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    A mixed integer linear programming model for long-term planning of municipal solid waste management systems: Against restricted mass balances
    (Pergamon-Elsevier Science Ltd, 2020) Batur, Maliki Ejder; Cihan, Ahmet; Korucu, Mahmut Kemal; Bektas, Nihal; Keskinler, Bulent
    Long-term planning of municipal solid waste management systems is a complex decision making problem which includes a large number of decision layers. Since all different waste treatment and disposal processes will show different responses to each municipal solid waste component, it is necessary to separately evaluate all waste components for all processes. This obligation creates an obstacle in the programming of mass balances for long-term planning of municipal solid waste management systems. The development of an ideal mixed integer linear programming model that can simultaneously respond to all essential decision layers including waste collection, process selection, waste allocation, transportation, location selection, and capacity assessment has not been made possible yet due to this important modeling obstacle. According to the current knowledge of the literature, all mixed integer linear programming studies aiming to address this obstacle so far have had to restrict many different possibilities in their mass balances. In this study, a novel mixed integer linear programming model was formulated. ALOMWASTE, the new model structure developed in this study, was built to take into consideration different process, capacity, and location possibilities that may occur in complex waste management processes at the same time. The results obtained from a case study showed the feasibility of new mixed integer linear programming model obtained in this study for the simultaneous solution of all essential decision layers in an unrestricted mass balance. The model is also able to provide significant convenience for the multi-objective optimization of financial-environmental-social costs and the solution of some uncertainty problems of decision-making tools such as life cycle assessment. (C) 2020 Elsevier Ltd. All rights reserved.
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    Recent advances in boron species removal and recovery using layered double hydroxides
    (Elsevier, 2023) Akdag, Sultan; Keyikoglu, Ramazan; Karagunduz, Ahmet; Keskinler, Bulent; Khataee, Alireza; Yoon, Yeojoon
    Anthropogenic boron discharge threatens ecosystem health and water quality. Although boron is a micronutrient necessary for plants, animals, and humans, excessive concentrations can have toxic effects. Layered double hydroxides (LDH) are two-dimensional anionic clay materials that exhibit intrinsic anion-exchange properties. In this paper, the use of LDH for the removal and recovery of boron species from water is presented. The main factors that affect boron removal, including the LDH dosage, initial boron concentration, solution pH, temperature, and the presence of other anions, are outlined. For boron removal, LDH containing Mg, Fe, Zn, or Ca cations have been mostly used owing to their limited toxicities and abundance in the environment. The boron removal capacity of LDH can be improved by transforming the layered structure into bimetallic oxides through calcination, increasing not only the surface area but also the interaction with anionic species during their regeneration. The main boron-removal mechanism of LDH is ion exchange with intercalated anions or the surface complexation with the surface groups of the LDH. A major advantage of using LDH for boron removal is the possibility of recovering and reusing the extracted boron. LDH synthesized with boron as the interlayer anion showed slow-release fertilizer properties, suggesting the use of boron-loaded LDH as plant growth regulators.
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    Removal of ammonium ions by capacitive deionization and membrane capacitive deionization units
    (Desalination Publ, 2017) Sakar, Hacer; Karataş, Okan; Canbolat, Cigdem Balcik; Keskinler, Bulent; Karagunduz, Ahmet
    In this study, capacitive deionization (CDI) and membrane capacitive deionization (MCDI) unit cells were used to remove NH4+ ions. The influences of operating parameters such as the applied voltage, the initial ammonium concentration and the flow rate on the effectiveness of ammonium removals were investigated. In addition, the effects of different membrane types on MCDI performances were also studied. The results showed that, the electrosorption performances of CDI and MCDI increased by increasing the initial concentration, flow rate and the applied potential. It was observed that the adsorption capacity of MCDI unit was much higher than that of CDI due to the presence of ion-exchange membranes. MCDI technology may provide better advantages on ammonium removal.