Removal of Thiram from Aqueous Solutions

In this study activated carbon was used for the removal of thiram from aqueous solutions. Adsorption experiments were carried out as a function of time, initial thiram concentration and temperature. Equilibrium data fitted well to the Freundlich and Langmuir equilibrium models in the studied concentration range. Adsorption kinetics followed a pseudo second‐order kinetic model rather than pseudo first‐order model. The results from kinetic experiments were used to describe the adsorption mechanism. Both boundary layer and intraparticle diffusion played important role in the adsorption mechanism of thiram. Thermodynamic parameters (ΔG₀, ΔH₀, and ΔS₀) were determined and the adsorption process was found to be an endothermic one. The negative values of ΔG⁰ at different temperatures were indicative of the spontaneity of the adsorption process.     

聚硫醚纤维素吸附阳离子染料的动力学与热力学

脱脂棉在碱存在下与环硫氯丙烷发生醚化反应,合成了一种环境功能材料--聚硫醚纤维素（PTCC）。 考察了溶液酸度对吸附容量的影响并研究了PTCC对3种阳离子染料的吸附动力学与热力学。 研究结果表明,中性介质较有利于吸附的进行;298 K、pH=7.0时,静态吸附2 h后,吸附趋于平衡,PTCC对碱性艳蓝B、碱性艳蓝R和夜蓝的饱和吸附量分别为726、652和320 mg/g;PTCC对阳离子染料的吸附过程符合Lagergren二级吸附动力学方程,吸附速率常数k2随着温度的降低而升高,低温有利于吸附反应的进行;吸附过程ΔG、ΔH和ΔS均为负值,表明该吸附是自发的放热过程,主要是通过范德华力实现的。 吸附过程的吸附等温模型符合Langmuir等温式,可以用单分子层吸附理论加以解释。     

介孔碳CMK-3对苯酚的吸附动力学和热力学研究

研究了介孔碳CMK-3对苯酚的吸附性能, 与传统商用活性碳(CAC)进行了比较, 结果表明, CMK-3比CAC的吸附量大、吸附速率快、达到平衡时间短, 是一种较好的吸附剂. 同时探讨了介孔碳CMK-3对苯酚的吸附热力学和动力学特征. CMK-3对苯酚的吸附行为可用Langmuir和Freundlich等温式进行描述, 相关性都较好, 但更符合Freundlich经验公式. 分别采用模拟一阶反应和二阶反应模型考察了吸附动力学, 并计算了这些动力学模型的速率常数. 模拟二级反应模型和实验数据之间有较好的相关性. 分别计算了热力学参数ΔG0, ΔS0和ΔH0, 结果表明, CMK-3对苯酚的吸附过程是吸热和自发的.     

Dissolution of Cellulose in Aqueous NaOH Solutions

Dissolution of a number of cellulose samples in aqueous NaOH was investigated with respect to the influence of molecular weight, crystalline form and the degree of crystallinity of the source samples. A procedure for dissolving microcrystalline cellulose was developed and optimized, and then applied to other cellulose samples of different crystalline forms, crystallinity indices and molecular weights. The optimum conditions involved swelling cellulose in 8–9 wt % NaOH and then freezing it into a solid mass by holding it at –20°C. This was followed by thawing the frozen mass at room temperature and diluting with water to 5% NaOH. All samples prepared from microcrystalline cellulose were completely dissolved in the NaOH solution by this procedure. All regenerated celluloses having either cellulose II or an amorphous structure prepared from linter cellulose and kraft pulps were also essentially dissolved in the aqueous NaOH by this process. The original linter cellulose, its mercerized form and cellulose III samples prepared from it had limited solubility values of only 26–37%, when the same procedure was applied. The differences in the solubility of the celluloses investigated have been interpreted in terms of the degrees to which some long-range orders present in solid cellulose samples have been disrupted in the course of pre- treatments.     

