多孔有机聚合物/壳聚糖复合材料的制备及其对Hg(Ⅱ)吸附性能探究

特定多孔结构和杂原子掺杂的吸附剂对提高重金属离子的吸附性能具有重要意义。传统的多孔有机聚合物材料大多在溶剂中合成,且为粉末状的形式,但在合成方法优化和实际应用便捷性方面仍有一定的发展空间。本文针对水体中的汞污染,采用简单快速的机械研磨法以1,3,5-三醛基间苯三酚(Tp)和硫脲(TU)制备硫掺杂的多孔有机聚合物(TpTU)与壳聚糖(CS)复合材料TpTU@CS。采用X射线衍射光谱、N2吸附-解吸和傅里叶变换红外光谱等技术对TpTU@CS复合材料进行表征。通过扫描电镜证实了TpTU@CS复合材料的多孔结构。由于在分子网络中引入了-C=S-基团,合成的TpTU@CS在水溶液中对Hg(Ⅱ)具有更高的吸附选择性和亲和力,吸附容量高(249.21mg/g),吸附动力学快(10min)。通过表征分析得出,TpTU@CS捕获Hg(Ⅱ)的主要机制是C=S中S与Hg的键合以及C-N与Hg(Ⅱ)的配位相互作用。与其他研究相比,TpTU@CS具有优异的吸附性能,且具有易于处理和可回收利用的优点。同时,该复合材料TpTU@CS对于Hg(Ⅱ)低浓度污染的实际水样和高浓度的加标水样,均具有较高的去除能力,去除率可...     

改性桑树叶吸附材料对废水中Cd(Ⅱ)的吸附性能研究

桑树叶富含植物多酚和黄酮类化合物,表面存在着大量羟基、羧基功能基团,在一定条件下通过络合作用或静电作用能与重金属离子发生吸附作用。但由于生物质中普遍存在着可溶性单宁,直接使用生物质吸附废水中的镉,去除效果不够理想。本文以生物质桑树叶为原料,经沸水蒸煮去除小分子和稀磷酸酸化改性,提高桑树叶的吸附容量,制备成活性吸附材料去除废水中的Cd(Ⅱ)。吸附条件实验表明:在p H=4.0时改性桑树叶对Cd(Ⅱ)的吸附效果最佳,当Cd(Ⅱ)初始浓度为150 mg/L,改性桑树叶的添加量为6 g/L时吸附率可达96.58%。化学改性桑树叶对Cd(Ⅱ)的吸附过程符合准二阶动力学方程,Langmuir等温吸附模型能更好地描述改性桑树叶的吸附行为,Cd(Ⅱ)最大吸附量为30.58 mg/g,与前人报道的吸附量显著提高。本项研究的改性桑树叶吸附材料价廉易得,为废水中镉的处理提供了一个新的方法。     

Pb(Ⅱ)Cu(Ⅱ)Hg(Ⅱ)和As(Ⅲ)在包气带土层中迁移机理的室内实验研究

本文从水-土系统质量均衡的观点,用热力学和数学模型方法,对室内土柱实验资料进行了科学的分析。从而较好地阐明了Pb(Ⅱ)、Cu(Ⅱ)、Hg(Ⅱ)和As(Ⅲ)在包气带土层中的迁移机理。含Pb(Ⅱ)、Cu(Ⅱ)、Hg(Ⅱ)的水溶液进入土层后,在短期内就能达到新的化学平衡。应向固相转移的质量,在土层上部30cm内已经结束。其迁移形式分别为PbOH~+、CuCO_3~0、Hg(OH)_2~0。而As(Ⅲ)由于溶解度大,被吸附能力弱,不向固转移质量,直接通过土层进入地下水。     

