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    A review on treatment of membrane concentrates generated from landfill leachate treatment processes
    (Elsevier, 2021) Keyikoğlu, Ramazan; Karatas, Okan; Rezania, Hamidreza; Kobya, Mehmet; Vatanpour, Vahid; Khataee, Alireza
    Landfill leachate (LL) is highly toxic wastewater and comprises various pollutants such as organic compounds, biological organisms, xenobiotics, heavy metals, inorganic salts, and ammonia. The integration of conventional methods with membrane processes has become indispensable due to the enforcement of stricter regulations for the LL discharge. The integrated membrane technologies achieve a pollutant removal efficiency of higher than 95% with a large volume of treated leachate and a low capital cost investment. However, the drawback of these processes is the production of a membrane concentrate with even more hazardous characteristics. This review presents the state of the art methods along with the recent improvements to the existing processes for the treatment of membrane concentrates. The techniques are mainly divided into two categories of conventional, advanced methods and the hybridization of them. The operating conditions, performances of the individual processes along with wastewater characteristics were summarized in detail. Generally, the leachate concentrate properties such as salinity, COD, BOD5/COD ratio, and toxicity are essential parameters for the selection of appropriate treatment methods. It was found that single treatment processes are not able to reach desirable membrane concentrate treatment and need an engineered combination of these techniques to achieve satisfactory removal efficiencies.
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    Different metal-doped ZnS quantum dots photocatalysts for enhancing the permeability and antifouling performances of polysulfone membranes with and without UV irradiation
    (Pergamon-Elsevier Science Ltd, 2022) Vatanpour, Vahid; Karatas, Okan; Amiri, Saba; Rajabi, Hamid Reza; Koyuncu, Ismail; Khataee, Alireza
    In this study, the effect of three different transition metal ion dopants (Mn2+, Fe2+, and Co2+) on the characteristics of zinc sulfide (ZnS) quantum dots (QDs) was investigated and the obtained QDs photocatalysts were applied for the modification of polysulfone (PSf) mixed matrix membranes to reduce membrane fouling. The synthesized QDs and fabricated membranes were fully identified with SEM, TEM, AFM, FTIR analyses, and also underwent porosity and contact angle tests. Flux recovery ratios (FRR) significantly increased from 69.8% (bare) to 85.0% (1% Fe-doped ZnS QDs) after modification of membranes with metal-doped QDs. The contact angles of the prepared membranes decreased with doping of dissimilar metals, therefore hydrophilicity increased, and reversible/non-reversible blockages were improved. Besides, the use of UV irradiation during the washing of the membranes increased the FRR of the photocatalytic activated membranes to 91.2%. Compared to the bare PSf membrane in dye solution filtration, 1% Fe-doped ZnS QDs membrane yielded twice as much flux and 15% higher FRR results. Therefore, the results proved that metal-doped QDs can be used in the modification of PSf membranes with high efficiency.
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    Electrochemical oxidation of perfluorooctanesulfonate (PFOS) from simulated soil leachate and landfill leachate concentrate
    (Elsevier, 2023) Karatas, Okan; Khataee, Alireza; Kobya, Mehmet; Yoon, Yeojoon
    The near-widespread presence of poly- and perfluoroalkyl substances (PFASs) in humans has generated concerns regarding the potential negative impact of these chemicals on human health, as some PFASs are exceedingly persistent and bioaccumulative. Among the perfluorinated PFASs, which exhibit high polarity and strong carbon-fluorine bonds, perfluorooctanesulfonate (PFOS) is one of the frequently encountered species. In this study, the efficiency of electrooxidation (EO) and its application in groundwater simulation were first evaluated as a realistic approach to PFOS removal. After optimizing EO parameters including the solution pH, current density, and the effects of inlet concentration and the anode material, 83 % total organic carbon (TOC) removal was obtained. In groundwater experiments, in which the infiltration of PFOS from soil layers into groundwater was simulated, 79 % TOC removal efficiency was achieved in the more complex groundwater; moreover, an F- ion concentration of 8.78 mg/L was obtained from the decomposition of PFOS. To increase the realism of the simulation, the leachate process was repeated four times, and the EO process was applied to each sequential leachate. In addition, the process efficiency was studied in real landfill leachate wastewater to which PFOS had been added. Despite the challenging wastewater composition, 84 % TOC removal efficiency was achieved. Together, these results indicate that BDD-anodic oxidation may be a practical method to treat PFOScontaminated groundwater and wastewater.
