The assessment of biochar-metal composite in removal of direct blue-71 from aqueous solution

In this study, biochar, metal-coated biochar, and biochar-metal composites of different metals were prepared using rice straw as the raw material. Three elements, iron, copper, and zinc, were selected for preparing the adsorbents for further tests. In this study, we used Direct Blue 71(DB71) as an anionic pollutant sample, which is abundant in the study region. The effects of pH (3.0–9.0), adsorption time (0-420 min), and sorbent dosage (2.5 25 g L ^-1 ) on the removal of DB71 were investigated, and a regeneration experiment was performed. In order to compare the effect of temperature, a leaching experiment was performed using biochar and metal-biochar composites produced at two temperatures (300 and 600°C) as adsorbents to remove DB71 from water. The results showed that the maximum adsorption capacity of DB71 was obtained at 180 min, pH 6, and dosage of 12.5 g L ^-1 . The Fe-biochar composite exhibited a better regeneration capacity. In the results of leaching experiment, the highest amount of dye solution removed by iron composites produced at 300 and 600 ̊C (100%) after three stages of leaching, and the lowest removal percentage was for copper produced at 300 ̊C (56.1%).