天然磁铁矿处理含Hg（Ⅱ）废水实验研究

利用重金属离子可在水合金属氧化物和氢氧化物矿物表面产生吸陵作用的原理，进行了天然磁铁矿处理含Hg(Ⅱ）废水的实验研究，结果表明：当温度为25℃，吸附平衡时间为60分钟、试样用量为20g/L，试样粒径为200目以下、pH值为6.40，离子强度为零时，Hg(Ⅱ）初始浓度为1.12mg/L的溶液的吸附率可达98%，使废水中Hg(Ⅱ）的浓度达到国家排放标准。pH值、离子强度、粒径、试样用量、废水浓度、温度、时间均对Hg(Ⅱ）的吸附率有一定的影响，其中pH值的影响最大，Hg(Ⅱ）在天然磁铁矿上的吸附等温曲线不同于Langmuir和Freundlich等温曲线，而是表现为台阶段，符合分级离子/配位子交换等温曲线。     

氢气还原富铁矿石制备零价铁富集磷

以褐铁矿、菱铁矿、赤铁矿和磁铁矿为原料,在600 ℃下氢气焙烧制备零价铁(ZVI).采用X射线衍射仪、X射线荧光光谱仪、比表面积和孔结构分析仪、扫描电镜、X射线光电子能谱、红外光谱表征了富铁矿石矿物组成及制备产物ZVI的形貌、比表面积和孔结构特征,考察了接触时间、初始磷浓度和pH值对磷富集的影响,并分析了pH值为3和5时,富铁矿石中Pb(Ⅱ)、Cu(Ⅱ)、Hg(Ⅱ)的释放情况,探讨了零价铁对磷的富集性能及作用机制.结果 表明,磁铁矿制备的ZVI中铁含量较高(Fe2O387.4％)、杂质较少、拥有大量的微纳米孔隙且矿石原样在15天内未检出Pb(Ⅱ)、Cu(Ⅱ)、Hg(Ⅱ)的释放,磁铁矿制备的ZVI表现出最好的磷富集效果,w(P)可达13.45 mg/g.使用NaOH (2.2 mol/L)溶液可以回收ZVI富集的磷,回收率可达到99.9％.表面络合、静电吸附和Fe氧化产生的Fe(Ⅱ)/Fe(Ⅲ)对磷的共沉淀作用是ZVI富集磷的主要机制.研究结果有助于推动富铁矿石的综合利用及其在磷的深度处理或磷资源循环利用方面的应用.     

天然褐铁矿处理含Hg（Ⅱ）废水的实验研究

利用水合金属氧化物和氢氧化物矿物表面重金属离子发生吸附作用的原理，进行了天然褐铁矿处理含Hg(Ⅱ)废水的实验。结果表明：试样用量、粒径、废水浓度、pH值、离子强度、反应时间、振荡器转速等因素对Hg(Ⅱ)的吸附率有一定的影响，其中pH值的影响最大；Hg(Ⅱ)在天然褐铁矿上的吸附等温曲线不同于Langmuir和Fre-undlich等温线，而为台阶型，符合分级离子／配位子交换等温曲线。     

Pb(Ⅱ),Cu(Ⅱ)和Hg(Ⅱ)在包气带上层系统中的自净作用

本文以野外土化学分析资料和室内原状土Ph(Ⅱ)、Cu(Ⅱ)和Hg(Ⅱ)的混合溶液淋滤实验资料为基础,以热力学基本原理为理论根据,建立Pb(Ⅱ)、Cu(Ⅱ)和Hg(Ⅱ)在土层系统中的迁移形式的数学模型。以此,评价Pb(Ⅱ)、Cu(Ⅱ)和Hg(Ⅱ)在包气带土层系统中的积累位置、积累方式及其迁移条件。确定配位体(∑HCO~-_3、∑Cl~-,∑SO~(2-)_4)浓度变化对于Pb(Ⅱ)、Cu(Ⅱ)和Hg(Ⅱ)稳定迁移形式和稳定迁移浓度大小的影响程度。     

