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    EXPERIMENTAL DATA AND MODELING FOR THE ADSORPTION/DESORPTION OF TETRACYCLINE AND DICLOFENAC ON THE AGRICULTURAL SOILS
    (2022) Guler, Ulker Asli; Tuncel, Eliza
    The adsorption-desorption characteristics of tetracycline and diclofenac onto two different agricultural soils (S1 and S2) were investigated using the batch equilibrium method. The adsorption experiments were used to optimize the two variable parameters (contact time (5-120 min), initial pollutant concentration (5-300 mg/L)) on the adsorption of tetracycline and diclofenac. The adsorption kinetics for tetracycline and diclofenac onto soil are well described by a bi-exponential adsorption model characterized by fast and slow adsorption rates. Non-linear adsorption curves fitted well to the Langmuir, Freundlich and Temkin equations. The maximum adsorption capacity (qm) of tetracycline and diclofenac onto the soils S1 and S2 were calculated to be 55.90 mg/g, 41.92 mg/g, 26 mg/g and 6.42 mg/g, respectively. Kd, Koc, foc and qa values were calculated. The adsorption efficiency of tetracycline and diclofenac by the soils S1 and S2 was over 97%. The Kd parameters for the adsorption of tetracycline and diclofenac onto the soils S1 and S2 were found to be 3537 L/kg, 654 L/kg, 1669 L/kg and 3105 L/kg, respectively. The reversibility of the adsorption process was evaluated by desorption experiments using different concentrations of HDTMA and Triton-x surfactants. The desorption rates were higher for diclofenac than for tetracycline.
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    Mono and simultaneous removal of crystal violet and safranin dyes from aqueous solutions by HDTMA-modified Spirulina sp.
    (INST CHEMICAL ENGINEERS, 2016) Guler, Ulker Asli; Ersan, Mehtap; Tuncel, Eliza; Dugenci, Feride
    The process of mono and binary removal of crystal violet and safranin dyes by Spirulina sp. (blue-green algae) modified with cationic surfactant is evaluated. The surfactant used was hexadecyltrimethylammonium bromide (HDTMA). Spirulina sp. was cultivated in Zarrouk's medium. The adsorptive properties of the modified Spirulina sp. (HDTMA-algae) were tested as a function of pH (2-10), contact time (5-180 min), temperature (25-45 degrees C, and initial dye concentrations (25-300 mg/L) and characterized with FTIR, SEM, EDX, XRD and BET analyses. The specific surface area of HDTMA-algae was 0.1990 m(2)/g. The data were fitted to non-linear Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models and non linear pseudo-first-order and pseudo-second-order kinetic models. The adsorption was 75% and 88% at pH 2 for Crystal Violet and Safranin dye, respectively. The maximum adsorption capacities were 101.87 mg/g and 54.05 mg/g and the k(F) values were 0.96 L/g and 3.56 L/g for Crystal Violet and Safranin, respectively. The kinetics of Crystal Violet and Safranin dyes onto HDTMA-algae were best described by the pseudo-second-order kinetic model. The negative values of free energy and enthalpy change indicated the feasibility, spontaneity, and exothermic nature of the adsorption process. Also, binary adsorption of Crystal Violet and Safranin dyes onto HDTMA-algae from binary dye mixtures is compared. (C) 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.