infrared spectroscopy, powder X-ray diffraction, and scanning electron microscopic microphotographs. The presence of analcime, phillipsite, and zeolite P in adsorbents confirms successful conversion of native BFA into zeolitic materials. Seizure modeling of Pb(II) and Cd(II) was achieved by batch sorption experiments, isotherms, and kinetic studies. These data were used to compare and evaluate the zeolitic materials as potential sorbents for the uptake of heavy metal ions from an aqueous media. The Langmuir isotherm correlation coefficient parameters best fit the equilibrium data which indicate the physical sorption. Pseudo-second-order and intra-particle diffusion model matches best which indicates that the rate of sorption was controlled by film diffusion. The column studies were performed for the practical function of sorbents, and breakthrough curves were obtained, which revealed higher sorption capacity as compared to batch method. Synthesized zeolitic material (CZBFA and ECZBFA), a low-cost sorbent, was proven as potential sorbent for the uptake of Pb(II) and Cd(II) heavy metal ions.     

碱熔预处理对粉煤灰溶解规律的影响及其动力学

在用粉煤灰合成沸石分子筛的过程中，粉煤灰在碱液中的溶解影响到合成反应的速率以及合成分子筛的性能。采用碱熔的方法处理粉煤灰，研究了粉煤灰在碱液中的溶解机理以及碱熔预处理对粉煤灰溶解规律的影响，并采用Noyes-Whitney方程分析其溶解动力学。结果表明，经过碱熔预处理的粉煤灰有36．11％的SiO2和16．33％的Al2O3转化为水溶性成分，剩余的非水溶性部分在碱液中的溶解速率也有大幅提高，硅铝离子达到平衡浓度的时间缩短，铝离子的平衡浓度有较大提升。Noyes-Whitney方程对粉煤灰在碱液中的溶解规律适用，相关系数都达到0．979以上。     

Immobilization of heavy metals in polluted soils by the addition of zeolitic material synthesized from coal fly ash

The use of zeolitic material synthesized from coal fly ash for the immobilization of pollutants in contaminated soils was investigated in experimental plots in the Guadiamar Valley (SW Spain). This area was affected by a pyrite slurry spill in April 1998. Although reclamation activities were completed in a few months, residual pyrite slurry mixed with soil accounted for relatively high leachable levels of trace elements such as Zn, Pb, As, Cu, Sb, Co, Tl and Cd. Phytoremediation strategies were adopted for the final recovery of the polluted soils. The immobilization of metals had previously been undertaken to avoid leaching processes and the consequent groundwater pollution. To this end, 1100 kg of high NaP1 (Na6[(AlO2)6(SiO2)10] .15H2O) zeolitic material was synthesized using fly ash from the Teruel power plant (NE Spain), in a 10 m3 reactor. This zeolitic material was manually applied using different doses (10000-25000 kg per hectare), into the 25 cm topsoil. Another plot (control) was maintained without zeolite. Sampling was carried out 1 and 2 years after the zeolite addition. The results show that the zeolitic material considerably decreases the leaching of Cd, Co, Cu, Ni, and Zn. The sorption of metals in soil clay minerals (illite) proved to be the main cause contributing to the immobilization of these pollutants. This sorption could be a consequence of the rise in pH from 3.3 to 7.6 owing to the alkalinity of the zeolitic material added (caused by traces of free lime in the fly ash, or residual NaOH from synthesis).     

锡冶炼含砷烟尘低温陶瓷固化技术

以锡冶炼过程中排放的含砷烟尘为研究对象,对浸出特性和低温陶瓷胶凝材料对其的固化效果进行了研究。结果表明,含砷烟尘As、Cu和Zn毒性浸出浓度分别为6 783、167和224 mg/L,严重超过国家毒性浸出鉴别标准值。其经低温陶瓷胶凝材料固化处理,当含砷烟尘掺量小于40%,自然养护3 d,As、Cu和Zn毒性浸出浓度急剧降低,且低于国家标准值。XRD和SEM分析表明,低温陶瓷胶凝材料在复合化学激发剂作用下,反应生成类沸石水化铝硅酸盐矿物(Al-O-Si);固化体中Ca-Fe-As-O盐是As固化的主要矿物相。Cu2+、Zn2+替换铝硅酸盐聚合物结构中的Na+、K+保持平衡电荷。胶凝材料水化产物填充于材料颗粒间,使其连接成一致密整体,有效降低了有害物质的毒性浸出浓度。     

粉煤灰和电石渣对聚丙烯塑料裂解的影响研究

研究了粉煤灰和电石渣对聚丙烯塑料裂解的影响,讨论了加入量对裂解速度和裂解产物的影响.结果表明:粉煤灰和电石渣都使裂解产物中的轻质部分(汽油和裂解气)增加、重油降低;粉煤灰比电石渣更能加快反应的进行,而且加入量越多,反应越快,需时越短;粉煤灰比电石渣对聚丙烯塑料的裂解具有明显的催化促进效果.     

