高氧化铁粉煤灰影响聚羧酸减水剂吸附特性的机理

采用净浆流动度、ζ电位、总有机碳(TOC)、红外光谱等实验,研究粉煤灰中氧化铁含量对不同结构聚羧酸减水剂吸附性能的影响,探讨氧化铁影响聚羧酸减水剂对水泥分散性能的机理,并提出了相应改进方法.结果表明:粉煤灰中氧化铁含量对掺不同结构聚羧酸减水剂的水泥净浆流动度均有很大影响,当氧化铁质量为粉煤灰总质量的18%时相应浆体基本失去流动性;加入硫化钠能使氧化铁与聚羧酸减水剂的吸附性能降低,浆体流动度有所改善.高氧化铁粉煤灰对聚羧酸减水剂的吸附性很强,与普通Ⅱ级粉煤灰相比,外加剂溶液中有机碳的含量要减少1/3.电泳实验表明:氧化铁的含量越多,体系ζ电位绝对值越小,分散稳定性越差.红外光谱表明:硫化钠的加入降低了高氧化铁粉煤灰对聚羧酸减水剂的吸附.     

飞灰残炭对零价汞蒸汽的吸附特征

研究了飞灰未燃残炭对零价汞蒸气的吸附特性.在低汞平衡浓度(<250μg/m³)条件下,残炭汞吸附能力与商业活性炭差距不显著,而商业活性炭在高汞浓度端的汞吸附量则明显升高.残炭汞吸附特性与其来源相关性较强.残炭的吸附等温线类似于Ⅱ型等温线,而商业活性炭则明显具有Ⅲ型吸附等温线特征.静态吸附实验结果表明炭质吸附剂表面存在活性点位,从而使其吸附过程得到加强.因为残炭制造成本相对低廉,所以在烟气汞污染物脱除方面更具有价格优势.     

粉煤灰活性炭吸附含Cr废水试验研究

利用电厂粉煤灰可制备出具有较高吸附性能的粉煤灰活性炭.研究了不同pH值、投加量、时间、温度、溶液浓度、脱附方法条件下粉煤灰活性炭对Cr(Ⅵ)吸附性能的影响.结果表明,吸附反应为吸热过程;当粉煤灰活性炭掺入比为1∶250、pH值为2、25℃恒温振荡120 min时,粉煤灰活性炭最大吸附容量能达到4.67 mg/g;Cr饱和的粉煤灰活性炭,用0.05 mol/L浓度的NaOH脱附效果最佳,脱附率为129%.废弃印刷线路板湿式处理工艺中产生的废水,含Cr(Ⅵ)0.62 mg/L,在上述条件下,Cr(Ⅵ)去除率达95.16%;若在自然pH条件下,Cr(Ⅵ)的去除率能达到91.94%,均符合污水综合排放标准.粉煤灰活性炭用于含金属废水的处理有着广阔的应用前景.     

Adsorption of Methylene Blue and Phenol by Wood Waste Derived Activated Carbon

The phosphoric acid activated carbon (PAC) was derived from waste wooden pallets by a two-step chemical activation technique, carbonization and phosphoric acid activation in sequence. A widely used commercial activated carbon, Calgon Filtrasorb 400 (F400), was studied in parallel for comparison. The physical properties and surface chemistry of the activated carbons were characterized using BET-N2 adsorption, elemental analysis, Boehm’s titration, Fourier transform infrared spectroscopy, and x-ray photoelectron spectroscopy. PAC possessed physical properties (surface area and pore volume) that were comparable to those of F400, but displayed distinct surface chemistry in terms of pHPZC, surface acidity and basicity, and surface functional groups. Batch studies were conducted to evaluate the methylene blue (MB) and phenol adsorption capacity of PAC and F400 and their dependence on pH, contact time, and initial adsorbate concentration. Experimental results showed that the solution pH slightly influenced the adsorption of MB and phenol on F400, whereas it had no effect on their adsorption on PAC. Equilibrium adsorption data were fitted with an Langmuir isotherm equation. In comparison with F400, PAC showed a higher adsorption capacity for MB but lower for phenol. Given the comparable physical properties of PAC and F400 and the polar nature of MB and phenol, surface chemistry of the two carbons appeared to determine the adsorption mechanism and capacity. The strongly negative surface of PAC, due to phosphoric acid activation, facilitated the adsorption of positively charged MB, whereas the presence of oxygen-containing functional groups on PAC inhibited phenol adsorption.     

