Theses supervised by Prof. Dr. Bahire Filiz Şenkal
10 theses · İstanbul Technical University
Synthesis and characterization of urethane based liquid crystal materials
Liquid crystalline polymers are usually synthesized by covalent linking of rigid mesogens and polymer backbones via flexible spacers. Side chain liquid crystalline polymers (SCLCPs) integrates low-molar mass liquid crystals and polymers' one of a kind characteristics. Since SCLCPs have appealing electrical and optical characteristics, they have been the object of intense researching mostly. Among these features they can be used in microelectronic devices in range of date storage and nonlinear optics. Liquid crystals which are the unique state of matter have a wide application area such as digital displays, sensors and LCD screens. In this thesis, urethane compounds and their hydrogen bonded liquid crystal polymers were synthesized and optoelectronic properties are characterized. First, Polyethylene glycol 500 monomethyl ether (PEG 500) was reacted with butyl isocyanate (BI) and toluene diisocyanate (TDI) separately. Also, diethyleneglycol monomethyl ether (DEGME) was reacted with butyl isocyanate and toluene diisocyanate. Urethane based liquid crystalline polymers were prepared by using intermolecular hydrogen bonding concept. For this aim, hydrogen-bonded crystalline polymer was synthesized reacting urethane compounds with H-bond donors. Synthesis of Hydrogen Bond Donors: 11-(4-Cyanobiphenyl-4'-oxy) undecan-1-ol (LC11) was synthesized as a bond donor. The structure of the LC11 was characterized by FT-IR and 1H-NMR spectroscopy. Preparation of urethane based liquid crystalline polymers: Urethane based polymers were engaged as hydrogen bond acceptors and LC11 was employed as a hydrogen bond donor to yield hydrogen bonded PEG based liquid crystalline mesogen. Intermolecular H-bonding between nitrogen of amine of the polymer and hydroxyl groups of the hydrogen donors formed the structure of the side chain liquid crystalline polymers. In characterization of hydrogen bonded urethane based polymers FT-IR (Fourier Transform Infra Red) spectroscopy, DSC (Differantial Scanning Calorimetry) and POM (Polarized Optic Microscope) methods were used. Hydrogen bonding donors and acceptors are positioned that intramolecular hydrogen bonding is favorable, displaying slightly broadened O-H stretching absorption band in the range of 3200 to 3500 cm-1, according to FT-IR spectra of the polymers. The phase behavior of all the hydrogen bonded liquid crystalline polymers was studied using a combination of DSC and POM methods. DSC thermograms were obtained in second heating cycles. The samples were heated with a 10°C/min scan rate in an N2 atmosphere. POM (X200) analysis also confirmed DSC results along with the results of phase transitions.
Preparation of cross-linked poly (styrene) based resin amidated by staudinger reaction, modification with iminopropylene glycole and removal of the boron from aqueous solutions
Boron is the fifth lightest element in the periodic table and just one place before carbon. It is the only non-metallic element of group III. Although boron is broadly dispersed in geosphere, it is found as low concentration. Boron salts and boric acid are widely used in industry production of porcelain, glass, carpets, cosmetics, fire-retardant fabrics, weather proofing wood and photographic chemicals. Moreover, boron is a crucial element for system of living organism. However, excessive boron has drawback effects on humans, animals and plants. To keep it up healthy levels, the World Health Organization (WHO) has set a boundary of 2.4 mg/L of boron in potable water. Subsequently, removal of boron from wastewater is crucial issue. Removing of boron from wastewaters and waters has no simple procedures. There are numerous method for the removal of boron that are precipitation-coagulation, adsorption on active carbon or polymeric resins, cellulose or clay minerals, solvent extraction, use of boron selective resins, membrane filtration, ion exchange with basic exchanger and adsorption on oxides. Adsorption as a removing of boron compound from water sources is the best in terms of low cost, effective and easily applicable method when it is compared with the other methods. To begin with part of this study, cross-linked poly (vinyl benzyl chloride) (PVBC) resin was prepared by suspension polymerization. PVBC was modified with sodium azide. Then, amination of the resin was provided by Staudinger reaction. The last part of preparation of boron selective resin is modification of aminated resin with glycidole. The resin was characterized thanks to Fourier-transform infrared spectroscopy (FTIR) in order to understand importance of functional groups for boron selectivity. Total amine content of was determined as 3.75 mmol/g sorbent. In the second part of this study, boron sorption experiments were carried with modified resin. Effect of different boron concentration was researched for the resin. Maximum boron loading capacity of the IPG-resin was found 3.727 mmol per gram sorbent. Moreover, effect of salt and foreign ion such as Ca+2 and Mg+2 on boron sorption capacity was investigated. In addition, capacities of boron sorption were considered with varying pH value between 2.0-8-0. The last of part of this study, sorption isotherm models that Freundlich, Langmuir and Tempkin, were examined for maximum sorption capacity of resin. Furthermore, kinetics of boron sorption was studied with the similar concentration of seawater. Pseudo first order, pseudo second order and intra-particular diffusion kinetics models were applied in order to understand of efficiency of the resin. Besides, regeneration of the resin was examined. Amount of boric acid, which was recovered of the loaded resin, is 3.57 mmol/g. It was indicated that the resin has ability of desorption almost entirely.
