بررسی امکان حذف کروم شش ظرفیتی از محیط آبی با استفاده از زئولیت کلینوپتیلولایت

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشیارگروه مهندسی آب دانشگاه بیرجند

2 دانشیار گروه مهندسی آب، دانشکده کشاورزی، دانشگاه بیرجند

3 دانشجوی دکتری ابیاری و زهکشی دانشگاه فردوسی مشهد

4 دانشجوی دکتری منابع اب بیرجند

چکیده

فلزات سنگین از مهم ترین آلاینده‌های موجود در طبیعت با سمیت و سرطان زایی بسیار بالا می‌باشند. سمیت زیاد این مواد حتی در غلظت های کم، نگرانیـهای زیادی را ایجاد کرده است.. یکی از مهم‌ترین و پرکاربردترین فلزات سنگین کروم می باشد.کروم جزو فلزات سنگینی است که هم از طریق سیستم گوارش و هم از طریق پوست در بدن انسان جذب و ذخیره میگردد. ترکیبات کروم به طور معمول در دو حالت کروم سه ظرفیتی و کروم شش ظرفیتی در محیط دیده می‌شود که کروم شش ظرفیتی 500 برابر سمی‌تر از کروم سه ظرفیتی می باشد. هدف از این مطالعه، بررسی امکان حذف کروم شش ظرفیتی با استفاده از زئولیت کلینوپتیلولایت بوده است. این پژوهش یک مطالعه تجربی-آزمایشگاهی بوده که در سیستم ناپیوسته و در آزمایشگاه آلودگی محیط زیست دانشکده کشاورزی و منابع طبیعی دانشگاه بیرجند انجام شد. کلیه مواد شیمیایی مصرفی در مطالعه با درجه خلوص بالای 99 % از شرکت مرک آلمان تهیه شدند. در این تحقیق جاذب(زئولیت معادن سمنان) تهیه شد. زئولیت خرد شد و ذرات آن با استفاده از روش غربالگری با الک به قطر میانگین ۳۶۰ میکرو متر (ذرات باقی ماندة بین الک-های با قطر ۳۱۵ تا ۴۲۵ میکرو متر) انتخاب شد(این مرحله دو بار تکرار شد). در این تحقیق فرآیند جذب، با تغییر در pH، زمان تماس، مقدار وزن جاذب، غلظت اولیه کروم و دما انجام شد. در ادامه برای سنجش غلظت کروم شش ظرفیتی از دستگاه جذب اتمی در آزمایشگاه محیط زیست دانشگاه بیرجند استفاده گردید. تجزیه و تحلیل داده‌ها و رسم نمودار‌ها توسط نرم افزار Excel صورت گرفت. دادهای تجربی تعادل جذب با مدل های ایزوترم جذب فروندلیخ و لانگمیر مورد بررسی قرار گرفت. نتایج حاصل از این پژوهش نشان داد؛ بیشترین حذف کروم شش ظرفیتی در pH برابر 5، زمان تماس 120دقیقه، وزن بهینه جاذب 3 گرم، غلظت اولیه 50 میلی گرم بر لیتر و دمای 22 درجه سانتی گراد به دست آمد. به دلیل محل‌های فعال محدود در جاذب با افزایش غلظت اولیه کروم، جرم جاذب و دما، راندمان حذف کاهش می-یابد و با افرایش زمان تماس، راندمان افزایش می‌یابد. دادهای تجربی تعادل جذب با مدل های ایزوترم جذب فروندلیخ و لانگمیر مورد بررسی قرار گرفت، نتایج نشان داد که سینتیک فرآیند جذب از مدل سینتیک شبه درجه دو، و داده های تعادلی از مدل ایزوترمی لانگمیر پیروی می کنند. در مجموع نتایج حاصل از انجام آزمایشات مشخص ساخت که می‌توان از زئولیت طبیعی کلینوپتیلولایت به عنوان یک روش اقتصادی جاذب، موثر و ارزان قیمت در جهت حذف کروم شش ظرفیتی از زه آب‌ها و پساب‌های آلوده استفاده کرد.

کلیدواژه‌ها

عنوان مقاله [English]

Exploring the Possibility of Removing Chromium(IV) from Aqueous Solution using Zeolite Clinoptilolite

نویسندگان [English]

  • Abbas Khashei-Siuki 1
  • Ali Shahidi 2

چکیده [English]

Pollution is one of the most important factors that lead to the wasting of water resources.This research was an experimental study in a batch system in a lab environment pollution College of Agriculture and Natural Resources, University of Birjand. All chemicals used in the study with high purity of 99% were obtained from Merck, Germany. The adsorbent (zeolite Semnan) was prepared. Zeolite particles with crushing and screening assay with an average diameter of 360 micrometer sieve (particles with a diameter of 315 to 425 micro-meters remaining balance of between only in particle size) was selected (this was repeated twice). After being washed with distilled water, incubated for 24 hours at a temperature of 40 ° C was placed inside to dry. Stoke-soluble chromium (1000 ppm) using potassium dichromate solution powder was prepared in distilled water twice. Results and Discussion The effect of pH as an important parameter in the absorption of heavy metal ions is clearly visible. Absorption of chromium ions increased with increasing pH and at pH 5 is the highest value. reason for this is that hexavalent chromium and absorbent surface charge are highly dependent on pH. The balance of absorption and adsorption efficiency as well as economic characteristics, the most important for the development of water treatment technology based on natural attraction. With increasing contact time from 20 to 120 minutes, with initial concentration of hexavalent chromium removal efficiency of 50 milligrams per liter of 79.3 to 81.9 percent percent increase in contact time of 120 minutes and after this time removal of garlic during the monotony. Another important parameter in the process of absorbing the contact time can be noted. Increase the rate of absorption from 0.3 to 3 g led to increase the absorption of chromium ions. This increase is due to the availability of larger and more is absorbed sites, is expected. The results clearly showed that the absorption efficiency is increased to an optimum value and then the optimal value, the increase is very small and negligible. Removal efficiency decreases with increasing initial concentration of hexavalent chromium. So that by increasing the concentration of 25 ppm to 200 ppm, removal from 95.6 to 88.7 percent percent. The optimum concentration of 50 ppm as the amount was used in the following experiments. Increasing the temperature from 22 ° C to 50 ° C, removal from 17/99 percent to 94.8 percent. This can be due to increased pore size and activate attributed absorbent surface. Further increasing the temperature increases mobility and reduces metal ions. The results showed the acidity of an aqueous solution Myknd.balatryn play a role in the absorption of hexavalent chromium absorption by absorbent 5pH = happens. The optimal time to absorb Chrome for clinoptilolite zeolite is about 120 minutes. The efficiency of removal sorbent concentration and initial concentration of soluble Cr (VI) to Cr (VI) ions in the solution depends on the capacity of balance by increasing the initial chromium concentration decreases because the absorber is saturated with increasing initial concentration of chromium. With the increasing amount of sorbent due to the increased surface area increases adsorbents removal of hexavalent chromium from wastewater dummy. The optimum temperature in order to attract Chrome for clinoptilolite zeolite powder at about 22 ° C. Conversion data with the Langmuir isotherm model, with a correlation coefficient higher than the Freundlich isotherm models. In kinetic studies, the pseudo-second-order kinetic model to attract hexavalent chromium knows index.

کلیدواژه‌ها [English]

  • Adsorption
  • chromium
  • zeolite clinoptilolite
  • isotherm model
  • kinetic model
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