Capacity and mechanism of phenol adsorption on lignite

A raw lignitic coal from Soma, Turkey was investigated to determine its potential as an adsorbent for phenol removal from wastewaters. Kinetic batch tests demonstrated that phenol could be completely removed from solution given sufficient solids loading and reaction time. The adsorption capacity of 10 mg/g obtained with the lignite is low compared to those achievable with activated carbons (around 300 mg/g). However, when normalized for the surface area, the adsorption capacity was much larger for the lignite (1.3 mg/m²) than that generally observed with activated carbons (0.05–0.3 mg/m²). Hydrogen-bonding of the phenolic –OH with the oxygen sites on the lignite surface is the most likely mechanism for adsorption. Though water molecules also have affinity for the same oxygen sites, lateral benzene ring interactions make phenol adsorption energetically more favorable. Since phenol molecules adsorbed in this fashion would project their benzene rings into solution, formation of a second layer through the action of the dispersive π–π interactions between the benzene rings is very likely. Residual water quality with respect to major elements and heavy metals was within acceptable limits defined by the ASTM standards. Dissolution of organic matter from the lignite was also observed to be negligible.     

铁氧化物矿物对苯酚和溶解性有机质表面吸附的初步研究

文中以铁氧化物矿物对苯酚和溶解性有机质(DOM)的吸附研究为例开展生态矿物学研究。铁氧化物矿物的吸附作用存在多种机制,这些吸附机制发生作用的条件主要取决于溶液化学性质和吸附质的理化性质。批处理实验研究表明,苯酚吸附在酸性微酸性条件下不强,吸附等温线符合Langmuir方程,属于表面分子吸附模型;DOM的吸附强并发生吸附分异,配体交换、憎水键和范氏力等多种模式并存,在酸性中性条件下对DOM在针铁矿上的吸附起着重要贡献。本文实验条件下DOM吸附等温线近于线性,不能采用Langmuir方程拟合,可能原因是DOM浓度较低。矿物表面荷电性对吸附影响显著,例如,当矿物表面净电荷为零(pH=pHpzc)时,矿物表面水化膜减薄甚至消失,苯酚分子、憎水DOM分子或片断都会倾向于在矿物表面上吸附。由于苯酚吸附机制单一,其受到的影响很明显,所以苯酚在pH值7～8范围内出现吸附最大值;由于配体交换作用主要发生在酸性微酸性条件下,所以在本文pH值约7.5的实验条件下,尽管配体交换仍在发生作用,但它不是主要吸附机制,针铁矿对DOM吸附的主要贡献应是憎水键和范氏力作用,此外,DOM吸附等温方程近于线性还可能与此有关。显然,铁矿物表面作用在对有机质含量低而铁矿物含量高的红壤中污染物和DOM的固定与归宿控制中扮演着重要的角色。     

Linearized and non-linearized isotherm models comparative study on adsorption of aqueous phenol solution in soil

Use of native soil in adsorption of phenol from industrial wastewater has been one of the attractive option for dephenolation, especially in view of low cost and ease in accessibility, as well as scope for regeneration (or, at least reuse). However, an effective usage of the adsorbent necessitates a deeper understanding of the adsorption characteristics. Most of the study of adsorption characteristics are confined to analysis of mono- and bi- parametric isotherm models (and rarely, linearized multi-parametric isotherm models), due to the difficulties in solving higher parametric models, as well as fairly satisfying results by lower-parametric models. In the present study, adsorption batch studies were carried out using a naturally and widely available common soil of south India (namely, Adhanur soil), for removal of phenol from the aqueous solution, with an explicit objective of comparison of linear and non-linear regression methods for finding variation in isotherm coefficients and fitness of the models. Six linearized isotherm models (including four linearized Langmuir models) and three non-linear isotherm model were discussed in this paper, and their coefficients were estimated. Although all the studied isotherm models showed fairly good fit to the experimental data, but Redlich—Peterson isotherm was found to be the best representative for phenol-sorption on the used soil adsorbent. Besides, it was observed that to determine the isotherm parameters non-linear isotherm models were found to be the best representative of adsorption characteristics, than their linearized counter-parts.     

