Application of an effective method in predicting breakthrough curves of fixed-bed adsorption onto resin adsorbent

Removal of many organic pollutants including phenolic compounds from industrial wastewater can always be achieved by fixed-bed adsorption onto the polymeric resin adsorbent, and the relevant breakthrough curves would provide much valuable information to help to design a fixed-bed adsorption process in field application. In the present study, a model developed based on the constant-pattern wave approach theory and the Freundlich model was adopted to describe the breakthrough curves of phenol and p-nitrophenol adsorption onto a macroreticular resin adsorbent NDA-100 from aqueous solution. Column experiments were performed at different conditions to verify the model and the results proved that the model would describe the breakthrough curves well. Effect of the operation parameters on breakthrough curves was also discussed to get helpful information in choosing the adsorption process.     

光氯化-烷基化两步法制备超高交联树脂及对苯酚的吸附性能

通过对二甲苯侧链光氯化产物(CP)与苯(BE)的Friede-l Crafts烷基化聚合反应制备比表面积高达905m2/g的超高交联吸附树脂(CP-BE)材料,并用红外光谱(FT-IR)、元素分析(EA)及比表面积(BET)对其结构进行表征。以XDC-BE和市售Amberlite XAD-4为参照,在不同温度下,测试了三种吸附树脂对水溶液中苯酚的吸附性能,结果表明,CP-BE和XDC-BE树脂对苯酚的吸附量分别高达171 mg/g和143 mg/g,远高于国内外用于酚类吸附的Amberlite XAD-4树脂,有望在酚类废水资源化治理中得到实际应用。     

Removal of aniline from aqueous solution by PVC-CDAE ligand-exchanger

The adsorption of aniline from aqueous solutions onto cobalt(II)-poly(vinyl chloride)-carboxylated diaminoethane (PVC-CDAE) resin has been studied using a mini-column apparatus at 25 ± 0.1 °C. First of all, experimental data obtained from the breakthrough curves were tested by using the Scatchard plot analysis, to have a preliminary prediction about the types of interaction of the resin with aniline. Our aim was to determine the model which best describes the experimental data. The aspect of the Scatchard plot indicated that the aniline adsorption did not follow the Langmuir model and the presence of two types of binding sites for aniline on the resin. However, the dynamics of aniline uptake were represented by the Freundlich model reasonably well. The kinetics of aniline adsorption from aqueous solution on the cobalt(II)-PVC-CDAE have also been tested using continuous column runs and rate-controlling step of the process was determined. In this study, homogeneous diffusion model was adapted to a column system to describe the change in the aniline concentration at the column exit beginning from breakthrough point as a function of time. Kinetic studies revealed that the rate-controlling step of the aniline adsorption was predominately film diffusion controlled rather particle diffusion.     

超高交联树脂对氯酚类化合物的吸附性能

通过静态吸附研究,比较了Am berlite XAD-4和ZH-01吸附树脂对水溶液中2-氯苯酚、2,4-二氯苯酚、2,4,6-三氯苯酚的吸附热力学特性。结果表明,在288 K~318 K和研究的浓度范围内,ZH-01、XAD-4对氯酚类化合物的吸附平衡数据符合F reund lich和L angm u ir吸附等温方程。2-氯苯酚在两树脂上的吸附为放热过程,是单分子层的物理吸附;而2,4-二氯苯酚和2,4,6-三氯苯酚在XAD-4吸附是单分子层物理吸附,在ZH-01的吸附属单分子层吸热过渡化学吸附,主要是毛细管凝聚和微孔填充作用造成的吸附。并计算了氯酚类化合物在两树脂上的吸附焓变、自由能变、吸附熵变,对吸附行为进行了合理的解释。     

Removal of Pb(II) using the modified lawny grass: Mechanism,kinetics, equilibrium and thermodynamic studies

