Thermodynamic study of adsorption of phenolic compounds onto Amberlite XAD-4 polymeric adsorbents and its acetylized derivative MX-4

Adsorption equilibrium isotherms of phenolic compounds, phenol, p-cresol, p-chlorophenol and p-nitrophenol, from aqueous solutions by Amberlite XAD-4 polymeric adsorbent and its acetyhzed derivative MX-4- within temperature range of 283-323K were obtained and fitted to the Freundlich isotherms. The capacities of equilibrium adsorption for all four phenolic compounds from their aqueous solutions increased around 20% on the acetylized resin, which may be contributed to the specific surface area and the partial polarity on the network.Estimations of the isosteric enlhalDV, free energy, and entropy for the adsorption process were reported.     

Physicochemical aspects of using natural scavengers in removing methylene blue (basic dye) from solution

Effluent from dyeing and finishing processes is an important source of water pollution. The effectiveness of bentonite, kaolinite and sediment from a local deposit in removing methylene blue as a cationic dye from aqueous solutions has been investigated. The adsorption equilibrium (isotherm) has been determined according to Freundlich and Langmuir equations. The optimum amount is 0.5 g for all adsorbents, and the optimum pH ranges are 2–8 for bentonite and 2–6 for kaolinite and sediment. With respect to kinetic modelling, the adsorption of methylene blue on various adsorbents was fitted to a second-order equation. Also, the thermodynamic parameters were determined. The negative free energy values indicate the feasibility of the process and spontaneous nature of adsorption. The positive ΔH° values indicate the endothermic nature of the process. Thus, Egyptian clay minerals and sediments have a great tendency to remove the dye from solutions.     

Thermal energy storage and thermodynamic properties of (E)-3-m-tolylbut-2-enoic acid as a medium temperature phase change material

Phase change materials (PCMs) that can store and release heat energy over the temperature range from 363 to 393 K are crucial for solar absorption cooling, and it is worthy to seek new solid-liquid PCMs candidates that melt and crystallize in this temperature range. In this paper, (E)-3-m-tolylbut-2-enoic acid (mTBEA) was applied as a PCM candidate. Its thermal energy storage properties and thermal stability were systematically investigated. The results showed that mTBEA melted at 382.9 ± 0.5 K and crystallized at about 364 K, with a melting enthalpy (Δ_fusH) of 138.4 ± 6.9 J g^?1 and showed good long-term cyclic stability and thermal stability. The supercooling of mTBEA was stabilized at about 20 K, indicating that the conservation condition of melted mTBEA could be simple. In addition, the melted mTBEA could release all the absorbed thermal energy upon crystallizing. Besides, mTBEA exhibited good thermal stability for it to be applied as PCM. Hence, mTBEA is a promising PCM candidate for solar absorption cooling. Furthermore, the heat capacity of mTBEA was measured by modulated temperature differential scanning calorimetry (MTDSC) over the temperature range from 198.15 to 431.15 K, and the molar thermodynamic functions, [H_T-H_298.15]_m and [S_T-S_298.15]_m, were calculated based on the fitted molar heat capacity data.     

Phenol removal from aqueous environments by natural & chemically modified kaolin clay

Natural, acid and base modified kaolin clays were studied for the sake of phenol and 4-chlorophenol removal from aqueous environments and their application to real ground and industrial wastewater samples. Scanning electron microscope (SEM), infrared spectroscopy (IR), X-ray diffraction (XRD), Thermo Gravimetric Analysis (TGA), Differential Thermal Analysis (DTA), and Surface area analysis were employed for characterization of the adsorbents microstructure. Operating factors such as adsorbent dose, solution pH, initial phenol concentration, and contact time were studied. The experimental data displayed that the increase of the adsorbent dose, contact time, and pH value from 2 to 7 increases the efficiency of the removal process. Optimal conditions for phenolic removal were; contact time of 300 min, primary phenol solution of 25 mg/L, pH 7 and 2.5 g/L as an appropriate adsorbent dose using crude (natural), acid modified and base modified kaolin clays. The higher phenolic removal efficiencies were obtained at 5 mg/L as 90, 97, 96.2%, respectively, for the adsorbents in the previously mentioned order. The adsorption capacity in the removal of phenol and 4-chlorophenol were 7.481 and 4.195, 8.2942 and 3.211, and 8.05185 and 18.565 mg/g, respectively, for the adsorbents in the same mentioned order. The adsorption equilibrium data were fitted and analyzed with four isotherm models, namely, Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm equations. The adsorption process of phenol on studied adsorbents was exothermic, spontaneous and thermodynamically favorable proved by the negative values of their thermodynamic parameters ΔH° and ΔG°. The correlation coefficient (R²) for all concentrations was higher than 0.94, which indicates that in the studied system, the data suitably fit the first-order kinetics. The % desorption capacity was amounted to 96%, 91.11%, and 87.06% of adsorbed phenol, respectively, for the adsorbents in the previous order using 0.1N NaOH and 10% V/V ethanol solutions as eluents at 25°C, indicating the reusability of the adsorbents. Kaolin and its modified forms can be introduced as eco-friendly and low-cost adsorbents in water remediation implementation.     

