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1.
A ternary composite consisting of carboxymethyl chitosan, hemicellulose, and nanosized TiO2 (CHNT) was prepared by incorporating TiO2 nanoparticles into the pre-synthesized carboxymethyl chitosan-hemicellulose polysaccharide network. The microstructure and chemical composition of the obtained CHNT was characterized by TEM, SEM, FTIR, and TGA. The adsorption of some toxic heavy metals including Ni(II), Cd(II), Cu(II), Hg(II), Mn(VII), and Cr(VI), onto the as-prepared CHNT composite was investigated. The effects of pH, temperature and contacting time on the adsorption process were studied. Results revealed that the CHNT composite exhibited efficient adsorption capacity of the above metal ions from aqueous solution due to its favorable chelating groups in structure. The adsorption process was best described by the pseudo-second-order kinetic model, while isotherm modeling revealed that the Langmuir equation better described the adsorption on CHNT as compared to Freundlich model. Moreover, the CHNT loaded metal ions can be easily regenerated with EDTA and reused repeatedly up to five cycles. The environmental friendly hybrids were expected to be a promising candidate for future practical application in heavy metal contaminated water treatment.  相似文献   

2.
Polypropylene-based chelating fibers grafted with acrylic acid and acrylamide side chains were simply synthesized, and subsequently employed as adsorbents for Pb(II) removal selectively from aqueous solutions. The assynthesized fibers were characterized by elemental analysis, Fourier transform infrared spectroscopy, scanning electron microscope, and water contact angle. The adsorption results revealed that kinetics data were fitted by a pseudo-second order model (semi-saturation time 6.2 min), thereby suggesting chelating interaction to be the main mechanism during the adsorption process. The adsorption isotherm data fitted well with a Langmuir model. The thermodynamic study revealed the adsorption of Pb(II) as an exothermic spontaneous chemisorptive process. Coexisting Na(I), Mg(II), and Al(III) in solution showed negligible effects in the adsorption process. As confirmed by carboxyl amination, the carboxylate oxygen preferentially chelates coexisting Ca(II) over Pb(II), thereby leading to lower extents of Pb(II)-O chelate interaction. The spent fibers were effectively and repetitively (five cycles) regenerated while maintaining high performance upon treatment with 1 M hydrochloric acid solutions.  相似文献   

3.
茶梗木质纤维素对儿茶素类吸附动力学研究   总被引：4，自引：1，他引：3  
以茶梗为原料制备木质纤维素,通过静态吸附,研究茶梗木质纤维素在绿茶提取物溶液中对儿茶素类的吸附动力学。结果表明,茶梗木质纤维素对儿茶素类总量的吸附等温线符合Freundlich经验方程,随着温度的升高,茶梗木质素纤维素对儿茶素类的平衡吸附量降低;动力学研究数据用拟一级速率方程和拟二级速率方程模拟,其中拟二级速率方程拟合程度更高,在不同温度下利用拟二级速率方程计算的总儿茶素类饱和吸附量与实测值吻合。随着温度的升高,速率常数k1和k2提高,而总儿茶素类的初始吸附速率降低。  相似文献   

4.
In this work, cellulose-based macroporous cryogels were fabricated by grafting with acrylic acid and acrylamide, which provided the carboxyl and amino functional groups, respectively. The effects of crosslinker, extra water, acrylic acid/ (acrylic acid+acrylamide) feeding ratio on the structure and swelling performance of the resultant cryogels were experimentally investigated. Cellulose-based cryogels with different pore size were prepared by adjusting the reaction parameters. The pore size and functional group contents influenced the swelling behavior of the cryogels. The fabricated cryogels were also investigated as an adsorbent for the removal of toxic methyl blue (MB) from aqueous solution. The interconnected macroporous structure as well as large number of functional groups of the cryogels led to the high adsorption capacity of MB. The maximum adsorption capacity was around 990.1 mg per 1 g dye gel within 60 min. The investigation of the adsorption kinetics revealed that the adsorption process of MB from aqueous solution was well described by pseudosecond order kinetic model. Large-scale preparation of cryogel adsorbents with tunable porous structure and surface functional groups are possible. Therefore, the macroporous cellulose-based cryogels can be used as an adsorbent for the removal of chemical toxic products from aqueous solution.  相似文献   