Time Effect on Shear Strength and Permeability of Fly Ash

This paper investigates the effect of time on the shear strength and the permeability of fly ash, a major solid by-product of thermoelectric power plants. Direct shear tests using Mikasa's apparatus, conventional permeability tests, and consolidation tests were conducted on two silt-size fly ashes, with low free lime contents, obtained from two different power plants. The results show that the immediate settling of both fly ashes takes place in a short period of time during consolidation and does not change with time. The rate of increase in shear strength with time is different depending on the pozzolanic reactions taking place for the two ashes. The permeability tests under constant stresses of 49 and 98 kPa for 12 days show that the coefficient of permeability for the tested ashes is between 10?6 and 10?7 m∕s. During this period the coefficient of permeability either remains constant (for the case of the ash with a lower free lime content) or is slightly reduced (for the ash with a higher free lime content). The practical implications and the limitations of using low lime silt-size fly ash in vertical drains in the stabilization of soft ground are also discussed.     

Thermal Removal of Mercury in Spent Powdered Activated Carbon from TOXECON Process

This research developed and demonstrated a technology to liberate Hg adsorbed onto powdered activated carbon (PAC) by the TOXECON process using pilot-scale high temperature air slide (HTAS) and bench-scale thermogravimetric analyzer (TGA). The HTAS removed 65, 83, and 92% of Hg captured with PAC when ran at 900°F, 1,000°F, and 1,200°F, respectively, while the TGA removed 46 and 100% of Hg at 800°F and 900°F, respectively. However, addition of CuO–Fe2O3 mixture and CuCl catalysts enhanced Hg removal and PAC regeneration at lower temperatures. CuO–Fe2O3 mixture performed better than CuCl in PAC regeneration. Scanning electron microscopy images and energy dispersive X-ray analysis show no change in PAC particle aggregation or chemical composition. Thermally treated sorbents had higher surface area and pore volume than the untreated samples indicating regeneration. The optimum temperature for PAC regeneration in the HTAS was 1,000°F. At this temperature, the regenerated sorbent had sufficient adsorption capacity similar to its virgin counterpart at 33.9% loss on ignition. Consequently, the regenerated PAC may be recycled back into the system by blending it with virgin PAC.     

Adsorption of Negatively Charged Azo Dyes onto Surfactant-Modified Sepiolite

The adsorption of reactive dyes on sepiolite has been investigated in a series of batch adsorption experiments. Three reactive dyes (Everzol Black B, Everzol Red 3BS, Everzol Yellow 3RS H/C) were used in bottle adsorption studies. While no significant adsorption capacity was obtained for natural sepiolite, high-adsorptive capacities were observed upon using sepiolite modified with quaternary amines. The electrokinetic measurements along with calculations using the cross-sectional area reveal that the quaternary amines adsorb close to bilayer coverage. A mechanism involving electrostatic attraction of the anionic groups of dye molecules onto oppositely charged amine-modified sepiolite surface is proposed to be responsible for the uptake of dyes. The adsorption data were fitted to the Langmuir isotherm. It is found that the modified sepiolite yields adsorption capacities (qe) of 169, 120, and 108 mg/g for Yellow, Black, and Red, respectively. These results are comparable to the adsorption capacity of the same dyes onto activated carbon.     

改性粉煤灰吸附稀土氨氮废水的机理研究

分别用氢氧化钠、硫酸和稀土镧对粉煤灰进行改性,然后用对比法研究了粉煤灰改性前后对稀土氨氮废水的吸附行为。结果表明,碱改性粉煤灰对稀土氨氮废水的吸附效果最佳。在室温下,pH为11.7,投加量5g,吸附达到平衡时,碱改性粉煤灰的吸附效率可以达到81.56%。碱改性粉煤灰吸附稀土氨氮废水的吸附过程符合Elovich吸附方程,属于良性吸附,吸附容量达到1.72mg/g。     

