转化方式对粉煤灰地聚物原位转化沸石及其Pb^(2+)吸附性能的影响

本工作以高铝粉煤灰为前驱体,通过碱激发及化学发泡的方式制备了富含类沸石相的多孔粉煤灰地聚物,并以此地聚物为骨架,通过原位转化将类沸石相转化为沸石,得到自支撑类沸石吸附材料。另外,研究了碱热、水热、微波三种原位转化方式下多孔粉煤灰地聚物的矿物组成变化规律、不同原位转化条件下制备的沸石类吸附材料对Pb^(2+)的静态吸附行为。研究结果表明:碱热转化有利于多孔粉煤灰地聚物中的类沸石相原位转化生成沸石相,明显提高了其对Pb^(2+)的吸附容量。碱热转化多孔粉煤灰地聚物对Pb^(2+)的吸附属于単分子层吸附。吸附动力学拟合表明,碱热转化多孔粉煤灰地聚物对Pb^(2+)的吸附方式分为物理吸附和化学吸附。当Pb^(2+)初始浓度为100 mg/L和300 mg/L时,吸附过程以物理吸附为主;当Pb^(2+)初始浓度为500 mg/L时,吸附过程伴随大量化学键形成,化学吸附作用更强。

铅分子印迹聚合物合成及其在痕量测量中的应用

以对乙烯基苯甲酸钠为功能单体,铅离子为模板,对乙烯基苯为交联剂,采用预组装方法结合表面印迹技术合成得到铅离子的分子印迹聚合物(Pb-MIPs)。研究了该聚合物对铅离子的吸附和选择识别能力,并对其进行了结构表征。结果表明,所合成的Pb-MIPs对铅离子具有良好的吸附和选择识别能力,最大吸附量为725μg/g。Pb-MIPs应用于地表水样中痕量铅的测定,显著地提高了石墨炉原子吸收光谱仪对铅的检出能力。

多孔壳聚糖接枝聚丙烯酸/钠基蒙脱土复合高吸水凝胶的制备及其对Pb^(2+)的吸附

以十二烷基苯磺酸钠(SDS)胶束为孔模板,过硫酸铵(APS)引发,N,N'-亚甲基双丙烯酰胺(MBA)交联,壳聚糖(CS)与丙烯酸(AA)、钠基蒙脱土(Na-MMT)在水溶液中接枝共聚,成功制备了多孔壳聚糖接枝聚丙烯酸/钠基蒙脱土(CS-g-PAA/Na-MMT)复合高吸水凝胶,提出了SDS胶束致孔机理。扫描电子显微镜(SEM)分析表明,添加SDS的样品,凝胶表面出现多孔结构。通过考察SDS浓度对复合高吸水凝胶平衡吸水倍率和吸水速率的影响,发现当SDS浓度为1.5 mmol/L时,复合凝胶在蒸馏水和生理盐水中的平衡吸水倍率相对于空白样分别提高53.9%和35.3%,初始溶胀速率常数Kis也由空白样的1.2652 g/(g·s)提高到5.1680 g/(g·s)。多孔结构也使复合凝胶对Pb2+的吸附速率加快,在10 min内即可达到饱和吸附量的95%,30 min完全达到吸附平衡。

阴-阳离子有机膨润土制备及其对铅离子的吸附

用十八烷基三甲基溴化铵(STAB)和十二烷基苯磺酸钠(SDBS)共同改性膨润土制备阴-阳离子有机膨润土,并用红外光谱分析法、热分析法和X粉晶衍射分析进行了表征;考察了阴-阳离子有机膨润土对铅离子的吸附性能。结果表明,用0.5CEC(cation exchange capacity)十八烷基三甲基溴化铵和0.4CEC十二烷基苯磺酸钠改性的膨润土吸附铅的效果最佳;阴-阳离子有机膨润土吸附铅离子的能力比改性前明显增加,达到吸附平衡所需要的时间缩短;pH值强烈影响有机膨润土对铅离子吸附;有机膨润土对铅离子等温吸附过程符合Langmuir吸附模型;吸附热力学分析表明该吸附是一个放热过程,降低温度有利于铅离子的吸附。

