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    An investigation of natural and modified diatomite performance for adsorption of basic Blue 41: Isotherm, kinetic, and thermodynamic studies
    (Desalination Publications, 2021) Kul A.R.; Aldemir A.; Koyuncu, Hülya
    In the present study, natural diatomite (ND) and Mn-modified diatomite (MD) were utilized for adsorption of Basic Blue 41 (BB 41) from aqueous solution at temperatures of 298, 308, and 318 K. Based on the results of isotherm studies, the Freundlich isotherm model is better than the Langmuir and Temkin models. Isotherm constants increase as the temperature increases, indicating that the removal process is favorable at higher temperatures. Adsorption kinetics for BB 41 on diatomite best fit the pseudo-second-order model which had kinetic constants that were higher than pseudo- first-order and intra-particle diffusion models. When the initial dye concentration rises from 10 to 80 mg L−1, adsorption capacity on ND and MD increase from 6.15 to 62.43 mg g−1 and 9.06 to 75.95 mg g−1 at 318 K, respectively. Gibbs free energy (ΔG°) values for BB 41 adsorption on ND and MD were determined as −11.224 and –15.586 kJ mol−1 at 318 K, respectively. Enthalpy (ΔH°) values for this removal process were calculated as 31.746 and 48.706 kJ mol−1, with entropy (ΔS°) values determined as 133.319 and 170.728 J mol−1 K−1 for ND and MD, respectively. Activation energy (EA) values were determined as 42.7 and 58.83 kJ mol−1 for BB 41 removal onto ND and MD adsorbents, respectively. Economic analysis of the preparation of Mn-modified diatomite was carried out. The results indicate that diatomite could be a good material compared to more costly adsorbents used for dye removal.
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    Biosorption study for removal of methylene blue dye from aqueous solution using a novel activated carbon obtained from nonliving lichen (Pseudevernia furfuracea (L.) Zopf.)
    (Elsevier, 2020) Koyuncu, Hülya; Kul, Ali Riza
    To the best of our knowledge, there is no study on the utilization of lichens in the production of activated carbon while lichens are natural, renewable and cheap sources. In this study, a novel activated carbon (ACLPF) from non-living lichen Pseudevernia furfuracea (L.) Zopf. (LPF) was produced, and physicochemical and morphological characterization of the ACLPF were examined with the help of Brauner-Emmett-Teller surface area (BET), X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) techniques. The obtained ACLPF had a high surface area (851.24 m(2)g(-1)) and a large pore volume (0.225 cm(3)g(-1)) with micropore size distribution (1.06 nm). To investigate the usability of the ACLPF in wastewater treatment, batch mode biosorption experiments were carried out, and the effect of various parameters on methylene blue (MB) dye removal from aqueous solution were studied. The experimental data were fitted with 4 different kinetic models (pseudo first-order (PFO), pseudo second-order (PSO), Elovich model (EM) and intra-particle diffusion (IDM)) and 3 different isotherm models (Langmuir, Freundlich and Dubinin-Radushkevich (D-R)). It was found that the maximum biosorption capacity and the removal efficiency (%) were as 243.9024 mgg(-1) and 91.38%, respectively. The biosorption of MB onto the ACLPF was chemical biosorption due to the activation energy (E-a) to be 42.63 kJmol(-1), and the process was endothermic (Delta H-0=61.4163 kJmol(-1)), feasible and spontaneous (Delta G(0)= -7.0278 kJmol(-1) at 318 K and Delta S-0 =0.1707 kJmol(-1)K(-1)) thermodynamically. The novelty of this study is that besides obtained and characterized the activated carbon (ACLPF) from the non-living LPF at the first time, the discussions on the biosorption capability of the ACLPF for the removal of MB dye from aqueous media are included in this paper.
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    Elma Kabuğundan Elde Edilen Aktif Karbon ile Sulu Ortamdan 2,4,6-Trinitrotolueni Uzaklaştırma Kinetiği
    (Atatürk Üniversitesi, 2025) Koyuncu, Hülya
    2,4,6-Trinitrotoluen (TNT), dünya çapında en yaygın kullanılan yüksek güçlü patlayıcılardan biridir. Üretimi sırasında ve kullanımından sonra önemli su ve toprak kirliliğine neden olur. Bu çalışmada, 1429 m2/g BET yüzey alanına sahip elma kabuğundan elde edilen aktif karbon (APAC) kullanılarak sulu ortamdan TNT'nin giderim kinetiği incelenmiştir. TNT konsantrasyonları, Meisenheimer kompleksi oluşturarak bir UV-VIS spektrofotometresi kullanılarak ölçülmüştür. Giderim kinetiğini analiz etmek için psödo-birinci mertebeden (PFO), psödo-ikinci mertebeden (PSO) ve parçacık içi difüzyon (IPD) modelleri kullanılmıştır. Bunlar arasında PSO kinetik modeli, yüksek korelasyon katsayısı (R2) ve düşük sapma (%) değerleriyle adsorpsiyon sürecini daha doğru bir şekilde açıklamıştır. TNT giderim verimliliği 60 dakika sonra %99,7'ye ulaşmış ve APAC'nin TNT'yi sulu ortamdan gidermede oldukça etkili olduğunu göstermiştir.