5.
Long term performance of conductivity of p-toluene sulfonic acid (pTSA) doped electrochemically synthesized polypyrrole (PPy) films was estimated from accelerated aging studies between 80 °C and 120 °C. Conductivity decay experiments indicated that overall aging behavior of PPy films deviated from first order kinetics at prolonged aging times at elevated temperatures. However, an approximate value for the activation energy of the conductivity decay of PPy was calculated as E=47.4 kJ/mol, enabling an estimate of a rate constant of k=8.35×10−6/min at 20 °C. The rate of decrease of conductivity was not only temperature dependent but also influenced by the dopant concentration. A concentration of 0.005 M pTSA in the electrolyte resulted in a conductive film and when this film was exposed to 120 °C for a period of 40 h, the conductivity decayed to about 1/20 of its original value. The concentration of pTSA was increased to 0.05 mol/l and when the resulting film was aged in the same way, it showed a decrease in the conductivity to about 1/3 of its original value. Both microwave transmission and dc conductivity data revealed that highly doped films were considerably more electrically stable than lightly doped films. The dopant had a preserving effect on the electrical properties of PPy.  相似文献   

6.
Quantitative adsorption kinetic and equilibrium parameters for indigo carmine dyeing of silk were studied using UV-visible absorption spectroscopy. The effect of initial dye concentration, contact time, pH, material to liquor ratio (MLR), and temperature were determined to find the optimal conditions for adsorption. The mechanism of adsorption of indigo carmine dyeing onto silk was investigated using the pseudo first-order and pseudo second-order kinetic models. The adsorption kinetics was found to follow a pseudo-second-order kinetic model with an activation energy (E a) of 51.06 kJ/mol. The equilibrium adsorption data of indigo carmine dye on silk were analyzed by the Langmuir and Freundlich models. The results indicate that the Langmuir model provides the best correlation. Adsorption isotherms were also used to obtain thermodynamic parameters such as free energy (ΔG o), enthalpy (ΔH o), and entropy (ΔS o) of adsorption. The negative values of ΔG o and ΔH o indicate the overall adsorption process is a spontaneous and exothermic one.  相似文献   

7.
Macroporous PVA/HAp composite cryogel was studied for cadmium removal in a fixed-bed column. The cryogel was made through a freeze-thawing process. The morphology of the cryogel was measured. The adsorption performance of the cryogel in the column was examined by varying bed height and HAp amount in PVA cryogel. The maximum adsorption capacity and exhaustion time were determined from the breakthrough curves. The experimental data was described using Adams-Bohart model. Bed height did not exert a large influence on the maximum adsorption capacity and exhaustion time. The kinetic rate constant and the adsorption capacity of the bed were found to be affected by HAp amount.  相似文献   

8.
In this study, amide and amine groups bound to poly(ethylene terephthalate) fibers are used to remove the colored toxic Congo red dye from aqueous solution. The effects of process variables like pH, contact time, graft yield, and initial dye concentration on the adsorption were investigated. The maximum adsorption of Congo red to amide and amine groups was observed at pH 3 and 5 respectively. Equilibrium was attained at approximately 60 min for the amine group. The adsorption capacity of amine group on the poly(ethylene terephthalate) fiber was 46.5 mg g−1 at 25 °C, which was higher than that of the amide group on the poly(ethylene terephthalate) fiber. Desorption was done using 0.1 M NH3, and recovery was measured at 58.2 %. The used adsorbent was regenerated and recycled six times. The results showed that the amine-functionalized fiber could be considered as potential adsorbents for removal of Congo red from aqueous solution.  相似文献   

