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    Pb (II) biosorption from the aqueous solutions by raw and modified tea factory waste (TFW)
    (Springer, 2021) Nuhoglu, Y.; Ekmekyapar Kul, Z.; Kul, S.; Nuhoglu, C.; Ekmekyapar Torun, F.
    The study is aimed to determine Pb (II) biosorption from synthetic wastewaters using natural and modified tea factory waste as biosorbent material. This process is carried out with this waste matter, which is found in large quantities, so cheap and has high metal adsorption ability. The sorption kinetic studies were determined as variations of initial pH value, particle size, initial Pb (II) and tea factory waste concentrations, stirring speed and temperature. Biosorption reached the equilibrium in 15 min. Zeta potential values of the biosorbent were defined in the range of pH 2 to 4. The adsorption isotherm models give the experimental values, and the thermodynamic characteristics of the patterns generally give insight about the sorption mechanism depending on the surface characteristics and affinity of the biosorbent. The biosorption mechanism was searched considering to Freundlich, Langmuir, BET and Temkin isotherm model, and the experimental adsorption values were conformed to Freundlich adsorption model. The optimum experimental conditions were investigated as pH 3.5, particle size of 0.125-0.25 mm, stirring speed of 200 rpm, biosorbent concentration of 7 g L-1 and 25 degrees C. In these conditions, the highest efficiency of biosorption was obtained as 94.07% and after the activating process the efficiency was reached to 97.73% at 70 mg L-1. The maximum Pb (II) removal capacity of raw tea factory waste was found to be 22.111 mg g(-1) at 200 mg L-1. The biosorption kinetics has complied with the pseudo-second-order model. Thermodynamic studies stated that this biosorption phenomenon was an endothermic process.
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    Removal of Cu(II) from aqueous solutions using modified sewage sludge ash
    (Springer, 2021) Kul, S.
    The study aims to determine Cu(II) adsorption from wastewater in the laboratory condition using modified sewage sludge ash as adsorbent which was obtained from a thermal drying and incineration facility. This procedure was completed with an inexpensive pollutant material which has high metal-binding capacity and is available in abundant amounts. During experiments, the effects of particle size, pH, stirring speed, initial ion concentration, adsorbent dosage and temperature were investigated. Adsorption equilibrium was obtained in 10 min. Maximum Cu(II) removal was calculated as 83.63% with 20 mg L-1 initial Cu(II) ion concentration and 5 g L-1 adsorbent dosage. Kolmogorov-Smirnov normality test was performed to test the conformity of the data obtained as a result of the study to variance analysis, and it was determined that the data were distributed normally (p > 0.05). Levene test was performed for homogeneity test, and it was determined that the data were distributed homogeneously (p > 0.05). Langmuir was determined as the most suitable isotherm model for Cu(II) adsorption. Adsorption kinetics abided by the pseudo-second-order model. Based on kinetic studies, the adsorption process was endothermic with maximum adsorption capacity calculated as 7.53 mg g(-1). The results of thermodynamic research showed the adsorption reaction was spontaneous (Delta G degrees < 0), endothermic (Delta H degrees > 0) and reversible (Delta S degrees > 0 and close to zero).