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    PATLAYICILAR İLE ATEŞLİ SİLAHLARIN KULLANIMINDAN KAYNAKLANAN KURŞUN VE BAKIR KİRLİLİĞİNİN GİDERİLMESİ
    (2024) Koyuncu, Hülya
    Patlayıcı maddeler, askeri amaçlarla ve sivil mühendislik uygulamalarında yaygın olarak kullanılmaktadır. Birincil patlayıcılar, daha az duyarlı ikincil patlayıcıları ateşleyebilmek için fünye ya da primer karışımlarında kullanılan ve alev, darbe, elektrik kıvılcımı, sürtünme ya da ısı gibi küçük bir etkiyle bir patlama dalgası oluşturabilen patlayıcılardır. Kurşun azid (Pb(N3)2), fünyelerde ya da primer karışımlarda halen günümüzün en yaygın kullanılan birincil patlayıcıları arasında yer alır. Yüksek maliyetli gümüş azid (AgN3) ve yüksek hassasiyetli bakır azidler (CuN3 ve Cu(N3)2) ise özel uygulamalarda kullanılmaktadır. Ateşli silahlar ve patlayıcıların kullanımıyla hava, toprak, yer üstü ve yer altı sularında metal kirliliği oluşur. Üstelik sadece kullanımla değil, üretim, paketleme, nakliye ve depolama aşamalarında da patlayıcılar çevre kirliliğine neden olarak insan ve diğer canlıların sağlığı için tehdit oluşturur. Bu nedenle kurşun ve bakırın sulardan uzaklaştırılması, çevresel sürdürülebilirlik ve insan sağlığı için oldukça önemlidir. Bu çalışmada kurşun ve bakır iyonlarının sulu ortamdan uzaklaştırılması araştırılmıştır. Farklı sıcaklık ve başlangıç konsantrasyonlarında likenden üretilen aktif karbon kullanılarak adsorpsiyon yöntemiyle deneyler gerçekleştirilmiştir. Giderim yüzdesi 25 oC’de ve 20 ppm başlangıç konsantrasyonunda kurşun ve bakır iyonları için sırasıyla % 81,40 ve % 80,30 olarak hesaplanmıştır. Sıcaklık 45 oC’ye yükseltildiğinde uzaklaştırma verimi kurşun için % 92,55 ve bakır için % 91,20 olmuştur.
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    Removal of aniline from aqueous solution by activated kaolinite: Kinetic, equilibrium and thermodynamic studies
    (Elsevier, 2019) Koyuncu, Hülya; Kul, Ali Riza
    In this study, the adsorption kinetics, equilibrium and thermodynamics of aniline on native (NK) and acid activated (AK) kaolinites were examined. It was shown that modification of kaolinite with acid not only increases the adsorption capacity of the adsorbent from 109.89 to 256.41 mgg(-1) for aniline but also its initial sorption rate for aniline, suggesting the activated kaolinite with higher adsorption capacity have great potential application in removal of aniline from water and wastewater. Adsorption efficiency for AK reached at about 91% while it was at about 75% for NK. The kinetics of adsorption of aniline was discussed using three kinetic models, the pseudofirst-order, the pseudo-second-order and the infra-particle diffusion model. The experimental data fitted very well the pseudo-second-order kinetic model due to the higher correlation coefficient and lower sum of squared errors (SSE,%) values, and a good agreement between the experimental and the calculated qe values. Experimental results were also analysed by the Langmuir, Freundlich and Dubinin-Redushkevich (D-R) isotherm models. R-L separation factor for Langmuir and the n value for Freundlich isotherm show that aniline are favourably adsorbed by NK and AK. The negative value of Delta G and positive value of Delta S showed that the adsorption of aniline onto NK and AK was feasible and spontaneous. The positive value of Delta H confirmed the endothermic nature of adsorption.