Emulsion polymerization of vinyl acetate by urethane based surfactant and high solid content water-based emulsion polymerization of acrylic monomers
Emulsifiers, another name are surfactants, are characterized by a chemical structure comprising a hydrophilic group having one and/or two hydrophobic flexible alkyl chains of a certain length. In small quantities dispersed in the aqueous phase, the surfactant is adequate for self-assembly into the micelle micro aggregates. Surfactants are used in several areas for different purpose such as painting, emulsion polymerizations, adhesives, textile industry, etc. Surfactants are divided into four main categories. They are anionic, cationic, non-ionic and zwitterionic. In this study, a new nonionic polymeric surfactant (PU) has been synthesized with the reaction between Poly(ethylene glycol) dimethyl ether (PEG500) and Toluene 2,4-diisocyanate (TDI). The polymeric surfactant was characterized by using FT-IR spectroscopy, GPC, critical micelle measurements via tensiometer. Critical micelle concentration of PU was determined by surface tension measurements. This value was calculated as 0.68x10 mg / mL. Molecular weight of the PU was determined by gel permeation chromotography (GPC). Mw, Mn and Mz molecular weight was measured as respectively 1361, 1163 and 1524 g / moles. Polydispersity index was obtained as 1.171 . PU was used emulsion polymerization of vinyl acetate and copolymerization of metyl methacrylate and butyl acrylate depending on surfactant quantity and time. Obtained latexes was characterized by particle size measurements, viscosity and surface tension measurements. In addition, molecular weight of the polymers were determined by GPC. High solid content water-based emulsion polymerization studies were performed in the another part of the thesis. Latexes produced by emulsion polymerization are versatile materials. It extensively used in very different industry such as adhesives, coatings, textiles, paper paints, floor polish and makeup. The solids content of the latexes produced in the industry is between 50-55%. High solids content (HSC) brings many advantages, such as maximizing reactor production, minimizing transportation and storage costs, providing greater flexibility in product formulation and improving surface coverage when applied. The increase in solids content negatively affects the latex viscosity. This also affects the heat removal rate, mixing ability, mass transfer and product stability. The way to obtain low viscosity (HSC / LV) high solids content is achieved by controlling the particle size distribution (PSD). Particles in a perfect monodisperse latex will contact the solids content of about 64% theorically. This explains that most industrial processes with relatively narrow particle size distribution generally operate at less than 55% by weight of solids content. Bimodal particle size distribution production is considered to come from above this limitation and to achieve the goals of high solids content and low viscosity. In this thesis, two different methods were used to produce twelve different high solid content emulsion polymerization. Firstly 42 nm seed emulsion was prepared by semi-continuous polymerization. Seed emulsion was grown with pre-emulsion via feeding. After the firstly added seed is required to grow, a precise amount of seed was introduced into the reactor shot wise, keeping the feeding of monomers, surfactant and ammonia to reach the desired solids content. Secondly, primary seed was not used in second method. The rest of experiment conditions are same with first method. 65% solid content latexes are obtained. The latexes were characterized by using, Brookfield viscometer, tansiometer, Zetasizer Nanaoseries NS. Unimodal particle size distributions were obtained at the final product that is produced with first method. Viscosities of these products are quite high, compared with other method. The surface tension of these products raise with increasing solid content. Another products which are produced second method, has bimodal particle size distribution. Viscosities of these products are quite low, due to bimodality. The surface tension of these products has nearly same values because of surfactant amount. To sum up, high solid content low viscosity bimodal and unimodal particle size distribution emulsion polymers were synthesized.
