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Öğe Adsorption Isotherms for Removal of Heavy Metal Ions (Copper and Nickel) from Aqueous Solutions in Single and Binary Adsorption Processes(Gazi Univ, 2023) Tekin, Burak; Acikel, UnsalThis study deals with the removal of single and binary heavy metals, which cause great problems in terms of the environment and human health, through very low cost, economical and easily obtainable materials. The purpose of this study is to investigate the single-and binary uptake of Copper (II) and Nickel (II) ions onto the Sepiolite in the terms of a thermodynamic perspective. For mono-component systems, the initial effluent concentration, mixing speed and temperature have been studied as a function of time to determine the conditions where the adsorbents show a great deal of affinity towards the Cu (II) and Ni (II) ions in aqueous solutions. Before the metal adsorption experiments, the Physical properties of Sepiolite were identified via Brunauer- Emmett-Teller (BET) analysis. The single metal ion uptake studies were performed at 20, 25, 30, and 35 degrees C. At equilibrium, the sorption data were individually shown to correlate well with the non-competitive Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms. Among the applied isotherm models, the one-component sorption values do fit the Langmuir isotherm best. The simultaneous and competitive uptake of Cu (II) and Ni (II) was assessed by the extended Langmuir and Freundlich isotherms. Both adsorption equations complied with the two -component sorption data perfectly. Single-and binary-sorption results unclose that the effect of Sepiolite to Cu (II) is greater than that of Sepiolite to Ni (II).Öğe Anaerobic digestion of cattle manure, corn silage and sugar beet pulp mixtures after thermal pretreatment and kinetic modeling study(Elsevier Sci Ltd, 2020) Senol, Halil; Acikel, Unsal; Demir, Serkan; Oda, VolkanIn this study, biogas production was investigated from cattle manure (CM), corn silage (CS) and sugar beet pulp (SBP) mixtures under mesophilic conditions. In anaerobic digestion (AD), CM, CS and SBP were mixed in different ratios and the optimum mixture ratio was determined as 2:1:1, w/w/w respectively. In this mixture, biogas production was 180.5 mL/g TS. After the optimum mixing ratios of CM, CS and SBP were determined, thermal pretreatments were applied to this mixture ratio. Thermal pretreatments were performed at 100, 120, 150 and 180 degrees C with 10, 20, 30, 60 and 120 min for each temperature. Considering biogas production after thermal pretreatment, the best thermal pretreatment time was determined as 60 min for all pretreatment temperatures. The highest biogas yield was 362.1 mL/g TS in the reactor which is pretreated at 180 degrees C for 60 min. After thermal pretreatment at 180 degrees C for 60 min, the SCOD value in the reactor increased by 124.6% compared to the control. This reactor produced 100.6% higher biogas production compared to the control. In addition, the solubilization of cellulose, hemicellulose and lignin in this reactor was 38.2%, 32.9% and 23.2%, respectively. Cumulative biogas production (CBP) fitted to modified Gompertz and modified Bertalanffy models.Öğe Comparison of heavy metal uptake capacities of growing, resting and dead cells of R. delemar via acid phosphatase activity(ELSEVIER SCIENCE BV, 2012) Ersan, Mehtap; Acikel, Unsal…Öğe Comparison of the bioaccumulation and biosorption of copper ions by Rhizopus delemar and Candida lipolytica(Taylor & Francis Inc, 2024) Baskan, Gulsah; Acikel, UnsalIn this study, the bioaccumulation of Cu(II) ion by Rhizopus delemar and Candida lipolytica was investigated and the bioaccumulation and biosorption of Cu(II) ions by Candida lipolytica compared. The specific growth rate and the maximum microorganism concentration of both microorganisms increased with increasing initial molasses concentration whereas decreased with increasing initial Cu(II) ion concentrations up to 250 mg/L. Accoding to Monod equation, the maximum specific growth rate and saturation constant for C. lipolytica and R. delemar were determined as 0.335 h(-1)-32.330 g/L and 0.406 h(-1)-24.182 g/L, respectively. The bioaccumulation efficiencies of R. delemar and C. lipolytica were determined as 74.18% and 67.30% in the presence of 50 mg/L Cu(II), respectively. At pH 4.0, the maximum biosorption rate (4.72 mg/g min) and the biosorbed Cu(II) ion concentration (49.0 mg/L) were obtained for C. lipolytica and these values increased with increasing Cu(II) concentration. Cu(II) biosorption by C. lipolytica fitted well to the Langmuir isotherm model and pseudo-second-order kinetic model and maximum adsorption capacity was found as 114.942 mg/g. The bioaccumulated Cu(II) was found to be 21.5 mg/g whereas the amounts of biosorbed Cu(II) were calculated as 53 mg/g by C. lipolytica at a concentration of 100 mg/L of Cu(II). [GRAPHICS] .