Green and Efficient Synthesis of an Adsorbent Fiber by Plasma-induced Grafting of Glycidyl Methacrylate and Its Cd(II) Adsorption Performance

A new chelating adsorbent for the removal of Cd(II) from aqueous solution, PP-g-GMA-DETA fibers, is prepared by plasma induced grafting of glycidyl methacrylate (GMA) onto the surface of polypropylene (PP) fibers, followed by modification with diethylenetriamine (DETA). The effects of grafting parameters on the grafting degree are investigated. Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy prove the successful grafting of GMA onto the surfaces of PP fibers and the subsequent conversion of epoxy groups of grafted GMA to amine groups, on reaction with DETA. The adsorption performances of Cd(II) by the chelating fibers are evaluated in detail. Kinetic and isothermal parameters are also evaluated. The data fit well with the pseudo-second order and Langmuir isotherm model, respectively. The maximum adsorption capacity of Cd(II) is 46.47 mg g^-1 and the prepared fibers show selective adsorbability towards target Cd(II) in presence of competing Mg(II) ions.     

Ternary carboxymethyl chitosan-hemicellulose-nanosized TiO<Subscript>2</Subscript> composite as effective adsorbent for removal of heavy metal contaminants from water

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.     

Use of amino-modified cotton fibers loaded with copper ions for anionic dye removal under batch and fixed-bed systems: A comparative study

Amine-functionalized supports were prepared by chemical modification of cotton fibers using amino compounds namely diethylenetriamine (DET) and 1,4-diaminobutane (DB) in order to be loaded with copper ions. Evidence of attaching amine groups onto cellulosic fibers was confirmed through nitrogen and SEM analysis. Adsorption behavior of Acid Blue 25 from aqueous solutions onto [Cu(II)/DET-cotton] and [Cu(II)/DB-cotton] has been evaluated via batch and column mode systems. During the batch experiments, the effects of temperature and type of adsorbent on dye removal were investigated. Results revealed the formation of ternary complexes of the type [AB25/Cu(II)/adsorbent] with a [5/2:3:1] stoichiometry for DET-cotton and a [1:1:1] stoichiometry for DB-cotton at 20 °C. In the isotherm studies, Langmuir, Freundlich, and Jossens equations were applied and it was found that the experimental data conformed to Jossens model. Thermodynamic parameters such as change in free energy (ΔG ⁰), enthalpy (ΔH ⁰), and entropy (ΔS ⁰) have also been calculated in this paper, and it was found that the adsorption process was exothermic and spontaneous. The column experiments were conducted to study the effect of bed height on adsorption performance of both adsorbents. Results exhibited that the column capacity of [Cu(II)/DET-cotton] complex was found to be higher than that of [Cu(II)/DB-cotton] as was obtained in batch process. BDST model was applied to experimental data in order to predict the breakthrough curves and determine the characteristics parameters of the column useful for process design. Results revealed that the used model was appropriate to fit the experimental data. Desorption studies to recover the adsorbed dye from both adsorbents were performed with NaOH and NH₄Cl solutions.     

Electrospun polyindole nanofibers as a nano-adsorbent for heavy metal ions adsorption for wastewater treatment

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.     

Chemical synthesis of polypyrrole film and its adsorption capacity for aromatic polycarboxylic acids

Polypyrrole (PPy) film was prepared via in-situ chemical polymerization of pyrrole monomer on the surface of red-clay-brick (RCB) substrate. The deposited PPy film was characterized and used as an adsorbent for removal of benzene polycarboxylic acids from aqueous solutions. The effects of solution pH, contact time, initial concentration, and temperature on the adsorption process were systematically investigated to find the optimum operating conditions. Adsorption kinetic data were best fitted by pseudo-second order kinetic model. The adsorption equilibrium data were most represented by the Freundlich isotherm model. The maximum adsorption amounts of Trimellitic, Hemimellitic, and Pyromellitic acids were 189.27, 177.26, and 203.31 mg/g, respectively. The thermodynamic studies indicate that the adsorption was an endothermic and spontaneous process. Also, the PPy-RCB film was successfully regenerated using sodium hydroxide solution. The regenerated PPy-RCB can be reused for more than four successive cycles with a low reduction in adsorption efficiency.     