Preparation of urethane modified poly(styrene) based resin for removal of phenol
The human being is influenced by the quality of water resources in the natural environment. In order to guarantee a secure and healthy life, the water consumed must be free from harmful chemical substances. The water released into the environment by water purification plants and private organizations should be regularly accessed and examined to maintain complete yielding to water framework act. Thus, treated waters should be safe for consumption and free from harmful compounds to guarantee a healthy life. However, there are environmental organizations for water quality which have given standards to ensure that water is free from contaminants, thus making safe water consumption possible. Water treatment requires adequate analysis and monitoring which includes determination of low level contaminants. The maximum level of contaminants which present in drinking water should be so small that the effect is harmless to human health. Thus analytical methods are important to quantify the contaminants. Phenol and derivatives are harmful substances found in water. Moreover, faced with more and more stringent regulations, the water contamination has also become noteworthy source of concern and priority for most industrial sectors. Phenols are aromatic components which contain one and more hydroxyl groups connected to aromatic ring. Phenol is a benzene derivative having chemical formula of C6H5OH with a structure of a hydroxyl group bonded to the phenyl ring. It is a colorless, crystalline substance of characteristic odor, soluble in water and organic solvents. Phenols are similar to alcohols but form stronger hydrogen bonds. Thus, they are more soluble in water than alcohols and have higher boiling points. Phenol was prepared mainly from coal tar, in the early 19th century. Presently, small quantities of phenol is still obtained from coal tar. The demand for phenol grew significantly with the commercialization of phenolic resin (Bakelite), during the 20th centuries. An advanced and popular phenol process is Hock Process after the World War II. It is currently the predominate route for the production of phenol which is accompanied by acetone as a co-product. The main commercial plant utilizing toluene as the feedstock was launched in the 1960's. Nowadays, the commercial production of phenol is not obtained from toluene. Phenols are used in many industrial activities for the production of pesticides, insecticides, herbicides, and synthetic products. Phenols in which certain amount of pesticides and wood preservatives contain can lead to specific health damages even at the lowest concentration levels. Some harmful effects of breathing phenol from the air have been occured for human. Short time effects of phenol include breathing infection and eyes burning. The chronic effects of high exposures cause muscle aches, weak spots, weight loss. Effects of long term and low level exposures cause to increases in cancers and effects on the immune system. Nevertheless, it is important to be aware of phenols and substituted phenols in environmental and biological samples. Many different techniques are used for the removal of phenol from wastewater. The methods can be separated into three categories: chemical, biological and physical. All of them have advantages and disadvantages. Because of high cost and disposal problems, many of these conventional techniques for treating phenol bearing wastewater have now not been widely applied at large scale in the textile and paper industries. Adsorption of phenol has three mechanisms; π-π dispersion interaction, electron donor-acceptor complex formation and hydrogen bond formation. In this thesis these mechanism were applied to synthesis new polymeric resins for phenol removal. Two types of polymeric resins were prepared for adsorption of phenol from the water. In the first part of this study, The Resin 1 was obtained with chloro-sulfonated polystyrene (CSPS) and it excess of ethanolamine. The resin was characterized with analytical methods and FT-IR spectroscopy to determine the functional groups. The Resin 2 was prepared through a reaction of the Resin 1 with butyl isocyanate in dimethyl formamide (DMF) solution. Polymers were characterized by using analytical methods and FT-IR. In the second part of the study, experimental measurements were performed on modified resins for phenol adsorption. The phenol sorption capacities of the resins were described by mixing 0.1 g polymer samples (resin1 and 2) with 10 mL phenol solutions with various concentrations (0.5 M, 0.35M, 0.25 M, 0.1M, 0.05 M, 0.025 M and 0.01 M). The phenol loading capacities were calculated from the initial and ending phenol contents of the solutions. Also, kinetics of phenol sorption was performed at low concentration to investigate the efficiency of the modified resin at trace concentration. For this purpose, pseudo-first order, pseudo-second order and intra particular diffusion kinetics models were used.