A series of new chemical-modified lawny grass adsorbents were prepared and the feasibility of absorbents to remove Pb(II) ion from aqueous solution was examined. The absorbents were characterized by FTIR spectra and elemental analysis. Kinetics, equilibrium, thermodynamics, column adsorption and mechanism were studied. The optimum pH is in the range of 5.0–5.8 for all adsorbents. The sorption system follows pseudo-second-order kinetic model and equilibrium time is obtained after 60 min. The maximum adsorption capacities obtained from Langmuir–Freundlich model are 1.55 and 1.26 mol/kg by using 1 CG and 0.6 CG (lawny grass modified by 1 mol/L or 0.6 mol/L citric acid, respectively). Thermodynamic parameters such as ΔG, ΔH and ΔS are evaluated for the adsorption process. The results indicates that the adsorption of Pb(II) is spontaneous and endothermic. The breakthrough point is achieved at 100 BV (bed volume) by a column of 0.6 CG. Desorption of Pb(II) and regeneration of the column is achieved by 0.1 mol/L HCl elution. After 3 adsorption/desorption cycles, the breakthrough point remains around 100 BV, which shows that grass adsorbent is regenerated easily and used repeatedly. Above results indicates that lawny grass have a good potential for removal of lead from dilute aqueous solution in the future.     

弱酸性吸附树脂对水溶液中咪唑烷的吸附

利用超高交联吸附树脂NDA150和NDA99对不同温度下水中咪唑烷的静态吸附实验,研究了NDA99和NDA150对咪唑烷的吸附情况,提出了对树脂表面修饰的设想,并进行了静态吸附和实际废水的动态吸附验证,结果表明,具有弱酸性的超高交联吸附树脂对咪唑烷具有较好的吸附选择性。     

啶虫脒在超高交联吸附树脂上的吸附及脱附性能研究

本文从动态和静态的角度研究了均苯四甲酸酐修饰的超高交联吸附树脂（PMAR）和1,2,4-苯三酸酐修饰的超高交联吸附树脂（TMAR）对啶虫脒的吸附和脱附行为。结果表明：两种树脂对啶虫眯的吸附和脱附效果都比较好,TMAR的静态吸附量为470．9mg·g^-1干树脂,饱和吸附量为562．7mg·g^-1干树脂;PMAR的静态吸附量为453．4mg·g^-1干树脂,饱和吸附量为559．1mg·g^-1干树脂。两种树脂都易于脱附,用2mol·L^-1 HCl：乙醇（体积比1：1）作脱附剂,温度323K,脱附剂体积为9．5BV（床体积）时,PMAR的脱附率为98．13％,TMAR的脱附率为99．83％。     

Adsorption of BTEX from aqueous solution by macroreticular resins

Theoretical and experimental investigations were conducted on the adsorption of benzene, toluene, ethylbenzene and xylene (BTEX) by macroreticular resins. A mass transfer model based on the squared-driving force principle is presented for describing the BTEX transfer between the aqueous and solid phases. Also proposed is a theoretical model for describing the BTEX breakthrough curves of the adsorption column. While the mass transfer model involves only an overall mass transfer coefficient, the column adsorption model has two model parameters. Those parameters are conveniently estimated using the observed mass transfer and breakthrough data. The predictions using the proposed models were found to compare well with the experimental data of batch and column BTEX adsorption tests.     

Adsorption characteristics of ammonium ion by zeolite 13X

With synthetic wastewater, lab-scale batch experiments and column experiments were carried out to investigate the adsorption characteristics of ammonium ion by zeolite 13X which is a hydrothermally synthetic byproduct accompanied with preparation of potassium carbonate from insoluble potash ores. The Langmuir and Freundlich models were applied to describe the equilibrium isotherms for ammonium ion uptake and the Langmuir model agrees very well with experimental data. Thermodynamic parameters including changes in the standard free energy (DeltaG(0)), enthalpy (DeltaH(0)) and entropy (DeltaS(0)) were also calculated. The results show that the exchange process of ammonium ion by zeolite 13X is spontaneous and exothermic. The pseudo second-order kinetic model was found to provide excellent kinetic data fitting (R(2)>0.999). The effects of relevant dynamic parameters, such as influent flow rate, adsorbent bed height and initial ammonium ion concentration on the adsorption of ammonium ion were examined, respectively. The Thomas model was applied to predict the breakthrough curves and to determine the characteristic parameters of column useful for process design and was found suitable for describing the adsorption process of the dynamic behavior of the zeolite 13X column. The total adsorbed quantities, equilibrium uptakes and total removal percents of ammonium ion related to the effluent volumes were determined by evaluating the breakthrough curves obtained at different conditions.     