改性半纤维素吸附剂的制备及其对Pb^(2+)的吸附

为了提高蔗渣半纤维素对重金属离子的吸附性能,以顺丁烯二酸酐为单体对蔗渣半纤维素进行改性,制备出新型重金属离子吸附剂—羧基化半纤维素材料。同时通过傅里叶红外光谱仪、扫描电镜、同步热分析仪对制备的吸附剂进行表征,并且探究了吸附剂用量、吸附浓度和温度、溶液pH以及吸附时间对改性半纤维素吸附Pb^(2+)的影响。结果表明:羧基化半纤维素在35℃下150min时吸附达到平衡,其最优的吸附pH值为6.0,吸附浓度为500mg/L,此时对Pb^(2+)的吸附量达最大98.5mg/g。

Adsorption Kinetics of Pb^(2+) and Cu^(2+) on Variable Charge Soils and Minerals: Ⅲ. Adsorption Kinetics of Pb^(2+) Within 30 Minutes

The adsorption kinetics of Pb^2+ on different soils and minerals with variable charges was studied by the two ion-selective electrode technique at different pH and concentrations.The results showed that more than 95% of adsorption on all the samples occurred during the first 5 minutes.All adsorption time-dependent data could fit the surface second-order equation very well.The values of Xm were goethite>kaolinite,and latosol>red soil at the same initial reaction concentration.The values of k were kaolinite>>goethite,and latosol>red soil at the same reaction pH and initial concentration.The higher the suspension pH,the faster the adsorption occurred.The meaning of Xm got by the two ion-selective electrode technique(one kind of batch technique) was different from that by the miscible displacement technique in that the former was only the equilibrium adsorption amount at a definite concentration and pH,but the latter was almost equal to the adsorption capacity at a definite pH with much less influence of concentration.One Pb^2+ was supposed to occupy two adsorption sites as the adsorption mechanism is concerned.

Adsorption Kinetics of Pb^(2+) and Cu^(2+) on Variable Charge Soils and Minerals:Ⅰ.Technique

A new technique for studying the adsorption kinetics of heavy metals,Pb^2+ and Cu^2+,on variable charge surfaces was established with two selective electrodes and microcomputer control system.Feasibility of the technique,including interference of other ions (mainly Fe^3+ and Al^3+),response time of electrodes,and the pH range of testing,was studied.Comparision with the most widely used miscible displacement technique,which was considered insufficient in studying 30-minute rapid reactions,at present time showed that the new technique was more advantageous in testing in situ,easy to operate,and economic.

Removal of Lead Ions from Ginseng Ethanol Extracts by Dynamic Adsorption in a Fixed-bed Column

The removal of lead from ginseng ethanol extracts by a fixed-bed column filled with an adsorbent bearing amine and carboxyl groups was investigated. The Pb2+ content was determined by inductively coupled plasma mass spectrometry. When the flowrate increased from 0.12 to 0.34 ml·min-1 , the column exhibited a marked increase in percentage of lead removal from 54.9% to 92.3%. Further increase in the flowrate did not bring evident changes to the lead removal, whereas an increase in the temperature could reinforce adsorption further, suggesting that the adsorption process was controlled by external film diffusion below the flowrate of 0.34 ml·min-1 , and by the intraparticle pore diffusion of lead ions when the flowrate exceeded it. A low remaining lead amount in extracts such as 0.11 mg·kg-1 (extracts powder) was achieved. The adsorbents also adsorbed effective constituents to some extent. But 88% of constituents adsorbed were taken off using a 70% ethanol aqueous solution.

Adsorption Kinetics of Pb^(2+) and Cu^(2+) on Variable Charge Soils and Minerals: Ⅱ. Equations for Describing Experimental Data

Different mathematical methods, including linearization, differential, integration and nonlinear least squares approximation (Newton-Marquardt method), were used to fit different kinetic equations, such as zero-order, first-order (i. e, membrane diffusion), second-order, parabolic-diffusion, Elovich, two-constant equations, to the experimental data of Pb2+ and Cu2+ adsorption on variable charge soils and kaolinite. Assuming each M2+ occupied two adsorption sites, two more equations, the so-called surface second-order equation and third-order equation were derived and compared with the above equations according to the fitting results, which showed that the second-order equation and surface second-order equation, being one equation in different expressions under some conditions, were better than the other equations in describing the Pb2+ and Cu2+ adsorption kinetics, and the latter was the best.