Preparation of new polymeric sorbents for removal of organic wastes
The environmental protection becomes a difficult task while many industries produce wastes that cause serious pollution. In the textile industry, large quantities of aqueous wastes and dye effluents are discharged from the dyeing process with strong persistent color. Most of these dye wastes are toxic and may be carcinogenic, and this poses a serious hazard to aquatic living organisms. As a result, the removal of dyestuffs from effluents becomes important, and many governments have established environmental restrictions with regard to the quality of colored effluents and have forced dye-using industries to decolorize their effluents before discharging. In this study, poly(styrene) based quaternary ammonium carboxlate based resins were prepared to remove acidic and basic dyes from aqueous solutions. In this study, a beaded polymer with quaternary amine functions were prepared in two steps, starting from poly(vinyl benzyl chloride-co-ethylene glycol dimethacrylate) based beads, according to the synthetic protocol; modification of ethyl piperazine and imidazole quaternization of chloroacetic acid, respectively. Poly (vinyl imidazole) grafted onto PVBC resin was prepared by using reverse ATRP technique. The grafting degree of the resin was found about 59% after 72 h. Therefore, core-shell type polymeric sorbent was obtained for removal of acidic dyes from water. Linear polymers grafted onto crosslinked polymer resin particles offer numerous potential applications due to the combination of the non-solubility resin and the flexibility of the graft polymer side-chains as the functional group carrier. The flexible side-chains can provide pseudo-homogeneous reaction conditions and better accessibility of the involved functional groups. The atom transfer radical polymerization (ATRP) technique, for instance, provides chain growing mostly on the solid surface if the initiator function is covalently bound to the surface. Dye sorption and desorption experiments were investigated under various operating conditions. Phenols are generally considered as one of the important organic pollutants discharged into the environment causing unpleasant taste and odor of drinking water. Three mechanisms of phenolic compounds adsorption is postulated namely, π-π dispersion interaction, electron-donor acceptor complex formation and hydrogen bond formation. This methodology was used to prepare new polymeric sorbents for phenol removal. Ethyl piperazine and imidazole modified PVBC beads were quaternized with chloroacetamide. The resulting polymer resins, which had a total nitrogen content of about 4.50 mmol/g, was effective in extracting phenol from aqueous solutions. The phenol sorption capacity was around 0.208 g phenol/g resin in non-buffered conditions. Another sorbent was prepared starting from the reaction of PVBC beads with N,N-dimethylethylenediamine. The resulting beads were quaternized with chloroacetamide to obtain quaternary amide containing sorbent. The phenol sorption capacity was around 0.220 g phenol / g resin in non-buffered conditions. The adsorption conditions (initial phenol concentration and pH) were varied to evaluate mechanism of adsorption of phenol on the prepared resins. These resins are also able to remove phenol completely even from highly diluted aqueous phenol solutions. Atrazine is another important organic pollutant. Many techniques have been researched and developed for removal of hazardous agricultural chemicals that migrate to the environment, including photocatalytic degradation, biological repair, sorption, etc. Sorption is recognized as one of the most applicable technologies for contamination removal. Regarding that adsorption on solid substrates, such as activated carbon, biosorbents or clay, are widely used method for removing atrazine from waters. In this study, poly (2-acrylamido-2-methylpropane sulfonic acid) (AMPS) grafted onto crosslinked PVBC resin by ATRP polymerization technique for removal of atrazine from water. Atrazine is a basic compound. Therefore, acidic type of sorbents can be used to remove atrazine. Atrazine sorption capacities of the polymeric sorbent was determined depending on different waste concentration and pH. Trace contaminants of atrazine removal experiments were also investigated and different kinetic models were applied. Prepared sorbents were characterized by using analytical and spectroscopic techniques to determine functional groups. Morphological characterization of core-shell type resins were studied with scanning electron microscope (SEM).
