Kinetic, Isotherm and Thermodynamic Analysis on Adsorption of Cr(VI) Ions from Aqueous Solutions by Synthesis and Characterization of Magnetic-Poly(divinylbenzene-vinylimidazole) Microbeads

The magnetic-poly(divinylbenzene-1-vinylimidazole) [m-poly(DVB-VIM)] microbeads (average diameter 53–212 μm) were synthesized and characterized; their use as adsorbent in removal of Cr(VI) ions from aqueous solutions was investigated. The m-poly(DVB-VIM) microbeads were prepared by copolymerizing of divinylbenzene (DVB) with 1-vinylimidazole (VIM). The m-poly(DVB-VIM) microbeads were characterized by N2 adsorption/desorption isotherms, ESR, elemental analysis, scanning electron microscope (SEM) and swelling studies. At fixed solid/solution ratio the various factors affecting adsorption of Cr(VI) ions from aqueous solutions such as pH, initial concentration, contact time and temperature were analyzed. Langmuir, Freundlich and Dubinin–Radushkvich isotherms were used as the model adsorption equilibrium data. Langmuir isotherm model was the most adequate. The pseudo-first-order, pseudo-second-order, Ritch-second-order and intraparticle diffusion models were used to describe the adsorption kinetics. The apparent activation energy was found to be 5.024 kJ mol−1, which is characteristic of a chemically controlled reaction. The experimental data fitted to pseudo-second-order kinetic. The study of temperature effect was quantified by calculating various thermodynamic parameters such as Gibbs free energy, enthalpy and entropy changes. The thermodynamic parameters obtained indicated the endothermic nature of adsorption of Cr(VI) ions. Morever, after the use in adsorption, the m-poly(DVB-VIM) microbeads with paramagnetic property were separeted via the applied magnetic force. The magnetic beads could be desorbed up to about 97% by treating with 1.0 M NaOH. These features make the m-poly(DVB-VIM) microbeads a potential candidate for support of Cr(VI) ions removal under magnetic field

Synthesis and characterization of magnetic poly(divinyl benzene-N-vinyl imidazole) [m-poly(DVB-VIM)] microbeads and investigation of physicochemical parameters of heavy metal ions adsorption from aqueous solutions