Evaluation of Jordanian faujasite tuff by comparison with other natural and synthetic zeolites

 The evaluation of the Jordanian faujasite tuff in wastewater treatment is investigated by comparison with synthetic faujasite (13X) and clinoptilolite-rich tuff. The material used (JORD-FAUJ) is concentrated by mineral processing techniques. It has a faujasite content of 57% and phillipsite content of 35%. Thorough characterization of the JORD-FAUJ revealed the high suitability of the product for use in column operation. It either compares closely or gives better thermal stability, attrition resistance, acid resistance, cation exchange capacity (CEC) and water absorption capacity, when compared with products already recommended in column operation. The study has also revealed that the JORD-FAUJ competes efficiently in ammonium removal with the synthetic faujasite 13X and clinoptilolite-rich tuff and gives similar performance. JORD-FAUJ gave a very high performance in removing Pb, Cr, Cu, Zn, and Ni from wastewater, equivalent to 83–100% of that of faujasite 13X and much higher than the clinoptilolite-rich tuff. Received: 13 April 2000 · Accepted: 1 August 2000     

Comparative study of the adsorption of organic ligands on aluminum oxide by titration calorimetry

Ligand adsorption on δ-Al₂O₃ at pH 8 was examined for a series of organic ligands (aromatic acids, monochlorophenols and aliphatic acids) including both monodentate and bidentate ligands. Adsorption isotherms for the aromatic acids exhibited saturation at high dissolved ligand concentrations; saturation was not observed (over the concentration range examined) for the chlorophenols. Small, though measurable, amounts of heat were evolved on reaction of the aromatic acids, the monochlorophenols and propionate (but not of the longer chain fatty acids) with the oxide surface; overall ligand adsorption reactions wereexothermic (ΔH_obs < O). For adsorption of (partially or fully) protonated ligands, the favorable ΔH_obs was due largely to the exothermic proton transfer reaction between phenolic hydroxyl groups of the ligands and hydroxide ions displaced from the oxide surface. The enthalpy corresponding to the ligand-exchange reaction of surface hydroxyl groups for the various ligands (as fully deprotonated species), ΔH_corr, appeared to be related to the ligand structure. The surface ligand-exchange reaction was more exothermic for the dicarboxylic acid phthalate than for the monocarboxylic acids benzoate or propionate or for salicylate and was endothermic for the chlorophenols.     

Physical and chemical activation of pyrolyzed oil shale residue for the adsorption of phenol from aqueous solutions

Batch kinetics and isotherm studies were carried out to evaluate the sorption of phenol by pyrolyzed and activated Jordanian oil-shale. The effects of contact time, initial sorbate concentration, sorbent concentration, temperature, pH and inorganic salts (NaCl and KCl), on the adsorption process by different sorbents were considered. Chemically activated oil shale, pretreated with ZnCl ₂, gave the highest uptake of phenol. The isotherm experimental data fit well to Freundlich and Redlich-Paterson models and to a less extent to the Langmuir model. The increase in the initial sorbate concentration resulted in an increase in the uptake. Three kinetics models, namely the Morris-Weber model, the Lagergren model, and the pseudo-second-order model (PSOM), were applied to represent the experimental results for pyrolyzed and ZnCl ₂-oil shale sorbents. Pyrolyzed oil shale was prepared using a fluidized bed reactor at 520 °C in the presence of nitrogen. Physical activation was carried out by treating the resulted pyrolyzed oil shale with CO ₂ at 830 °C, while chemical activation of oil shale was carried out using KOH and ZnCl ₂ as impregnating agents.     

煤层气─固界面作用与吸附模型

按照毛细管模型与单分子层作用模型, 推导了煤层气-固界面作用与煤层渗透性的关系;根据煤层气吸附实验资料, 运用非线性回归方法, 分别按Langmuir吸附理论和BET吸附理论计算了煤层气吸附规律。实例分析表明:煤层气-固界面作用的强弱与煤层介质的渗透率平方根或煤层介质的孔径大小成反比, 它揭示了低渗透煤层气解吸困难、开采难度较大的机理;BET吸附模型比Langmuir吸附模型能更好地描述煤层气的吸附规律。研究结果为煤层气开发工程提供了科学依据。     