Grafting of poly(acrylamide) onto crosslinked poly(HEMA-co-MMA) resin for removal of phenol and bisphenol A
Phenol and its substituted derivatives are widely found in the effluents from pesticides, synthetic rubber, plastic, pharmaceuticals, petrochemicals, and other industries. It is also used in the production of caprolactam and bisphenol A. They are intermediates in the manufacture of nylon and epoxy resins, respectively. It is primarily used in the production of phenolic resins, which are needed in the automotive plywood, construction and appliance industries. Other important uses of phenol are as a disinfectant and in medicinal products. Minor uses of phenol contain the manufacture of paint and varnish removers, lacquers, paints, rubber, ink, illuminating gases, tanning dyes, perfumes, soaps and toys Phenol and phenolic compounds are generally considered as one of the important organic pollutants discharged into the environment causing unpleasant taste and odor of drinking water. Even at very low concentrations in the presence of water, is undesirable and toxic to the aquatic beings including fish. Especially, chlorinated phenols are more toxic to aquatic life. Phenols have great risk to the human health and cause negative effects on the brain, digestive system, heart, eye, liver, kidney, lung, peripheral nerve, skin and the unborn child. 0.002 mg L-1 is the permissible limit for phenol concentration in potable water according to the World Health Organization regulation. Removal of phenolic pollutants in aqueous solutions can be divided into three main categories: chemical, physical and biological treatment. Several wastewater treatment methods for removal of phenolic pollutants have been used including membrane filtration, advanced oxidation, biological degradation, photocatalytic degradation, electrochemical oxidation and adsorption. Adsorpsion is very important method to remove organic and inorganic pollutants. Different adsorbents such as zeolites, carbon nanotubes, polymeric sorbents and clay have been investigated for the removal of phenol and phenolic pollutants from wastewater. Three mechanisms of phenolic compounds adsorption is postulated namely, π-π dispersion interaction, electron-donor acceptor complex formation and hydrogen bond formation. This methodology was used to prepare new polymeric sorbents for phenol removal. In this thesis, two types of polymeric sorbents were prepared for removal of phenol and BPA from water. The poly(HEMA-MMA-EGDMA) terpolymer were prepared by using suspension polymerization method starting from polymerization of hydroxyethyl methacrylate (HEMA) (50%), methyl methacrylate (MMA) (40%) and ethylene glycol dimethacrylate (EGDMA) (10%) as crosslinkerin the presence of toluene as porogen and AIBN as an initiator (resin 1). Other polymeric resin was prepared grafting polymerization of poly (acrylamide) onto resin 1 by redox polymerization method. Grafting reaction is carried out through the hydroxyl groups on HEMA units. The resulting polymer resin2 , which had a total nitrogen content of about 7.0 mmol/g, was effective in extracting phenol from aqueous solutions.The phenol and BPA sorption capacities were found depending on concentration and pH. Also, phenol and BPA sorption kinetics of the resins were investigated. Kinetic models were applied for Resin 1 and Resin 2.
Synthesis of tris(hydroxymethyl)aminomethane modified polystyrene based polymeric sorbent and removal of boron from aqueous solutions
Boron is placed in-group 13 of periodic table and found at low concentration in a wide area range such as rock, soil and water in nature. Boron is used in many industrial applications, especially in insulation, retardant fiberglass and ceramic industry. In addition, boron is an essential element for living organism systems. Excess amount of it causes water and other environmental pollution. As high concentration causes adverse effects, boron level is limited in irrigation or drinking water. The World Health Organization (WHO) currently recommends the concentration of boron in drinking water to be 2.4 mg/L. Consequently, boron removal from wastewater is an important topic. Various removal methods are available for boron separation. Some of them are; precipitation-coagulation, solvent extraction, membrane filtration, reverse osmosis, electro dialysis and adsorption. Adsorption is completely different from others because it is a very useful method and needs low price equipment for removal of boron from wastewater. In the first part of this study, tris(hydroxymethyl)aminomethane was interacted with poly(vinyl benzyl chloride) resin to obtain boron selective sorbent. The resin was characterized with FT-IR spectroscopy to determine the functional groups important for boron sensitivity. Total amine content of the resin was calculated analytically as 2.45 mmol.g-1 sorbent. In the second part of the study, experimental measurements were performed on modified resin about boron adsorption. Adsorption capacity of the sorbent was investigated for different boron concentrations. Boron loading capacity of the sorbent is 2.17 mmol.g-1 resin, in non-buffered conditions. Sorption behavior was also observed in the presence of different concentration foreign ions such as Ca+2 and Mg+2. Besides that, boron adsorption was further studied at varying pH in the range of 2.0-10.0. Kinetics of boron sorption was performed at low concentration to investigate the efficiency of the modified resin at this condition. For this purpose, pseudo-first order, pseudo-second order and intraparticular diffusion kinetics models were used. Regeneration of the loaded resin was also studied. 2.10 mmol.g-1 boric acid was recovered of the loaded sample, which showed that the resin was able to desorp nearly completely.
