镧改性沸石改良太湖底泥的磷吸附特征

采用镧改性沸石对太湖底泥进行改良,通过吸附试验分析镧改性沸石改良太湖底泥的磷酸盐吸附特征.结果表明,Langmuir和Freundlich等温吸附模型可以较好地描述太湖底泥对水体中较高浓度磷酸盐(1～15 mg·L-1)的吸附平衡,根据Langmuir吸附方程,未改良太湖底泥对水体中磷的最大吸附容量为791 mg·kg-1,镧改性沸石添加量为10、25和50 g·kg-1的改良太湖底泥对水体中磷的最大吸附容量分别为937、1 037和1 505mg.kg-1.准二级动力学模型可以较好地描述太湖底泥对磷酸盐的吸附动力学过程.太湖底泥对磷酸盐的去除能力随pH值增加而降低,其对磷酸盐的吸附属于自发和吸热过程.改良太湖底泥对磷酸盐的吸附能力明显高于未改良太湖底泥,并且其吸附能力随镧改性沸石添加量的增加而增加.镧改性沸石添加量为10～50 g · kg-1的改良太湖底泥的磷吸附-解吸平衡浓度为0.129～0.241 mg·L-1,明显低于未改良太湖底泥(0.386 mg·L-1).被改良底泥中镧改性沸石所吸附的磷以NaOH-P和HCl-P等较稳定的形态存在,厌氧状态下不易释放.     

镧和阳离子表面活性剂联合改性活性炭对水中磷酸盐和硝酸盐的吸附作用

采用镧(La)和阳离子表面活性剂十六烷基三甲基氯化铵(HDTMA-Cl)对活性炭进行联合改性,并考察了La和HDTMA联合改性活性炭(La-HDTMA改性活性炭)对水中磷酸盐和硝酸盐的吸附性能.实验结果表明,La-HDTMA改性活性炭对磷酸盐和硝酸盐具备一定的吸附去除能力.La-HDTMA改性活性炭对水中磷酸盐和硝酸盐的吸附动力学过程符合准二级动力学模型,吸附平衡数据可以采用Langmuir、Freundlich和Dubinin-Radushkevich(D-R)等温吸附模型加以描述.根据Langmuir等温吸附模型计算得到的La-HDTMA改性活性炭对磷酸盐和硝酸盐最大吸附量分别为4.15 mg·g-1和11.2 mg·g-1.当p H值由4增加到8时,La-HDTMA改性活性炭对水中磷酸盐的吸附能力增加;当p H值超过8时,对磷酸盐的吸附能力则下降.LaHDTMA改性活性炭对水中硝酸盐的吸附能力随p H值的增加而下降.水中共存的Cl-、HCO-3和SO2-4等阴离子会抑制La-HDTMA改性活性炭对磷酸盐和硝酸盐的吸附.水中共存的硝酸盐会抑制La-HDTMA改性活性炭对磷酸盐的吸附,共存的磷酸盐亦会抑制La-HDTMA改性活性炭对硝酸盐的吸附.采用1 mol·L-1Na OH溶液可以使71%吸附剂上的磷酸盐解吸下来,采用1 mol·L-1的Na Cl溶液可以使97%吸附剂上的硝酸盐解吸下来.La-HDTMA改性活性炭对水中磷酸盐的吸附机制主要是阴离子交换、静电吸引、配位体交换作用和路易斯酸碱反应,对硝酸盐的吸附机制主要是阴离子交换和静电吸引作用.     