9.
Polyindole nanofibers were prepared via electrospinning method using acetonitrile as solvent. The obtained electrospun polyindole nanofibers were characterized with SEM, TEM, FTIR and BET surface areas measurements. Adsorption experiments were carried out in batch sorption mode to investigate the effect of pH, contact time and diameter of polyindole nanofibers. The Cu(II) adsorption was highly pH dependent and the optimum pH was found to be 6. The maximum adsorption capacities for electrospun polyindole nanofibers and polyindole powders were 121.95 and 18.93 mg/g attained in 15 and 60 min, respectively. With the diameter of polyindole nanofibers increasing, the adsorption capacity slightly decreased. The adsorption isotherm data fitted well to the Langmuir isothermal model which indicates that the monolayer adsorption occurred. The kinetics data analysis showed that the adsorption process could be described by pseudo-second order kinetic model, suggesting a chemisorption process as the rate limiting step. Thermodynamic parameters ΔHº, ΔSº and ΔGº for the Cu(II) adsorption by polyindole nanofibers were calculated. The results showed that the Cu(II) adsorption was feasible, spontaneous and endothermic. Desorption results revealed that the adsorption capacity can remain up to 75 % after 10 times usage. The electrospun polyindole nanofibers would have promising application for removal of Cu(II) from wastewater treatment.  相似文献   

10.
In this work, an affinity nanofiber membrane was successfully prepared by solution blowing of arginine-modified chitosan (CS-Arg) for bovine serum albumin (BSA) adsorption. CS-Arg was firstly synthesized by coupling L-arginine onto chitosan backbone. Then, CS-Arg nanofiber membranes (CANFs) were fabricated using solution blowing process with Polylactide (PLA) as assistant polymer. The results showed that CANFs effectively adsorbed BSA, and the adsorption capacities were influenced by the degrees of substitution (DS) of arginine in CS, pH value, contact time, and initial protein concentration. The highest adsorption capacity of 445.19 mg/g was achieved uvnder the following conditions: DS of 43.7 %, pH of 7.14, and initial concentration of 3.0 mg/ml. BSA adsorbed on the CANFs membrane conformed to Langmuir model, and the adsorption rate was consistent with the second-order kinetics model. This work implies that an arginine-modified chitosan nanofiber-based novel biomaterial has a potential application in adsorption of BSA.  相似文献   

11.
Poly(methyl methacrylate-glycidiyl methacrylate) p(MMA-GMA) film was fabricated by UV initiated photo-polymerization. Iminodiacetic acid ligand (IDA) was covalently immobilized to the p(MMA-GMA) film via ring opening reaction of epoxy groups. Cu(II) ion was chelated with the immobilized ligand. The morphology and properties of the films were characterized with SEM, FTIR, AFM, water content, the specific surface area, and contact angle. HSA (human serum albumin) was used as a model protein to describe the adsorption propency of the support. The information obtained in this research will serve for scaling up the process in industrial applications. The HSA adsorption capacity of the metal chelated film was found to be 2.7 mg/cm2 film. The p(MMA-GMA)-IDA-Cu(II) films exhibited a high adsorption capacity and fast adsorption rate compared to Cu(II) ion free counterpart.  相似文献   

12.
Polyurethane (PU) films containing different amounts of fly ash particles (FAPs) were prepared by simple solution casting method. The morphological, thermal, and mechanical properties of the composite films were investigated by several characterization methods. Results show that sufficient amounts (up to 40 wt%) of FAPs can be incorporated throughout the film. The presence of FAPs within PU film not only acts as filler to increase the mechanical strength of the film but also increases its volatile organic compounds (VOCs) adsorption capacity. The VOCs adsorption capacity of FAPs/PU composite films were investigated on three different compounds (chloroform, toluene, and benzene). It showed consistent trend in the order of toluene > benzene > chloroform for all the samples. The VOCs adsorption capacity of PU film was found to be increased by two fold when 20 wt% of FA was incorporated through it. The present results suggest the potential use of FAPs as filler materials for PU films with improved VOCs adsorption from outdoor and indoor air.  相似文献   