Öğe Effect of Thermal, Acid and Alkaline Pretreatments on Biogas Production from Cattle Manure(Springer, 2024) Yilmaz, Ayhan; Baskan, Gulsah; Acikel, UnsalThis study examined biogas production from cattle manure obtained from Sivas (T & uuml;rkiye) province under anaerobic conditions. Thermal, acid, base and thermochemical pretreatment methods were applied to cattle manure to increase the biogas production rate. The biogas production rate of cattle manure was found as 150.3 mL/gsolid waste without any pretreatment in the fermentation media. Thermal pretreatments were applied at 25-180 degrees C for 60 min. The highest biogas production rate was found to be 282.6 mL/gsolid waste at 150 degrees C. By increasing the temperature to 150 degrees C, the biogas production rate increased by 88.02% compared to the normal condition. In the next stage of the experimental studies, acidic (15% H2SO4 and 15% HNO3 by mass) and basic (8N KOH and 8N NaOH) pretreatments were applied to the cattle manure. Pretreatments were carried out by adding acid and base at the rates of 5, 10, 20 and 30% of the mass of the solid material in the reactor. The highest biogas production rate was found as 235.7 mL/gsolid waste in the media containing 20% KOH. This value showed a 56.82% increase in biogas production rate compared to the normal condition media. The combined effects of temperature, acid and base on the rate of biogas production were investigated in the last section of the study. The highest biogas production rate was as 320.2 mL/gsolid waste in media containing 20% KOH at 150 degrees C. This value showed a 113.04% increase in biogas production rate compared to the normal condition media.Öğe Effects of stirring and aeration rates on lipase production and growth of R. delemar(ELSEVIER SCIENCE BV, 2012) Ersan, Mehtap; Acikel, Unsal; Acikel, Yesim Sag…Öğe EFFECTS OF STIRRING AND AERATION RATES ON LIPASE PRODUCTION AND GROWTH OF R. DELEMAR IN THE MEDIA CONTAINING GLUCOSE OR MOLASSES SUCROSE AND PFC(GAZI UNIV, FAC ENGINEERING ARCHITECTURE, 2013) Sag Acikel, Yegim; Ersan, Mehtap; Acikel, UnsalLipases (triacylglycerol hydrolases) are hydrolytic enzymes that can catalyze the hydrolysis of the ester bond of long-chain acylglycerols at the oil-water interface. The effects of stirring rate, aeration rate, and the amount of perfluorocarbon (PFC), as an oxygen carrier, in the nutrient media containing glucose or molasses sucrose as main carbon sources were investigated in a batch bioreactor. The maximum lipase activities in the media containing glucose or molasses sucrose as main C source were found to be 43.0 U/L and 102.83 U/L, respectively, at the stationary phase of growth (120th hour of fermentation), at 150 and 200 revolution per minute stirring rates, respectively. The effect of aeration rate on lipase activity was investigated in range of 1-4 vvm. The maximum lipase activities in the media containing glucose or molasses sucrose and 10% PFC were determined as 102.67 U/L, 171.20 U/L, respectively, at 2 vvm aeration rate.Öğe Equilibrium, hysteresis and kinetics of cadmium desorption from sodium-feldspar using rhamnolipid biosurfactant(TAYLOR & FRANCIS LTD, 2012) Asci, Yeliz; Acikel, Unsal; Acikel, Yesim SagIn this study, the sorption/desorption equilibruim and the desorption kinetics of Cd by rhamnolipid biosurfactant from Na-feldspar as a soil component were investigated. The linear, Langmuir and Freundlich isotherms adequately fitted the equilibrium sorption data with regression coefficients ranging from 0.9836-0.9879. However, both the sorption/desorption equilibria were well characterized by the Freundlich model. The extent of hysteresis was quantified based on the differences obtained from sorption and desorption isotherms regarding the quantity of Cd(II) sorbed, the Freundlich exponent, concentration-dependent metal distribution coefficients, and the irreversibility index based on the metal distribution coefficient. The kinetics of desorption of Cd from Na-feldspar was investigated using 77 mM rhamnolipid and at pH 6.8. The first-order, an empirical first-order desorption model (two-coefficient), Lagergren-pseudo-first-order, pseudo-second-order, Elovich and modified Freundlich models were used to describe the kinetic data to estimate the rate constants. To determine the rate-controlling step, the intra-particle diffusion model was also applied to the desorption process. The desorption kinetics of Cd(II) on Na-feldspar was represented better by the pseudo-second-order, Elovich and modified Freundlich equations with correlation coefficients ranging from 0.9941-0.9982 than by first-order equations. The rate-controlling stage was suggested to be mainly the surface reaction mechanism.