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    Nitrogen- and oxygen-doped carbon particles produced from almond shells by hydrothermal method for efficient Pb(II) and Cd(II) adsorption
    (Springer Heidelberg, 2024) Saka, Cafer; Tegin, Ibrahim; Kahvecioglu, Kubra; Yavuz, Omer
    In this study, a two-step method was applied to obtain an effective adsorbent for cadmium (Cd) (II) and lead (Pb)(II) adsorption. The first stage includes the production of activated carbon (AC) from almond shells, which is agricultural waste, by microwave heating and potassium hydroxide (KOH) chemical agent. The second stage includes nitrogen and oxygen doping by hydrothermal heating treatment of the obtained ACs with nitric acid. The obtained materials were characterized by thermogravimetric/differential thermal analyser (TG-DTA); Fourier transform infrared spectroscopy (FTIR); scanning electron microscope (SEM); energy-dispersive spectroscopy (EDS); C, H, N, S elemental analysis; and nitrogen adsorption analyses. The adsorption performance, mechanism, kinetics, and thermodynamics of nitrogen- and oxygen-doped activated carbons were evaluated. The obtained isotherm and kinetic results showed that the adsorption of Cd (II) and Pb (II) on nitrogen- and oxygen-doped ACs followed Langmuir isotherm and pseudo-second-order kinetics. The adsorption capacity values (Qm) obtained for Cd (II) and Pb (II) adsorption were 106.38 mg/g and 76.33 mg/g, respectively.
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    Öğe
    Phosphorus and oxygen co-doped carbon particles based on almond shells with hydrothermal and microwave irradiation process for adsorption of lead (II) and cadmium (II)
    (Springer Heidelberg, 2023) Kahvecioglu, Kubra; Tegin, Ibrahim; Yavuz, Omer; Saka, Cafer
    In this study, the production of activated carbon based on almond shells by microwave heating with KOH activation and then the modification of activated carbon with phosphorus and oxygen as a result of hydrothermal heating with phosphoric acid were carried out to increase the Cd(II) and Pb(II) adsorption efficiency. The resulting materials were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric/differential thermal analyzer (TG-DTA), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and nitrogen adsorption. Adsorption performance, kinetics and thermodynamics of phosphorus, and oxygen-doped activated carbons were evaluated. The results showed that the adsorption of both Cd(II) and Pb(II) on phosphorus and oxygen-doped activated carbons obeyed the Langmuir isotherm and pseudo-second-order kinetics. The adsorption capacity values (Q(m)) obtained from the Langmuir isotherm for Cd(II) and Pb(II) adsorption were 185.18 mg/g and 54.64 mg/g, respectively. At the same time, the adsorption mechanism of Pb(II) and Cd(II) on the respective adsorbents was evaluated. As a result of phosphorus and oxygen atoms, Lewis base sites on carbon atoms and Lewis acid sites on phosphorus atoms are likely to form on the surface. These Lewis base sites can act as important active sites in adsorption reactions, especially of positively charged Pb(II) and Cd(II) ions.
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    Öğe
    Sulphur-doped carbon particles from almond shells as cheap adsorbent for efficient Cd(II) adsorption
    (Elsevier Science Sa, 2023) Saka, Cafer; Tegin, Ibrahim; Kahvecioglu, Kubra
    One of the ways to increase the adsorption capacity of carbon-based materials is to add heteroatoms. However, the use of sulphur-doped carbons is quite limited. This study includes the production of activated carbon (AC) from almond shells by microwave heating and KOH chemical agent and sulphur doping by hydrothermal heating treatment of the obtained ACs with sulphuric acid for Cd(II) adsorption. The thermogravimetric/differential thermal analyser (TG-DTA), Fourier transforms infrared spectroscopy (FTIR), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and nitrogen adsorption analyses were performed for character-ization. For KOH-MA-S, the FTIR spectra peaks associated with the S--O stretching vibration appeared at approximately 1153 cm-1 and 1024 cm -1. The SEM image of the KOH + MA + S sample shows that a het-erogeneous and layered structure is formed again due to the collapse or coalescence of the pores with the hy-drothermal sulphuric acid activation on the carbonaceous surface. While there is almost no sulphur in the KOH-MA sample, there is approximately 9 % sulphur in the KOH-MA-S sample in the EDS results. The adsorption performance, kinetics, thermodynamics and mechanism for Cd(II) adsorption on sulphur doped ACs were evaluated. The isotherm and kinetic results showed that Cd(II) adsorption on sulphur-doped AC fits the Langmuir isotherm and pseudo-second-order kinetics with high correlation values. The adsorption capacity values (Qm) obtained for Cd(II) adsorption were 282.70 mg/g.