جذب سطحي رنگ كاتيوني از محلول‌هاي آبي با استفاده از كربن فعال پوست گريپ فروت و روش بهينه سازي تاگوچي

Cationic dye adsorption from aqueous soluble using activated carbon of Grapefruit peel, optimized by Taghuchi method

رنگ‌ يكي از مهم‌ترين آلاينده‌هاي موجود در پساب صنايع نساجي است. يكي از روش‌هاي كارآمد در حذف رنگ از فاضلاب، استفاده از فرآيند جذب سطحي، به خصوص براي حذف آلاينده‌هاي غير قابل تجزيه مي‌باشد. اين پژوهش با هدف بررسي پتانسيل پوست گريپ فروت در حذف رنگ متيلن‌بلو انجام شد. به منظور بهينه‌سازي شرايط جذب، تأثير عوامل مختلف مانند غلظت اوليه رنگ (400-50 ميلي‌گرم بر ليتر)، مقدار جاذب (1-0/10 گرم بر ليتر)، زمان تماس (70-10 دقيقه) و دانه‌بندي جاذب (2-1 ميلي‌متر) مورد بررسي قرار گرفت. براي كاهش تعداد آزمايش‌هاي مورد نياز و صرفه‌جويي در زمان و هزينه، از روش طرح آزمايش تاگوچي استفاده شد و تعداد آزمايش‌ها از 256 به 64 آزمايش كاهش يافت. خصوصيات سطحي جاذب‌ نيز با استفاده از تبديل فوريه مادون قرمز و ميكروسكوپ الكتروني روبشي مورد ارزيابي قرار گرفت. نتايج نشان داد غلظت اوليه رنگزا، بيشترين تأثير را در فرآيند حذف رنگ داشت. شرايط بهينه آزمايش براي حذف رنگ متيلن‌بلو در زمان 10 دقيقه، غلظت رنگزا 400 ميلي‌گرم بر ليتر و مقدار جاذب يك گرم با دانه بندي يك ميلي‌متر بدست آمد. مدل لانگموير با ضريب همبستگي 0/9738 تطابق بهتري را با نتايج نشان داد. با توجه به اينكه pH بهينه حذف رنگ با اين جاذب در محدوده 12-8 است و اغلب فاضلاب‌هاي نساجي داراي pH قليايي هستند، به نظر مي‌رسد اين جاذب از پتانسيل مطلوبي جهت حذف رنگزاي كاتيوني از پساب برخوردار باشد.

Data showed that by increasing the adsorbent dose, the availability of sorption sites eased resulting in greater percentage removal of the dye. The percent adsorption increased with increased contact time. Maximum quantitative removal of MB from an aqueous solution was obtained in 10 min for GFP contact time. The pH of an aqueous solution is an important factor in dye adsorption, as it affects the surface charge of the sorbent material and the degree of ionization of the dye molecule.The effect of pH on the amount of MB adsorbed onto fruit pulp was investigated over the pH range from 2 to 12. amount of dye adsorbed per unit mass of the adsorbent increased with increase in the initial concentration up to 25 mg/L. The When the of the solution was 2-6, the sorption of methylene blue was slightly weaker than at pH 6-12 due to poor dissociation of carboxyl Groups. The qe was found to increase with increasing pH. Optimal pH was determind 9. This can be on the basis of a decrease in competition between positively charged H and MB for surface sites and also by decrease in positive surface charge on the adsorbent, which results in a lower electrostatic repulsion between the surface and MB. SEM is one of the useful tools to examine the surface morphology of the biosorbent the SEM micrograph shows that the surface of GFP was porous.FTIR analysis showed that the main functional sites taking part in the sorption of MB included carboxyl and hydroxyl groups. Adsorption data are most commonly represented by the equilib-rium isotherm value, which is a plot of the quantity of the sorbate removed per unit sorbent (qeq) as the solid phase concentration of the sorbent against the concentration of the sorbate in the liq-uid phase (Ceq). The equilibrium isotherm value is of fundamental importance for the design and optimization of the adsorption sys-tem for the removal of a dye from an aqueous solution. Therefore, it is necessary to establish the most appropriate correlation for the equilibrium curve. Several isotherm models have been used to predict validity of the experimental data. The Langmuir isotherm is based on the assumption of monolayer adsorption on a structurally homogeneous adsorbent, where all the adsorption sites are identical and energetically equivalent, wherein the adsorption occurs at specific homogeneous sites within the adsorbent, and once a dye molecule occupies a site no further adsorption can take place at that site. The results indicate that the data for adsorption of dye (R2= 0/9738) fitted well with Langmuir isotherm. Studies suggest that GFP can be effectively used as a cost-effective adsorbent for removal of MB from aqueous solution. Batch adsorption studies show that removal is dependent upon process parameters like pH, sorbate and sorbent concentrations and contact time. The experimental equilibrium sorption data obtained from batch studies at optimized conditions fit well to Langmuir adsorption isotherm equation, indicating monolayer adsorption. FTIR analysis showed that the main functional sites taking part in the sorption of CV included carboxyl and hydroxyl groups. The number of experiments decreased of 256 to 64 by Taguchi method. Based on this that many textile industrial waste waters have an alkaline pH(8-12),this adsorbent can be used instead of effective compound. The present work shows that GFP is an efficient sorbents for the removal of methylene blue from aqueous solution and it may be an alternative to more costly sorbents such as activated carbon. The Taguchi method was efficient manner for optimizing process.