Öğe Green Synthesis of ZnO Nanoparticles from Onion Peel Wastes(Mehmet Sinan Bilgili, 2020) Canbaz, Gamze Topal; Acikel, Unsal; Acikel, Yesim SagOnion peel and Zn(CH3COO)(2). 2H(2)O were used as a starting material for the synthesis of zinc oxide nanoparticles (ZnONPs). The formation of ZnONPs was first observed by changing the color of the Zn(CH3COO)(2). 2H(2)O solution from colorless to yellow. The Zn-extract solution was tested by a UV-Vi spectrophotometer, and the maximum absorbance peak formation at 362 nm, which belongs to ZnONPs, was observed. For the synthesis of ZnONPs, the optimum Zn(CH3COO)(2). 2H(2)O concentration was determined to be 0.2 M, the optimum temperature was 60 degrees C, the optimum pH was 12.0, and the optimum extract volume was 10 mL. The formation of ZnONPs was identified with the evaluation of SEM images and UV spectra. It was shown that agricultural wastes are re-used and onion peel waste is suitable for the production of ZnONPs.Öğe Investigation of inhibition kinetics of Zn(II) Ions on the acid phosphatase activity and growth of R-delemar and Zn(II) bioaccumulation(TAYLOR & FRANCIS INC, 2016) Acikel, Unsal; Ersan, MehtapThis study investigated the production of acid phosphatase enzyme, which plays a direct role in the metal bioaccumulation and growth of Rhizopus delemar, in the presence of increasing concentrations of Zn(II) ions. Inhibition of the organism's growth rate by Zn(II) ions was found to be of the partially competitive type, with an inhibition constant of 301.4mg Zn(II)/L. In addition, Zn(II) ions exhibited a non-competitive mixed-type inhibition on the activity of acid phosphatase. For the mixed-type inhibition, the inhibition constant (K-I) and the binding affinity (alpha) were determined as 116.67mg Zn(II)/L and 0.395, respectively.Öğe OPTIMIZATION OF ACID PHOSPHATASE PRODUCTION AND ZN(II) BIOACCUMULATION by R. delemar USING RESPONSE SURFACE METHOD(GAZI UNIV, FAC ENGINEERING ARCHITECTURE, 2014) Ersan, Mehtap; Acikel, UnsalAcid phosphatase activity, Zn (II) bioaccumulation and growth of R. delemar were investigated as a function of pH, temperature and initial Zn(II) ion concentration. Experimental design was performed by response surface method (RSM) and Box-Behnken design. The proposed mathematical models were evaluated by analysis of variance (ANNOVA) statistically method. The best fit for acid phosphatase activity was obtained by linear model, the Zn(II) bioaccumulation and microorganism growth were characterized by quadratic equations. The optimum conditions for acid phosphatase activity, Zn(II) bioaccumulation and growth of R. delemar were found to be pH 5,03, 31,82 degrees C and an initial Zn(II) ion concentration of 30,15 mg/L. At these conditions the maksimum acid phosphatase activity Zn(II) bioaccumulation and microorganism concentration were determined as 794,098 mmol / L-min, 17,62 mg / L and 3,2038 g / L respectively. To test sensivity and validity of the optimum conditions the validation experiments were performed.Öğe Phenol Removal from Aqueous Environments with ZnO Nanoparticles Produced from Onion Peel Wastes by Green Synthesis(Mehmet Sinan Bilgili, 2020) Canbaz, Gamze Topal; Acikel, Unsal; Acikel, Yesim SagPhenolic compounds are important industrial wastes and are classified as hazardous substances polluting seas, streams, stagnant waters, and groundwater resources. Therefore, they must be reduced to the permissible levels before being released into natural environments. The removal of nanomaterials and various pollutants by the adsorption method is gradually becoming more important with new technologies developed. In this study, the phenol adsorption capacity of ZnO nanoparticles (NPs) produced from onion peel wastes by the green synthesis method was investigated. In order to determine the optimum adsorption conditions of phenol to ZnO NPs, the effects of the ambient pH, contact time, initial phenol concentration, and temperature were investigated.