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    Application of heterogeneous ion exchange membranes for simultaneous separation and recovery of lithium and boron from aqueous solution with bipolar membrane electrodialysis (EDBM)
    (Elsevier, 2020) Ipekci, Deniz; Kabay, Nalan; Bunani, Samuel; Altiok, Esra; Arda, Muserref; Yoshizuka, Kazuharu; Nishihama, Syouhei
    In this study, heterogeneous ion exchange membranes were tested for separation and recovery of boron and lithium from aqueous solutions with bipolar membrane electrodialysis (EDBM). the results indicated that separation efficiencies and recoveries of both boron and lithium were strongly influenced by the acid and base solutions employed in acid and base cells, flow rate of sample solution and electrical potential applied. It was concluded that separation efficiencies and recoveries of boron and lithium were improved with an increase in the flow rate of sample solution. the highest separation efficiencies were 93% and 69% for lithium and boron, respectively at 50 L/h of sample solution flow rate. the highest recoveries of lithium and boron were achieved as 57% and 41%, respectively at this condition. When electrical potential increased from 15 V to 25 V, boron and lithium separation efficiencies and recoveries obtained were higher. At 30 V of electrical potential, pH of sample solution decreased because of the proton leakage into the sample cell. Since anionic borate ions in sample solution cell were considered to be converted to neutral boric acid, this situation resulted in lower separation efficiencies and recovery of boron from sample solution. By applying optimal process conditions (25 V and 50 L/h of sample solution flow rate), 59% of boron recovery and 73% of lithium recovery were obtained in acid and base cells, respectively.
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    Comparison of two electrodialysis stacks having different ion exchange and bipolar membranes for simultaneous separation of boron and lithium from aqueous solution
    (Elsevier, 2021) Jarma, Yakubu A.; Cermikli, Ezgi; Ipekci, Deniz; Altiok, Esra; Kabay, Nalan
    Two electrodialysis (ED) stacks having different ion exchange and bipolar membranes were compared for separation of boron and lithium simultaneously and their recoveries from an aqueous solution. As operational parameters, types and concentrations of the solutions employed in the acid and base chambers of ED stacks and their initial concentrations, types of the electrode solutions (NaOH, LiOH), the electrical potential applied (15, 20 V) on efficiencies of two stacks were investigated. When 0.05 mol/L of H3BO3 and 0.05 mol/L of LiOH were employed in the acid and base chambers, respectively along with 0.1 mol/L of LiOH as the electrode solution at 15 V, both ED stacks did not exhibit a remarkable difference with respect to separations and recoveries of both boron and lithium. However, the highest separations with the percent removals of 77.5% and 99.8% along with the percent recoveries of 54.0% and 86.4% were achieved, respectively for boron and lithium at 20 V of electrical potential when 0.05 mol/L of H3BO3 in the acid chamber and 0.05 mol/L of LiOH in the base chamber along with 0.1 mol/L of LiOH as the electrode solution were employed in ED-1 stack. The tests conducted with ED-2 stack using 0.05 mol/L of H3BO3 and 0.05 mol/L of LiOH as acid and base chambers solutions, respectively, with an electrode solution of 0.1 mol/L of LiOH at 20 V showed a greater performance for boron removal (81%) than with ED-1 stack. While lower boron and lithium recoveries (38.8 and 50.2%) in ED-2 system were achieved, there was almost no difference between two stacks in terms of lithium removal with a value of about 99.8%.
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    Effect of acid-base solutions used in acid-base compartments for simultaneous recovery of lithium and boron from aqueous solution using bipolar membrane electrodialysis (BMED)
    (Elsevier Science Bv, 2018) Ipekci, Deniz; Altiok, Esra; Bunani, Samuel; Yoshizuka, Kazuharu; Nishihama, Syouhei; Arda, Muserref; Kabay, Nalan
    Application of bipolar membrane electrodialysis (BMED) for simultaneous separation and recovery of lithium and boron from aqueous solution was investigated using Astom Acilyzer EX3B model ED device. In the laboratory scale experiments performed, effects of acid and base solutions types and their concentrations employed in acid and base compartments, electrical potential applied on process efficiency were investigated. The results showed that separations and recoveries of both boron and lithium were effective when 0.05 M HCl and 0.05 M NaOH solutions have been used in acid and base compartments, respectively. The percent separations of boron and lithium were 86.9% and 94.7%, respectively, while their respective recoveries were 50% and 62% at 30 V. The maximum separation and recovery values for boron and lithium were obtained when a 30 V of electrical potential was applied. With optimal initial acid and base concentrations (0.05 M) used in acid and base compartments, the specific power consumption (SPC) was calculated as 7.9 kWh/m(3) at 30 V. While higher initial acid and base concentrations showed higher boron and lithium separation efficiencies, relatively lower concentrations of acid and base solutions employed in acid and base compartments improved the recoveries of boron and lithium. Acid and base solutions generating a moderate conductive medium in acid and base compartments improved separations along with recoveries of boron and lithium from solution. When the solutions of 0.1 M HCl and 0.1 M NaOH were used in acid and base compartments, recoveries of boron and lithium were 27% and 33%, respectively. On the other hand, the recoveries of boron and lithium were 62% and 56%, respectively when 0.1 M H3BO3 and 0.1 M LiOH solutions were employed in acid and base compartments.
