Abstract    The present study seeks to investigate the capacity of polyaniline/titanium dioxide (PAn/TiO2) and Polypyrrole/titanium dioxide (PPy/TiO2) nano-adsorbents to adsorb Congo red anionic dye (CR) from aqueous solution. The variables effective in CR adsorption, including adsorbent dose, pH of the solution, contact time, initial dye concentration, and temperature were examined. The study yielded the result that a decrease in pH increases the adsorption capacity of both nano-adsorbents. The adsorbent dose and optimum contact time of PAn/TiO2 and PPy/TiO2 nano-adsorbents were [0.1 gr and 20 min] and [0.2 gr and 60 min], respectively. The adsorption kinetics was studied with the pseudo-first-order, pseudo-second-order, and Weber–Morris equations. Kinetic studies showed that the CR adsorption process onto both nano-adsorbents followed the pseudo-second-order kinetics model, which indicates that the adsorption process is chemisorption-controlled. Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich Isotherms were applied to the adsorption data to estimate the maximum adsorption capacity as well as the intensity and energy of adsorption. The experimental data were best represented by Freundlich isotherm model compared to the other models. Analysis of data with Dubinin-Radushkevich isotherm showed that the adsorption of CR onto both nano-adsorbents is a chemisorption process. Moreover, Thermodynamic parameters such as ∆G, ∆H, and ∆S were calculated. The results showed that the adsorption of CR onto both nano-adsorbents was spontaneous and exothermic.

Keywords    Polyaniline, Polypyrrole, Titanium dioxide, Adsorption, Kinetic studies, Isotherm, Thermodynamic, Congo red.‎

چکیده    در پژوهش حاضر، توانایی نانوجاذب های پلی آنیلین/دی اکسید تیتانیوم و پلی پیرول/دی اکسید تیتانیوم در جذب سطحی رنگزای آنیونی قرمز کنگو (CR) از محلول های آبی مورد بررسی قرار گرفت. تاثیر متغیرهای موثر بر فرآیند جذب سطحی CR از جمله مقدار جاذب، pH محلول، زمان تماس، غلظت اولیه رنگزا و دما بررسی شد. نتایج حاصل از پژوهش نشان داد که با کاهش pH راندمان جذب سطحی رنگزا در مورد هر دو نانوجاذب افزایش یافت. مقدار جاذب و زمان بهینه جذب برای نانوکامپوزیت های پلی آنیلین/دی اکسید تیتانیوم و پلی پیرول/دی اکسید تیتانیوم به ترتیب (0.1گرم و 20دقیقه) و (0.2گرم و 60 دقیقه) بدست آمد. سینتیک های جذب سطحی توسط سه معادله شبه مرتبه اول، شبه مرتبه دوم و موریس وبر مورد مطالعه قرار گرفت. مطالعات سینتیکی نشان داد که فرآیند جذب سطحی CR بر روی هر دو نانوجاذب از معادله سینتیکی شبه مرتبه دوم تبعیت می کند که بیان کننده این است که فرآیند به وسیله جذب شیمیایی کنترل می شود. ایزوترم های لانگمویر، فروندلیچ، تمکین و دابینین رادشکویچ، جهت تخمین حداکثر ظرفیت جذب، شدت و انرژی جذب برای داده های جذب سطحی بکار گرفته شدند. ایزوترم فروندلیچ بهترین همخوانی را با داده های تجربی در مقایسه با دیگر ایزوترم ها از خود نشان داد. آنالیز داده ها توسط ایزوترم دابینین رادشکویچ نشان داد که جذب سطحی رنگ CR بر روی هر دو نانوجاذب، فرآیند شیمیایی می باشد. همچنین پارامترهای ترمودینامیکی از جمله DH، DG و DS محاسبه گردیدند. نتایج نشان داد که فرآیند جذب سطحی رنگ CR بر روی هر دو نانوجاذب، خود به خودی و گرمازا می باشد.

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