تاثیر نانو زغال زیستی بر سینتیک و هم‌دمای جذب کادمیوم در خاک آهکی

آلودگی خاک با فلزات سنگین مانند کادمیوم به یک نگرانی محیط زیستی جهانی تبدیل شده است. نانو زغال زیستی می‌تواند از موثرترین اصلاح‌کننده‌های خاک باشند، اما اهمیت آن‌ها در اصلاح خاک‌های آلوده‌ آهکی به خوبی شناخته نشده است. هدف از این پژوهش بررسی تاثیر نانو زغال زیستی نی بر سینتیک و هم‌دمای جذب کادمیوم در خاک آلوده‌ آهکی بود. نانو زغال زیستی نی با روش آسیاب گلوله‌ای تهیه و سپس ویژگی‌های آن اندازه‌گیری شد. برای بررسی تاثیر نانو زغال زیستی در خاک، یک آزمایش انکوباسیون با سه نوع جاذب شامل زغال زیستی نی، زغال زیستی نی اصلاح شده با کلرید آهن و نانو زغال زیستی، در سه سطح کاربرد شامل صفر، 0.5 و یک درصد وزنی/وزنی در سه تکرار به‌مدت 60 روز در دمای 25 درجه‌ سلسیوس انجام شد. پس از پایان دوره‌ انکوباسیون، برخی ویژگی‌های خاک اندازه‌گیری شد و آزمایش هم‌دمای جذب کادمیوم (غلظت‌های صفر تا 50 میلی‌گرم بر لیتر) و سینتیک جذب کادمیوم (زمان‌های 0.5 تا 48 ساعت) انجام شد. سپس داده‌های آزمایش با مدل‌های سینتیک و هم‌دمای جذب به‌صورت غیرخطی برازش داده شد و پارامترهای مدل‌ها محاسبه شد. نتایج نشان داد کاهش اندازه‌ زغال زیستی به نانو سبب افزایش سطح ویژه و ظرفیت تبادل کاتیونی شد. کاربرد نانو زغال زیستی در سطح یک درصد سبب افزایش درصد ماده‌ آلی خاک شد. نانو زغال زیستی نی در سطح 0.5 و یک درصد در مقایسه با تیمار شاهد به‌ترتیب سبب افزایش 33.02 و 83.02 درصد از ماده‌ آلی خاک شد. نانو زغال زیستی بیش‌ترین تاثیر را بر جذب کادمیوم در خاک داشت. مدل لانگمویر نسبت به رابطه‌ فروندلیچ و تمکین برازش بهتری بر داده‌های آزمایش داشت. حداکثر ظرفیت جذب کادمیوم (qmax) با کاربرد جاذب‌ها افزایش داشت و بیش‌ترین ظرفیت جذب در تیمار یک درصد نانو زغال زیستی با مقدار 1048 میلی‌گرم بر کیلوگرم مشاهده شد. مدل سینتیکی شبه درجه‌ دوم با توجه به ضریب تبیین بالا (r2) و خطای استاندارد پایین (se) برازش بهتری بر داده‌های سینتیکی جذب داشت. ظرفیت جذب کادمیوم (qe) با کاربرد جاذب‌ها در مقایسه با تیمار شاهد افزایش یافت و این افزایش در سطح نانو زغال زیستی یک درصد بیش‌تر از سطح 0.5 درصد بود. به‌طورکلی کاربرد نانو زغال زیستی تولید شده توسط آسیاب گلوله‌ای، در جذب کادمیوم توسط خاک آلوده‌ آهکی موثرتر بود.