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    Investigations on the effects of operational parameters in reverse electrodialysis system for salinity gradient power generation using central composite design (CCD)
    (Elsevier, 2022) Altiok, Esra; Kaya, Tugce Zeynep; Othman, Nur Hidayati; Kinali, Orhan; Kitada, Soma; Guler, Enver; Kabay, Nalan
    Reverse electrodialysis (RED) can be utilized for the production of renewable energy from salinity gradients. However, there are many key parameters that could influence the performance of RED. This study investigates the use RSM for development of a predictive power density (PD) and open-circuit voltage (OCV) model for the RED system. A three-factor central composite design (CCD) was used to quantify the effects of flow velocity (X-1), salinity ratio (X-2), and number of cell pairs (X-3) towards PD and OCV. A total of 17 experimental data were fitted and ANOVA was used to validate the accuracy of the models. 3D and surface plots were created to foresee the optimal levels of each variable. It was found that flow velocity and salinity ratio have the most dominant influences on the RED performances as compared to number of cell pairs. The predicted PD and OCV values were found to be reasonably fit with the experimental data, validating the predictability of applied models. Therefore, this study suggests that CCD can be considered an effective tool for evaluating and optimizing the RED system using a minimum number of experiments.
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    Performance of Reverse Electrodialysis System for Salinity Gradient Energy Generation by Using a Commercial Ion Exchange Membrane Pair with Homogeneous Bulk Structure
    (Mdpi, 2021) Altiok, Esra; Kaya, Tugce Zeynep; Guler, Enver; Kabay, Nalan; Bryjak, Marek
    Salinity gradient energy is a prominent alternative and maintainable energy source, which has considerable potential. Reverse electrodialysis (RED) is one of the most widely studied methods to extract this energy. Despite the considerable progress in research, optimization of RED process is still ongoing. In this study, effects of the number of membrane pairs, ratio of salinity gradient and feed velocity on power generation via the reverse electrodialysis (RED) system were investigated by using Fujifilm cation exchange membrane (CEM Type 2) and FujiFilm anion exchange membrane (AEM Type 2) ion exchange membranes. In the literature, there is no previous study based on a RED system equipped with Fujifilm AEM Type II and CEM Type II membranes that have homogeneous bulk structure. Using 400 mu m of intermembrane distance, maximum obtainable power density by 5 pairs of Fujifilm membranes at 1:45 salinity ratio and with a linear flow rate of 0.833 cm/s was 0.426 W/m(2).
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    Performances of novel chelating ion exchange resins for boron and arsenic removal from saline geothermal water using adsorption-membrane filtration hybrid process
    (Elsevier, 2020) Cermikli, Ezgi; Sen, Fatma; Altiok, Esra; Wolska, Joanna; Cyganowski, Piotr; Kabay, Nalan; Yuksel, Mithat
    The aim of this study is to investigate the performances of new N-methyl-D-glucamine functionalized resins revealing gel (1JW), expanded gel (2JW) and epidermal-like structure (2PTN) for simultaneous removal of boron and arsenic from saline geothermal water by means of adsorption-membrane filtration hybrid process. the effects of adsorbent concentration and resin replacement rate were particularly studied for boron removal from geothermal water. Boron removal with 1JW resin increased from 66% to 86% by doubling the resin concentration while the respective values found for 2PTN resin were 61% and 73%. in the case of the microporous 2PTN resin, due to its epidermal-like structure, the efficiency of the hybrid process was improved by increasing the replacement rate of fresh and saturated resins. Unlike the 2JW resin as the most efficient resin for boron removal among novel resins, the maximum arsenic removal of 35.8% was obtained by the 1JW resin using a resin concentration of 4 g/L. the Dowex XUS 43594.00 resin exhibited lower arsenic removal of 21.5% than 2PTN (4 g/L) and 2JW (2 g/L) giving arsenic removals of 22.4% and 28.8%, respectively.