锆负载量对锆镁改性膨润土吸附水中磷酸盐的影响

制备了锆氧化物(ZrO_2)含量分别为2.98%、7.81%、13.73%和33.70%的4种锆镁改性膨润土,并考察了锆负载量对锆镁改性膨润土吸附水中磷酸盐的影响.结果表明,较高的吸附剂投加量有利于水中磷酸盐被锆镁改性膨润土所吸附去除.锆镁改性膨润土吸附水中磷酸盐的动力学过程符合准二级动力学模型.锆镁改性膨润土对水中磷酸盐的吸附等温行为可以采用Langmuir、Freundlich和Dubinin-Redushckevich (D-R)等温吸附模型进行描述.增加溶液pH值不会导致锆镁改性膨润土对水中磷酸盐吸附能力的下降.锆镁改性膨润土对水中磷酸盐的吸附能力随其锆含量的增加而增加.但是,从总体上,锆镁改性膨润土中单位质量ZrO_2对水中磷酸盐的最大吸附量则随其锆含量的增加而降低.研究结果说明,锆镁改性膨润土适合作为一种吸附剂去除水中的磷酸盐,较高的锆负载量有利于增强锆镁改性膨润土吸附水中磷酸盐的能力,而较低的锆负载量则有利于提高锆镁改性膨润土中单位质量ZrO_2对水中磷酸盐的吸附能力.     

改性腐殖酸对铀的吸附的试验研究

通过静态吸附实验,探讨了改性HA对U(Ⅵ)吸附影响。考查pH值、时间、U(Ⅵ)的初始浓度和温度等对吸附的影响。结果表明:pH值对改性腐殖酸的吸附效果影响较大,改性腐殖酸吸附U(Ⅵ)的最佳pH值为6,最大去除率为99.37%,吸附在60 min内基本达到平衡。UO22+在改性腐殖酸上的吸附是放热过程,符合Freundlich等温吸附方程,相关系数达0.99以上,表明IHA对铀的吸附是以表面为主要吸附位,并不是均匀的单层吸附。图8,参9.     

改性硅藻土的制备、表征及其在富营养化水体除磷中的应用

利用吉林原土和FeCl3作为主要原料,制备应用于抑制湖泊富营养化的除磷材料—改性硅藻土,并利用物理吸附仪、扫描电镜、射线粉末衍射仪（XRD）等对改性硅藻土进行表征,此外,探讨了吸附时间、pH以及温度等对改性硅藻土除磷性能的影响。结果显示：（1）经改性后,硅藻土中Fe元素的含量有所增加,杂质含量则有所降低;微孔明显增多,孔径增大,表面负载一定量的颗粒物,粗糙度增大,比表面积较原硅藻土增大6倍。（2）在水体除磷应用中,当吸附时间达到20min时,吸附趋向平衡;在酸性条件下改性硅藻土的除磷效果好于碱性条件下的除磷效果;在25℃下改性硅藻土对磷的吸附能力较其他温度下强;（3）Langmuir和Freundlich等温吸附方程都能较好地描述硅藻土对磷的等温吸附特征,用Freundlich吸附等温方程来描述改性硅藻土对水中磷的吸附更为准确。     

二氧化钛改性油页岩渣对水溶液中亚甲基蓝和六价铬的吸附

以油页岩渣及其二氧化钛改性材料为吸附剂,探究它们去除水溶液中亚甲基蓝和六价铬的能力.通过实验,控制溶液的pH值、温度、初始浓度和接触时间,观察吸附效果变化特征,研究其动力学和热力学性能.实验表明,改性油页岩渣吸附亚甲基蓝和六价铬的吸附率是未改性的2—3倍,且改性油页岩渣对亚甲基蓝的吸附率可达97%,对六价铬的吸附率不到25%.吸附亚甲基蓝时,pH值越大,吸附效果越好;而吸附六价铬时,最适pH值为4.改性油页岩渣吸附亚甲基蓝实验符合准二阶动力学方程,计算得反应活化能为13.29 kJ.mol-1,表明此过程主要是物理吸附.在热力学方面,由范特霍夫方程计算得ΔG〈0、ΔH〉0,表明此过程自发吸热,可见此过程还伴有化学吸附.Langmuir和Freundlich等温模型拟合结果表明,Langmuir模型数据拟合甚佳,R2=0.9999,说明改性油页岩渣吸附亚甲基蓝是单分子层吸附.二氧化钛改性油页岩渣经7次回收利用后,对亚甲基蓝的吸附效果仅减少约1.5%.     