Extraction of vanadium from athabasca tar sands fly ash

The production of refinery grade oil from the Alberta tar sands deposits as currently practiced by Suncor (formally Great Canadian Oil Sands Ltd.—GCOS) generates a substantial amount of petroleum coke fly ash which contains appreciable amounts of valuable metals such as vanadium, nickel and titanium. Although the recovery of vanadium from petroleum ash is a well established commercial practice, it is shown in the present work that such processes are not suitable for recovery of vanadium from the GCOS fly ash. The fact that the GCOS fly ash behaves so differently when compared to other petroleum fly ash is attributed to its high silicon and aluminum contents which tie up the metal values in a silica-alumina matrix. Results of experiments carried out in this investigation indicate that such matrices can be broken down by application of a sodium chloride/water roast of the carbon-free fly ash. Based on results from a series of preliminary studies, a detailed investigation was undertaken in order to define optimum conditions for a vanadium extraction process. The process developed involves a high temperature (875 to 950 °C) roasting of the fly ash in the presence of sodium chloride and water vapor carried out in a rotary screw kiln, followed by dilute sodium hydroxide atmosphereic leaching (98 °C) to solublize about 85 pet of the vanadium originally present in the fly ash. It was found that the salt roasting operation, besides enhancing vanadium recovery, also inhibits silicon dissolution during the subsequent leaching step. The salt roasting treatment is found to improve vanadium recovery significantly when the fly ash is fully oxidized. This is easily achieved by burning off the carbon present in the “as received” fly ash under excess air. The basic leaching used in the new process selectively dissolves vanadium from the roasted ash, leaving nickel and titanium untouched.     

垃圾焚烧飞灰预处理后水泥固化实验研究

为实现焚烧飞灰的无害化和资源化,采用对飞灰进行预处理后再与水泥混合固化的方法来处理飞灰,并比较了不同方式的处理效果:(1)用去离子水润湿飞灰再厌氧堆放24h后用水泥固化;(2)用绿矾溶液处理后再用水泥固化;(3)飞灰直接与水泥混合固化。研究3种方式所得水泥固化砌块试件强度的发展和控制重金属浸出的效果与直接固化物的对比,研究结果表明:在飞灰与水泥的质量比相同的条件下,采用先用绿矾处理飞灰再进行固化的处理方式,不但稳定重金属的效果好,而且试件强度最高,有望加以应用。     

粉煤灰颗粒HF酸表面改性处理

粉煤灰颗粒表面由于在收集、贮存过程中的物理、化学吸附，使颗粒与颗粒相互聚集。分散性差。作复合材料增强相时，颗粒的分散性直接影响复合材料的性能。经HF酸处理后，HF酸与粉煤灰表面上的OH^-发生反应，降低了表面的极性，粉煤灰颗粒的分散性提高。SEM结果表明，随着HF酸浓度的增加，表面侵蚀加剧。XRD分析结果表明，莫来石、SiO2、Fe2O3的特征峰强度都随着HF酸浓度的增加而增加，这是因为低浓度HF酸只溶解粉煤灰中的玻璃相，而主要的莫来石、石英、磁铁矿等晶体相是不能溶解的，结果使玻璃相含量减少，而晶体相含量相对增加，所以特征峰相对强度增加。     

Methylene Blue Sorption onto Oxygenated Pyrolytic Tire Char: Equilibrium and Kinetic Studies

A novel method is presented for pyrolyzing and activating waste tires for adsorptive removal of aqueous contaminants. The adsorption characteristics of a cationic dye (methylene blue, MB) by pyrolytic tire char were evaluated. Mechanistic insights into the adsorption of MB onto char made from pyrolyzed tires are discussed on the basis of equilibrium and kinetic studies. A comparative evaluation of the performance of unoxygenated, pyrolyzed chars (NoPPO) and oxygenated chars (P550250) is reported. Despite having similar surface areas between the oxygenated and unxoygenated chars, the adsorption capacity of the former was much higher than that of the latter. However, adsorption of MB is thermodynamically unfavorable (ΔG>0) although oxygenation lowers the free energy of adsorption. MB sorption onto P550250 is inhibited by an external film, which was not observed in the case of NoPPO. An increase in the solution temperature was found to reduce the adsorption rates of MB onto P550250 but increase the sorption capacity of NoPPO. Overall, oxygenation was found to improve the sorption of MB onto pyrolytic chars.     

