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Öğe Anionic dye removal from aqueous solutions using modified zeolite: Adsorption kinetics and isotherm studies(Elsevier Science Sa, 2012) Alver, Erol; Metin, Aysegül ÜlküThe natural zeolite was modified with hexamethylenediamine (HMDA) and used as adsorbent to remove anionic dyes, namely Reactive Red 239 (RR-239) and Reactive Blue 250 (RB-250). And, the adsorption equilibrium and kinetic studies of anionic dyes were carried out. In presented work, the origin of the zeolite (Heulandite) used was in Turkey. The adsorption of reactive dyes on modified zeolite (HMDA-Z) was investigated by batch adsorption experiments. The effects of pH, temperature, sorbent dosage and the initial dyes concentrations were investigated. While the increase in temperature resulted in a higher RB-250 loading per unit weight of the modified zeolite, adsorption capacity of modified zeolite did not constitute a noticeable change for RR-239. As an additional factor effecting the removal of reactive dyes, the effects of competitive ions such as nitrate, sulfate and chloride were investigated. The adsorption results indicate that the natural zeolite had a limited adsorption capacity for reactive dyes but is substantially improved upon modifying its surfaces with HMDA. The isotherm data of both investigated dyes were analyzed by the Langmuir, Freundlich, and Redlich-Peterson isotherm model according to temperature. The most appropriate model for the equilibrium process of both dyes was the Freundlich model. The kinetic studies indicated that the adsorption of reactive dyes followed the pseudo-second-order kinetic. Thermodynamic calculations showed that the adsorption of both investigated dyes was a spontaneous and endothermic process for RB-250 and an exothermic process for RR-239. (C) 2012 Elsevier B.V. All rights reserved.Öğe Basit bir yöntemle hazırlanan ?-aluminanın yüksek basınç sıvı kromatografide (HPLC) kolon dolgu maddesi olarak ve bazı inorganik anyonların tayininde kullanılması(Kırıkkale Üniversitesi, 2005) Alver, Erol; Özcimder, MustafaÖZET BASİT BİR YÖNTEMLE HAZIRLANAN a - ALUMİNANIN YÜKSEK BASINÇ SIVI KROMATOGRAFİDE (HPLC) KOLON DOLGU MADDESİ OLARAK VE BAZI İNORGANİK ANYONLARIN TAYİNİNDE KULLANILMASI ALVER, Erol Kırıkkale Üniversitesi Fen Bilimleri Enstitüsü Kimya Ana Bilim Dalı, Yüksek Lisans Tezi Danışman Prof. Dr. Mustafa ÖZCİMDER Şubat 2005, 67 sayfa Laboratuar koşullarında hazırlanan a-aluminamn Yüksek Basınç Sıvı Kromatografide (HPLC) kolon dolgu maddesi olarak iyodür, bromür, nitrat, nitrit ve bromat iyonlarının ayırımında kullanımı ve kolonun performansı araştırılmıştır. Bu amaçla önce a - alumina ile doldurulan 15 cm'lik HPLC kolonun kararlılığı, kolon ömrü, pik asimetrisi, ayıncılık seçicilik gibi özellikleri incelenmiştir. Ayrıca anyonların ayırımı üzerine pH, hareketli faz bileşimi, akış hızı, iyon şiddeti ve karşıt iyon türü etkileri ve tayin limitleri incelenmiştir. a - alumina çalışılan inorganik anyonların kromatografik ayırımı için iyi bir HPLC kolon dolgu maddesidir. Kullanılan anyonlar için ayıncılık kabul edilebilir mbulunmuştur. Kolon ömrü en az altı aydır. İnorganik anyonların ayrılması için optimum kromatografik şartlar pH = 4.15, iyonik kuvvet 0.05 M NaC104, akış hızı İmL/dak., asetonitril yüzdesi %30 olarak bulunmuştur. Kullanılan anyonlar için en küçük tayin sınırları iyodür, bromür, nitrat ve nitrit için 5 ng, bromat için ise 25 ng olarak bulunmuştur. Anahtar Kelimeler : Kromatografi, HPLC, alumina, anyon ivÖğe Chitosan based metal-chelated copolymer nanoparticles: Laccase immobilization and phenol degradation studies(Elsevier Sci Ltd, 2017) Alver, Erol; Metin, Aysegul UlkuImmobilization improves the stability and reusability of enzymes. In this study, laccase, which is a green biocatalyst, was immobilized onto Cu (II)-chelated chitosan nanoparticles via adsorption and successfully applied to