13.
In this paper, the surface of magnetic manganese ferrite nanoparticles (MFN) was modified using cetyl trimethylammonium bromide (CTAB). The modified MFN was studied using Fourier transform infrared spectroscopy (FTIR). The adsorption capacity of surface modified MFN (MFN-CTAB) was investigated for dye removal for single and ternary systems. Three anionic dyes, C.I. Direct Red 80 (DR80), C.I. Direct Red 31 (DR31), and C.I. Acid Blue 92 (AB92), were used as model compounds. The effects of operational parameters on dye removal (i.e. adsorbent dosage, dye concentration and salt) and the kinetic and isotherm of dye adsorption were studied. The adsorption kinetic for the dyes was found to be well described by the pseudo-second order model. The maximum dye adsorption capacity (Q 0) of MFN-CTAB for DR80, DR31 and AB92 was 83 mg/g, 59 mg/g and 70 mg/g, respectively. The adsorption isotherm data were analyzed using the Langmuir, Freundlich, and Temkin equations. The results revealed that the Langmuir model fitted the adsorption data better. The results showed that the MFN-CTAB as a magnetic adsorbent might be a suitable alternative to remove dyes from colored aqueous solutions.  相似文献   

14.
Novel regenerated cellulose material which was prepared from cellulose acetate fiber through the hydrolysis of acetyl groups have been developed by an environmentally friendly process without emitting toxic substances in addition to be at low production cost. They have composite crystalline structure constituted of cellulose II and cellulose IV. Also, they show a lamellar morphology with an increased amorphous region, as compared to conventional regenerated cellulose such as viscose rayon and cupra rayon. Our data obtained by several independent methods demonstrated that the adsorption properties of cellulose fibers depend predominantly on the amorphous region.  相似文献   

15.
研究了咖啡壳对亚甲基蓝和碱性品红的吸附性能,考察了咖啡壳的粒径、投加量、溶液p H、吸附时间、温度等条件对吸附效果的影响。应用准一级动力学方程和准二级动力学方程模拟了咖啡壳吸附亚甲基蓝和碱性品红的动力学过程,结果表明准二级动力学方程适合描述整个吸附过程。文中计算了吉布斯自由能(ΔG0)、焓变(ΔH0)、熵变(ΔS0)等热力学参数,ΔG0、ΔH0均小于0、ΔS0大于0,说明此吸附过程是一个自发的无序的放热过程。  相似文献   

16.
Cellulose hybrids containing polyhedral oligomeric silsesquioxane (POSS) were synthesized by crosslinking reaction. The chemical and morphological structures of the hybrids were characterized by elemental analysis, infrared spectrum, scanning electron microscope and atomic force microscope. The hybrids were used for adsorbing C.I. Reactive Red 250 in aqueous solution. Adsorption kinetic and equilibrium isotherm of the cellulose hybrids for the dye were investigated. The hybrids formed new adsorptive positions for dyes because of a nanometer-sized cubic core and numerous organic functional groups (-C-N-). The adsorption capacity of the hybrid materials was significantly higher than that of the control cellulose. The adsorption of the dye on the hybrids was good fit with Langmuir isotherm equation and the second-order model. The apparent activation energy of the dye on the hybrid was 14.87 kJ/mol.  相似文献   