Adsorption Kinetics,Equilibrium, and Thermodynamics of Copper From Aqueous Solutions using Silicon Carbide Derived from Rice Waste

Adsorption of Cu(II) from aqueous solution on a novel adsorbent, silicon carbide ash (SiC ash), was studied using batch technique. The adsorbent was prepared by pyrolysis of Egyptian rice waste (rice straw and rice husk) and was characterized by scanning electron microscopy (SEM), energy-dispersive x-ray (EDX), Fourier-transform infrared (FTIR) spectroscopy, x-ray diffraction (XRD), and surface area analysis by Brunauer-Emmett-Teller (BET) Theory. The influence of pH, contact time, initial Cu(II) concentration, adsorbent dose, agitation speed, and temperature was investigated. Adsorption kinetics was analyzed using the pseudo-first-order, the pseudo-second-order, and intraparticular diffusion model. The adsorption process was found to follow a pseudo-second-order rate mechanism. The adsorption isotherm data could be well described by the Langmuir and Freundlich than the Dubinin–Radushkevich adsorption model. The adsorption capacity of 22.06 mg g^?1for SiC ash was obtained at pH = 5 and temperature of 298 K. Thermodynamic parameters, change in the free energy (ΔG°), the enthalpy (ΔH°), and the entropy (ΔS°), were also calculated. The overall adsorption process was exothermic, spontaneous in nature, and proceeds with decreased randomness as the entropy is negative value. Adsorption process was successfully applied to remove Cu(II) from an industrial wastewater sample.     

立方体纳米Cu2O吸附热力学及动力学的粒度效应研究

采用不同粒径的单一(100)晶面的立方体纳米Cu₂O作为模型材料, 研究了粒径和温度对其吸附动力学和吸附热力学性质的影响规律. 基于已建立的纳米材料吸附热力学和动力学理论, 推导出了单一(100)晶面立方体纳米Cu₂O材料的吸附热力学和吸附动力学性质与粒径之间的关系式. 实验结果与理论预测结果一致: 随着纳米Cu₂O粒径的减小, 吸附速率常数增大而吸附活化能和吸附指前因子减小; 标准摩尔吸附Gibbs自由能 Δ_a $G^{\rlap{-}0}_{m}$减小而标准吸附平衡常数ln $K^{\rlap{-}0}$、 标准摩尔吸附焓 Δ_a $H^{\rlap{-}0}_{m}$和标准摩尔吸附熵 Δ_a$S^{\rlap{-}0}_{m}$均增大, 且以上参数均与粒度的倒数具有较好的线性关系.     

Study on Thermodynamics and Kinetics of Association Interactions between Malachite Green and OP-10 in Aqueous Solutions

The absorption spectrum of malachite green (MG) in a series of aqueous solutions with surfactant octylphenol polyoxyethylene ether (10) (OP-10) has been determined by the UV–Vis spectrophotometer. The association interaction between the MG and nonionic surfactant OP-10 in aqueous solutions resulted in obvious fading of MG. We established the thermodynamics model of association between MG and OP-10, and determined the association equilibrium constant in aqueous solutions. By measuring the absorbance of a series of aqueous solutions which have different molar concentrations of OP-10 but same concentration of MG at different time points, the order and rate constants of association reactions were determined and the reaction kinetics equation was set up.     

Adsorption of Hazardous Azorhodanine Dye from an Aqueous Solution Using Rice Straw Fly Ash

The potential of using rice straw fly ash (RSFA) as low-cost adsorbents for the removal of hazardous azorhodanine (AR) dye from aqueous solution was investigated. The effects of different variables in the batch method as a function of solution pH, contact time, concentration of adsorbate, adsorbent dosage, and temperature were investigated, and optimal experimental conditions were ascertained: 0.05 g for initial dye concentration of 20–100 mg/L at pH 2. The experimental equilibrium data were tested by the isotherm models, namely the Langmuir and Freundlich adsorption and the isotherm constants were determined. The kinetic models, pseudo-first-order and pseudo-second-order, were employed to analyze the kinetic data. The activation energy of adsorption was also evaluated and found to be +10.89 kJ.mol^?1, indicating that the adsorption is physisorption. Various thermodynamic parameters, such as Gibbs free energy, entropy, and enthalpy of the ongoing adsorption process, have been calculated and found to be spontaneous and exothermic, respectively.     