矿物材料与环境污染治理—以粘土矿物和沸石为例

矿物的性能，矿区地质测试和吸附能力实验表明，粘土矿物和沸石等矿物材料对于Cr,Cd,Pb,Hg,As等有害元素具有很强的吸附能力，是理想的低成本吸附剂，在废水处理中可用来取代活性炭或离子交换树脂来去除重金属等有害元素。     

巯基改性蒙脱石对Cd(Ⅱ)的吸附机理研究

蒙脱石对镉有良好的吸附性,但吸附力较弱,巯基改性蒙脱石可增强对镉的吸附,而关于蒙脱石的巯基改性及改性后对镉的吸附机理研究少见报道.本文以(3-巯丙基)三甲氧基硅烷作为改性剂,采用简单的溶液法对蒙脱石原土(简称MMT)进行巯基改性,并探讨了改性蒙脱石(简称MMT-SH)对镉的吸附机理.红外和X射线衍射表征显示MMT被成功接上巯基.吸附条件实验表明,MMT-SH对Cd(Ⅱ)的吸附效果显著优于原土,对Cd(Ⅱ)的饱和吸附容量是原土的39倍;吸附容量受pH值影响大,受离子强度的影响较大;MMT-SH对Cd(Ⅱ)的吸附作用除了静电吸附、离子交换吸附、羟基配位吸附,还主要存在巯基配位吸附.热力学及动力学实验表明,MMT-SH吸附Cd(Ⅱ)的反应符合Langmiur等温模型和Lagergren二级动力学方程,是易于发生的化学反应;吸附过程的热力学参数(△H、△G、AS)表明此吸附是一个自发的吸热过程.     

纳米金银材料在比色检测汞中的应用

汞具有生物富集性和剧毒性,对人体健康和环境产生严重的危害和影响,因此开发准确测定样品中微量汞的方法具有重要的实际意义。原子光谱法、电感耦合等离子体质谱法、电化学分析法、分光光度法等测定Hg(Ⅱ)的传统方法,由于存在样品预处理过程复杂、仪器昂贵、分析周期长等问题,难以满足实际分析的需求,而比色法作为快速检测Hg(Ⅱ)的一种有效方法虽然得到了广泛的应用,但其灵敏度和选择性仍很难满足复杂基体中微量Hg(Ⅱ)的测定要求。纳米金银材料由于具有独特的表面等离子体共振效应,Hg(Ⅱ)可引起纳米金银溶液发生团聚或氧化还原反应导致溶液颜色发生改变,基于此近年来纳米金银材料在比色测定Hg(Ⅱ)中的应用受到了高度关注,所建立的新方法已成功用于实际样品中微量及痕量Hg(Ⅱ)的测定;但检测的样品主要是水样,用于测定其他的样品干扰较大。本文综述了近年来纳米金银比色检测Hg(Ⅱ)的原理及研究进展,指出建立简单、快速、高灵敏度、高选择性、可用于复杂样品体系中Hg(Ⅱ)的比色检测新方法是该领域今后的主要发展方向。     

Adsorption of methyl tert-butyl ether using granular activated carbon: Equilibrium and kinetic analysis

The adsorption of methyl tert-butyl ether by granular activated carbon was investigated. The experimental data were analyzed using the Freundlich isotherm and the Langmuir isotherm. Although equilibrium data were found to follow Freundlich isotherm model, it were fitted better by the Langmuir model with a maximum adsorption capacity of 204.1 mg/g. The kinetic data obtained at different concentrations were analyzed to predict the constant rate of adsorption using three common kinetic models: pseudo-first-order, pseudo-second-order equation and intraparticle diffusion equation. The pseudo-second-order model was suitable for describing the adsorption kinetics for the removal of methyl tert-butyl ether from aqueous solution onto granular activated carbon. Both the Lagergren first-order rate constant k ₁ and pseudo-second-order rate constant k ₂ decrease with increasing initial concentrations of methyl tert-butyl ether and the intraparticle diffusion rate constant k _p shows the reverse characteristic. Analysis of sorption data using a boyd plot confirmed that external mass transfer is the main rate-limiting step at the initial stage of adsorption. Results illustrate that granular activated carbon is an effective adsorbent for methyl tert-butyl ether and also provide specific guidance into adsorption of methyl tert-butyl ether on granular activated carbon in contaminated groundwater.     