effect of nanobiochar on the kinetics and isotherm of cadmium adsorption in calcareous soil

extended abstractintroduction soil pollution with heavy metals such as cadmium has become a global environmental concern. adsorption is widely used as a remediation method due to its advantages, including cost-effectiveness and high performance in removing metal ions. biochar is an effective way to improve soil properties and act as a sorbent for various toxins. in particular, nanobiochar, with its unique properties such as high specific surface area, has the potential to be one of the most effective soil amendments. nanobiochar has gained attention recently due to its unique properties and potential applications in various fields. its high specific surface area and small particle size make it an effective adsorbent for polluted soils and water contaminants. nanobiochar has demonstrated the ability to adsorb many pollutants, including heavy metals, organic compounds, and nutrients, making it a promising material for environmental remediation. despite the potential applications of nanobiochar, more research is needed to fully understand its properties and potential uses. the field of nanobiochar is still emerging, and many questions remain unanswered. furthermore, the importance of nanobiochar in remediating polluted calcareous soils is not well known. this study aimed to investigate the effect of nanobiochar made from reed on the cadmium adsorption isotherms and kinetics in polluted calcareous soil. materials and methods for this research, a composite soil sample was collected from a depth of zero to 30 cm from the farm of the faculty of agriculture, shahid chamran university of ahvaz. the soil sample was air-dried and passed through a two-mm sieve, then some physical and chemical characteristics of the soil were measured. to prepare biochar, the raw common reed was collected, air-dried, and passed through a two-mm sieve, and the common reed was soaked in 0.5 m fecl2. the raw and fe-soaked common reed biomass was then pyrolyzed at 500 °c for three hours with a heating rate of six °c min−1 in an electrical furnace under anaerobic conditions. nanobiochar was prepared using a ball milling method, and its properties were analyzed. to investigate the effect of the adsorbents on the cd adsorption isotherm and kinetic in soil, an incubation experiment was conducted with three types of adsorbents, including common reed biochar, iron-modified common reed biochar, and common reed nano-biochar at three application rates of 0, 0.5, and 1 % in three replicates for 60 days at a temperature of 25°c. at the end of the incubation period, some soil properties were measured, and the isotherms of cadmium adsorption at different concentrations (zero, five, 10, 20, 30, 40, and 50 mg l-1) were determined. the kinetics of cadmium adsorption at cd concentration of 40 mg l-1 under different periods (0.5, 1, 2, 4, 8, 12, 24, and 48 h) were also studied. then, the experimental data were fitted using nonlinear adsorption and kinetic models, and the model parameters were calculated. results and discussion the results showed that reducing the size of biochar to nano-scale increased the specific surface area and cation exchange capacity. the application of nanobiochar at one percent application rate increased the percentage of soil organic matter compared to other treatments. soil treated with nanobiochar at 0.5 percent and one percent application rates increased soil organic matter by 33.02% and 83.02% compared to the control treatment, respectively. nanobiochar gave rise to the highest cd adsorption in the soil. the langmuir model provided a better fit to the experimental data than the freundlich and temkin models. the maximum adsorption capacity of cadmium (qmax) boosted upon adsorbents application, and the highest adsorption capacity was obtained in soil treated with nanobiochar at one percent application rate with maximum cd adsorption capacity of 1048 mg kg-1 of soil. the pseudo-second-order kinetic model provided the best fit to the kinetic adsorption data due to its high coefficient of determination (r2) and low standard error (se). the adsorption capacity of cadmium (qe) increased with the use of reed biochar, iron-modified reed biochar, and nanobiochar compared to the control treatment, with a higher increase observed at the one percent application rate compared to 0.5 percent. additionally, the rate constant k2 showed a higher surface adsorption rate of cadmium in soil treated with nanobiochar compared to the other treatments. conclusion in general, the study findings confirmed the effectiveness of nanobiochar produced by ball milling in cadmium adsorption in polluted calcareous soils. the results showed that the nanobiochar amending cadmium-polluted soils demonstrated better improvement compared to biochar treatments. nanobiochar at one percent application rate was the best treatment for improving soil properties and increasing cd adsorption due to its exceptional properties (high surface area and improved adsorption capabilities). as a result, the application of nanobiochar as an adsorbent offers environmental and economic advantages. the application of nanobiochar as a strong and effective adsorbent for cadmium removal from the soil can be considered as an effective solution to protect the environment and human health.