Removal of Pb(II) and Cr(VI) ions from aqueous solutions using chitosan/cobalt ferrite nanofibrous adsorbent

In the present study, the chitosan/cobalt ferrite nanofibrous adsorbent was produced via electrospinning process and its application for the removal of Pb(II) and Cr(VI) ions from aqueous systems was investigated. The cobalt ferrite nanoparticles were synthesized via convectional hydrothermal method and were characterized using XRD, SEM and TEM analysis. The influence of sorption parameters in a batch mode including cobalt ferrite content, pH, contact time, metal ions initial concentration and temperature on the sorption efficiency of Pb(II) and Cr(VI) ions was evaluated. The kinetic data were fitted using pseudo-first-order and pseudo-second-order kinetic models and the isotherm models including Freundlich, Langmuir and Redlich-Peterson were used to describe the equilibrium data of Pb(II) and Cr(VI) sorption using synthesized nanofibrous adsorbent. Thermodynamic parameters investigation showed the spontaneous and endothermic sorption of Pb(II) and Cr(VI) ions. The Pb(II) and Cr(VI) sorption efficiency was also examined during five sorption-desorption cycles by regeneration of nanofibers via 1 M HNO₃. The simultaneous influence of metal ions initial concentration on the Pb(II) and Cr(VI) sorption in a binary system was also investigated.     

Surface modification and ternary system dye removal ability of manganese ferrite nanoparticle

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.     

Adsorption of Graphene Oxide onto Synthetic Fibers: Experimental Conditions

Comparative studies on the adsorption capacity of two synthetic fibers, polyamide (PA 66) and polyester (PET) pre-treated with N-cetylpyridinium chloride (PET-NCPCl), towards graphene oxide (GO) have been carried out. The fiber samples were characterized by scanning electron microscopy (FE-SEM) and Raman spectroscopy. The results of adsorption isotherms, kinetics, and zeta potential determinations as a function of the GO concentration, pH, and temperature show that at a low pH of 2.5 and a high temperature of 323 K, almost 99 % of the 75 mg/l GO solution is adsorbed onto PA 66 and 70 % onto the PET-NCPCl fibers. The interaction should be first attributed to electrostatic forces, also the adsorption data exhibited a good fit to the Freundlich isotherm model and the free energy value of 10 kJ/mol was in the range of physical adsorption, which could suggest that the interaction is driven mainly by physical forces. Due to the increasing development of wastewater treatments based on the GO reactivity with metals and cationic contaminants, synthetic fibers coated with GO could be considered an adsorbent for environmental applications.     

Polyacrylic acid-grafted magnetite nanoparticles for remediation of Pb(II)-contained water

Toxic Pb(II) contaminants in water pose a significant threat to the environment and public health, and thus technologies for Pb(II) remediation are attracting increasing industrial interests. In the present work, polyacrylic acid, offering abundant carboxyl groups capable of coordination with Pb(II) cations, was grafted from the magnetite nanoparticle surface via the bridging function of silane coupling agent for remediation of Pb(II)-contained water. Multiple techniques were employed to characterize the structure of the nanocomposite, and the effects of nanoadsorbent dose, pH value, and temperature on Pb(II) removal capability of the nanocomposite were investigated, respectively. Furthermore, adsorption kinetics and isotherms studies were performed for better understanding the mechanism by which Pb(II) cations were adsorbed. Finally, the feasibility of regenerating the exhausted nanoadsorbent by simply changing pH value was explored. According to these results, we intend to offer an efficient, separable, and reusable magnetic nanoadsorbent that may be a potential candidate for remediating Pb(II) contamination in water.     

Coating of PET Textiles with Anionic Cyclodextrin Polymer for Paraquat Removal from Aqueous Solution

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.     