Öğe PRODUCTION OF Candida BIOMASSES FOR HEAVY METAL REMOVAL FROM WASTEWATERS(Trakya Univ Balkan Yerlesesi Enstituler Binasi, 2021) Mersin, Gulsah; Acikel, UnsalYeasts can accumulate heavy metals and grow in acidic media. In the present study, it was shown that Candida yeasts in an aqueous solution accumulate single Cu(II) and Ni(II) cations. The effect of heavy metal ions on the specific growth rate of biomasses and the uptake of metal ions during the growth phase was investigated in a batch system. Bioaccumulation efficiency decreased with increasing metal ion concentrations at constant sucrose concentrations. Both the specific growth rate and the biomass concentration were more inhibited in the bioaccumulation media containing Ni(II) ions singly as compared with the bioaccumulation media containing Cu(II) ions singly. The maximum specific growth rate and the saturation constant of yeasts were examined with a double-reciprocal form of Monod equation. Metal uptake performance decreased from 81.68% to 46.28% with increasing Ni(II) concentration from 25 mg/L to 250 mg/L for Candida lipolytica. Candida biomasses may be an alternative way of removal of heavy metals from wastewaters and may constitute a sample to produce new biomass. The study showed that Candida yeasts can be used as economical biomass due to their metal resistance and efficient production.Öğe Removal of heavy metal by using green synthesis ZnO NPs and ZnO-HNT composite(Springer Heidelberg, 2023) Canbaz, Gamze Topal; Acikel, Unsal; Acikel, Yesim SagIn this study, Copper (II) adsorption from an aqueous solution with nanoparticles synthesized using organic waste was investigated. For this purpose, the extract obtained from Allium cepa (A. cepa) peel was used as a reducing agent, and zinc oxide nanoparticles (ZnO NPs) were synthesized by the green synthesis method. The synthesized ZnO NPs were obtained as composite adsorbents with halloysite (HNT), a type of clay. The adsorbents were characterized by Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray (EDX), scanning electron microscopy (SEM), X-ray diffractometer (XRD), dynamic light scattering spectrometry (DLS), N-2 adsorption-desorption analysis and zero charge point (pH(PZC)) analysis. Parameters affecting the adsorption process such as pH, adsorbent dose, contact time, initial metal concentration, and temperature were investigated. According to the correlation coefficient, the data obtained with ZnO NPs were best summarized by the Langmuir isotherm with an adsorption capacity of 500 mg g(-1). The kinetic description of the adsorption system was performed by pseudo-second-order kinetic and intraparticle diffusion kinetic models. Thermodynamic parameters were calculated and the adsorption process was found to be spontaneous and exothermic.Öğe Removal of oxytetracycline hydrochloride from aqueous solutions using natural zeolite(Gazi Univ, Fac Engineering Architecture, 2023) Baskan, Gulsah; Acikel, Unsal; Levent, MenderesPurpose: Antibiotics have been widely used in human and veterinary medicines and the presence of antibiotics in the environment causes environmental pollution. For this reason, in this study, we investigated the adsorption of OTC-HCL from aqueous solutions with natural zeolite in a batch reactor.Theory and Methods: Adsorption is commonly known as the mass transfer of organic matter from a liquid phase onto the surface of a solid and it is extensively used in water treatment due to its cheap and efficient treatment. In the present study the effects of some parameters such as pH, initial concentration, adsorbent dosage, contact time, stirring speed and temperature on adsorption were examined. The adsorption process at equilibrium was investigated with Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Temkin models. Kinetic data were examined with pseudo-first order (PFO), pseudo-second order (PSO), intraparticle diffusion and Elovich kinetics. Zeolite characterization was analyzed by N2 adsorption-desorption, XRD, FTIR, SEM-EDX instruments.Results: Adsorption of OTC-HCL on natural zeolite fitted well to the Freundlich and pseudo-second-order models. The maximum adsorption capacity of natural zeolite was determined as 60.97 mg/g at 323 K. Thermodynamic studies indicated that the adsorption of OTC-HCL on natural zeolite was spontaneous and endothermic. Characterization results showed that the adsorption of OTC-HCL on natural zeolite was successfully achieved.Conclusion: Natural zeolites may be an efficient adsorbent for the removal of antibiotics and the present study may constitute a sample for a new adsorbent.