remove phenol from aqueous solution. Cu (II)-chelated chitosan-graft-poly (glycidyl methacrylate) nanoparticles were prepared using poly (ethylene imine), PEI, which is employed as both a spacer arm and metal chelator and used to immobilize laccase by coordination. Properties of chitosan based nanoparticles were characterized using FTIR, TGA, SEM and zeta-sizer analysis. The maximum laccase loading capacity of Cu (II)-chelated chitosan based nanoparticles (CHT-PGMA-PEI-Cu (II) NPs) was calculated as 65.75 +/- 2.51 mg/g. This immobilized system exhibited broad pH and temperature profiles, and better stability and reusability than free enzyme; after eight cycles of continuous use, the activity of the immobilized enzyme remained above 50 +/- 0.62%. The K-m and V-max values of free and immobilized laccase were 0.055 mM, 0.070 mM, and 0.19 U/mg, 0.14 U/mg, respectively. The catalytic efficiencies (V-max/K-M) of the free and immobilized laccase were 3.45 and 2.0, respectively. Feasibility of the laccase immobilized system in the removal of phenol was investigated in a batch system. The results showed that the CHT-PGMA-PEI-Cu (II) NPs have great potential for industrial applications. More than 96% of phenol was removed with laccase immobilized metal chelated NPs in the presence of mediator, ABTS, indicating that the metal-chelated chitosan based NPs is a promising support for both laccase immobilization and further applications in the removal of phenolic compounds. (C) 2017 Elsevier Ltd. All rights reserved.Öğe Determination of polycyclic aromatic hydrocarbons in cigarette filter tar by means of hollow-fiber liquid phase microextraction-HPLC-UV system(Taylor & Francis Inc, 2013) Demirci, Ayla; Alver, ErolA high-pressure liquid chromatographic method was developed to determine polycyclic aromatic hydrocarbons (PAHs) in cigarette filter tar using hollow fiber-liquid-phase microextraction (HF-LPME) for the clean-up and enrichment steps. The donor phase for HF-LPME is a mixture of acetonitrile and water. Before analyzing real cigarette samples, some preliminary experiments were necessary to find the optimum starting HF-LPME conditions, including donor phase composition (acetonitrile/water), pH, acceptor phase type, mixing rate, and extraction time. These experiments were performed with model PAH solutions. The chromatographic analysis of the acceptor solution was performed using a C18 reversed-phase column and a UV detector system. Under optimum conditions, percent recoveries and enrichment factors ranged from 63 to 97% and from 208 to 320, respectively, for model PAH solutions. The recoveries from real samples were between 8 and 71%, whereas the enrichment factors ranged from 27 to 234. The limit of detection (LOD) of the six PAHs was found to be between 0.040 and 0.136ngmL1. The concentrations of the six PAHs in real samples (various brands of cigarettes) were determined. The total amounts of PAHs (six) found in the filter tar of the three brands filter tar were 165.49, 50.49, and 51.04ng/cigarette, respectively.Öğe Efficient Removal of Acidic Dye Using Low-Cost Biocomposite Beads(Amer Chemical Soc, 2013) Metin, Aysegul U.; Ciftci, Hakan; Alver, ErolThe objective of this study is to prepare and characterize chitosan/zeolite biocomposite beads and utilize them as adsorbent for removal of anionic dye, Acid Black 194 (AB194). Characterization studies of biocomposite beads were carried out by using Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDX). The ability of chitosan/zeolite biocomposite beads as an adsorbent for the removal AB 194 from an aqueous solution has been investigated under various experimental conditions. Maximum adsorption capacity of biocomposite beads was calculated as 2140 mg/g. The increase in temperature resulted in a higher AB194 loading per unit weight of biocomposite beads. As an additional factor affecting the adsorption behavior of