Sunulan çalışmada; manyetik poli(divinil benzen-N-vinil imidazol) [m-poli(DVB-VIM)] mikroküreleri Fe3O4 nanopartikül varlığında süspansiyon polimerizasyonu yöntemiyle sentezlenerek ağır metal iyonlarının uzaklaştırılmasında kullanıldı. m-poli(DVB-VIM) mikroküreleri elementel analiz, N2 adsorpsiyon-desorpsiyon izoterm testi, şişme testi, yoğunluk ölçümleri, taramalı elektron mikroskobu (SEM) ve manyetizma ölçümleri ile karakterize edildi. m-poli(DVB-VIM) mikrokürelerinin spesifik yüzey alanı 29.47 m2/g, boyut dağılımı 53-212 µm, şişme oranı %44 ve ortalama Fe3O4 içeriği %10,2 olarak belirlendi. Mikrokürelerin yapısındaki VIM miktarı 3,021 mmol/g polimer olarak bulundu. Bu durum m-poli(DVB-VIM) mikrokürelerinin manyetik olduğunu ve N-vinil imidazol ligantının polimerik yapıya girdiğini göstermektedir.Elde edilen mikrokürelerin ağır metal iyonları uzaklaştırılmasında kullanılabilirliğini araştırmak için; Cr(VI), Ni(II), Zn(II), Pb(II) ve Cu(II) iyonları örnek iyon olarak kullanıldı. Mikrokürelerin adsorpsiyon kapasitesi üzerinde etkili parametrelerden pH, başlangıç ağır metal iyonu konsantrasyonu, sıcaklık, zaman ve adsorban miktarı etkisi incelendi. Maksimum uzaklaştırma Cr(VI) iyonları için pH 2,0'de; Cu(II) iyonları için pH 5,0'te; Zn(II), Ni(II) ve Pb(II) iyonları için pH 6,0'da gözlendi. Sıcaklığın adsorpsiyona etkisi incelendi ve sıcaklığın 4oC'den 65oC'ye çıkarılmasıyla ağır metal iyonları adsorpsiyonunun arttığı gözlendi.m-poli(DVB-VIM) mikrokürelerinin 100 ppm konsantrasyonda ve 65oC'deki adsorpsiyon kapasitesi Cu(II), Cr(VI), Pb(II), Ni(II) ve Zn(II) iyonları için sırasıyla 52,90 mg/g, 46,85 mg/g, 45,01 mg/g, 23,07 mg/g ve 22,39 mg/g olarak belirlendi. Bu durum sulu çözeltilerden ağır metal iyonlarını uzaklaştırılmasında m-poli(DVB-VIM) mikrokürelerinin etkili olduğunu göstermektedir. Kütle bazında ilgi sırası Cu(II) > Cr(VI) > Pb(II) > Ni(II) > Zn(II) şeklindedir. Adsorpsiyon kinetikleri incelenerek mevcut sistem için 4, 25, 45 ve 65oC'de Langmuir ve Freundlich adsorpsiyon izotermlerine uygulanabilirlik test edildi. Denge verileri Langmuir modeline uygun bulundu. Ayrıca yalancı (pseudo) 1. derece, yalancı (pseudo) 2. derece ve partikül içi difüzyon modelleri de adsorpsiyon kinetiğinin incelenmesinde kullanıldı. Gibbs serbest enerji, entalpi ve entropi değişimi gibi termodinamik parametreler hesaplanarak sıcaklık etkisi belirlendi. Bu çalışmada adsorpsiyon sürecinin endotermik olduğu ve kendiliğinden gerçekleştiği belirlendi. Manyetik mikrokürelerin rejenerasyonu Cu(II), Pb(II), Ni(II) ve Zn(II) için 0,1 M HNO3; Cr(VI) için 1 M NaOH kullanılarak gerçekleştirildi. Aynı manyetik mikroküreler kullanılarak adsorpsiyon-desorpsiyon döngüsü 10 kez tekrarlandı ve ağır metal iyon kapasitesinde önemli bir değişim gözlenmedi.In present study, magnetic poly(divinyl benzene-N-vinyl imidazole) [m-poly(DVB-VIM)] microbeads were synthesized by suspension polymerization technique in the presence of magnetite Fe3O4 nano-powder and used for heavy metal ions removal studies. m-poly(DVB-VIM) microbeads were characterized by elemental analysis, N2 adsorption-desorption isotherm tests, swelling studies, density measurements, scanning electron microscope (SEM) and magnetism measurements. The specific surface area of the m-poly(DVB-VIM) beads was found to be 29.47 m2/g with a size range of 53-212 µm in diameter and the swelling ratio was 44%. The average Fe3O4 content of the resulting m-poly(DVB-VIM) microbeads was 10,2%. The incorporation of the VIM was found 3,021 mmol/g polymer. It was determined that m-poly(DVB-VIM) microbeads are magnetic and the ligand N-vinyl imidazole was inserted into the polymer structure.Cr(VI), Ni(II), Zn(II), Pb(II) and Cu(II) ions were used as model species to investigate the usability of the obtained microspheres in heavy metal removal. Effects of pH, initial heavy metal ions concentration, temperature, contact time and adsorbent dosage were investigated as the effective parameters on the adsorption capacities of the microspheres. Maximum uptake was obtained for Cr(VI) ions at pH 2,0; Cu(II) ions at pH 5,0; Zn(II), Ni(II) and Pb(II) ions at pH 6,0. The effect of temperature on the adsorption was studied and the adsorption of heavy metal ions was increased with the rise in temperature from 4 to 65oC.The adsorption capacities of the m-poly(DVB-VIM) beads for Cu(II), Cr(VI), Pb(II), Ni(II) and Zn(II) were found 52,90 mg/g, 46,85 mg/g, 45,01 mg/g, 23,07 mg/g and 22,39 mg/g, respectively at 100 ppm and 65oC. In other words m-poly(DVB-VIM) beads were found to efficiently remove heavy metal ions from aqueous solutions. The affinity order on mass basis is Cu(II) > Cr(VI) > Pb(II) > Ni(II) > Zn(II). Adsorption kinetics have been tested and the applicability of the Langmuir and Freudlich adsorption isotherms for the present system have been tested at 4, 25, 45 and 65oC. Equilibrium data agreed well with the Langmuir model. Also pseudo-first-order, pseudo-second order and intraparticle diffusion models were used to describe the adsorption kinetics. The study of temperature effect was quantified by calculating various thermodynamic parameters such as Gibbs free energy, enthalpy and entropy changes. In this study, adsorption process was endothermic in nature and spontaneous. Regeneration of the magnetic microbeads was easily performed with 0,1 M HNO3 for Cu(II), Pb(II), Ni(II) and Zn(II); 1 M NaOH for Cr(VI). Adsorption-desorption cycles were be performed ten-times by using same magnetic microbeads and any noticeable loss was not determined

ADSORPTION OF Ni(II) IONS FROM AQUEOUS SOLUTIONS ONTO MAGNETIC POLY( DIVINYLBENZENE-CO-VINYLIMIDAZOLE) MICROBEADS: PHYSICOCHEMICAL STUDIES