Adsorption kinetics and intraparticulate diffusivities of Hg, As and Pb ions on unmodified and thiolated coconut fiber

As, Hg and Pb are examples of heavy metals which are present in different types of industrial effluents responsible for environmental pollution. Their removal is traditionally made by chemical precipitation, ion-exchange and so on. However, this is expensive and not completely feasible to reduce their concentrations to the levels as low as required by the environmental legislation. Biosorption is a process in which solids of natural origin are employed for binding the heavy metal. It is a promising alternative method to treat industrial effluents, mainly because of its low cost and high metal binding capacity. The kinetics was studied for biosorption experiments using coconut fiber for As (III), Hg (II) and Pb (II) ions adsorption. The specific surface area and surface charge density of the coconut fiber are 1.186×10²⁵ (m²/g) and 5.39 ×10²⁴ (meq/m²), respectively. The maximum adsorption capacity was found to be the highest for Pb (II) followed by Hg (II) and As (III). The modification of the adsorbent by thiolation affected the adsorption capacity. Equilibrium sorption was reached for the metal ions at about 60 min. The equilibrium constant and free energy of the adsorption at 30 °C were calculated. The mechanism of sorption was found to obey the particle-diffusion model. The kinetic studies showed that the sorption rates could be described by both pseudo first-order and pseudo second-order models. The pseudo second-order model showed a better fit with a rate constant value of 1.16 × 10^?4/min. for all three metal ions. Therefore, the results of this study show that coconut fiber, both modified and unmodified, is an efficient adsorbent for the removal of toxic and valuable metals from industrial effluents.     

Adsorption kinetic studies for removal of methylene blue using activated carbon prepared from sugar beet pulp

Sugar beet pulp is an abundant, renewable and low-cost precursor for production of activated carbon. In the present study, sugar beet pulp based activated carbon was prepared by using phosphoric acid as activating agent for adsorption of methylene blue. The conditions of preparation process had a significant influence on the adsorption of methylene blue, and the optimal preparation conditions were obtained as follows: liquid-to-solid ratio of 5, temperature of 450 °C and phosphoric acid concentration of 3 mol/L. The properties of sugar beet pulp based activated carbon were characterized by nitrogen adsorption isotherm. The adsorption increases as the increase of contact time, adsorption temperature and pH, and initial concentration of methylene blue. Batch kinetic studies showed that an equilibrium time of 100 min was needed for the adsorption, and the adsorbance of methylene blue is 244.76 mg/g at equilibration. Kinetic models, Weber’s pore diffusion model and Boyd’s equation were applied to the experimental data to study the mechanism of adsorption and the controlled step. The results showed that the adsorption kinetics followed the pseudo-second-order type kinetic model, intraparticle diffusion was not the rate-limiting mechanism and adsorption process was controlled by film diffusion.     

Hexavalent chromium removal from aqueous solutions by using low-cost biological wastes: equilibrium and kinetic studies

The batch removal of hexavalent chromium from aqueous solutions using almond shell, activated sawdust, and activated carbon, which are low-cost biological wastes under different experimental conditions, was investigated in this study. The influences of initial concentration, adsorbent dose, adsorbent particle size, agitation speed, temperature, contact time, and pH of solution were investigated. The adsorption was solution pH dependent and the maximum adsorption was observed at a solution pH of 2.0. The capacity of chromium adsorption under equilibrium conditions increased with the decrease in particle sizes. The equilibrium was achieved for chromium ion after 30?min. Experimental results showed that low-cost biosorbents are effective for the removal of pollutants from aqueous solution. The pseudo-second-order kinetic model gave a better fit of the experimental data as compared to the pseudo-first-order kinetic model. Experimental data showed a good fit with the Freundlich isotherm model. Changes in the thermodynamic parameters, including Gibbs free energy (??G_o), enthalpy (??H_o), and entropy (??S_o), indicated that the biosorption of hexavalent chromium onto almond shell, activated sawdust, and activated carbon was feasible, spontaneous, and endothermic in the temperature range 28?C50?°C.     