荔枝皮吸附孔雀绿的性能和机理

采用批量试验方法研究了荔枝皮对水中孔雀绿染料吸附的影响因素(吸附剂剂量、pH值和接触时间)、吸附等温线、吸附动力学和吸附热力学等,并探讨了其吸附机理。结果表明,荔枝皮和改性荔枝皮对孔雀绿的最佳吸附剂用量分别为4和2 g·L-1,最适pH值均为7.0,吸附平衡时间均为120 min;吸附过程均能用Langmuir和Freundlich等温线模型进行很好的描述,且均符合假二次动力学模型。荔枝皮和改性荔枝皮对孔雀绿的最大吸附量分别为72.46和169.49 mg·g-1。此外,吸附热力学试验结果表明,荔枝皮和改性荔枝皮对孔雀绿的吸附均属于自发吸热过程。     

磷酸改性生物炭-LDHs(Mg-Al-NO3)复合材料对双酚A的吸附

本研究选取油菜秸秆为原料,在600℃下热解得到生物炭和磷酸改性生物炭,并用共沉淀法制备3种改性生物炭-LDHs(Mg-Al-NO_3)复合材料.采用批量吸附法研究不同pH、吸附时间和不同生物炭/LDHs配比条件下复合材料对双酚A的吸附特性,借助XRD、FTIR和BET等测试手段探究了复合材料吸附双酚A的机制.结果表明,改性生物炭-LDHs(Mg-Al-NO_3)复合材料吸附双酚A的吸附平衡时间为4 h,符合准二级动力学方程(R~20.99);复合材料对双酚A的吸附效果稍逊于改性生物炭,改性生物炭在复合材料中所占比重越大,吸附效果越好.当pH值在5.0—9.0范围内变化时,改性生物炭-LDHs(Mg-Al-NO_3)复合材料对双酚A的吸附量呈下降趋势,且在pH=9.0时达到最小值.等温吸附模型数据表明,复合材料用Freundlich等温吸附模型效果更好.通过XRD、BET、FTIR测试研究发现,由于LDHs占据了生物炭表面的活性位点,致使生物炭与双酚A之间的相互作用减弱,降低了复合物的吸附能力.本研究结果初步阐释了改性生物炭-LDHs(Mg-Al-NO_3)复合材料吸附双酚A的机理,为生物炭-LDHs复合材料处理水体中有机污染物的应用提供了借鉴和参考.     

松香基季铵盐表面活性剂改性沸石对水中刚果红的吸附性能

以松香基季铵盐阳离子表面活性剂(N,N,N-三甲基-N-松香基氯化铵,TAAC)对天然沸石进行改性得到TAAC改性沸石并进行红外光谱、扫描电镜和X射线粉末衍射等手段表征.考察了TAAC改性沸石对水中刚果红的吸附性能的影响因素,如粒径、改性剂投加量、温度、pH值等,结果表明这一改性能显著地提高沸石对刚果红的吸附量;在pH值4.0—10.0范围内,CR的吸附量随着pH值增加而下降;反应温度从20℃上升至40℃,TAAC改性沸石对CR的吸附容量有所下降.TAAC.改性沸石对水中刚果红的吸附动力学过程符合准二级动力学模型.Langmuir等温吸附模型可以较好的描述TAAC改性沸石对水中刚果红的吸附过程,其最大吸附容量为78mg·g-1(pH6.0,T=20℃).热力学分析表明,TAAC改性沸石对水中刚果红的吸附是自发和放热的过程,是化学吸附和物理吸附共同作用的过程,其吸附机制主要为静电吸引、氢键和芳香基的疏水作用.TAAC改性沸石吸附刚果红后可通过NaOH再生,且随着NaOH浓度的增加到0.1mol·L~(-1),其解吸率明显增大.     