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    Nanoarchitecturing of CuFeLa layered double hydroxide on graphite felt for photo-electrocatalytic degradation of emerging pollutants
    (Elsevier Science Inc, 2025) Seifi, Azam; Keyikoglu, Ramazan; Karatas, Okan; Cosut, Bunyemin; Khataee, Alireza
    Due to the importance of wastewater decontamination from emerging pollutants, various approaches have been established as treatment processes. In the present study, a graphite felt (GF) electrode was modified with a layered double hydroxide (LDH) to degrade rifampicin in a combined photo-electrocatalytic process. The synthesized CuFeLa LDH was deposited on the GF (CuFeLa LDH@GF) via the electrophoretic deposition method. SEM images showed the uniform coverage of GF fibers by two-dimensional flake-like LDH nanoparticles. The CuFeLa LDH coating improved the electron transfer kinetics of GF and reduced charge transfer resistance. The photo-electrocatalytic process employing the CuFeLa LDH@GF cathode could achieve 79.4% and 65.7% degradation efficiency for rifampicin at pH 6 and 8, respectively. The apparent reaction rate constant (kapp) of the process with CuFeLa@GF (photo-electrocatalysis) was 7.98 times that of the raw GF electrode (photo-electrolysis). This was due to the increased production of hydroxyl radicals (center dot OH), which was shown by radical scavenging and center dot OH trapping experiments. Moreover, the coated electrode had a high stability with only a 4.7% performance loss in 5 successive application tests. The liquid chromatography-mass spectrometry (LC-MS/MS) analysis revealed the intermediates produced during the degradation process. The CuFeLa LDH@GF, with its consistent performance under nearly neutral conditions and catalytic activity over extended periods, indicates potential for effective and environmentally friendly approaches to wastewater treatment.
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    Perfluorooctanoic acid (PFOA) removal from real landfill leachate wastewater and simulated soil leachate by electrochemical oxidation process
    (Elsevier, 2022) Karatas, Okan; Kobya, Mehmet; Khataee, Alireza; Yoon, Yeojoon
    Poly and perfluoroalkyl compounds (PFASs) are a group of chemicals that are widely used and are difficult to purify. Within this group, perfluorooctanoic acid (PFOA), known for its highly polar and strong carbon-fluorine bonds, is a frequently encountered species in surface water, drinking water, and groundwater. In this study, we investigated the efficiency of electrooxidation (EO) in PFOA removal, optimization of EO parameters, and groundwater simulation in a realistic scenario. The EO optimization experiments were performed with a boron-doped diamond (BDD) anode for different values of pH, current density, and inlet concentration, and the effects of different anode materials were investigated for comparison. Under optimum conditions, total organic carbon (TOC) removal of up to 90% was achieved. In the groundwater simulation, we applied optimized EO parameters after obtaining leachates from the soil. A TOC removal of up to 86% was obtained in the EO of simulated groundwater contaminated with PFOA. In the case of realistic leachate simulation, four different leachate treatments were applied to PFOA-contaminated soil, and high TOC removal was achieved in all matrices. Additionally, the EO with BDD was applied to landfill leachate wastewater supplemented with PFOA to monitor the effectiveness of the process. A TOC removal of 85% was achieved, and it was observed that the number of free F-ions increased. The results showed that the BDD EO has a high potential for the treatment of PFOA-contaminated groundwater.(c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
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    Recent progress on the phytotoxic effects of hydrochars and toxicity reduction approaches
    (Pergamon-Elsevier Science Ltd, 2022) Karatas, Okan; Khataee, Alireza; Kalderis, Dimitrios
    Hydrothermal carbonization of wet biomasses has been known to produce added-value materials for a wide range of applications. From catalyst substrates, to biofuels and soil amendments, hydrochars have distinct advantages to offer compared to conventional materials. With respect to the agricultural application of hydrochars, both positive and negative results have been reported. The presence of N, P and K in certain hydrochars is appealing and may contribute to the reduction of chemical fertilizer application. However, regardless of biomass, hydrothermal carbonization results in the production of phytotoxic organic compounds. Additionally, hydro chars from sewage sludge often contain heavy metal concentrations which exceed the regulatory limits set for agricultural use. This review critically discusses the phytotoxic aspects of hydrochar and provides an account of the substances commonly responsible for these. Furthermore, phytotoxicity reduction approaches are proposed and compared with each other, in view of field-scale applications.
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    Treatment of real printing and packaging wastewater by combination of coagulation with Fenton and photo-Fenton processes
    (Pergamon-Elsevier Science Ltd, 2022) Sayin, Fatma Ece; Karatas, Okan; Ozbay, Ismail; Gengec, Erhan; Khataee, Alireza
    Printing and packaging process wastewater (PPPW) with high flow rates causes severe damage to the environment due to high organic pollution (3830.0 mg O-2/L of COD and 813.6 mg/L of TOC) and turbidity (9110 NTU). This study examined the efficiencies of coagulation, Fenton, and photo-Fenton procedures, and their combinations in the treatment of PPPW. The three inorganic salts (FeCl3, Al-2(SO4)(3), and Fe-2(SO4)(3)) were used in a wide range of pH (2.5-10) as a coagulant, and FeCl3 was chosen as the optimum coagulant. The 71.3% of TOC removal and the decreasing of turbidity up to 5.8 NTU were obtained at 0.5 g/L FeCl3 and pH of 6.0. Then, Fenton and photo-Fenton processes were applied to the effluent of the coagulation process. The Fenton process engaged the TOC removal efficiencies up to 85.2% in the presence of 7.350 g/L iron catalysts and 36.0 mL/L H2O2. The combined coagulation and Fenton process is a promising way to decrease the COD up to 119 mg O-2/L, meeting the wastewater discharge standards of COD (200 mg O-2/L) in Turkey. However, adding UV sources to the Fenton process showed a little bit of engagement (only %1.4 extra removal). When evaluated for PPPW, it is seen that the usage of combined coagulation and the Fenton process is an important treatment alternative. Furthermore, Zeta potential measurements and size exclusion chromatography were used to understand the removal mechanism.