热活化胶状黄铁矿去除酸性溶液中的Cd(Ⅱ)

利用XRD和SEM测试方法表征了热活化胶状黄铁矿结构和微观形貌,考察了溶液pH、溶解氧和热活化温度对热活 化胶状黄铁矿去除水中Cd（Ⅱ）的影响,并探讨了除Cd（Ⅱ）反应动力学和作用机理。胶状黄铁矿在N2氛围下650℃热活化 5 min可完全分解生成多孔结构化单斜磁黄铁矿（PMPyr）。在pH 2~6的无氧水溶液中PMPyr除Cd（Ⅱ）效率均达到88%以 上,除Cd（Ⅱ）效率受pH影响较小;PMPyr表面氧化会抑制其与Cd（Ⅱ）的反应。PMPyr除Cd（Ⅱ）动力学可用准二级动力学模型拟合（R2> 0.9992）,结合溶液pH变化趋势、Fe（Ⅱ）和SO42-浓度变化推测,PMPyr除Cd（Ⅱ）机理主要是Fe1-xS和CdS溶度积差异推动了PMPyr与Cd（Ⅱ）交换反应,表面络合属于次要作用。     

Removal of heavy metal ions from aqueous solutions with multi-walled carbon nanotubes: Kinetic and thermodynamic studies

Multi-walled carbon nanotubes were used successfully for the removal of Copper(II), Lead(II), Cadmium(II), and Zinc(II) from aqueous solution. The results showed that the % adsorption increased by raising the solution temperature due to the endothermic nature of the adsorption process. The kinetics of Cadmium(II), Lead(II), Copper(II), and Zinc(II) adsorption on Multi-walled carbon nanotubes were analyzed using the fraction power function model, Lagergren pseudo-first-order, pseudo-second-order, and Elovich models, and the results showed that the adsorption of heavy metal ions was a pseudo-second-order process, and the adsorption capacity increased with increasing solution temperature. The binding of the metal ions by the carbon nanotubes was evaluated from the adsorption capacities and was found to follow the following order: Copper(II) > Lead(II) > Zinc(II) > Cadmium(II). The thermodynamics parameters were calculated, and the results showed that the values of the free energies were negative for all metals ions, which indicated the spontaneity of the adsorption process, and this spontaneity increased by raising the solution temperature. The change in entropy values were positives, indicating the increase in randomness due to the physical adsorption of heavy metal ions from the aqueous solution to the carbon nanotubes’ surface. Although the enthalpy values were positive for all metal ions, the free energies were negative, and the adsorption was spontaneous, which indicates that the heavy metal adsorption of Multi-walled carbon nanotubes was an entropy-driving process.     

Adsorption studies of 1,2,4-Trichlorobenzene onto shallow aquifer media at the Luhuagang landfill site in Kaifeng,China