Rare earth elements of fly ash from Wyoming's Powder River Basin coal

The advancement and increasing interests in green energy production and environmental protection technologies have spurred the demand for rare earth elements.On the other hand,the U.S.has to rely 100% on import of these materials as the industry was crashed because of the environmental issues associated with mining and processing,and more importantly lack competitiveness.As rare earth elements have many applications in defense and national security sectors,some of the elements were listed as strategic materials or critical materials because of the uncertainties in supply and prices.Therefore,it has become imperative in searching for alternative resources for supplying rare earth elements including unconventional resources.With the strong incentive,coal fly ash is identified as one of the candidates among them.In this study,we present rare earth element data for the 42 ash samples(all derived from Powder River Basin coal) that we collected from seven states(UT,WY,10,WI,ND,CO,and MI) representing 158 million tons of fly ash.The results indicate scattered distributions of rare earth elements with concentration ranging from 156 to 590 ppm although all the ash samples originated from the same coal basin(Powder River Basin).The rare earth element resource in these ashes is estimated between 74000 and 106000 t.The ash samples were also characterized by elemental analysis,XRD,SEM-EDS and BET surface area.The characterizations of the ashes were discussed as they might have implications in the subsequent rare earth element extraction processes.In summary,fly ash may represent a potential resource for rare earth element production.     

Adsorption of Polycyclic Aromatic Hydrocarbons in Aged Harbor Sediments

Polycyclic aromatic hydrocarbons (PAHs) are a group of hydrophobic organic contaminants which have low aqueous solubilities and are common pollutants in harbor sediments. Adsorption and desorption isotherms for PAHs are conducted to study the abiotic sorption of PAHs in uncontaminated harbor sediments in contact with the natural overlaying water. Representative 2-, 3-, and 4-ring PAHs are used to obtain PAH adsorption/desorption data. Linear adsorption onto sediment is obtained for the following PAHs: Naphthalene and 2-methyl naphthalene (2 ring), acenaphthene, anthracene, and phenanthrene (3 ring), and fluoranthene and pyrene (4 ring). Linear adsorption is followed by a significant hysteresis in desorption from sediment, due to strong retention by the aged sediment organic carbon. Sediment organic carbon–water partition coefficients (log?Koc) for the seven PAHs range from 2.49 to 4.63. Based on the sorption data for these representative PAHs, sediment organic carbon–water partition coefficients may be predicted for other PAH compounds, particularly the less soluble and the more hydrophobic PAHs (5 or more rings).     

Investigating Role of Growing Adsorbent Bed in a Dead-End PAC/UF Process

A two-stage mathematical model was developed to describe adsorbate removal in a dead-end powdered activated carbon/ultrafiltration (PAC/UF) membrane process. Para-nitrophenol (PNP) was used as the model organic compound. The first stage accounted for adsorbate removal during transport from the initial PAC contact with the PNP solution to the membrane system, and the second stage accounted for additional PNP removal due to the retention of the PAC in a growing bed on the membrane surface. The PAC adsorptive capacity was described using the Langmuir isotherm, whose parameters were estimated from isotherm experiments. Transport of the PNP through the PAC particle was described using the homogeneous surface diffusion model and the surface diffusivity was estimated from batch experiments. The two stage model predicted the effluent concentrations from the PAC/UF process during the early stages of the experiments, but model improvements are required to more accurately predict the latter stages. A batch model can be used to describe the effluent PNP concentration from the PAC/UF process if dispersion is neglected.     

Glycine functionalized activated carbon derived from navel orange peel for enhancement recovery of Gd(Ⅲ)

Glycine functionalized activated carbon adsorption material (NOPAC-GLY-X) was successfully prepared by one-step thermal decomposition using agricultural waste navel orange peel as a precursor. Through batch adsorption experiments, it is found that the adsorption performance of Gd(III) on activated carbon can be significantly enhanced by glycine modification. The adsorption isotherms of the NOPACs conform to the Langmuir isotherm model, and the maximum adsorption capacity of the activated carbon sample NOPAC-Gly-60 is approximately 48.5 mg/g. The Gd(III) adsorption capacity of navel orange peel activated carbon can be doubled after glycine modification, and the adsorption efficiency of gadolinium can reach 99% at pH = 7. The physicochemical properties of the prepared adsorbents were characterized by Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), elemental analysis (EA), and X-ray photoelectron spectroscopy (XPS). The characterization test shows that the specific surface area of the sample increases from 1121 to 1523 m²/g, and the ratio of (N + O)/C increases from 10.8% to 30.0% by the glycine modification. After five cycles of adsorption–desorption, the adsorption capacity can still be maintained at 88% of the initial capacity. NOPAC-GLY-60 has excellent adsorption selectivity for Gd(III). With the obvious advantages of simple synthesis steps and low cost, the activated carbon modification method adopted in this study has great application value in the field of rare earth adsorption and recovery.     