AB194, the effect of ionic strength was investigated, and the adsorption capacity of biocomposite beads significantly decreased. Four isotherm models were employed to elucidate the adsorption process. The most appropriate model for the equilibrium process was the Freundlich. The kinetic studies indicated that the adsorption of AB194 followed the pseudo-second-order kinetics. Thermodynamic calculations showed that the adsorption of reactive dye was a spontaneous and endothermic process. The obtained results indicate that chitosan/zeolite biocomposite beads as an adsorbent are promising for dye removal from wastewater.Öğe Electrochemical copper (II) sensor based on chitosan covered gold nanoparticles(Springer, 2014) Ciftci, Hakan; Tamer, Ugur; Metin, Aysegul U.; Alver, Erol; Kizir, NevinThis study outlines a new sensing platform based on glassy carbon electrodes modified by gold nanoparticles (AuNPs) for the determination of heavy metal. A glassy carbon electrode was modified by chitosan stabilized AuNPs. AuNPs were prepared by reducing gold salt with a polysaccharide chitosan. Here, chitosan acted as a reducing/stabilizing agent. The AuNPs were characterized with UV-Visible absorption spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. Chitosan covered AuNPs were immobilized on the glassy carbon electrode for the determination of Cu (II) in aqueous solutions. The electrochemical determination of Cu (II) ions was performed using the differential pulse voltammetry technique. Some parameters for Cu (II) determination, such as pH, preconcentration time and electrolysis potential of Cu (II), were optimized. The detection limit was calculated as 5 x 10(-9) mol L-1 by means of the 3:1 current-to-noise ratio. The interference of Cr(III), Fe(II), Ni(II), Pb(II), Mg(II), Zn(II), Ba(II) ions was investigated and showed a negligible effect on the electrode response. Recovery studies were carried out using tap water.Öğe Environmentally friendly pathway applying sustainable resources to remove anionic dye from aqueous solutions: encapsulation in carboxymethyl cellulose nanoneedles(Springer Int Publ Ag, 2023) Alver, Erol; Dogan, Deniz; Mert, Humeyra; Metin, Aysegul UlkuEncapsulation technique was used for the rapid and efficient removal of RB-250 from aqueous solutions. This technique involves the simultaneous formation of carboxymethyl cellulose (CMC) particles and the entrapment of the anionic dye RB-250 within the particles. TEM and zeta analyses of dye-encapsulated CMC particles showed needle type agglomeration of nanoparticles. Various parameters were investigated to optimize the RB-250 removal efficiency of CMC by encapsulation. Remarkably, while pH and time significantly affect the dye removal efficiency in adsorption, which is a widely used dye removal technique, the effect of these parameters is negligible in the proposed technique. In addition, it was determined that the temperature and stirring rate does not have a significant effect on the entrapment of the dye molecules in nanoparticles. More importantly, unlike conventional dye removal techniques such as adsorption, this technique allowed the rapid and efficient removal of an anionic dye with unmodified CMC. RB-250 encapsulation capacity of CMC nanoparticles was determined as 2809 mg RB-250/g CMC. These results revealed that the encapsulation is a promising candidate in dye removal applications where time and ease are important.Öğe Fabrication and characterization of gold-nanoparticles/chitosan film: a scaffold for L929-fibroblasts(Taylor & Francis Ltd, 2013) Turk, Mustafa; Tamer, Ugur; Alver, Erol; Ciftci, Hakan; Metin, Aysegul U.; Karahan, SiyamiThe objective of the present study was to fabricate a gold nanoparticle crosslinked chitosan (Ch/AuNPs) composite film simple and to evaluate its use as a carrier matrix for L929-fibroblasts. L929-fibroblasts were seeded either onto Ch or Ch/AuNPs scaffolds. The Ch/AuNPs scaffold exhibited a higher cell proliferation and growth rate. The cytotoxicity test determined trypan blue staining indicated that Ch scaffolds devoid of AuNPs expressed almost no toxicity while the Ch/AuNPs composite scaffolds expressed a very limited toxicity only at higher doses. The Ch/AuNPs scaffold promotes cell attachment, growth and proliferation with almost no cytotoxicity.