The Luhuagang landfill site (LLS) in Kaifeng, China, lacks liner and leachate collection systems. Thus, leachate generated from the waste dump has contaminated the surrounding subsoil and shallow aquifer with various chemicals, including 1,2,4-Trichlorobenzene (1,2,4-TCB). This paper is a part of a series of studies on adsorption, transport and biodegradation and fate of 1,2,4-TCB in the shallow aquifer beneath LLS. Here, adsorption of 1,2,4-TCB onto silt, fine sand and medium sand aquifer deposits collected at LLS was conducted by performing batch experiments involving four common adsorption kinetic models. The results of the analyses showed that the pseudo-second-order adsorption kinetic model provided the best fit for the equilibrium data with a coefficient of determination (R ²) greater than 0.99. Least squares analysis of Henry, Freundlich and Langmuir linearly transformed isotherm models was used to establish the best isotherm for 1,2,4-TCB adsorption onto the three aquifer materials. The Freundlich isotherm provided the best fit for experimental data with R ² > 0.99. The results further suggested that the highest adsorption rate of 1,2,4-TCB (27.55 μg/g) was onto silt deposit, followed by fine sand (21.65 μg/g) and medium sand (14.88 μg/g). This showed that silt layer beneath the LLS was critical for retarding the downward percolation and migration of 1,2,4-TCB into the shallow aquifer systems under the landfill. The findings of the study were adopted as basis for designing the slated transport and biodegradation study of 1,2,4-TCB in aquifer system at LLS.     

Hexamine adsorption study on activated carbon from aqueous solutions for application in treatment of hexamine industrial wastewater

The adsorption of hexamine onto powdered activated carbon from aqueous solutions was studied in a fixed bed system. Langmuir, Freundlich, Redlich–Peterson and Toth isotherm models were used to fit the experimental data and isotherm parameters were determined. The results revealed that the adsorption isotherm models fitted the data in the order of Langmuir > Toth > Redlich–Peterson > Freundlich. Lagergren pseudo-first order kinetic model was found to correlate well with the experimental data. The effects of solution pH, temperature, initial hexamine concentration and added salts concentration on the adsorption capacity and the rate of adsorption were studied. The results indicate that the rate of adsorption increases and then decreases as temperature of the hexamine solution increases, however, the adsorption capacity decreases. The addition of low concentration of salt significantly increases the adsorption capacity of activated carbon. The results showed that the activated carbon has potential for the adsorption of hexamine from industrial hexamine wastewater.     

Biosorption of hexavalent chromium from aqueous solution onto pomegranate seeds: kinetic modeling studies

Hexavalent chromium has been proved to be the reason of several health hazards. This study aimed at evaluating the application of pomegranate seeds powder for chromium adsorption (VI) from aqueous solution. Chromium adsorption percentage (VI) increased with increasing the adsorbent dosage. Chromium adsorption capacity (VI), at pH = 2 and 10 mg/L initial metal concentration, decreased from 3.313 to 1.6 mg/g through increasing dosage of adsorbent from 0.2 to 0.6 g/100 ml. The adsorption rate increased through increase in chromium initial concentration (VI). However, there was a removal percentage reduction of chromium (VI). Chromium adsorption kinetics by different models (pseudo-first-order, modified pseudo-first-order, pseudo-second-order, Elovich, intraparticle diffusion, Boyd kinetic) was investigated as well. Studies on adsorption kinetic indicated that the experimental data were matched by pseudo-second-order model (R ² = 0.999) better. Obtained results demonstrated the pomegranate seeds can be used as an effective biomaterial and biosorbent for hexavalent chromium adsorption from aqueous solutions.     

Adsorptive removal of textile reactive dye using Posidonia oceanica (L.) fibrous biomass

The Mediterranean seagrass Posidonia oceanica (L.) leaf sheaths were used as low cost, available and renewable biological adsorbent for the removal of reactive textile dye from aqueous solutions. Batch experiments were carried out for sorption kinetics and isotherms. Operating variables studied were temperature, pH and chemical pre-treatment. Biosorption capacity seems to be enhanced by increasing the temperature. Maximum colour removal was observed at pH 5. Pre-treating fibres with H₃PO₄ and HNO₃ solutions increased the adsorption efficiency up to 80 %. Experimental sorption kinetic data were fitted to both Lagergren first-order and pseudo-second-order models and the data were found to follow first-order equation for raw fibres and pseudo-second-order for pre-treated ones. Equilibrium data were well represented by the Freundlich isotherm model for all tested adsorption systems. Besides, the thermodynamic study has showed that the dye adsorption phenomenon onto P. oceanica biomass was favourable, endothermic and spontaneous.