Structural Features and Properties of Bacterial Cellulose Produced in Agitated Culture

The structure and some properties of bacterial cellulose produced in agitated culture were studied. Scanning electron microscopy revealed that there was almost no difference between reticulated structures of bacterial cellulose fibrils produced in agitated culture and in static culture. Nevertheless, bacterial cellulose produced in agitated culture exhibited microstuctural changes, namely, a low degree of polymerization and a low crystallinity index. A CP/MAS ¹³C NMR analysis revealed that the cellulose I content of the cellulose produced in agitated culture was lower than that of the cellulose produced in static culture. The bacterial cellulose produced in agitated culture had a lower Young's modulus of sheet, a higher water holding capacity and a higher suspension viscosity in the disintegrated form than that produced in static culture.     

Bacterial Cellulose Production by Acetobacter xylinum Strains from Agricultural Waste Products

Bacterial cellulose is a biopolysaccharide produced from the bacteria, Acetobacter xylinum. Static batch fermentations for bacterial cellulose production were studied in coconut and pineapple juices under 30 °C in 5-l fermenters by using three Acetobacter strains: A. xylinum TISTR 998, A. xylinum TISTR 975, and A. xylinum TISTR 893. Experiments were carried out to compare bacterial cellulose yields along with growth kinetic analysis. Results showed that A. xylinum TISTR 998 produced a bacterial cellulose yield of 553.33 g/l, while A. xylinum TISTR 893 produced 453.33 g/l and A. xylinum TISTR 975 produced 243.33 g/l. In pineapple juice, the yields for A. xylinum TISTR 893, 975, and 998 were 576.66, 546.66, and 520 g/l, respectively. The strain TISTR 998 showed the highest productivity when using coconut juice. Morphological properties of cellulose pellicles, in terms of texture and color, were also measured, and the textures were not significantly different among treatments.     

阴离子型有机化合物在LDHs上的动力学和热力学研究

本文考察水滑石焙烧产物MgAl-LDO吸附3种阴离子染料AcidRed88（AR88）、AcidOrange 3（AO3）、AcidViolet90（AV90）过程中的热力学和动力学机理,并在不同温度下探究该吸附过程的热力学参数。实验结果表明：MgAl-LDO对染料阴离子的吸附过程复合Langmuir吸附等温模型,且为自发、放热的过程。3种染料在MgAl-LDO上的吸附过程均符合准二级反应动力学模型,且该吸附过程是由MgAl-LDO与阴离子染料之间的反应速率控制而不是两者之间的扩散作用。计算所得的吉布斯自由能绝对值在7~15kJ·mol^-1,这主要是由染料阴离子与MgAl-LDHs层板的氢键作用产生,结合MaterialsStudio 5.5软件模拟染料分子在MgAl-LDHs上的排列分布,推测MgAl-LDO对阴离子染料的吸附机理是表面吸附（占优势）与层间插层的协同作用。     

Tailoring Thermodynamics and Kinetics for Hydrogen Storage in Complex Hydrides towards Applications

Solid‐state hydrogen storage using various materials is expected to provide the ultimate solution for safe and efficient on‐board storage. Complex hydrides have attracted increasing attention over the past two decades due to their high gravimetric and volumetric hydrogen densities. In this account, we review studies from our lab on tailoring the thermodynamics and kinetics for hydrogen storage in complex hydrides, including metal alanates, borohydrides and amides. By changing the material composition and structure, developing feasible preparation methods, doping high‐performance catalysts, optimizing multifunctional additives, creating nanostructures and understanding the interaction mechanisms with hydrogen, the operating temperatures for hydrogen storage in metal amides, alanates and borohydrides are remarkably reduced. This temperature reduction is associated with enhanced reaction kinetics and improved reversibility. The examples discussed in this review are expected to provide new inspiration for the development of complex hydrides with high hydrogen capacity and appropriate thermodynamics and kinetics for hydrogen storage.