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    Reclamation of RO permeate and concentrate of geothermal water by new chelating resins having N-methyl-D-glucamine ligands
    (Elsevier, 2021) Sen, Fatma; Altiok, Esra; Cyganowski, Piotr; Wolska, Joanna; Bryjak, Marek; Kabay, Nalan; Yuksel, Mithat
    The paper presents a studies on decreasing boron and arsenic concentrations in processed geothermal water. Reverse osmosis leads to obtain permeate and concentrate characterized by concentrations of 3.99 and 9.82 mg B L-1, as well as 2.93 and 120 mu g As L-1, respectively. This disqualifies the possible use of forth streams for irrigation and makes them inacceptable to be discharged to the surface aquifers. Hence, they have to be treated using chelating resins to further decrease concentrations of boron and arsenic. the new chelating resins 1PTN and 2PTN were synthesized by polymerization of vinylbenzyl chloride (VBC) within a matrix of Amberlite XAD-4 followed by the modification with N-methyl-D-glucamine (NMDG). the so-synthesized NMDG-functionalized resins were evaluated for the removal of boron and arsenic from RO streams and compared to commercial boron selective chelating resin (Diaion CRB 05). Removals and its kinetics followed the pseudo-second order model. Based on diffusional and reactional kinetic models, it was determined that diffusion in pores of the chelating resins was the critical step and the boron sorption rate of epidermal-activated resin was mostly controlled by the reacted layer mechanism. Based on the obtained results, it was found that the resin 2PTN, characterized by macroporous, epidermal-like structure revealed 94% removal of boron and 97% removal of arsenic from RO concentrate. These performances allowed to effectively decrease concentrations of both species to the permissible levels for drinking and irrigation water. What is more, the synthesized resins successfully competed with the commercial boron selective resin Diaion CRB 05 in the boron removal, and outperformed the commercial resin in the arsenic removal, making them a very attractive alternative for reclamation of geothermal water.
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    Surface-Activated Chelating Resins Containing N-Methyl-D-Glucamine Functional Groups for Desalination of Geothermal Water Aimed for Removal of Boron and Arsenic
    (Taylor & Francis Inc, 2021) Cyganowski, Piotr; Sen, Fatma; Altiok, Esra; Wolska, Joanna; Bryjak, Marek; Kabay, Nalan; Yuksel, Mithat
    Within the present study, novel chelating resins containing a layer loaded with N-methyl-D-glucamine functionalities were synthesized. The procedure involved impregnation of macroporous Amberlite XAD-4 adsorbent using mixture of vinylbenzyl chloride (VBC) and divinylbenzene (DVB) further subjected to free radical suspension polymerization. The so-obtained 1PTN and 2PTN adsorbents were characterized by expanded-gel or microporous structure of VBC-co-DVB layer, respectively. The both materials were used in desalination of geothermal water aimed to decrease levels of boron and arsenic. As a part of this, he research on boron and arsenic removal included batch adsorption and kinetic studies. The results have shown that the resin 1PTN showed maximum boron removal of 64% and arsenic removal of 18% from the geothermal water. The resin 2PTN exhibited competitive boron removal performance as compared to the commercial Diaion CRB 05 resin, reaching its efficiency by removing over 96% of boron. Also, the sample 2PTN outmatched Diaion CRB 05, removing 97% of arsenic and leading to decrease of its concentration to permissible level.
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    Synthesis of Silver Nanoparticle-Immobilized Antibacterial Anion-Exchange Membranes for Salinity Gradient Energy Production by Reverse Electrodialysis
    (Amer Chemical Soc, 2024) Eti, Mine; Cihanoglu, Aydin; Hamaloglu, Kadriye Ozlem; Altiok, Esra; Guler, Enver; Tuncel, Ali; Kabay, Nalan
    Biofouling, stemming from the attachment of living microorganisms, such as bacteria, which form resilient biofilms on membrane surfaces, presents a significant challenge that hampers the efficiency of anion-exchange membranes (AEMs) in reverse electrodialysis (RED) applications. This limitation curtails the generation of electrical power from salinity gradients, which notably is a sustainable form of energy known as osmotic energy. RED stands as a clean and promising process to harness this renewable energy source. This study aimed to impart antibacterial activity to synthesized AEMs by using silver nanoparticles (AgNPs). For that purpose, AgNPs were synthesized at 30 degree celsius using two different pH values (6.0 and 9.0) and immobilized into synthesized AEMs using the dip-coating technique. In nanoparticle synthesis, ascorbic acid and trisodium citrate were used as a reductant and a stabilizer, respectively, to take control of the particle size and agglomeration behavior. The results indicated that AgNPs synthesized at pH 6.0 were dispersed on the AEM surface without agglomeration. The stability of AgNPs immobilized on the membrane surface was tested under low- and high-saline solutions. The antibacterial activities of AEMs were determined with the colony-counting method using Gram-negative (Escherichia coli) bacterial suspension. The viability of bacteria dramatically decreased after the immobilization of AgNPs in the AEMs. In the short- and long-term RED tests, it has been observed that the AEMs having AgNPs have high energy-generating potentials, and power density up to 0.372 W/m(2) can be obtained.