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    Removal of methylene blue dye from aqueous solution by nonliving lichen (Pseudevernia furfuracea (L.) Zopf.), as a novel biosorbent
    (Springer Heidelberg, 2020) Koyuncu, Hülya; Kul, Ali Riza
    The use of lichens is insufficient in industry. To the best of our knowledge, there is no study on the use of lichens in the removal of dyes from aqueous media. The aim of this study is to draw attention to the biosorption capabilities of lichens which are natural, renewable and inexpensive sources, and to investigate the usability of nonliving lichen Pseudevernia furfuracea (L.) Zopf. (LPF) in methylene blue (MB) dye removal from aqueous solution. With the green chemistry approach, no chemical treatment was applied to the LPF and it was used as a natural biosorbent for the biosorption. The LPF samples were prepared and characterized and performed batch mode biosorption experiments studying the effect of various parameters on MB biosorption. The experimental data were fitted with four different kinetic models (pseudo-first order, pseudo-second order, Elovich model and intra-particle diffusion) which were evaluated for their validity. Identification of the biosorption mechanism of MB onto the LPF was performed by isotherm studies via three isotherm models [Langmuir, Freundlich and Dubinin-Radushkevich (D-R)], and the parameters of each model were determined. It was concluded that the biosorption rate and yield were high, the type of biosorption of MB onto the LPF was defined as chemical biosorption, and the surface of the LPF was decided energetically heterogeneous. The results indicate that the LPF biomass can be attractive options for MB dye removal from aqueous media.
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    Synthesis and characterization of a novel activated carbon using nonliving lichen cetraria islandica (L.) ach. and its application in water remediation: Equilibrium, kinetic and thermodynamic studies of malachite green removal from aqueous media
    (Elsevier, 2020) Koyuncu, Hülya; Kul, Ali Riza
    Although lichens are natural and cheap sources, there is no study in the literature about the production of activated carbon from lichen species. In this study, a novel activated carbon (ACCI) from non-living lichen Cetraria islandica (L.) Ach. (LCI) was produced, and physicochemical and morphological characterizations of the LCI and ACCI were examined with the help of Brauner-Emmett-Teller surface area (BET), X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) techniques. The BET surface area, Barrett-JoynerHelenda (BJH) adsorption total volume of pores and BJH adsorption average pore diameter of the ACCI were determined as 394.417 m(2).g(-1), 0.1216 cm(3).g(-1) and 12.768 angstrom (1.28 nm), respectively, while these values for non-living LCI were 1.103 m(2).g(-1), 0.0044 cm(3). g(-1) and 140.18 angstrom (14.02 nm), respectively. To investigate and compare the biosorption properties of the LCI and ACCI in wastewater treatment, batch mode biosorption experiments were carried out, and the effect of various parameters on malachite green (MG) dye removal from aqueous media were studied. The experimental data were fitted with 4 different kinetic models (pseudo first order (PFO), pseudo second-order (PSO), Elovich model (EM) and intra-particle diffusion (IDM)) and 3 different isotherm models (Langmuir, Freundlich and Dubinin-Radushkevich (D-R)). The biosorption of MG onto both the LCI and ACCI follows well the PSO kinetics. The rate constants k(2) for the LCI and ACCI were found as 0.0125-0.0157 g.mg(-1).min(-1) and 0.00612-0.00979 g.mg(-1).min(-1), respectively (298-318 K). The equilibrium time was 80 min for the ACCI, and the maximum biosorption capacity and the removal efficiency (%) for the ACCI were found as 666.22 mg.g(-1) and 93.46%, respectively. The biosorption mechanism of MG onto both the LCI and ACCI was physical biosorption. This result was confirmed by the activation energies (9.095 kJ.mol(-1) for LCI and 18.450 kJ.mol(-1) for ACCI), the D-R mean energies (6.8041-7.4536 kJ.mol(-1) for LCI and 7.3323-8.0582 kJ.mol(-1) for ACCI in the temperature range 298-318 K), and FTIR, XRD, TGA and SEM/EDX results. The enthalpy change (Delta H-0) values for the LCI and ACCI were found to be in the range of 8.7987-17.2582 kJ.mol(-1) and 20.4899-29.2728 kJ.mol(-1), respectively (20-70 mg.L-1 initial MG concentrations). This indicated the endothermic behaviour of the biosorption. The novelty of this study is that besides obtained and characterized the activated carbon (ACCI) from the nonliving LCI for the first time, the comparisons and discussions on the biosorption capability of the ACCI and LCI for the removal of MG dye from aqueous media are included in this paper. All results showed that the synthesized ACCI is an effective, cheap and promising biosorbent for the cleaning treatment of MG dye from wastewaters.