Remediation of metal-contaminated soils with the addition of materials - part II: leaching tests to evaluate the efficiency of materials in the remediation of contaminated soils

The effect of the addition of materials on the leaching pattern of As and metals (Cu, Zn, Ni, Pb, and Cd) in two contaminated soils was investigated. The examined materials included bentonites, silicates and industrial wastes, such as sugar foam, fly ashes and a material originated from the zeolitization of fly ash. Soil + material mixtures were prepared at 10% doses. Changes in the acid neutralization capacity, crystalline phases and contaminant leaching over a wide range of pHs were examined by using pH_stat leaching tests. Sugar foam, the zeolitic material and MX-80 bentonite produced the greatest decrease in the leaching of pollutants due to an increase in the pH and/or the sorption capacity in the resulting mixture. This finding suggests that soil remediation may be a feasible option for the reuse of non-hazardous wastes.     

Distribution of mercury in the combustion products from coal-fired power plants in Guizhou,southwest China

Method 30B and the Ontario Hydro Method (OHM) were used to sample the mercury in the flue gas discharged from the seven power plants in Guizhou Province, southwest China. In order to investigate the mercury migration and transformation during coal combustion and pollution control process, the contents of mercury in coal samples, bottom ash, fly ash, and gypsum were measured. The mercury in the flue gas released into the atmosphere mainly existed in the form of Hg°. The precipitator shows a superior ability to remove Hg^p (particulate mercury) from flue gas. The removal efficiency of Hg²⁺ by wet flue gas desulfurization (WFGD) was significantly higher than that for the other two forms of mercury. The synergistic removal efficiency of mercury by the air pollution control devices (APCDs) installed in the studied power plants is 66.69–97.56%. The Hg mass balance for the tested seven coal-fired power plants varied from 72.87% to 109.67% during the sampling time. After flue gas flowing through APCDs, most of the mercury in coal was enriched in fly ash and gypsum, with only a small portion released into the atmosphere with the flue gas. The maximum discharge source of Hg for power plants was fly ash and gypsum instead of Hg emitted with flue gas through the chimney into the atmosphere. With the continuous upgrading of APCDs, more and more mercury will be enriched in fly ash and gypsum. Extra attention should be paid to the re-release of mercury from the reutilization of by-products from APCDs.

Implications: Method 30B and the Ontario Hydro Method (OHM) were used to test the mercury concentration in the flue gas discharged from seven power plants in Guizhou Province, China. The concentrations of mercury in coal samples, bottom ash, fly ash, and gypsum were also measured. By comparison of the mercury content of different products, we found that the maximum discharge source of Hg for power plants was fly ash and gypsum, instead of Hg emitted with flue gas through the chimney into the atmosphere. With the continuous upgrading of APCDs, more and more mercury will be enriched in fly ash and gypsum. Extra attention should be paid to the re-release of mercury from the reutilization of by-products from APCDs.     

Remediation of metal-contaminated soils with the addition of materials--part I: characterization and viability studies for the selection of non-hazardous waste materials and silicates

Contamination episodes in soils require interventions to attenuate their impact. These actions are often based on the addition of materials to increase contaminant retention in the soil and to dilute the contaminant concentration. Here, non-hazardous wastes (such as sugar foam, fly ash and a material produced by the zeolitization of fly ash) and silicates (including bentonites) were tested and fully characterized in the laboratory to select suitable materials for remediating metal-contaminated soils. Data from X-ray fluorescence (XRF), N₂ adsorption/desorption isotherms, X-ray diffraction (XRD) and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM-EDX) analyses revealed the chemical composition, specific surface area and the phases appearing in the materials. A pH titration test allowed the calculation of their acid neutralization capacity (ANC). The metal sorption and desorption capacities of the waste materials and silicates were also estimated. Sugar foam, fly ash and the zeolitic material were the best candidate materials. Sugar foam was selected because of its high ANC (17 000 meq kg⁻¹), and the others were selected because of their larger distribution coefficients and lower sorption reversibilities than those predicted in the contaminated soils.     

A pilot study of mercury liberation and capture from coal-fired power plant fly ash

The coal-fired electric utility generation industry has been identified as the largest anthropogenic source of mercury (Hg) emissions in the United States. One of the promising techniques for Hg removal from flue gas is activated carbon injection (ACI). The aim of this project was to liberate Hg bound to fly ash and activated carbon after ACI and provide high-quality coal combustion products for use in construction materials. Both bench- and pilot-scale tests were conducted to liberate Hg using a thermal desorption process. The results indicated that up to 90% of the Hg could be liberated from the fly ash or fly-ash-and-activated-carbon mixture using a pilot-scale apparatus (air slide) at 538 degrees C with a very short retention time (less than 1 min). Scanning electron microscope (SEM) evaluation indicated no significant change in fly ash carbon particle morphology following the thermal treatment. Fly ash particles collected in the baghouse of the pilot-scale apparatus were smaller in size than those collected at the exit of the air slide. A similar trend was observed in carbon particles separated from the fly ash using froth flotation. The results of this study suggest a means for power plants to reduce the level of Hg in coal-combustion products and potentially recycle activated carbon while maintaining the resale value of fly ash. This technology is in the process of being patented.