Öğe Fibrous polymer-grafted chitosan/clay composite beads as a carrier for immobilization of papain and its usability for mercury elimination(Springer, 2016) Metin, Aysegul Ulku; Alver, ErolPapain, which is an industrially important enzyme, has been immobilized on fibrous polymer-modified composite beads, namely poly(methacrylic acid)-grafted chitosan/clay. Characterization studies have been done using FTIR and SEM analysis. Operating parameters such as pH and initial concentration of papain have been varied to obtain the finest papain immobilized polymermodified composite beads. The immobilization capacity of composite beads has been determined as 34.47 +/- 1.18 (n = 3) mg/g. The proteolytic activity of immobilized papain was operated using bovine serum albumin (BSA) and maximum velocity (V-max) and Michaelis-Menten constant (K-m) values of the free and immobilized enzymes were determined using Lineweaver-Burk and Eadie-Hofstee equations. Usability of papain immobilized polymermodified composite beads as adsorbents for the elimination of mercury was investigated. The maximum removal capacity of PIPMC beads has been found to be 4.88 +/- 0.21 mg Hg/g when the initial metal concentration and weight of polymer-modified composite beads were 50 mg/L and 0.04 g at pH 7, respectively. Mercury removal performance of the papain immobilized polymer-modified composite beads was investigated in conjunction with Cu (II), Zn (II) and Cd (II) ions. The mercury adsorption capacity of papain immobilized polymer-modified composite beads was a slight reduction from 1.15 to 0.89 mg/g in presence of multiple metal salts.Öğe INVESTIGATION THE PERFORMANCE OF CHITOSAN BASED COMPOSITE BEADS ON REMOVAL OF ANIONIC DYE (AY-204)(Yildiz Technical Univ, 2015) Alver, Erol; Metin, Aysegul Ulku; Ciftci, HakanThe aim of this study is to investigate the utility of chitosan/zeolite composite beads as adsorbent for removal of anionic textile dye, Acid Yellow 204. It was investigated the influence of parameters such as pH, time, zeolite content in the composite structure, electrolyte concentration, dye concentration and sorbent dosage on the efficiency of dye removal. It was determined that the adsorption capacity increased significantly with decreasing pH Langmuir and Freundlich isotherm models were applied to the experimental data to determine the adsorption mechanism. and The Langmuir isotherm model was determined to be more consistent with the experimental data. It was observed that the reaction kinetics is suitable for the pseudo-second-order.Öğe Methylene blue adsorption on magnetic alginate/rice husk bio-composite(ELSEVIER, 2020) Alver, Erol; Metin, Aysegul Ulku; Brouers, FrancoisMagnetic alginate/rice husk (m-ALG/RH) bio-composite beads prepared with ionotropic gelation method and used for methylene blue (MB) removal. Structural analysis of magnetic alginate/rice husk composite beads was performed using FTIR, SEM-EDS and TGA techniques. The accomplishment of magnetic alginate/rice husk composite beads as an adsorbent for the removal methylene blue was investigated from aqueous solution. Maximum experimental adsorption capacity of the bio-composite beads was calculated as 274.9 mg/g. The various process parameters such as pH, temperature and initial MB concentration optimized. It was determined that pH no significant effect on dye removal efficiency of beads while temperature and ionic strength caused a decrease on removal efficiency. The various isotherm models were applied for determine the