Moisture sorption isotherms, heat of sorption and properties of sorbed water of raw bamboo (Dendrocalamus longispathus) shoots

Moisture sorption isotherms of raw bamboo shoot were determined by static gravimetric technique based on isopiestic transfer of water vapor at 20, 30 and 35 °C. Inorganic saturated salt solutions in the range of 11.2-97.2% were used to create the required controlled humidity environment in a closed chamber. In the study, the sorption isotherms obtained were of sigmoid shape and of BET II type classification. Out of three sorption models i.e., BET, Caurie and GAB, fitted to the experimental data, Caurie model was found superior in interpreting the moisture sorption characteristics of bamboo shoot at three temperatures. The monolayer moisture content M_m as estimated by the best fitted Caurie's model for the sorption processes were 6.012%, 5.801%, 5.014%, and 5.987%, 5.816%, 4.998% (dry basis) at 20, 30, and 35 °C, respectively. The isosteric heats of sorption for both the adsorption and desorption process of bamboo shoots were found to increase with decrease in moisture content suggesting endothermic reaction at lower moisture content and it approached the value of heat of vaporization of free water at higher moisture content.     

Tobacco stems as a low cost adsorbent for the removal of Pb(II) from wastewater: Equilibrium and kinetic studies

Adsorption of Pb(II) ions from aqueous solution onto tobacco stems has been investigated to evaluate the effects of initial lead ion concentration, adsorbent dosage, contact time, pH and temperature on the removal of Pb(II) systematically. The optimal pH value for Pb(II) adsorption onto the tobacco stems was found to be 5.0. The removal of lead ions for concentrations 10, 30 and 50 mg L⁻¹ using 0.8 g adsorbent at contact time of 120 min and at temperature of 299 K were 94.37%, 92.10% and 90.43%, respectively. Thermodynamic parameters such as standard Gibbs free energy (ΔG°), standard enthalpy (ΔH°), and standard entropy (ΔS°) were evaluated by applying the Van’t Hoff equation, which describes the dependence of equilibrium constant on temperature. The thermodynamics of Pb(II) adsorption onto the tobacco stems indicated that the adsorption was spontaneous and endothermic. Langmuir and Freundlich isotherms were used to analyze the equilibrium data at different temperatures and the equilibrium data were found to fit Freundlich isotherm equation better than Langmuir isotherm. The adsorption was analyzed using pseudo-second-order kinetic equation.     

Controlling supermolecular structures and improving colorfastness in cotton fibers

A new discovery was made in which commercially available triethanolamine could reduce the lattice volume of the supermolecular structure of cotton from the periphery of the lattice by moving cellulose chains on the surface of the crystallites to the amorphous regions, thereby decreasing the close-packed crystallization volume and leading to an increased free volume of the amorphous regions. Subsequently, several supermolecular structures for cotton fibers were successfully controlled to improve the colorfastness in cotton fibers at the molecular level. With the decrease in the degree of crystallinity, more unfixed dyes could be removed by washing reagents, whereas the remaining dyes were mostly fixed to the cotton by covalent bonds, causing a stronger colorfastness, with the best wet rubbing fastness reaching a relatively permanent grade 4. Moreover, the effect mechanism revealed that the unfixed dyes were detached from the cotton fibers according to the reverse process of the adsorption models and that there were additional methods for the unfixed dyes in the fibers to be removed in the presence of triethanolamine than when using pure water. In addition, the binding forces of dye adsorption in the cotton fibers decreased, while the entropy of dye adsorption was higher than that measured when using pure water. Thus, the results suggested that controlling the supermolecular structures of the cotton fibers promoted the removal of unfixed dyes from the fibers and achieved improved colorfastness.     

Modified polyamide 66 fibers for the removal of reactive dyes from aqueous suspension

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.     

Enzymatic treatment on cotton fibers: degradation kinetics of pectin and influence of shape change on adsorption

Alkaline pectinase was one of the most effective enzymes to treat cotton as alternative agent to replace the conventional alkaline method. Removal of pectin and cutin was considered the explanation for improvement of wettability as well as water adsorption on cotton fiber. However, degradation kinetics of pectin is unclear, and the influence of fiber shape on property changes after enzymatic treatment was ignored. The main objective of this work was to reveal interactions between pectinase and cotton fiber for mechanism study. A heterogeneous catalysis kinetic equation, which is associated with Langmuir adsorption model and enzyme deactivation, was used to describe the heterogeneous catalysis. The enzymatic process conditions were optimized. Raw cotton fibers, pectinase-treated and alkali-treated fibers were characterized by impurities content determination, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscope (SEM). Mechanism of water adsorption enhancement on treated fibers was discussed. In addition to elimination of the outer impurities, flat fibers with less twist and shape changes of lumen were also obtained to ensure better accessibility and water adsorption after enzymatic treatment.     