Equilibrium,kinetic and thermodynamic studies on the adsorption of 2-nitroaniline onto activated carbon prepared from cotton stalk fibre

Activated carbon prepared from cotton stalk fibre has been utilized as an adsorbent for the removal of 2-nitroaniline from aqueous solutions. The influence of adsorbent mass, contact time and temperature on the adsorption was investigated by conducting a series of batch adsorption experiments. The equilibrium data at different temperatures were fitted with the Langmuir, Freundlich, Tempkin, Redlich–Peterson and Langmuir–Freundlich models. The Langmuir–Freundlich isotherm was found to best describe the experimental data. The adsorption amount increased with increasing temperature. The maximum adsorption capacity of 2-nitroaniline was found to be 383 mg/g for initial 2-nitroaniline concentration of 200 mg/L at 45 °C. The kinetic rates were modeled by using the Lagergren-first-order, pseudo-second-order and Elovich models. The pseudo-second-order model was found to explain the adsorption kinetics most effectively. It was also found that the pore diffusion played an important role in the adsorption, and intraparticle diffusion was the rate-limiting step at the first 30 min for the temperatures of 25, 35 and 45 °C. FTIR and ¹³C NMR study revealed that the amino and isocyanate groups present on the surface of the adsorbent were involved in chemical interaction with 2-nitroaniline. The negative change in free energy (ΔG°) and positive change in enthalpy (ΔH°) indicated that the adsorption was a spontaneous and endothermic process.     

Preparation and application of acrylic acid grafted polytetrafluoroethylene fiber as a weak acid cation exchanger for adsorption of Er(III)

In this work, a weakly acidic ion exchange fiber (PTFE-g-AA) has been prepared by ⁶⁰Co irradiation grafting with acrylic acid (AA) onto the polytetrafluoroethylene (PTFE) fiber. The grafted fiber was characterized by FTIR, SEM and TGA technique. The exchange capacity of the PTFE-g-AA fiber is 3.87 mmol/g. The adsorbent material was employed for Er(III) uptaking by batch and column experiments. Kinetics studies showed that the adsorption process obeyed pseudo-second-order kinetics. The adsorption isotherms followed both the Freundlich model and Langmuir model. The maximum adsorption capacity of the PTFE-g-AA fiber for Er(III) was evaluated to be 142.0 mg/g for the Langmuir model. It was found that 0.75 M HCl–0.25 M NaCl solution provided effectiveness of the desorption of Er(III) from the PTFE-g-AA fiber. Various thermodynamic parameters such as standard enthalpy (ΔH⁰), standard entropy (ΔS⁰) and standard free energy (ΔG⁰) were evaluated. The adsorption of Er(III) on the PTFE-g-AA fiber was found to be endothermic in nature. The Thomas model was successfully applied to experimental data to predict the breakthrough curves and to determine the characteristics parameters of the column useful for process design.     

Heterogeneity analysis of single-walled carbon nanotubes from the adsorption equilibria of nitrogen and benzene

Nitrogen adsorption/desorption isotherms and gravimetric methods were employed to examine the structural and adsorption properties of selected adsorbent. The equilibrium data of benzene were also obtained at three different temperatures (303.15, 313.15, and 323.15 K) with pressures up to 7 kPa. The results of nitrogen and benzene sorption isotherm revealed that SWCNTs exhibit type II with the features of type I. The Toth and UNILAN models were found to provide a reasonable correlation between the adsorption isotherm data. In addition, the adsorption second virial coefficient and the isosteric heat of adsorption were determined by using these isotherm models. The isosteric heat of adsorption and adsorption energy distribution indicated that SWCNTs have energetically and structurally heterogeneous surfaces.     