adsorption mechanism and Freundlich isotherm model is more compatible with the experimental data. The kinetic studies showed that the adsorption of methylene blue can be well described by the fractal Brouers-Sotolongo kinetic model. The thermodynamic calculations indicated that methylene blue adsorption was a spontaneous and exothermic nature. The results showed that the magnetic alginate/rice husk bio-composite as low-cost and eco-friendly adsorbent can be effectively used for cationic dye removal steps in the environmental engineering applications. (C) 2020 Elsevier B.V. All rights reserved.Öğe MICROEXTRACTION METHODS(Yildiz Technical Univ, 2012) Alver, Erol; Demirci, Ayla; Ozcimder, MustafaAccurate, rapid and economic qualitative and quantitative analysis of trace amount substances in biological, environmental and food products is an important issue. Mostly, such substances must be taken from the matrix (separation) and concentrated (enrichment) before determining with analytical equipment. For these processes liquid-liquid, solid-liquid extraction and solid phase extraction are commonly used. However these methods are recently replaced by microexraction methods minimizing organic solvent consumption, simplifying sample preparation steps, providing high enrichment rates and appropriate to automation.Öğe Non-enzymatic sensing of glucose using a glassy carbon electrode modified with gold nanoparticles coated with polyethyleneimine and 3-aminophenylboronic acid(Springer Wien, 2016) Ciftci, Hakan; Alver, Erol; Celik, Filiz; Metin, Aysegul U.; Tamer, UgurA non-enzymatic electrochemical method was developed for sensing glucose by using a glassy carbon electrode modified with 3-aminophenylboronic acid (APBA) immobilized on polyethyleneimine (PEI)-coated gold nanoparticles. The modified electrode was characterized by TEM, zeta potential measurements and UV-Vis spectroscopy. Its analytical performance was evaluated in pH 9 solution by potentiometry. The respective calibration plot, established at open circuit potential (vs. Ag/AgCl) covers the 0.5-50 mM glucose concentration range, which makes it suitable for blood glucose assays. The detection limit is 0.025 mM, and no interference is caused by ascorbic acid, dopamine, and uric acid. Effects of other carbohydrates such as fructose, galactose and saccharose were also investigated. The electrode was used to determine glucose in human serum samples and the results agreed well with those obtained with commercial amperometric enzymatic sensors.Öğe One step effective removal of Congo Red in chitosan nanoparticles by encapsulation(Pergamon-Elsevier Science Ltd, 2017) Alver, Erol; Bulut, Mehmet; Metin, Aysegul Ulku; Ciftci, HakanChitosan nanoparticles (CNPs) were prepared with ionotropic gelation between chitosan and tripolyphosphate for the removal of Congo Red. The production of chitosan nanoparticles and the dye removal process was carried out in one-step. The removal efficiency of Congo Red by encapsulation within chitosan from the aqueous solution and its storage stability are examined at different pH values. The influence of some parameters such as the initial dye concentration, pH value of the dye solution, electrolyte concentration, tripolyphosphate concentration, mixing time and speed on the encapsulation is examined. Congo Red removal efficiency and encapsulation capacity of chitosan nanoparticles were determined as above 98% and 5107 mg Congo Red/g chitosan, respectively. (C) 2016 Elsevier B.V. All rights reserved.