Removal of Cr (VI) from aqueous solutions with magnetic biochars obtained from hawthorn seed and mahaleb seed shell

The goal of this thesis is to use adsorption to remove Cr (VI) from an aqueous medium. For this purpose, hawthorn seed pods (CRA) (Crataegus azarolus L.) and mahaleb seed pods (MÇK) (Prunus mahaleb L.) selected as natural adsorbents were used as raw adsorbents. These natural adsorbents were converted into biochar using a muffle furnace, and then the magnetic biochar was obtained by treating the adsorbents with FeSO4.7H2O and FeCl3.6H2O separately. The adsorption capacities of raw seed shells used in the production of a new magnetic biochar were investigated in order to remove Cr (VI) ion from industrial wastewater by adsorption method. The effects of parameters such as solution pH, amount of adsorbent, initial Cr (VI) concentration, contact time for raw, biochar and magnetic biochar states of natural adsorbents on adsorption studies were examined and optimum adsorption conditions of each adsorbent were determined. After the adsorption was completed, the amount of Cr (VI) adsorbed on the surface of the adsorbents was calculated by measuring the Cr (VI) remaining in the solution phase using an UV-visible spectrophotometer. FT-IR and SEM instruments were used to examine the structure and surface images of raw adsorbents, biochar, and magnetic biochar adsorbents. Freundlich, Langmuir, Dubinin-Redushkevich (D-R), Tempkin and Scatchard isotherm models were used to analyze the obtained adsorption data and the adsorption parameters (qm, KL, RL, KF, n, B, KT, Qs, Ks, Xm, K, ve E) were calculated. The Langmuir isotherm curve was the most compatible among the adsorption models applied by drawing the adsorption equilibrium curves. The maximum adsorption capacities calculated using the Langmuir isotherm equation are 7.64 mg/g for AÇK, 11.19 mg/g for BAÇK, 15.7 mg/g for m-BAÇK, 5.3 mg/g for MÇK, 10.53 mg/g for BMÇK, and 18.28 mg/g for m-BMÇK. It has been observed that Cr (VI) ions from aqueous solutions are chemically and electrostatically bound to the adsorbents produced. In order to determine the kinetic model describing the adsorption kinetics, pseudo-first and pseudo-second-order kinetic models were applied to the adsorption equilibrium data. When the adsorption kinetics were examined, it was seen that the most suitable kinetic model was the pseudo-second-order kinetic model by controlling the values of the high correlation coefficient. It has been observed that the synthesized adsorbents can be used as an alternative adsorbent to remove Cr (VI) from aqueous solutions in treatment plants.