Sorption of Pb(II), Cr(III), Cu(II), As(III) to peat,and utilization of the sorption properties in industrial waste landfill hydraulic barrier layers

The low conductivity landfill barrier layers protect the groundwater and soil by limiting the water flow through the bottom layers of the landfill material. Many materials used in hydraulic barrier layers also have sorption properties which could be used to reduce environmental risks. The adsorption of lead, chromium, copper, and arsenic to peat was studied with a batch-type test and a column test for compacted peat, both without pH adjustment in acidic conditions. Peat adsorbed all the metals well, 40 000 mg/kg of lead, 13 000 mg/kg of chromium, and 8400 mg/kg of copper in the column test. Arsenic was only tested in a batch-type test, and in that peat adsorbed 60 mg/kg of arsenic. The column test showed heavy metals to be adsorbed on the surface layers of the compacted peat sample, on the first centimeter of the sample. The adsorption was much greater in the column test than in the batch-type test, partly due to the different pH conditions and the buffer capacity of the peat in the column test. The liquid/solid ratio of the column experiment represented a time period of approximately 40 years in a landfill, under Finnish climate conditions. The hydraulic conductivity of the peat decreased as it was compressed, but it already met the hydraulic conductivity limits set by European Union legislation for the hydraulic barrier layer (1 × 10⁻⁹ m/s at a pressure of 150 kPa for a 5-m layer), with a pressure of 50 kPa. The results show that peat would be an excellent material to construct compacted, low hydraulic conductivity layers with adsorption properties in, e.g. industrial waste landfills.     

Adsorption and thermodesorption characteristics of benzene in nanoporous metal organic framework MOF-5

This study has been prepared and characterized a highly nanoporous metal organic framework (MOF-5). The nitrogen adsorption isotherm, gravimetric adsorption and thermodesorption method that utilize a quartz spring balance are used to examine the unusual adsorption behavior. Especially, the hybrid Langmuir–Sips isotherm equation is employed to correlate the experimental isotherm data. Moreover, the unusual adsorption behavior in MOF-5 is discussed in relation to its isosteric enthalpy of adsorption, adsorption energy distribution and desorption energy distribution calculated from benzene adsorption and thermodesorption measurements.     

Effect of aggregate structure on VOC gas adsorption onto volcanic ash soil

The understanding of the gaseous adsorption process and the parameters of volatile organic compounds such as organic solvents or fuels onto soils is very important in the analysis of the transport or fate of these chemicals in soils. Batch adsorption experiments with six different treatments were conducted to determine the adsorption of isohexane, a gaseous aliphatic, onto volcanic ash soil (Tachikawa loam). The measured gas adsorption coefficient for samples of Tachikawa loam used in the first three treatments, Control, AD (aggregate destroyed), and AD-OMR (aggregate destroyed and organic matter removed), implied that the aggregate structure of volcanic ash soil as well as organic matter strongly enhanced gas adsorption under the dry condition, whereas under the wet condition, the aggregate structure played an important role in gas adsorption regardless of the insolubility of isohexane. In the gas adsorption experiments for the last three treatments, soils were sieved in different sizes of mesh and were separated into three different aggregate or particle size fractions (2.0–1.0 mm, 1.0–0.5 mm, and less than 0.5 mm). Tachikawa loam with a larger size fraction showed higher gas adsorption coefficient, suggesting the higher contributions of macroaggregates to isohexane gas adsorption under dry and wet conditions.     

Application of surfactant enhanced permanganate oxidation and bidegradation of trichloroethylene in groundwater

The industrial solvent trichloroethylene (TCE) is among the most ubiquitous chlorinated solvents found in groundwater contamination. The main objectives of this study were to evaluate the feasibility of using non-ionic surfactant Simple Green™ (SG) to enhance the oxidative dechlorination of TCE by potassium permanganate (KMnO₄) employing a continuous stir batch reactor system (CSBR) and column experiments. The effect of using surfactant SG to enhance the biodegradation of TCE via aerobic cometabolism was also examined. Results from CSBR experiments revealed that combination of KMnO₄ with surfactant SG significantly enhanced contaminant removal, particularly when the surfactant SG concentrated at its CMC. TCE degradation rates ranged from 74.1% to 85.7% without addition of surfactant SG while TCE degradation rates increased to ranging from 83.8% to 96.3% with presence of 0.1 wt% SG. Furthermore, results from column experiments showed that TCE was degraded from 38.1 μM to 6.2 μM in equivalent to 83.7% of TCE oxidation during first 560 min reaction. This study has also demonstrated that the addition of surfactant SG is a feasible method to enhance bioremediation efficiency for TCE contaminated groundwater. The complete TCE degradation was detected after 75 days of incubation with both 0.01 and 0.1 wt% of surfactant SG addition. Results revealed that surfactant enhanced chemical oxidation and bioremediation technology is one of feasible approaches to clean up TCE contaminated groundwater.     

