چكيده به لاتين
The main purpose of this research was to modify the surface of Leca absorbent by using acidic and alkaline agents and choosing the optimal conditions for surface modification in order to improve its performance in removing three pollutants, malachite green, methylene blue and paraquat from aqueous solution. For this purpose, after performing various pre-tests and specifying different levels of acid and base concentrations, in order to determine the optimal absorbent, tests related to the removal of all three pollutants were carried out under specific conditions. Among the 15 modified adsorbents, the adsorbent with the highest removal efficiency (for malachite green leca modified with potassium hydroxide (3.5M) and for methylene blue and paraquat leca modified with sulfuric acid (1.5M) - potassium hydroxide ( (3.5M)) was chosen as the optimal absorber. Then, in order to investigate the structural properties and morphology of the Leca absorbent surface and modified Leca, BET, XRD, XRF and FE-SEM analyzes and zeta potential have been investigated. Also, the effect of different parameters such as amount of adsorbent, contact time, solution pH, initial concentration of pollutant, salt and temperature on the performance of modified adsorbents was studied. Examining the results showed that the removal efficiency of pollutants increased with increasing amount of adsorbent and contact time, while it decreased with increasing initial concentration of pollutants and salt. In order to check the absorption temperature of the three pollutants, the results of the laboratory data were fitted with Langmuir, Friendlich and Temkin isotherms and according to the results obtained for all three pollutants, the Langmuir isotherm was in better agreement with the laboratory data. The maximum adsorption capacity obtained from the Langmuir isotherm for malachite green, methylene blue and paraquat by Leca adsorbent is 14.17 mg.g-1, 9.10 mg.g-1, and 6.12 mg.g-1 for modified Leca The order of is 42/91 mg.g-1, mg.g-1 31/74 mg.g-1 and 23/21 mg.g-1. Comparison of laboratory data with pseudo-first-order kinetics, pseudo-second-order kinetics and intraparticle penetration showed that second-order kinetics was more consistent for all three pollutants. The results of investigating the effect of temperature on the absorption of pollutants showed that with the increase in temperature, the removal efficiency of malachite green and methylene blue increased, while the removal efficiency of paraquat decreased. The study of thermodynamic parameters also showed that the adsorption of cationic dyes malachite green and methylene blue on modified heat absorbing absorbents and surface adsorption of paraquat was an exothermic process. Examining the results of competitive absorption between methylene blue and paraquat confirmed that the presence of methylene blue has led to a decrease in the absorption capacity of paraquat by 26.75%, which is 5.67% for methylene blue dye in the presence of paraquat.
