بررسی کارایی ماسه‌های مناطق بیابانی در حذف رنگینه متیل‌اورانژ از پساب به عنوان یکی از عوامل کاهش میزان فرسایش

با توجه به اینکه صنایع مختلف، حجم زیادی از پساب های رنگی از جمله متیل اورانژ را وارد محیط می کنند، محققین همواره در جستجوی روش های مختلفی برای حذف این دسته از آلاینده ها از پساب ها هستند. باز چرخانی آب، می تواند کمک شایانی  به جبران کمبود آب کند و لازمه آن کاهش میزان آلودگیهای مختلف پساب ها می باشد. رنگهای مختلفی در پسابها وجود دارد و برای ازبین بردن متیل اورانژ، نسبت به سایر تکنیک های حذف رنگ، جذب سطحی مناسبتر به نظر می آید. جذب سطحی، ارزان قیمت بوده و دارای سادگی در طراحی و عملکرد است. هدف از پژوهش حاضر ارزیابی عملکرد ماسه های مناطق بیابانی در کاهش متیل اورانژ از پساب می باشد. بررسی با یک سری آزمایش‌ها به منظور تاثیر دوز جاذب ( 0.003 تا 0.02 گرم)، زمان تماس (1 تا 30 دقیقه)،  ph(3 تا 11) و غلظت اولیه رنگ (5 تا 65) در دمای محیط انجام شد. درصد حذف رنگ حدود 81 درصد از 5 میلی گرم در لیتر متیل اورانژ، در 7=ph ، زمان 5 دقیقه  و وزن جاذب 0.006 گرم  به دست آمد. داده های تعادلی با استفاده از مدل های ایزوترم جذب لانگمویر و فروندلیچ، تمکین و دوبینین مورد تجزیه و تحلیل قرار گرفت. با توجه به 0.98 =r2 در ایزوترم لانگمویر، حداکثر ظرفیت جذب 28.011 میلی گرم رنگ در هر گرم ماسه بیابانی به دست آمد. سینتیک های شبه مرتبه اول و دوم به بررسی گذاشته شد و نتایج نشان دهنده پیروی از سینتیک شبه مرتبه دوم با99.16 =r2 بود. نتایج نشان داد ماسه بیابانی می تواند به عنوان جاذبی ارزان، در دسترس و سازگار با محیط زیست برای حذف رنگ متیل اورانژ استفاده شود. 

investigating the efficiency of desert sands in removal methyl orange dye from wastewater, as one of the factors reducing erosion

1- introduction             the importance of water is undeniable. water pollution caused by the discharge of colored pollutants is a serious threat. on the other hand, due to the expansion of the industry, the entry of pollutants into water resources has become very widespread, and for this reason, many researchers have conducted numerous studies to remove pollution from waste water. one of the common colors in industries is methyl orange. therefore, the demand for effective adsorbents to remove methyl orange from wastewater has increased. in this research, the ability of desert sands to remove methyl orange was investigated. because this type of sand is found abundantly in desert areas, it is possible to prepare the adsorbent without spending fossil energy.2- materials and methodsin this study, the effects of four parameters (contact time, ph, amount of adsorbent and initial concentration of dye) on the removal of methyl orange in solution were tested, and isotherm and kinetic models of absorption were investigated. in order to perform experiments, methyl orange was dissolved with distilled water for color stock solution, with different concentrations. sand was collected as a raw material and washed with distilled water, then placed in an oven and dried for 48 hours and passed through a 125-micron sieve so that the absorbent particles are the same size. in order to investigate the effect of ph of the solution, this step was tested with different ph. about the influence of time, the same solution was prepared with the optimal ph of the previous step and the same conditions as the previous step of the experiment. however, at this stage, investigations were done at different times from 1 to 30 minutes to obtain the optimal time for color removal. this optimization path for the initial concentration of dye (5 to 65 mg per gram) and amount of absorbent (0.003 to 0.01 g) was done similarly to the previous steps. adsorption isotherms are useful quantitative tools to show the behavior of an adsorbent. in this study, the adsorption isotherms of langmuir, freundlich, temkin and dubinin-radoshkevich were investigated. kinetics describes the absorption rate, which in turn controls the absorption reaction time.3- results the results showed that first, with increasing ph, the percentage of removal also increased, and the best percentage was at ph=7, and then the removal rate decreased. regarding the effect of absorbent time, it led to the removal of 84.68% of methyl orange dye in the first 5 minutes, and in the next minutes, the absorption process decreased, and this decrease is due to the saturation of the active sites. also, dye absorption is highly dependent on the concentration of the solution, and the absorption capacity has increased from 18.1 to 23.3 mg/g with the increase in the concentration of methyl orange, and this is because the absorption sites are reduced for absorption. the increase in the removal of dyes with the amount of absorbent is due to the increase of adsorption sites, however, after some increase in the amount of absorbent, the absorption capacity showed a decreasing trend with the increase of absorbent. in this study, it was observed that the optimum amount of adsorbent for good removal occurred in the weight of 0.006 grams of adsorbent and the amount of color removal was about 81.94%. the results of the absorption isotherm investigation showed that the dye absorption data are more consistent with the langmuir isotherm and these results indicate the homogeneous nature of the sand surface. the pseudo-second-order kinetic model has a high correlation coefficient, and the present study follows the pseudo-second-order kinetic model.4- discussion & conclusionsthe present study showed that desert sand can be used as a suitable adsorbent to remove methyl orange from aqueous solutions. sand is easily available in large quantities and in optimal conditions, the highest removal efficiency was achieved by the sand absorber, which was 81.84%, and the absorption process follows the langmuir isotherm. the adsorption kinetics is pseudo-second order, which shows that the adsorption of methyl orange on sand can be controlled by the chemical adsorption process. the results of the present research showed that sand adsorbent can be used as an inexpensive and environmentally friendly adsorbent. also, the possibility of water recycling should be provided.