Öğe Removal of tetraclycine by biocomposites synthesized with immobilization of Rhizopus delamar and Candida types(GAZI UNIV, FAC ENGINEERING ARCHITECTURE, 2019) Kip, Feray; Acikel, UnsalIn this study, tetracycline adsorption using the biocomposites prepared by the immobilization of chitosan polymer and Candida yeasts (Candida lipolytica, Candida membranaefaciens, Candida tropicalis, Candida utilis) and Rhizopus delemar fungus as a microorganism on chitosan was examined. In the used parameter ranges, temperature was determined as 25-550 degrees C, pH as 2-7, concentration as 10-100 mg / L, optimum pH value as 4.0 and optimum temperature as 25 degrees C, maximum capacity chitosan-Candida utilis biocomposite 1.179 mg / g as determined. The experimental equilibrium data were adjusted to the Freundlich isotherm model of chitosan and biocomposites and the kinetic data were adjusted to the pseudo-first-order kinetics model. Enthalpy, entropy and Gibbs free energy change of adsorption processes operating according to the thermodynamic parameters were determined to be exothermic and spontaneous. Chitosan-Candida utilis biocomposite for before and after adsorption FTIR, SEM analysis and characterization studies was realized. This study proved that the new PAN-Candida utilis biocomposite might emerge as alternatives for the removal of tetracycline.Öğe STUDY OF LIPASE ENZYM ACTIVITY WITH Candida utilis YEAST IN DIFFERENT MEDIA CONDITION(GAZI UNIV, FAC ENGINEERING ARCHITECTURE, 2015) Keklikcioglu Cakmak, Nese; Acikel, UnsalLipases (triacylglycerol hydrolases, EC 3.1.1.3) are hydrolytic enzymes that can catalyze the hydrolysis of the ester bond of long chain acylglycerols at the oil-water interface. In this study; the effects of initial pH, initial sucrose concentration, activators and inhibitors on Candida utilis yeast, lipase enzym are searched. It is qualified that the optimum pH value for growth rate of Candida utilis yeast and production of lipase enzym is 4. Molasses which is a remnant of sugar industry is used as a main carbon source in nutrient media that is prepared for experimental studies in which lipase enzym activity is worked out. In the media in which molasses is used as a main carbon source, it is observed that lipase enzym activity increases with the increase of initial sucrose concentration. Soybean oil, corn oil, olive oil, sunflower oil and canola oil are added to the nutrient media and when the additive effect of enzym activity is observed it is found out that the highest activity increase is 788,5 U/L with the addition of 1,25% soybean oil. The result is that; Cu(II) and Ni(II) metal ions in the fermantation media lower the lipase activity severly and besides, lowering effect of Ni(II) is much more than that of Cu(II).Öğe Synthesis of hydroxyapatite/clay and hydroxyapatite/pumice composites for tetracycline removal from aqueous solutions(INST CHEMICAL ENGINEERS, 2015) Ersan, Mehtap; Guler, Ulker Asli; Acikel, Unsal; Sarioglu, MeltemSynthesized hydroxyapatite/clay (HA-C) and hydroxyapatite/pumice (HA-P) composites were used for tetracycline (TC) uptake studies from aqueous solution and their uptake capacities were compared. HA-C and HA-P composites were synthesized by precipitation method and the structures of the synthesized composites were characterized by XRD, SEM and BET analyses. Cation exchange capacities of HA-C and HA-P were found to be 84 meq/100 g and 33 meq/100 g, respectively. The TC adsorption using HA-C and HA-P was studied on batch mode. Various parameters such as contact time, solution pH, initial TC concentration, composite dosage, salinity and temperature were optimized. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models were applied to the equilibrium data. The maximum adsorption capacity onto HA-C was found to be 76.02 mg/g and about four times larger than the adsorption capacity of the HA-P (17.87 mg/g). The results indicated that the TC uptake onto HA-C and HA-P composites is mainly by a surface complexation and ion-exchange mechanism which depend on the solution pH. The calculated values of thermodynamic parameters indicated that the TC adsorption is favorable, physicochemical in nature. The sorption process follows pseudo-second-order and intraparticle diffusion kinetic models. The TC adsorption mechanism by HA-C and HA-P has been proposed. (C) 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