Öğe One-pot green approach for rapid and effective anionic dye remediation: encapsulation within alginate nanocapsules(Wiley, 2024) Alver, Erol; Dogan, Deniz; Mert, Humeyra; Metin, Aysegul UlkuBACKGROUNDThe encapsulation technique was applied to efficiently eliminate Congo red (CR) from aqueous solutions. During the ionotropic gelation between calcium (Ca2+) ions and alginate (AL), CR was effectively entrapped within the AL nanocapsules in a one-step process. Suitable conditions for efficient CR removal via encapsulation were revealed by the systematic optimization of parameters including pH, time and stirring speed, etc.RESULTSAccording to the experimental observations, the stirring rate and temperature were found to have an insignificant effect on the encapsulation of CR molecules. When the pH value of the medium was 3, the highest level of encapsulation efficiency was achieved in a period of 15 min. At a preliminary CR concentration of 2000 mg L-1 and pH 3, the encapsulation efficiency was calculated at approximate to 98.9%, with an encapsulation capacity of 2800 mg dye g-1 AL. The zeta potential values of AL and CR/AL nanocapsules were determined to be +7.05 eV and -14.9 eV, respectively, and the results showed that the particles tended to agglomerate. TEM micrographs also showed that the nanocapsules were nanosized and agglomerated. Soil and UV degradation studies showed that the dye-entrapped nanocapsules degraded remarkably. These results highlighted the great potential of encapsulation for dye removal in economical and practical applications.CONCLUSIONEncapsulation was confirmed to be an economical and practical technique for effectively eliminating CR from aqueous solutions. Under UV light irradiation, the dye molecules entrapped within alginate nanocapsules displayed photodegradation. (c) 2024 Society of Chemical Industry (SCI).Öğe Sigara izmarit zifirinde pah'ların HPLC/UV sistemde tayini: Zenginleştirme ve ön temizlemede oyuk (Hollow) fiber sıvı faz mikroekstraksiyon'un (HFLPME) kullanılması(Kırıkkale Üniversitesi, 2011) Alver, Erol; Özcimder, Mustafa; Demirci, AylaBu çalışmada, sigara izmarit zifirindeki polisiklik aromatik hidrokarbonların (PAH) tayini için yüksek basınç sıvı kromatografik (HPLC) yöntem geliştirilmiştir. Yöntem, zenginleştirme ve ön temizleme için oyuk (hollow) fiber sıvı faz mikroekstraksiyonun (HF?LPME) uygulanmasına dayanmaktadır. Sigara filtresi ve filtre zifiri asetonitrilde çözüldü. HF?LPME'de verici faz asetonitril/su karışımı kullanıldığı için gerçek sigara örnekleri ile çalışmadan önce model PAH çözeltileri ile verici fazdaki asetonitril/su oranı, pH, alıcı faz türü, karıştırma hızı, karıştırma zamanı gibi parametreler optimize edilmiştir. Alıcı fazın kromatografik analizi C18 ters faz kolon ve UV detektör sistemi ile yapılmıştır. Belirlenen optimum koşullarda model örnekler ile ekstraksiyon sonrasında geri alınabilirlik yüzdeleri 63 ile 97 arasında, zenginleştirme faktörleri ise 208 (BaP) ile 319 (An) arasında bulunmuştur. Gerçek örneklerden geri alınabilirlikler % 8 ile % 71 arasında, zenginleştirme faktörleri 27 (BbF) ile 234 (An) arasında bulunmuştur. Çalışmada farklı marka sigara izmaritlerindeki altı polisiklik aromatik hidrokarbon tayin edilmiştir. Altı PAH'ın en küçük tayin sınırları (LOD) 1.65 ng/sigara ile 14.15 ng/sigara arasında bulunmuştur.Anahtar Kelimeler: Sigara, PAH, HPLC, MikroekstraksiyonÖğe Synthesis and Characterization of Chitosan/Polyvinylpyrrolidone/Zeolite Composite by Solution Blending Method(Springer, 2014) Alver, Erol; Metin, Aysegul U.; Ciftci, HakanPolymer/clay composites have been studied for several decades; in the study, polymer/zeolite composite beads have been prepared by a simple solution blending method using chitosan, polyvinylpyrrolidone and zeolite particles as organic and inorganic components, respectively. Different techniques, such as SEM, FTIR spectroscopy, and thermogravimetry have been used to characterize the composite beads. Chitosan/polyvinylpyrrolidone/zeolite (CH/PVP/Z) beads are expected to have a potential as an adsorbent for wastewater treatment. To investigate its applicability, copper (II) was selected as a model compound. The results showed that the composite beads had effective loading capacity and it is a promising adsorbent for heavy metal removal.