凹凸棒土负载铁盐吸附剂的制备及其对As(Ⅴ)的吸附性能

研究凹凸棒土负载铁盐吸附剂的制备及其对As(Ⅴ)的吸附性能.考察了pH、凹凸棒土热改性温度、粒度、铁盐浓度等因素对吸附As(Ⅴ)性能的影响.结果表明,热改性温度为600℃的凹凸棒土负载铁盐吸附剂吸附As(Ⅴ)效果比200℃和400℃都好,其对As(Ⅴ)的吸附行为符合Freundlich模型.当pH值6.0时,600℃热改性200—400目的凹凸棒土负载0.5 mol·L-1Fe(NO3)3吸附剂的最大吸附量为1.1669 mg·g-1,重复使用时性能稳定,具有处理含As(Ⅴ)废水的应用前景.     

Recovery of molybdenum from fly ash by gibbsite

The effectiveness of gibbsite (GB), an amorphous aluminum oxide, for the recovery of Mo(VI) from eluates of fly ash of two coal-fired thermal power stations and of roof tile waste was investigated. Upon the qualitative analysis of an eluate of fly ash, 16 elements were detected. Greater amounts of these elements were eluted under acidic conditions (pH 2) than from the neutral or basic eluate of fly ash. GB was used for the adsorption of Mo(VI). Equilibrium adsorption was reached within 1?min. Optimal solution acidity for the adsorption of Mo(VI) onto GB400 (calcined at 400°C) was pH 2. The main adsorption mechanism was ion exchange with a number of hydroxyl groups of GB400. For repeated ad- and desorption of Mo(VI), GB400 could be used at least four times and the recovery percentage of Mo(VI) with sodium hydroxide solution as eluent surpassed 90%. Our results showed that GB400 was very effective for the recovery of Mo(VI) from fly ash.     

A contribution to the study of phosphate sorption by three Greek fly ashes

Three fly ashes from Greece, produced from lignite burning, proved efficient in removing phosphate from solution. Maximum amounts of phosphate removed ranged from 0.064 to 0.099 mmol PO³ ₄ ^– per g of material. Fly ashes that contained higher amounts of calcite and anhydrite seemed to be better sinks for phosphate. From the various adsorption isotherm equations tested, the Langmuir equation described phosphate sorption satisfactorily. Although, the exact mechanism of phosphate sorption could not be revealed, it is believed that it involved an adsorption and/or precipitation process.     

Use of fly ash agglomerates for removal of arsenic

The aim of this work is to investigate the application of fly ash adsorbent for removal of arsenite ions from dilute solution (100–1,000 ppm). Experiments were carried out using material from the “Turów” (Poland) brown-coal-burning power plant, which was wetted, then mixed and tumbled in a granulator to form spherical agglomerates. Measurements of arsenic adsorption from aqueous solution were carried out at room temperature and natural pH of fly ash agglomerates, in either a shaken flask or circulating column, to compare two different methods of contacting solution with adsorbent. Adsorption isotherms of arsenic were determined for agglomerated material using the Freundlich equation. Kinetic studies indicated that sorption follows a pseudo-second-order model. Preferable method to carry out the process is continuous circulation of arsenite solution through a column.     

Assessment of contamination by percolation of septic tank effluent through natural and amended soils

Fly ash has been found to be a potential material for the treatment of municipal and industrial wastewater, and may be useful in the treatment of septic tank effluent. Laboratory columns (30 cm) were used to determine the sorption capacity and hydraulic properties of lagoon fly ash, loamy sand, sand, and sand amended by lagoon fly ash (30 and 60%) and red mud gypsum (20%). The removal of chemical oxygen demand (COD) was high in all column effluents (71-93%). Extent of nitrification was high in Spearwood sand, Merribrook loamy sand and 20% red mud gypsum amended Spearwood sand. However, actual removal of nitrogen (N) was high in columns containing lagoon fly ash. Unamended Spearwood sand possessed only minimal capacity for P sorption. Merribrook loamy sand and red mud gypsum amended sand affected complete P removal throughout the study period of 12 weeks. Significant P leakage occurred from lagoon fly ash amended sand columns following 6-10 weeks of operation. Neither lagoon fly ash nor red mud gypsum caused any studied heavy metal contamination including manganese (Mn), lead (Pb), zinc (Zn), cadmium (Cd) and chromium (Cr) of effluent. It can be concluded that Merribrook loamy sand is better natural soil than Spearwood sand as a filter medium. The addition of lagoon fly ash enhanced the removal of P in Spearwood sand but the efficiency was lower than with red mud gypsum amendment.     

