‌جذب فلز کروم شش ظرفیتی توسط لجن دفعی فاضلابهای شهری

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانش آموخته کارشناسی ارشد مهندسی عمران- محیط زیست، دانشکده مهندسی عمران، دانشگاه صنعتی اصفهان

2 استادیار، دانشکده مهندسی عمران- محیط زیست، دانشگاه صنعتی اصفهان

3 استاد دانشکده مهندسی عمران- مهندسی محیط زیست، دانشگاه صنعتی اصفهان

چکیده

حذف یا کاهش غلظت کروم شش ظرفیتی از فاضلاب تا مقادیر مجاز، به‌دلیل تجزیه‌‌ناپذیری، زیست‌انباشتگی، سرطان‌زایی و سمیّت آن از اهمیت زیادی برخوردار است. در این تحقیق، جذب فلز کروم شش ظرفیتی از محلولهای آبی، توسط مواد جامد خشک‌شده حاصل از لجن فعال دفعی فاضلاب بهداشتی، مورد بررسی قرار گرفت و تأثیر عوامل مختلف بر جذب از جمله غلظت اولیه (در محدوده 5 تا 90 میلی‌گرم در لیتر)،pH  (در محدوده 2 تا 8)، سرعت اختلاط (در محدوده 50 تا 200 دور بر دقیقه)، دز جاذب (در محدوده 2 تا 10 گرم در لیتر) و زمان اختلاط (در محدوده 5 تا 480 دقیقه) در راکتور ناپیوسته مطالعه شد. طراحی آزمایش‌ها بر مبنای روش فاکتوریل کامل انجام شد. نتایج آزمایش‌ها نشان داد که زمان تعادل، حدود 120 دقیقه است. ایزوترم جذب کروم توسط لجن فعال دفعی با مدل فروندلیچ و سینتیک آن با مدل شبه مرتبه دوم تطابق دارد. در راکتور ناپیوسته، در شرایط بهینه (غلظت اولیه 90 میلی‌گرم در لیتر، pH معادل 2، زمان تعادل 120 دقیقه، سرعت اختلاط 200 دور بر دقیقه و دز جاذب 4 گرم در لیتر) بازدهی جذب به 96 درصد رسید و حداکثر ظرفیت 69/41 میلی‌گرم کروم بر گرم جاذب برآورد شد. به‌طور کلی می‌توان نتیجه گرفت که لجن فعال دفعی فاضلابهای بهداشتی، به‌عنوان یک جاذب زیست تجزیه‌پذیر، فراوان و ارزان قیمت، عملکرد مناسبی برای حذف کروم از محلولهای آبی دارد.

کلیدواژه‌ها


عنوان مقاله [English]

Sorption of Chromium (VI) Using Excess Municipal Sludge

نویسندگان [English]

  • Farzaneh Mohammadi 1
  • Hasti Hashemi nejad 2
  • Amir Taebi 3
چکیده [English]

Removing or decreasing hexavalent Chromium from wastewater to the permitted levels is important due to its non-biodegradation, bioaccumulation, cancer-causing and toxic effects. In this study, biosorption of Cr(VI) from aqueous solutions by Excess Active Municipal Sludge was investigated as a function of initial Chromium (VI) concentration (in the range of 5-90 mg/l), initial pH (in the range of 2-8), agitation speed (in the range of 50-200 rpm), adsorbent dosage (in the range of 2-10 g/l) and agitation time (in the range of 5-480 min) in a batch system. The optimum conditions were found by full factorial design approach. The results showed that the equilibrium time for adsorbent is 120 minutes. Also, sorption data have a good fitness by Freundlich isotherm model and adsorption kinetic is adopted with pseudo-second order model. In batch studies, at optimum condition (90 mg/l initial concentration, pH 2, agitation speed 200 rpm and adsorbent dosage 4 g/l), the adsorption performance was about 96%; the maximum adsorption capacity was calculated about 41.69 mg of Cr/g of adsorbent. Overall, it can be concluded that Excess Active Municipal Sludge, has a good performance as a biological, biodegradable, abundant and low-cost adsorbent for the removal of Cr (VI) from aqueous solutions.

کلیدواژه‌ها [English]

  • Chromium (VI)
  • Biosorption
  • Wastewater Treatment
  • Excess Activated Sludge
  • Chromium Removal
  • Biosolid
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