A modified suspension polymerization was used for the preparation of the mesoporous magnetic-poly(divinylbenzene-co-vinylimidazole) (m-poly(DVB-VIM)) microbeads in size 53-212 μm of average diameter. The specific surface area and the DVB/VIM mol ratio of the microsphereswere determined as 29.47 m2/g and 1:4 mol/mol with Fe3O4, respectively. The physicochemical studies of adsorption of Ni(II) ions from aqueous solutions such as pH, initial concentration, amountof mesoporous m-poly(DVB-VIM) microbeads, contact time, and temperature onto the m-poly(DVBVIM) microspheres were carried out. The maximum adsorption capacities of the m-poly(DVB-VIM)microspheres towards Ni(II) ions were determined as 13.51, 20.14, 21.00 and 23.62 mg/g at 277 K, 298 K, 318 K, and 338 K, respectively. The dynamic and equilibrium adsorption behaviours of the system were adequately described by the pseudo-second-order kinetic and the Langmuir isotherm models, respectively. Various thermodynamic parameters, such as the Gibbs’ free energy change (ΔGo), the standard enthalpy change (ΔHo) and the standard entropy change (ΔSo) were also determined. Morever, after use in the adsorption, the m-poly(DVB-VIM) microbeads with paramagnetic property was separated from the via the applied magnetic force. These results indicate that the material studied could be used as a purifier for the removal of Ni(II) ions from water and wastewater under magnetic field

MANYETİK-POLİ (DİVİNİLBENZEN-KO-VİNİLİMİDAZOL) MİKROKÜRELER İLE SULU ÇÖZELTİLERDEN Ni(II) İYONLARININ ADSORPSİYONU: FİZİKOKİMYASAL ÇALIŞMALARI

Ortalama çapı 53-212 μm olan mezogözenekli manyetik-poli(divinilbenzen-ko-vinilimidazol) (mpoli(DVB-VIM)) mikrokürelerinin hazırlanması için modifiye süspansiyon polimerizasyonu kullanıldı. Mikrokürelerin spesifik yüzey alanı 29.47 m2g-1 ve Fe3O4 ilavesiyle birlikte, DVB/VIM mol oranı 4:1 mol/mol olarak belirlendi. Fizikokimyasal çalışmalar m-poli (DVB-VIM) mikroküreleri üzerine pH, başlangıç konsantrasyonu, mikroküre miktarı, temas süresi ve sıcaklık gibi parametrelerle incelendi. m-poli(DVB-VIM) mikrokürelerinin Ni(II) iyonlarına karşı maksimum adsorpsiyon kapasitesi 277 K, 298 K, 318 K ve 338 K’de sırasıyla 13.51, 20.14, 21.00 ve 23.62 mg.g-1 olarak belirlendi. Sistemin dinamik ve denge adsorpsiyon davranışları sırasıyla yalancı ikinci derece model ve Langmuir izoterm modeliyle açıklandı. Gibbs serbest enerji değişimi (ΔG0), standart entalpi değişimi (ΔH0) ve standart entropi değişimi (ΔS0) gibi termodinamik parametreler belirlendi. Ayrıca adsorpsiyonda kullanımdan sonra, paramanyetik özellikli m-poli (DVB-VIM) mikroküreleri uygulanan manyetik kuvvet yardımıyla ayrıldı. Bu sonuçlar, çalışılan malzemenin manyetik alan altında su ve atık sulardan Ni(II) iyonlarının uzaklaştırılması için kullanılabilir olduğunu gösterdi

Diethyl phthalate removal from aqueous phase using poly(EGDMA-MATrp) beads: kinetic, isothermal and thermodynamic studies

<div><p>In this study, poly(ethylene glycol dimethacrylate-N-methacryloyl-l-tryptophan methyl ester) [poly(EGDMA-MATrp)] beads (average diameter = 106–300 µm), which were synthesized by co-polymerizing of N-methacryloyl-l-tryptophan methyl ester (MATrp) with ethylene glycol dimethacrylate (EGDMA), were used for diethyl phthalate (DEP) adsorption. The various factors affecting the adsorption of DEP from aqueous solutions such as pH, initial concentration, contact time and temperature were analysed. Adsorption behaviour of DEP on the poly(EGDMA-MATrp) beads was investigated by varying pH values of solution, contact time, initial concentration and temperature. An optimum adsorption capacity of 590.7 mg/g for DEP was obtained at 25 °C. The present adsorption process obeyed a pseudo-second-order kinetic model. All the isotherm data can be fitted with the Langmuir, Freundlich and Dubinin–Radushkevich isotherm models. Thermodynamic parameters Δ<i>H</i> = 7.745 kJ/mol, Δ<i>S</i> = 81.92 J/K/mol and Δ<i>G</i> = −16.69 kJ/mol to −18.31 kJ/mol with the rise in temperature from 25 °C to 45 °C indicated that the adsorption process was endothermic and spontaneous.</p></div