钠基蒙脱石对菜籽油中磷脂的吸附行为研究

为了解钠基蒙脱石（sodium montmorillonite, Na-MMT）在油脂脱胶过程中的吸附行为以及吸附机理,采用钠化方法将钙基蒙脱石制备成Na-MMT,并对其进行X射线衍射和热重分析;利用Na-MMT对菜籽油中的磷脂（phospholipids, PL）进行吸附,探讨PL在Na-MMT上的静态吸附平衡、吸附动力学和吸附热力学。结果表明,Na-MMT对PL的最大理论吸附量为833.3mg/g;Na-MMT对PL的吸附是属于优惠吸附,吸热且自发进行。Freundlich吸附模型能够较好地拟合其静态吸附行为;同时拟二级吸附动力学模型适用于描述Na-MMT吸附PL的动力学特性。 [     

Medical Waste Treatment via Waste Electrospinning of PS

Body fluid medical wastes are infectious clinical wastes (blood, saliva, urine) due to their high pathogenic content. Incineration is the most commonly used method in waste management that possess high water content along with molecularly dissolved species such as proteins. The process is costly; so that the removal of solid content dissolved in aqueous part by preliminary filtration can reduce the volume of the waste material. In this study, fibrous mats were prepared by electrospinning of PS wastes from DMF and THF solutions. Then they are employed in the removal of protein-based solid contents of body fluid medical wastes before their disposal. Two sources of PS waste (CD cover and Styrofoam) were employed along with virgin PS for comparison. The adsorption capacity of as-prepared electrospun fibers was examined for three model proteins: Bovine Serum Albumin (BSA), Myoglobin (MYO), and Trypsin (TRY). The fibers obtained from PS CD wastes have remarkably larger protein sorption capacities (particularly BSA) than the fibers obtained from virgin PS. XPS reveals the presence of CaCO₃ domains in CD covers added into PS during their production steps probably to increase mechanical properties. There may be an electrostatic interaction between Ca²⁺ and the negatively charged groups of the protein. In this way, PS wastes could be converted to a beneficial secondary product by electrospinning and also resulting materials promises for the disposal of body fluid medical wastes. This may be one of the frontiers study on the removal of medical wastes by adsorbents produced via electrospinning of waste polymers.     

离子交换纤维对麦田土壤铅污染的修复效果

为探讨土壤Pb污染的治理方法,通过盆栽试验,比较了离子交换纤维的两种不同放置方式(分层放置与混匀放置)对麦田土壤Pb污染的修复效果。结果表明,在土壤1 000 mg·kg~(-1) Pb污染水平下,Pb污染处理(T1:Pb胁迫;T2:Pb+在土壤中分三层放置纤维;T3:Pb+在土壤中混匀剪碎的纤维)的土壤pH值、总有机碳含量较对照(CK:未添加Pb和离子交换纤维)有所降低。在小麦成熟期,T2、T3处理下土壤和植株各部位的Pb含量均低于T1处理,其中T3处理变化显著;T2、T3处理中纤维吸附的Pb含量则分别达到115.01和128.26 mg·kg~(-1)。T2、T3处理的Pb富集系数低于T1处理及CK。由此说明,离子交换纤维能够有效吸附土壤中的Pb,降低Pb从土壤向植株的转运能力,且离子交换纤维混匀放置方式的修复效果较好。     

Synthesis of cross-linked graft copolymer from acrylic acid, poly(vinyl alcohol), and glutaraldhyde for extraction of lead ion from aqueous solution

A novel graft copolymer of acrylic acid onto poly(vinyl alcohol) has been synthesized and it is cross-linked by glutaraldehyde for the investigation of its efficiency in removing lead ion from aqueous solution. The chemical nature of the ion exchange resin has been elucidated with the help of chemical, spectral, and thermal analysis. Particle size, surface area, ion exchange capacity, optimum pH, time, and temperature for Pb(II) adsorption were determined. Metal ion adsorption kinetics, isotherms, and thermodynamics have been studied. A plausible mechanism for lead ion exchange has been suggested.     

Poly(methyl methacrylate-glycidiyl methacrylate) film with immobilized iminodiacetic acid and Cu(II) Ion: For protein adsorption

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.