Yeni kalgon bazlı sıvı kristal polimerlerin sentezi ve incelenmesi
Side chain liquid crystalline polymers (SCLCPs), which combine the unique properties of low-molar mass liquid crystals and polymers, have been the subject of intensive research mainly due to their interesting electrical and optical properties which makes them good candidates for applications in microelectronic devices ranging from optical data storage and nonlinear optics. Side chain liquid-crystalline polymers (LCPs) are usually prepared by covalently linking rigid mesogens to a polymer backbone through flexible spacers. In thesis, new chalcone compound and its methacrylate monomer were synthesized aand characterized. 1-(4-hydroxyphenyl)-3-(pyridin-4-yl)prop-2-en-1-one as a chalcone compound was synthesized by using Claisen-Schmidt method. 1-(4-hydroxyphenyl)-3-(pyridin-4-yl)prop-2-en-1-one was reacted with methacryloyl chloride to obtain monomer. This chalcone based monomer was polymerized by using free radical polymerization method. Chalcone side chain liquid crystalline polymer was prepared by using intermolecular hydrogen bonding concept. For this purpose, firstly H-bonded crystalline polymer was synthesized starting from tertiary amine containing methacrylate based polymers as H-bond acceptor and 4'-(-hydroxyalkoxy)-4-cyanobiphenyl derivatives as H-bond donor. Synthesis of Hydrogen Bond Donors: 8-(4-Cyanobiphenyl-4'-oxy) octan-1-ol (LC8) and 11-(4-Cyanobiphenyl-4'-oxy) undecan-1-ol (LC11) were synthesized. The structure of the LC8 and LC11 were characterized by FT-IR and 1H-NMR spectroscopy. Preparation of chalcone based liquid crystalline polymers Chalcone based polymer and LC8 or LC11 were employed as a hydrogen bond acceptor and a hydrogen bond donors, respectively to yield hydrogen bonded liquid crystalline polymers. The structure of the side chain liquid crystalline polymers formed by intermolecular H-bonding between nitrogen of amine of the polymer and hydroxyl group of the hydrogen donors. The hydrogen bonded methacrylate based polymers were characterized by FT-IR spectroscopy, DSC and POM methods. According to the FT-IR spectra of the polymers hydrogen bonding donors and acceptors located so that intramolecular hydrogen bonding is favored, display slightly broadened O-H stretching absorption in the 3200 to 3500 cm-1 range. The phase behavior of all the hydrogen bonded liquid crystalline polymer was studied using a combination of DSC and POM. DSC thermograms were obtained in second heating cycles. The samples were heated with a scan rate of 10°C/min in an N2 atmosphere. POM (X200) studies also confirmed DSC results along with the results of phase transitions. Also, 1-(4-hydroxyphenyl)-3-(pyridin-4-yl)prop-2-en-1-one was interacted with LC8 and LC11 to compare with liquid crystaline polymers.
Tris asetamid modifiye çapraz bağlı sülfonamid esaslı reçinenin sentezi ve cıva tuzlarının sulu ortamlardan uzaklaştırılmasında kullanılması
In this study, crosslinked chlorosulfonated polystyrene resin (CSPS) was prepared starting from crosslinked polystyrene-divinyl benzene (DVB) resin. The CSPS was reacted with excess tris (2-aminoethyl) amine to obtain resin1. And then, the resin 1 was amidated with excess of acetyl chloride to obtain sulfonamide based tris amide containing resin (resin 2). Resin 1 and Resin 2 were characterized by using analytical methods and FT-IR. HgCl2 was used in mercury adsorption experiments. The mercury sorption capacities of the sorbent were determined by mixing weighed amount of polymer sample (0.1 g) with 10 mL aqueous Hg (II) solutions (0.1-0.00625 M). The mercury loading capacities were calculated from the initial and final Hg (II) contents of the solutions. Also, the resin 2 was interacted with HgCl2 depending on pH. According to the results obtained mercury adsorption capacity of the resin increased by increasing pH. Mercury sorption capacity of the resin 2 was found as 4.33 mmol/g resin at pH=6. Because of proton releasing during the binding, pH values closer to neutral condition are much favorable. Sorption capacities of the other metal ions were studied and sorption capacity was found between 2.20-1 mmol/g resin. Batch kinetic sorption experiment was performed by using HgCl2 solution (1.0x10-4 M). The rate constant of adsorption was studied with the help of the pseudo-first-order rate expression of Lagergren model and the pseudo-second-order kinetic rate expression of Ho and McKay. The pseudo-first-order equation assumes that the adsorption rate decreases linearly as the adsorption capacity increases, which is suitable especially for low concentrations. Also, the