Kinetics of Cu Desorption in a Cu -Contaminated Sandy Loam Soil Using Modified Biochar

Pollution and accumulation of heavy metals in the soil are the most important environmental challenges that threaten the lives of plants, animals and humans. One of the effective methods to reduce the harmful effects of heavy metals in contaminated soils is the application of biochar as a soil amendment. In this study, the efficiency of almond soft husk and rice husk biochars (temperature of 500 °C) as well as their modified biochars with NaOH and HNO3 were investigated to reduce soil contamination by copper. The experiment was performed in a factorial experiment in a completely randomized design with three replications. For this purpose, two biochar treatments of almond soft husk and rice husk (unmodified and modified with NaOH and HNO3) were used in two levels (without biochar as a control and 4% by weight). Copper was added in the soil of each pots in three levels (0, 50 and 200 mg kg-1) from the copper sulfate salt source (CuSO4.5H2O). In this regard, different kinetics desorption models of copper were evaluated. Copper concentrations in different time periods (from 30 minutes to 48 hours) were determined using EDTA method in the samples. The results showed that the application of modified biochars at different times caused a significant reduction in copper desorption compared to the control treatment. There was a statistically significant difference between almond soft husk and rice husk and also between different Modified biochar at 5% level. Modified rice husk is more effective than almond soft husk. Sodium hydroxide-modified rice husk biochar reduced copper by 21% and 37%, respectively, compared to almond soft husk modified biochar at 50 and 200 mg kg-1 in 480 minutes, respectively. The power function was introduced as the best Copper desorption kinetics equations due to its high values coefficient of determination (R2) and low values standard error of estimation (SE).