Effect of Anions on Adsorbability and Extractability of Lead Added in Soil

The effect of accompanying anions on the adsorbability and extractability of Pb added in soils was studied by using bach equilibria and incubation-extraction mothods.Pb concentration ranged between 0.48-2.41 mM in the adsorption experiment,and Pb added to soil from 2.14 to 19.31mM Pb/kg with an incubation time of 2-16 weeks in the incubation-extraction test in which 1M NH4OAc(pH 7) was taken as an extraction agent,and the Pb compounds used are PbCl2,Pb(NO3)2 and Pb(OAc)2.The values of pH50 for Pb retention and the parameters,b and k values,of Langmuir equation were used to distinguish the difference of adsorbability and extractability of Pb affected by anions,respectively.Judging from the results of either pH50 value or b value,the influences of Cl^- and NO3^- on the adsorbability and extractability of Pb in soils were similar but quite different from those of OAc^-.The relative loading capacities of soils to Pb calculated according to the extraction rate showed that the values of Pb(OAc)2 were higher than those of PbCl2 and Pb(NO3)2.

Adsorption of Cu（ll）, Ni（ll） and Pb（ll） Ions in Aqueous Solutions by a Biopolymer Chitosan at Different Molecular Weights

In this study, the feasibility of using chitosan, a multifunctional environmentally friendly biopolymer, at different molecular weights to simultaneously adsorb various metal ions from aqueous solutions was evaluated. The experiments were carried out to estimate adsorptivity and selectivity of three molecular weights chitosan, 3.60 × 105 （Chl）, 5.97 × 105 （Ch2） and 9.47 × 105 （Ch3） g/mol, towards Cu（II）, Ni（II）, and Pb（II） ions in aqueous solutions. Experimental results indicated that chitosan of high molecular weight （Ch3） was the best at adsorption capacity than the others. On chitosan solutions followed by Ni（II） and then Cu（II）. the other hand, Pb（lI） had the highest adsorption ability in the three

铅分子印迹聚合物合成与性能研究

以bis[(3-甲氧基硅)丙基]乙二胺为功能单体,铅离子为模板分子,正硅酸乙酯为交联剂,无水乙醇与二甲基甲酰胺混合液为络合溶剂,十二胺为扩孔剂,采用预组装方法结合二重印迹技术合成得到铅分子印迹聚合物.研究了该聚合物对铅的吸附和选择识别能力,采用红外光谱及比表面测定仪进行了结构表征.结果表明,所合成的聚合物对铅离子具有良好的吸附和选择识别能力,最大吸附量为1076μg/g,对铅离子的分配系数为172.4,是其它金属离子的10倍以上.填充有印迹聚合物的分离柱应用于痕量铅的处理,具有优良的分离富集能力.

Synthesis of molybdenum disulfide/reduced graphene oxide composites for effective removal of Pb(Ⅱ) from aqueous solutions

In this work, a facile method was adopted to synthesize molybdenum disulfide/reduced graphene oxide （MoS2/rGO） composites through an c-cysteine-assisted hydrothermal technique, The as-prepared MoS2/ rGO composites were firstly applied as adsorbents for efficient elimination of Pb（Ⅱ） ions. Batch adsorption experiments showed that the adsorption of Pb（Ⅱ） on MoS2/rGO followed pseudo-second-order kinetic model well. The adsorption of Pb（Ⅱ） was intensely pH-dependent, ionic strength-dependent at pH 〈 9.0 and ionic strength-independent at pH 〉 9,0, The presence of humic acid （HA） enhanced Pb（Ⅱ） adsorption obviously. The MoS2/rGO composites exhibited excellent adsorption capacity of 384.16 mg g 1 at pH 5.0 and T = 298.15 K, which was superior to MOS2 （279.93 mg g 1） and many other adsorbents. The thermodynamic parameters suggested that the adsorption process of Pb（Ⅱ） on MoS2/rGO composites was spontaneous （zSG＂ 〈 O） and endothermic （△H 〉 0）. The interaction of Pb（Ⅱ） and MoS2] rGO was mainly dominated by electrostatic attraction and surface comple^ation between Pb（Ⅱ） and oxygen-containing functional groups of MoS2]rGO. This work highlighted the application of MoS21rGO as novel and promising materials in the efficient elimination of Pb（Ⅱ） from contaminated water and industrial effluents in environmental pollution management.