Assessment of Contamination By Percolation Of Septic Tank Effluent Through Natural and Amended Soils

Fly ash has been found to be a potential material for the treatment of municipal and industrial wastewater, and may be useful in the treatment of septic tank effluent. Laboratory columns (30 cm) were used to determine the sorption capacity and hydraulic properties of lagoon fly ash, loamy sand, sand, and sand amended by lagoon fly ash (30 and 60%) and red mud gypsum (20%). The removal of chemical oxygen demand (COD) was high in all column effluents (71–93%). Extent of nitrification was high in Spearwood sand, Merribrook loamy sand and 20% red mud gypsum amended Spearwood sand. However, actual removal of nitrogen (N) was high in columns containing lagoon fly ash. Unamended Spearwood sand possessed only minimal capacity for P sorption. Merribrook loamy sand and red mud gypsum amended sand affected complete P removal throughout the study period of 12 weeks. Significant P leakage occurred from lagoon fly ash amended sand columns following 6–10 weeks of operation. Neither lagoon fly ash nor red mud gypsum caused any studied heavy metal contamination including manganese (Mn), lead (Pb), zinc (Zn), cadmium (Cd) and chromium (Cr) of effluent. It can be concluded that Merribrook loamy sand is better natural soil than Spearwood sand as a filter medium. The addition of lagoon fly ash enhanced the removal of P in Spearwood sand but the efficiency was lower than with red mud gypsum amendment.     

Utilization of fly ash in adsorption of heavy metals from wastewater

The aim of this study was to assess the toxicity reduction of wastewaster after treatment with fly ash. Fly ash is a waste material which is formed as a result of coal burning in power plants, but has the potential to adsorb heavy metal ions. The present study examined the adsorption capacity of fly ash to adsorb Pb²⁺, Cu²⁺, and Zn²⁺ from waste water under different conditions of contact time, pH, and temperature. Uptake of metal ions by fly ash generally rose with increasing pH. At lower temperatures the uptake of heavy metal adsorption were enhanced. Significant reduction in Pb²⁺ (79%), Cu²⁺ (53%), and Zn²⁺ (80%) content was found after treatment with fly ash of waste water treatment. Using the microtox test toxicity of the effluent was reduced by 75% due to removal of Pb²⁺ ion by the fly ash. Data indicated that fly ash generated by power plants may be used beneficially to remove metals from waste water.     

Leaching of arsenic from coal fly ashes 2. Arsenic pre‐leaching with sodium gluconate solution

The present study deals with the development of an efficient and reliable process for safe disposal of coal fly ash to remove arsenic that has been found to be the most easily leachable and hazardous heavy metal in coal fly ash. Pre‐leaching of fly ash prior to disposal by a natural chelating agent, sodium gluconate (SG), was proposed and studied. Several operational factors influencing arsenic leachability, such as concentration of SG solution, liquid to solid ratio, pH, length of leaching time and leaching temperature were examined. Arsenic was found to leach out substantially with SG, but almost no further release was observed from the ash pre‐leached by SG. After the pre‐leaching treatment, the desirable high buffering capacity of the ash was well sustained. SG solution was effectively regenerated by activated alumina adsorption so that it could be successfully reused for multiple leaching/adsorption cycles.     

