نوع مقاله : پژوهشی
نویسندگان
1 1- دانشجوی سابق کارشناسی ارشد، گروه علوم و مهندسی خاک، دانشکده کشاورزی، دانشگاه تبریز
2 دانشگاه تبریز
3 استاد، گروه علوم و مهندسی خاک، دانشکده کشاورزی، دانشگاه تبریز
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
Background and Objectives
Chromium (Cr) is considered as a priority pollutant by the US Environmental Protection Agency (EPA) and is released into the environment by many industrial process including electroplating, tanning, pigments, refractories, and metallurgical. Today, with the increase in the world's population and the development of urbanization, the use of water in various fields such as agriculture and industry has increased, causing the discharge of various sewage and effluents into surface water receiving sources and as a result, it has created pollution and reduced their quality. Biochar has great potential in the field of wastewater treatment and quality management of water resources with its physical and chemical properties, diverse functions, wide variety of raw materials, as well as low cost compared to many other adsorbents and adjustable chemical and physical characteristics. In the present study, the kinetics of chromium (Cr+3) adsorption from tanning industry wastewater by herbaceous and woody biochars were investigated.
Methodology
To prepare grassy biochar from straw and wheat stubble, and for woody biochar, a mixture of pomegranate and plum wood and a mixture of apple and grape wood were used at slow pyrolysis temperatures of 400 and 600 °C. The adsorption kinetics experiment was conducted in diluted tanning industry wastewater at an initial concentration of 40 mg Cr/L, pH 4, and at two doses of 0.5 and 2 g biochar/L for 150 minutes. The kinetic equations we used in this study were the zero-, first-, and second- order rate equations, parabolic diffusion, two constant and Elovich models.
They were evaluated by least-squares regression analysis for their suitability for describing Cr adsorption data.
Results
According to the results, chromium adsorption increased with time for up to 150 minutes and the kinetics of chromium adsorption differed greatly between used biochars. In all three types of biochars used, the amount of chromium adsorption in biochars with a pyrolysis temperature of 600 degrees Celsius was higher than that in biochars with a pyrolysis temperature of 400 degrees Celsius and the reason was attributed to the increase in specific surface area with pyrolysis temperature. In addition, the amount of chromium adsorption by biochars used at a dose of 0.5 g/L was higher than that at a dose of 2 g/L. The adsorption kinetic was poorly described by zero-order and the parabolic diffusion equation. However, the zero-order equation found a relatively good fit to the data at times less than 50 minutes. The best model for describing sorption data for all used biochars in this study were the Elovitch, pseudo-first-order (Lagergren) and pseudo-second-order (Blanchard) equations.
Conclusions
This study showed that environmentally friendly biochar could be a candidate as an effective option in the treatment of chromium-contaminated wastewater. Comparison of chromium adsorption by biochar with other expensive adsorbents such as activated carbon and nanoparticles is suggested in future research.
کلیدواژهها [English]
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