     

阴离子型有机化合物在LDHs上的动力学和热力学研究

考察了水滑石焙烧产物MgAl-LDO吸附3种阴离子染料Acid Red 88(AR88)、Acid Orange 3(AO3)、Acid Violet 90(AV90)过程中的热力学和动力学机理,并在不同温度下探究该吸附过程的热力学参数。实验结果表明:MgAl-LDO对染料阴离子的吸附过程复合Langmuir吸附等温模型,且为自发、放热的过程。3种染料在MgAl-LDO上的吸附过程均符合准二级反应动力学模型,且该吸附过程是由MgAl-LDO与阴离子染料之间的反应速率控制而不是两者之间的扩散作用。计算所得的吉布斯自由能绝对值在7~15 kJ·mol-1,这主要是由染料阴离子与MgAl-LDHs层板的氢键作用产生,结合Materials Studio 5.5软件模拟染料分子在MgAl-LDHs上的排列分布,推测MgAl-LDO对阴离子染料的吸附机理是表面吸附(占优势)与层间插层的协同作用。     

溶剂气浮法去除水中腐殖酸的动力学和热力学初步研究

研究了溶剂气浮法去除水中的腐殖酸,该技术可以作为生物处理后的填埋渗出液的后处理方法。腐殖酸通过与表面活性剂十六烷基三甲基溴化铵生成离子缔合物气浮进入有机溶剂异戊醇而从水中去除。大于计量比的表面活性剂的量在10 m in之内可达92%的去除率。气浮速率在一定程序上随着气流速率的增加而增加,基本上与有机溶剂的体积无关。同时,还考察了电解质、乙醇及溶液的pH值对水中腐殖酸的溶剂气浮过程的影响。研究表明,该溶剂气浮过程遵从一级动力学。气浮过程的表观活化能作为一个特征参数被提出来,其值为2.87 kJ/mol。     

Thermodynamics of nanoadsorption from solution: Theoretical and experimental research

In this study, the effect of nanoparticle size on adsorption thermodynamics was investigated. The results of theoretical and experimental studies show that particle size significantly affects the equilibrium constant and thermodynamic properties of nanoadsorption. Relationships between the equilibrium constant, thermodynamic properties and particle size were derived using the thermodynamic theory of nanoadsorption. The equilibrium constant and thermodynamic properties were obtained by investigating the adsorption of Cu²⁺ onto different sizes of nano-ZnO and the adsorption of Ag⁺ onto different sizes of nano-TiO₂. Good agreement was achieved between results obtained by experiments and predicted by theoretical analyses. The equilibrium constant and the molar Gibbs free energy of nanoadsorption were found to increase with smaller nanoparticle size. However, the effects of particle size on the molar enthalpy and the molar entropy are uncertain. In addition, the molar Gibbs free energy, the molar enthalpy, the molar entropy and the logarithm of the equilibrium constant are linearly related to the reciprocal of the diameter of the nanoparticle. The thermodynamic properties revealed in this study may provide important guidelines for research and application in the field of nanoadsorption.     

Oxidized Biomass and Its Usage as Adsorbent for Removal of Heavy Metal Ions from Aqueous Solutions

Nowadays, very coarse wool fibers are considered waste biomass and are discarded at random or burned. Therefore, it is of actual interest to valorize coarse wool fibers as utile products. In this sense, we report herein an environmentally-friendly process for the preparation of a new material based on oxidized wool fibers and designed for efficient adsorption of heavy metals from wastewater. The morphology and the structure of the obtained product were characterized by scanning electron microscopy (SEM) coupled with an X-ray energy-dispersive module (EDX) and by Fourier-transform infrared spectroscopy (FTIR). Likewise, the performances of the oxidized wool fibers for the adsorption of heavy metal cations (Cu²⁺, Cd²⁺, Pb²⁺) from aqueous solutions were tested. The adsorption kinetics data were analyzed by applying the pseudo-first-order (PFO) and pseudo-second-order (PSO) kinetic models. The equilibrium of the adsorption process was investigated by using the Freundlich and Langmuir isotherm models. According to the Langmuir isotherms registered at 300 K, the maximum adsorption capacities of the oxidized wool were found to increase from Cu²⁺ (9.41 mg/g) and Cd²⁺ (10.42 mg/g) to Pb²⁺ (30.71 mg/g). Consequently, the removal efficiency of metal ions was found to vary in the range of 96.8–99.7%. The thermodynamic parameters (e.g., enthalpy, entropy, and Gibbs free energy) were calculated and discussed.     