水淬钢渣碳酸化固定CO2

利用HSC-Chemistry 软件平台对以气-液-固三相为基础的水淬钢渣碳酸化固定二氧化碳进行了热力学分析,结果表明,温度700 K以下钢渣主要含钙相在水溶液中能够自发与CO2反应,碳酸化固定CO2是可行的;并通过实验研究了反应时间、钢渣粒径、CO2流量及液固比等主要参数对水淬钢渣碳酸化固定CO2的影响。结果显示,在初期阶段反应迅速,固碳率在3 h达到27.9%,即固定二氧化碳的能力约为279 kg/t(钢渣),随后逐渐趋于平衡。粒度越细对固碳过程越有利,液固比及CO2流量影响不明显; XRD及SEM结果也验证了水淬钢渣固定CO2是可行的。     

三聚磷酸钠在层状氢氧化镁铝及其焙烧产物上的吸附特性

通过静态吸附实验,研究了水溶液中三聚磷酸钠(STPP)在层状氢氧化镁铝(Mg-Al LDH)及其焙烧产物(Mg-Al CLDH)上的吸附性能,并用多晶X射线衍射对Mg-Al LDH,Mg-Al CLDH及Mg-Al CLDH吸附STPP后Mg-Al RLDH的结构进行了表征.结果表明,STPP在层状氢氧化镁铝及其焙烧产物上的吸附量和脱除率在pH为4.7-10.0时受溶液初始pH值的影响较小;饱和吸附量随温度的升高而增大,在25-50℃下,STPP在层状氢氧化镁铝上的饱和吸附量为34.52-40.20 mgP3 O105-·g-1,在25-60℃下,STPP在焙烧层状氢氧化镁铝上的饱和吸附量为118.67-179.57mgP3O105-·g-1.静态吸附热力学结果证明STPP在层状氢氧化镁铝及其焙烧产物上的吸附为自发的物理吸热过程,焓变与熵增是吸附的主要驱动力.     

垃圾填埋场衬垫对Cr(Ⅵ)和Zn(Ⅱ)吸附的动力学研究

通过静态平衡吸附试验对垃圾填埋场衬垫土壤材料对Cr(Ⅵ)和Zn(Ⅱ)的吸附进行了观察.在试验中考察了溶液的初始浓度、pH值和溶液的温度对吸附的影响,通过动力学实验确定了动力学参数,并探讨了天然黏土材料对重金属Cr(Ⅵ)和Zn(Ⅱ)的吸附机理.结果显示,黏土对重金属的吸附过程可以通过伪二阶动力模式来描述.根据对lnk2与1/T线形图斜率的计算,可以确定Cr(Ⅵ)和Zn(Ⅱ)的活化能(Ea)分别为22.7 kJ·mol1-和26.88 kJ·mol-1.活化能的计算结果说明,温度的升高能促进黏土材料对Cr(Ⅵ)和zn(Ⅱ)的吸附,同时也表明吸附很可能是一个化学吸附.热力学参数(△H0,△S0,△G0)值可以通过图1gKD与1/T的斜率与截距来计算.热力学参数值的结果表明,天然黏土材料对Cr(Ⅵ)和Zn(Ⅱ)的吸附是吸热反应.     

Adsorption and thermodynamic parameters of chlorantraniliprole and dinotefuran on clay loam soil with difference in particle size and pH

The behavior of chlorantraniliprole (CAP) and dinotefuran (DNF) insecticides was investigated in clay loam soil, a common type of the Egyptian soil. Effect of temperature, pH and particle size of the soil on the adsorption process was studied. Adsorption isotherm by bulk soil and its constituents; humic acid (HA), clay, silt and sand fractions was measured using batch equilibration technique. The results showed that the adsorption of the insecticides tested was significantly affected by the temperature and was a spontaneous interfacial process in the soil. Freundlich model accurately predicted the adsorption behavior of both insecticides. The interaction between soil and insecticides was endothermic and the highest adsorption for CAP and DNF was obtained at pH 9. However, the effect of pH on the adsorption of DNF was lower than that of CAP. Sorption of CAP and DNF on HA fraction was significantly greater than on clay fraction and bulk soil. In addition, the adsorption was significantly increased with particle size decrease. It could be inferred that the adsorption of CAP and DNF on clay loam soil was physical in nature and greatly influenced by the soil components, pH and temperature.     

Adsorption of caesium from aqueous solution using cerium molybdate–pan composite

In this study, a cerium molybdate–polyacrylonitrile (CM–PAN) composite ion exchanger was synthesised and its characteristics were determined by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetry (TGA), specific area measurement (BET), X-ray fluorescence and CHN elemental analyses. The adsorption of caesium from aqueous solutions by CM–PAN composite was investigated under batch and continuous conditions. The distribution coefficient of caesium on the composite sorbent was studied as a function of pH, solution temperature and the presence of interfering cations, and the optimum conditions for a batch system were determined. Pseudo-first- and second-order sorption kinetic models were used to investigate the kinetics of adsorption and the results pointed to the pseudo-second-order model for caesium sorption kinetics. The intraparticle diffusion model was used to the predict rate-limiting step of the ion exchange process in order to specify the sorption mechanism. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherm models were fitted to the experimental sorption data, where the Freundlich model showed a good agreement. The adsorption thermodynamic parameters, standard enthalpy, entropy and Gibbs’ free energy were calculated and the reaction was found to be endothermic and spontaneous. Finally, the dynamic sorption capacities of the sorbent at two breakthroughs were calculated from the continuous system.     

不同环境激素吸附行为及机理的对比研究

文章研究了环境激素类污染物在土壤中吸附的动力学、热力学过程,并进行相关参数分析和模型构建。结果显示,5种环境激素的吸附过程分为快速吸附、慢速吸附、平衡3个阶段,动力学过程均符合二级动力学方程;Freundlich等温模型的拟合度最高,吸附过程均为物理过程,并且放出热量。