岩爆与峰后岩石力学特性

峰后岩石特性是产生岩爆的根本原因;地质力学因素是产生岩爆的外部因素。从地下工程开挖过程中围岩部分的能量释放、集聚、转移入手,揭示了高地应力是产生岩爆的重要外因;岩爆产生的时空特点是在破坏后塑性软化阶段,并从非线性岩石力学理论角度,研究了此阶段岩爆条件。得出以下结论：一是块系结构岩体变形稳定性与块体几何特性、尺度大小,以及破坏后物理性质有关;二是判断岩体是否发生岩爆,可采用： 和 < 判据。     

煤层气与页岩气吸附差异性分析

查明页岩气与煤层气的吸附差异对指导其勘探开发具有重要意义。通过测试不同成熟度和有机质(TOC)的煤与页岩的等温吸附曲线,结果表明:TOC含量是影响页岩吸附的主要因素,成熟度相当的煤与页岩相比,煤的吸附量远远大于页岩,主要是由于成藏特征、物质组成和孔隙结构不同造成的;页岩吸附过程中出现的异常吸附可能有其他的吸附理论支撑。     

粗粒土与结构接触面特性的离散-连续耦合数值研究

三维变形体离散元法能够自动检索接触关系,并对具有不规则形状的粗粒土颗粒和结构物进行有限差分网格离散,因此,具有模拟离散-连续耦合问题的先天优势。采用随机模拟技术生成粗粒土三维数值试样,基于变形体离散元进行粗粒土与结构接触面特性的数值试验,研究了不同接触面粗糙程度的接触面力学特性,对比了粗粒土与结构物在单剪和直剪状态下的接触面力学特性,从宏观和细观两个层面分析了数值试验结果。结果表明,数值试验能较好地反映粗粒土与结构接触面的力学特性,其剪应力-相对剪切位移曲线与试验结果规律相似;接触面粗糙程度对接触面的强度和变形特性影响较大,其机制在于剪切对试样的扰动程度不同;直剪和单剪状态下试样剪应力-相对剪切位移均为双曲线,单剪试验的初始剪切刚度低于直剪试验,两种试验得到接触面抗剪强度指标比较接近。     

刚性桩和柔性桩荷载传递性状的比较

为了比较刚性桩和柔性桩的荷载传递规律,在温州地区选择了钻孔灌注桩和水泥搅拌桩进行静荷载试验。试验前在钻孔灌注桩桩身埋设了钢筋应力计,在水泥搅拌桩桩身埋设了振弦式应变计。在静荷载试验过程中同步检测传感器的变化情况,根据试验成果对两种不同类型桩进行对比分析,得出一些有益的结论,供工程设计施工人员参考。     

煤的吸附常数与最高试验压力关系的研究

研究煤的吸附性能时,意外地发现同一试验条件下获得煤的L angmuir等温吸附常数并非常数,是一变值,其变化是由试验采用的最高试验压力不同而引起。通过对中国主要煤田不同变质程度煤的等温吸附试验数据处理,证明煤的L angmuir等温吸附常V_L,p_L与最高试验压力分别呈正线性相关,并具有普遍性。为了确保煤的吸附常数之间的可比性以及对已有资料的正确利用,建立了将不同最高试验压力的等温吸附试验结果统一到同一最高试验压力的方法。     

天然锰钾矿氧化降解水体中苯酚机理研究

根据锰的溶出、氧气不参与反应、酸度是影响苯酚降解的主要因素等实验结果，推测天然锰钾矿与苯酚的作用机制。研究表明：反应8h，总有机碳去除率达88．7％；锰钾矿在硝酸存在时产生的氧自由基与苯酚发生氧化还原反应，使苯酚降解。根据检出的对苯醌、联苯二酚、2-羟基-苯并呋喃等中间物质推测出苯酚降解的反应途径。     

紫外光及日光下天然金红石光催化降解苯酚的研究

研究了山西代县天然金红石在紫外光和日光照射条件下对苯酚的光催化降解性能,考察了光照时间、pH值、苯酚初始浓度以及H2O2添加量对降解过程的影响。在紫外光照射下,酸性条件(pH=3.5)利于光催化降解,中性和碱性条件下降解效率较低;当初始浓度为60mg/L时,降解速率可达1.922mg/(L.h);H2O2作为电子捕获剂可提高苯酚降解速率,最佳投加量为2mL/L。在日光条件下,天然金红石对苯酚表现出良好的降解性能,照射7h后,降解率达87.68%,仅略低于P25型TiO2(99.72%),可在14h内完全降解。根据电子探针和X射线衍射分析结果,认为天然金红石晶格中的V、Fe等杂质可能是提高其可见光响应效果和光催化活性的主要原因。     