Use of zeolitized coal fly ash in the simultaneous removal of ammonium and phosphate from aqueous solution

Discharge of wastewater containing nitrogen and phosphate can cause eutrophication. Therefore, the development of an efficient material for the immobilization of the nutrients is important. In this study, a low calcium fly ash and high calcium fly ash were converted into zeolite using the hydrothermal method. The removal of ammonium and phosphate that coexist in aqueous solution by the synthesized zeolites were studied. The results showed that zeolitized fly ash could efficiently eliminate ammonium and phosphate at the same time. Saturation of zeolite with Ca²⁺ rather than Na⁺ favored the removal of both ammonium and phosphate because the cation exchange reaction by the NH₄ ⁺ resulted in the release of Ca²⁺ into the solution and precipitation of Ca²⁺ with PO₄ ^3? followed. An increase in the temperature elevated the immobilization of phosphate whereas it abated the removal of ammonium. Nearly 60% removal efficiency for ammonium was achieved in the neutral pH range from 5.5 to 10.5, while the increase or decrease in pH out of the neutral range lowered the adsorption. In contrast, the removal of phosphate approached 100% at a pH lower than 5.0 or higher than 9.0, and less phosphate was immobilized at neutral pH. However, there was still a narrow pH range from 9.0 to 10.5 favoring the removal of both ammonium and phosphate. It was concluded that the removal of ammonium was caused by cation exchange; the contribution of NH₃ volatilization to immobilization at alkaline conditions (up to pH level of 11.4) was limited. With respect to phosphate immobilization, the mechanism was mainly the formation of precipitate as Ca₃(PO₄)₂ within the basic pH range or as FePO₄ and AlPO₄ within acidic pH range.     

Characteristics of the stabilized/solidified municipal solid wastes incineration fly ash and the leaching behavior of Cr and Pb

Fly ash is a hazardous byproduct of municipal solid wastes incineration (MSWI). An alkali activated blast furnace slag-based cementitious material was used to stabilize/solidify the fly ash at experimental level. The characteristics of the stabilized/solidified fly ash, including metal leachability, mineralogical characteristics and the distributions of metals in matrices, were tested by toxic characteristic leaching procedure (TCLP), X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectrometer (SEM-EDS) respectively. Continuous acid extraction was utilized to extract metal ions and characterize their leaching behavior. The stabilization/solidification procedure for MSWI fly ash demonstrates a strong fixing capacity for the metals by the formation of C-S-H phase, hydrated calcium aluminosilicate and ettringite. The stabilized/solidified fly ash shows a dense and homogeneous microstructure. Cr is mainly solidified in hydrated calcium aluminosilicate, C-S-H and ettringite phase through physical encapsulation, precipitation, adsorption or substitution mechanisms, and Pb is mainly solidified in C-S-H phase and absorbed in the Si-O structure.     

Effects of fly ash, Pseudomonas striata and Rhizobium on the reproduction of nematode Meloidogyne incognita and on the growth and transpiration of pea

Glasshouse experiments were conducted twice to assess the ash amendments (0, 20, and 40% with soil), a phosphate solubilizing microorganism Pseudomonas striata and a root-nodule bacterium Rhizobium sp on the reproduction of root-knot nematode Meloidogyne incognita and on the growth and transpiration of pea. Amendments of fly ash with soil had no effect on transpiration. However, M. incognita reduced the rate of transpiration from 1st week onward after inoculation while inoculation of Rhizobium sp and P. striata increased transpiration from 1st week onward after their inoculation both in nematode inoculated and uninoculated plants. Increase in transpiration was greater when both organisms were inoculated together. Addition of 20 and 40% fly ash with soil was beneficial for plant growth both in nematode inoculated and uninoculated plants. Inoculation of above organisms also increases plant growth of nematode inoculated and uninoculated plants in different fly ash soil mixture but increase in growth was greater when both organisms were inoculated together. Use of 20% fly ash increased galling and nematode multiplication over plants grown in without fly ash while 40% fly ash had adverse effect on galling and nematode multiplication. Rhizobium sp had greater adverse effect on galling and nematode multiplication than P. striata. Use of both organisms together had greater adverse effect on galling and nematode multiplication than caused by either of them alone. Highest reduction in galling and nematode multiplication was observed when both organisms were used in 40% fly ash amended soil. However, highest transpiration was observed in plants without nematodes and inoculated with both organisms together both in with or without fly ash amended soil.