Li-Mg-N-H体系储氢材料的热力学和动力学调控

Mg（NH₂）₂-2LiH体系储氢材料具有较高的储氢容量和较适宜的热力学性能,并且其吸放氢过程完全可逆,是目前最有望实现大规模应用的固态储氢材料之一。然而,由于该体系在吸放氢过程中具有较高的动力学壁垒,导致其在200℃以上才能实现快速地吸放氢。因此,国际上对该体系储氢材料的研究主要集中在热力学和动力学的调控方面。本文从成分调变、纳米化和掺杂改性等方面,详细综述了Mg（NH₂）₂-2LiH体系储氢材料热力学和动力学调控的研究现状,并提出了其中存在的问题和相应对策,同时指出了将来的研究方向。     

细菌纤维素纳米纤维稳定乳液的性能

采用超声和高压均质两种方式分散的细菌纤维素(BC)悬浮液制备了BC纳米纤维稳定的水包油型Pickering乳液, 并考察了纤维用量、 pH值和机械分散方式对乳液稳定性的影响. 结果表明, 乳液的稳定性随纳米纤维用量的增加而增加; 碱性条件比酸性条件制备的乳液稳定性高, 且在pH=12时达到最高. 用高压均质方式分散的BC稳定乳液的效果优于采用超声方式分散的BC的效果, 这是由于高压均质后的纤维较短, 可以提供更多的纳米纤维稳定乳液. 计算结果表明, BC纳米纤维在液体石蜡/水界面上的三相接触角为72.5°, 说明BC适合稳定水包油型乳液.     

Kinetics of Cathodic Reduction of Hypophosphite Anions in Aqueous Solutions

The kinetics of the cathodic reduction of hypophosphite anions in aqueous solutions is studied as a function of the electrode nature, the sodium hypophosphite concentration, and the solution pH. It is shown that the product of the reduction of hypophosphite anions is phosphorus. A scheme is proposed for the reduction process, according to which the phosphorus formation can proceed via two parallel routes—electrochemical and chemical—whose realization depends on the nature of the metal catalyst.     

Kinetics and thermodynamics of bromophenol blue adsorption by a mesoporous hybrid gel derived from tetraethoxysilane and bis(trimethoxysilyl)hexane

A mesoporous hybrid gel is prepared with tetraethoxysilane (TEOS) and bis(trimethoxysilyl)hexane (TSH) as precursors without using any templating agent. Nitrogen sorption, TG-DTA, FTIR, and point of zero charge (PZC) measurement are used to characterize the gel. The gel has a specific surface area of 695 m(2) g(-1) with a pore size of 3.5 nm, a pore volume of 0.564 cm(3) g(-1), and a point of zero charge (PZC) of 6.2. The kinetics and thermodynamics of bromophenol blue (BPB) adsorption by the gel in aqueous solution are investigated comprehensively. The effects of initial BPB concentration, pH, ionic strength, and temperature on the adsorption are investigated. Kinetic studies show that the kinetic data are well described by the pseudo-second-order kinetic model. Initial adsorption rate increases with the increase in initial BPB concentration and temperature. Adsorption activation energy is found to be 62.5-67.5 kJ mol(-1) depending on the initial BPB concentration. Internal diffusion appears to be the rate-limiting step for the adsorption process. The equilibrium adsorption amount increases with the increase in the initial BPB concentration, solution acidity, and ionic strength, but decreases with the increase in temperature. The thermodynamic analysis indicates that the adsorption is spontaneous and exothermic. The adsorption isotherms can be well described with Freundlich equation indicating the heterogeneity of the hybrid gel surface. Electrostatic and hydrophobic interactions are suggested to be the dominant mechanism for adsorption.