Adsorption of Perfluorinated Compounds onto Activated Carbon and Activated Sludge

The adsorption of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) onto powdered activated carbon (PAC) was investigated in the presence and absence of effluent organic matter (EfOM) at an environmentally relevant concentration range (0.1–500??μg/L). Adsorption of PFOS and PFOA to PAC fitted the Freundlich model well (r2>0.98), and adsorption capacity of PFOS (KF = 17.48) and PFOA (KF = 10.03) in the absence of EfOM was more than one order of magnitude higher than that in the presence of EfOM (KF = 0.66 for PFOS, KF = 0.20 for PFOA), indicating that EfOM greatly reduces the adsorption capacity of PAC. Moreover, EfOM was characterized by ultrafiltration, and fractions of nominal molecular weights were obtained to investigate their effect on the PFOS and PFOA adsorption. The fraction of <1??kDa had greater effect on adsorption than the fraction of >30??kDa, indicating that the similar molecular size of target compounds was the major contributor to adsorption competition. Additionally, biosorption of PFOS and PFOA to activated sludge fitted the linear isotherm (r2>0.9) within a concentration range of 50–400??μg/L. On the basis of our data, the estimated partition coefficient, Kd, was 729??L/kg for PFOS and 154??L/kg for PFOA, respectively, suggesting that PFOS and especially PFOA have a low tendency to partition onto sludge.     

粉煤灰负载铈吸附剂的制备研究

研制了一种新颖的铈负载粉煤灰吸附剂.研究了在各种制备条件下制得的吸附剂对氟离子的去除效果.实验结果表明,在pH为8～10,接触时间为16h,焙烧温度为400℃,铈离子浓度为0.2g/L,改性酸浓度为6mol/L时制得的稀土粉煤灰吸附剂,在处理氟离子水溶液时,该吸附剂除氟能力达到了90%以上.并且对比了原状粉煤灰、酸改性粉煤灰和稀土粉煤灰去除氟离子的吸附效率和最佳pH值.     

粉煤灰处理含钼废水的效果及吸附机理研究

利用粉煤灰对模拟的含钼废水进行除钼吸附实验,分别研究了吸附过程中溶液pH值、吸附剂投加量对吸附效果的影响,并对吸附等温方程及动力学进行了探讨。结果表明,在吸附质钼初始浓度为10mg/L、pH=3.1条件下,粉煤灰对钼的吸附效果最好,除钼率为74.3%;对于50mL的含钼溶液,当吸附剂投加量为2.5g时除钼率达到最高值85.4%。粉煤灰对钼的吸附符合Langmuir吸附等温方程,以表面单分子层吸附为主;吸附过程符合二阶动力学模型,同时具有物理吸附和化学吸附的特征。     

Adsorption Characteristics of Oxide Coated Buoyant Media (ρs<1.0) for Storm Water Treatment. II: Equilibria and Kinetic Models

Divalent metal species adsorption onto a manganese oxide coated polymeric medium (MOPM) was evaluated through batch adsorption experiments using a flow-through batch reactor. In this paper, Part II, the batch equilibrium and kinetic data examined in Part I are modeled using a triple layer surface complexation model and a potential driving second order kinetic model. Surface complexation modeling using FITEQL-TLM generated intrinsic surface acidity constants for the MOPM of log?K?a1int = 3.196 and log?K?a2int = ?5.802. The intrinsic surface reaction constants for Pb(II), Cu(II), and Zn(II) were log?K?Pbint = ?1.91, log?K?Cuint = ?2.53, and log?K?Znint = ?4.45, respectively. A potential driving second order kinetic model was developed to predict sorption of the divalent metal ions onto the MOPM. The general adsorption kinetics for MOPM can be described as a fast reaction occurring within 30 min and a slower reaction continuing from 5 to 15 h. Kinetic results can be interpreted using assumptions of the potential driving second order model that the dominant control forces are the chemical potential of the MOPM activated surface sites and chemical potential of sorbate in the solution.