Date

2022-9-8

Author

Polat, Cansu

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The removal of phorate from aqueous solution by adsorption on two different adsorbents, powdered activated carbon (PAC) and natural zeolite chabazite (CHA), has been studied. Effects of operational conditions, such as initial phorate concentration (1, 0.75 and 0.5 mg/L), PAC and CHA doses (12.5, 25 and 37.5 mg/L), pH (3, 7 and 9), temperature (15, 25 and 35 ºC) and mixing intesities (120, 160 and 200 rpm) were investigated. Under acidic conditions (pH=3), PAC and CHA performes better. Especially when the adsorbent is CHA, the removal efficiency increased to appraximately 80% from 50% when pH is acidic. The initial concentration of phorate affects the adsorption on PAC and CHA differently. For PAC, the overall rate increases with decreasing initial concentration while it decreases for CHA. The effect of adsorbent amount for the removal of phorate is observed up to 25 mg/L for PAC and CHA which indicates that there is no enhancement in the removal of phorate after the aforementioned dose of adsorbent. The adsorption of phorate on CHA is especially affected by the shaking speed as the speed increases from 120 rpm to 200 rpm, the removal efficiency increases to 80% from 60%. The changes in temperature does not affect the equilibrium conditions significantly; however overall adsorption rates for the two adsorbents react oppositely to the changes. The rate constant for PAC increases with increasing temperature while the rate constans for CHA decreases. Pseudo-first order (PFO) and pseudo-second-order (PSO) models were tested for adsorption kinetics of phorate on PAC and CHA under different operational conditions. For all operational conditions, PSO model is the best-fitted model for both PAC and CHA. In order to investigate the equilibrium behavior of phorate when adsorbed on PAC and CHA, adsorption isotherm experiments are conducted at neutral pH and room temperature with shaking speed of 160 rpm. Langmuir and Freundlich istoherm models are tested for this purpose. Adsorption onto PAC is well-defined by both Langmuir and Freundlich models while the equilibrium behavior is well-described by Freundlich model when adsorbent is CHA. Based on the Langmuir model, maximum adsorption capacity of PAC for phorate was calculated as 26 mg/g.

Subject Keywords

Phorate, Adsorption, Chabazite, Kinetics, Isotherm, Powdered activated carbon

URI

https://hdl.handle.net/11511/99717

Collections

Graduate School of Natural and Applied Sciences, Thesis