pseudo-second-order kinetic model assumes that the rate limiting step is the interaction between two reagent particles. To examine the nature of the diffusion process for the adsorption of mercury onto the resin attempts were made to calculate the pore diffusion coefficients as intra-particle transport is supposed to be the rate-controlling step. According to result of the kinetic models, the pseudo-first-order kinetic model having a low value for R2, does not present a good fit with experimental data. In contrast, in the case of pseudo-second-order kinetic model, the high values of correlation coefficients showed that the data fitted well to the pseudo-second-order rate kinetic. Adsorption isotherm models were applied. Three theoretical isotherm models Langmuir, Freundlich and Dubinin–Radushkevich were used to analyze the experimental data. One of the most widely used isotherm equations for modeling adsorption data is the Langmuir equation. Based on the Langmuir equation; Ce is the equilibrium concentration of mercury in solution (mmol/L), qe is the equilibrium amount of mercury adsorbed on the beads at time t (mmol/g). qm is the maximum adsorption capacity of the beads (mmol/g) and b (i.e., the adversely of dissociation constant of the ligand/surface interaction, Kd, or equal to association constant, Ka, (b = Ka = (1/Kd)) is the energy of adsorption dissociation constant. The Freundlich expression is an empirical equation based on adsorption on a heterogeneous surface. Based on the Freundlich equation; KF and n are the Freundlich constants characteristic of the system. KF and n are indicator of the adsorption capacity and adsorption intensity, respectively. The slope and the intercept of the linear Freundlich equation are equal to 1/n and ln KF, respectively. The linear plots of ln q versus ln C showed that the Freundlich isotherm can be representative for the mercury adsorption. The magnitude of KF and n values of Freundlich model showed easy uptake of mercury from aqueous medium with a high adsorption capacity of the beads at room temperature. Values of n>1 for affinity beads indicates positive cooperativity in binding. The Dubinin–Radushkevich (D–R) isotherm is also widely used in adsorption studies because it does not assume a homogeneous surface or constant adsorption potential. The Dubinin–Radushkevich (D–R) constant can give the valuable information regarding the mean energy of adsorption. The adsorption behavior might be predicted the physical adsorption in the range of 1–8 kJ/mol of the mean adsorption energies (E), and the chemical adsorption in more than 8 kJ/mol of the mean adsorption energies (E), respectively. E value was calculated as 2.016 kJ/mol for mercury, and found to be in the range of a typical free energy attributed to physical adsorption. So, the D–R isotherm also is a model which describes the experimental data compared to other applied isotherm models.
Tris(Hidroksimetil)aminometan ile modifiye edilmiş reçinenin sulu çözeltilerden bor giderilmesinde kullanılması
Boron compounds are used in the glass and ceramic industry to produce borosilicate glass, insulation fiberglass, flame retardant fiberglass, ceramic glazes, neutron absorbers, porcelain enamels, herbicides or fertilizers.Boron presents in groundwater or surface water in various locations where it occurs mainly in the form of boric acid. Common boron sources in water are urban wastewater containing detergents and cleaning products and also industrial effluents from a great number of industrial waste and diverse chemical products used in agriculture.There is no easy method available for the removal of boron from water and wastewater. One or more methods may be applied according to boron concentration in the medium. Adsorption is a very useful and economical technique at low boron concentration. In this study, glycidyl methacrylate (GMA) and ethylene glycol dimethacrylate (EGDMA,10%) were copolymerized to obtain crosslinked poly GMA by using suspension polymerization method. The resin was reacted with excess of tris(hydroxymethyl)aminomethane to obtain tris(hydroxymethyl)aminomethane modified methacrylate based crosslinked bead polymers.The resin was used to remove boron from water. Therefore, loading capacity of the boron was studied depending on different boron concentration and pH. Batch kinetic sorption experiments were performed with highly diluted boric acid solution (4.9x10-3 M) to investigate the efficiency of the resin in the presence of low boron concentrations. Sorption kinetic models were applied to the resin. Loaded polymer samples, when treated with HCl, become almost boron-free.