17.
Different silk substrates in form of spun silk tops, nonwoven web, yarn, and fabric were coated with electrically conducting doped polypyrrole (PPy) by in situ oxidative polymerization from an aqueous solution of pyrrole (Py) at room temperature using FeCl3 as catalyst. PPy-coated silk materials were characterized by optical (OM) and scanning electron (SEM) microscopy, FT-IR spectroscopy, and thermal analysis (DSC, TG). OM and SEM showed that PPy completely coated the surface of individual silk fibers and that the polymerization process occurred only at the fiber surface and not in the bulk. Dendrite-like aggregates of PPy adhered to the fiber surface, with the exception of the sample first polymerized in the form of tops and then spun into yarn using conventional industrial machines. FT-IR (ATR mode) showed a mixed spectral pattern with bands typical of silk and PPy overlapping over the entire wavenumbers range. DSC and TG showed that PPy-coated silk fibers attained a significantly higher thermal stability owing to the protective effect of the PPy layer against thermal degradation. The mechanical properties of silk fibers remained unchanged upon polymerization of Py. The different PPy-coated silk materials displayed excellent electrical properties. After exposition to atmospheric oxygen for two years a residual conductivity of 10–20 % was recorded. The conductivity decreased sharply under the conditions of domestic washing with water, while it remained essentially unchanged upon dry cleaning. Abrasion tests caused a limited increase of resistance. PPy-coated silk tops were successfully spun into yarn either pure or in blend with untreated silk fibers. The resulting yarns maintained good electrical properties.  相似文献   

18.
In this present study, an organic-inorganic hybrid membrane was prepared by embedding yttrium(III) into chitosan matrix for the removal of Cr(VI) from aqueous solutions. Several techniques, including fourier infrared spectrum (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), and transmission electron microscope (TEM) are employed to characterize the properties of the membrane. The mechanical properties of the membrane were also examined. The chitosan/poly(vinyl alcohol) containing yttrium(III) (CY) membrane was experimentally used for the removal of Cr(VI) ions from aqueous solution under the optimized conditions. The results showed that the adsorption capacity for the removal of Cr(VI) ions was enhanced when yttrium(III) was introduced. The adsorption data from the experiment were fit well by Langmuir isotherm. Based on Langmuir model, q m was calculated to be 38.48 mg g?1. Kinetic study results indicated that the adsorption process followed a pseudo-second-order kinetics.  相似文献   

19.
Polyethylene terephthalate (PET) textile was coated with anionic cyclodextrin polymer issued by crosslinking between β-CD (β-Cyclodextrin) and BTCA (1,2,3,4-butanetetracarboxylic acid) for paraquat (PQ) removal from aqueous solution. The polymer covering operated by the thermofixation method (170 ºC and 30 minutes) comprised 23.52 % of weight gain, which was related to 0.76 mmol/g of ionic exchange capacity. The functionalized textile was also characterized by FTIR, SEM and TGA. Adsorption experiment was performed employing different parameters such as the pH of the solution, adsorption time, the initial concentration of paraquat and the adsorption temperature. The suitable pH was equal to 8 and the equilibrium time was 420 minutes. At 30 ºC, the adsorption capacity of PQ was increased (5.0, 20.4, and 25.9 mg/g) when the initial concentration of paraquat was enhanced (10, 50, and 250 mg/l). Adsorption kinetics was appropriated to the pseudo-second-order model and adsorption isotherm was fitted to the Langmuir model. Thermodynamic parameters were studied at different temperatures (30, 40, and 50 ºC), in which the negative ΔH displayed an exothermic adsorption process, the negative ΔG showed a spontaneous adsorption process and the positive ΔS revealed an enhanced disorder. Eventually, the recyclability of the modified textile in methanol reached 85 % after four reusability cycles.  相似文献   

20.
In this paper, we report the modification of polyamide sample (PA) with different contents of chitosan (CS) using citric acid (CA) as a cross-linker [PA-CA-CS]. New materials were confirmed to be formed in PA using FT-IR spectrum. It is also checked in terms of the change in thermal stability event and decomposition behavior in thermogravimetry through TG-DTA instruments. Then, the ability of unmodified and modified supports was tested for the adsorption of two reactive dyes i.e. Cibacron Brilliant Yellow 3G-P and Cibacron Blue P-3R. Sorption experiments were performed under varying several experimental conditions such as pH, contact time, initial dye concentration, and temperature. The isotherm and kinetic models were undertaken to assess the dye removal mechanism. The applicability of Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin equations was checked and data were fitted using Langmuir model. The second-order equation was shown to fit the adsorption kinetics. Data gleaned from both thermodynamic results and modeling data indicate that the adsorption follows a chemical and exothermic process.  相似文献   

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