Grass waste: A novel sorbent for the removal of basic dye from aqueous solution

The aim of the present work was to investigate the feasibility of grass waste (GW) for methylene blue (MB) adsorption. The adsorption of MB on GW material was studied as a function of GW dose (0.05–1.20 g), solution pH 3–10, contact time and initial concentration (70–380 mg/L). The influence of these parameters on the adsorption capacity was studied using the batch process. The experimental data were analyzed by the Langmuir and Freundlich isotherms. The adsorption isotherm was found to follow the Langmuir model. The monolayer adsorption capacity was found to be 457.640 mg/g. The kinetic data were fitted to the pseudo-first-order and pseudo-second-order models, and were found to follow closely the pseudo-second-order kinetic model. The results revealed that GW adsorbent is potentially low-cost adsorbent for adsorption of MB.     

Nitrate removal from aqueous solutions by cross-linked chitosan beads conditioned with sodium bisulfate

The investigation of adsorption of nitrate onto chitosan beads modified by cross-linking with epichlorohydrin (ECH) and surface conditioning with sodium bisulfate was performed. The results indicated that both cross-linking and conditioning increased adsorption capacity compared to normal chitosan beads. The maximum adsorption capacity was found at a cross-linking ratio of 0.4 and conditioning concentration of 0.1 mM NaHSO₄. The maximum adsorption capacity was 104.0 mg g⁻¹ for the conditioned cross-linked chitosan beads at pH 5, while it was 90.7 mg g⁻¹ for normal chitosan beads. The Langmuir isotherm model fit the equilibrium data better than the Freundlich model. The mean adsorption energies obtained from the Dubinin-Radushkevich isotherm model for all adsorption systems were in the range of 9.55–9.71 kJ mol⁻¹, indicating that physical electrostatic force was potentially involved in the adsorption process.     

Boron removal from aqueous solutions by ion-exchange resin: column sorption-elution studies

A column sorption-elution study was carried out by using a strong base anion-exchange resin (Dowex 2 x 8) for the removal of boron from aqueous solutions. The breakthrough curve was obtained as a function of feed flow rate and the total and breakthrough capacity values of the resin were calculated. The boron on the resin was quantitatively eluted with 0.5M HCl solution at different flow rates. Three consecutive sorption-elution-washing-regeneration-washing cycles were applied to the resin in order to investigate the reusability of the ion-exchange resin. Total capacity values remained almost the same after three sorption-elution-regeneration cycles. The Thomas and the Yoon-Nelson models were applied to experimental data to predict the breakthrough curves and to determine the characteristic column parameters required for process design. The results proved that the models would describe the breakthrough curves well.     

Prediction of hot compression flow curves of Ti–6Al–4V alloy in α + β phase region

Prediction of material flow behavior is essential for designing the forming process of any material. In this research, experimental flow curves of Ti–6Al–4 V alloy were obtained using the isothermal hot compression test done at 750–950 °C with 50 °C intervals and constant strain rates of 0.001, 0.005 and 0.01 s⁻¹. For prediction of hot deformation flow curves two methods of modeling were applied. In the first method, an entire flow curve was modeled using Sellars equation. In the second one, modeling of a flow curve up to the peak point was carried out with Cingara model, and modeling beyond that was performed with a model developed based on the Johnson–Mehl–Avrami–Kolmogorov (JMAK) theory. The accuracy of each model was examined through a statistical method. Results showed that flow curve modeling using Cingara model and JMAK theory leads to results that are more consistent with the experimental data.