Radioactive removal by adsorption on Yesan clay and zeolite

The adsorption of Cs, Sr, Ni, and Co radioactive substitutes onto Yesan clay and zeolite was studied through batch and column tests using Cs, Sr, Ni, and Co as substitutes for radioactive isotopes. Adsorption values of 0.189–1.865 μg/g onto Yesan clay and 0.595–9.055 μg/g onto zeolite were observed, with the radioactive substitutes being almost 100 % adsorbed from the onset of column testing. Adsorption was achieved through ionic bonding. These materials demonstrated suitability for use as backfill or foundation materials for nuclear power plants, radioactive waste disposal facilities, and other radioactive facilities.     

土与结构界面位移特性静动力单剪试验研究

土与结构接触面是工程中经常遇到的,剪切试验是研究界面特性的主要方法之一。单剪试验既可以研究界面的特性,又可以考虑土体受力变形的实际特征,土体变形和界面错动位移的关系是尚未被注意的问题。通过淤泥质粉质黏土的静、动力单剪试验和进行不同法向应力、不同剪切应力幅值的对比试验,得到界面位移与循环周数、土体应变的试验曲线。结果表明,静力单剪试验的初期剪应力迅速增大,其后增长速率逐渐减小,没有出现软化现象;在剪切初期,主要是土体发生剪切位移,达到一定位移量后,土体和钢板之间开始出现较为明显的滑移;在一定的土体应变范围内静力单剪界面错动位移和土体应变有近似线性关系;动力单剪的界面错动位移和土体应变有很好的线性关系;静动力试验界面位移与土体应变关系线的斜率总体上静力试验结果高于动力试验值,线性关系的斜率变化范围不大     

大兴安岭南部幸福之路组的时代及二叠—三叠系界线研究——来自凝灰岩LA-ICP-MS锆石U-Pb年龄的证据

多数研究者认为西拉木伦河—长春—延吉断裂带为华北与西伯利亚两大板块的最后缝合带,但最后拼合时间仍存在分歧,原因之一是对晚二叠世—早三叠世地层研究不足,尤其是对上二叠统与下三叠统接触关系研究更为欠缺。幸福之路组分布于大兴安岭南部,为一套以红层为主要特征的杂色碎屑岩组合,含有叶肢介、介形虫、双壳、植物及孢粉化石。笔者对采自巴林右旗幸福之路苏木幸福之路组上段的岩屑晶屑凝灰岩样品进行了LA-ICP-MS锆石U-Pb测年分析,结果为(254.3±2.6)Ma。结合已有的火山岩测年及化石资料认为,幸福之路组上段下部时代为晚二叠世,上部为早三叠世早期,大兴安岭地区上二叠统与下三叠统为连续沉积,晚二叠世晚期两大板块发生碰撞拼合,古亚洲洋消失,发生南北生物群的混生,早三叠世西伯利亚板块和华北板块碰撞结束。     

基于Langmuir吸附的瓦斯含量和瓦斯压力的对应关系

为探讨煤层瓦斯含量和瓦斯压力的对应关系,应用Langmuir方程,分析总结了吸附常数测值的影响因素,初步阐述了瓦斯含量和瓦斯压力的内在联系,并进行了不同变质程度煤的相关实验研究和理论计算。研究结果表明：Langmuir吸附常数测试受吸附时间、压力点设置、温度和水分含量等多种因素影响;利用修正的Langmuir方程换算的瓦斯含量或瓦斯压力与煤的变质程度有关,在低煤级阶段表现为高压低含量特点,而高煤级阶段正好相反,瓦斯压力0.74 MPa和瓦斯含量8 m³/t只有在贫煤阶段才近似一致。建议综合考虑地质构造和构造煤发育情况,以实测瓦斯压力为主要依据,针对不同变质程度煤的矿井制定合理的突出预测指标。