Study on the adsorption characteristics of lead in soil by biochar from co-pyrolysis of rice straw and sludge

The adsorption kinetics and short-term soil adsorption experiments were carried out for the biochar (mixed charcoal) prepared by co-pyrolysis of rice straw and sludge. The results showed that the specific surface area and total pore volume of co-pyrolysed biochar were significantly increased compared with sludge pyrolysis biochar. In the lead solution adsorption experiment, the removal rate of lead ions in the solution reached 99.34% using mixed-burning biochar produced at 600 °C for 24h, and the unit mass adsorption capacity was 64.57 mg/g. In the soil adsorption experiment, 12 g/kg of mixed charcoal was added to lead-contaminated soil, and the leaching toxicity and bioavailability of lead-contaminated soil after stabilization for 30 days decreased by 45.3% and 37.0%, respectively. The soil pH value with 12 g/kg of mixed charcoal added within 30 days fluctuated between 7.03 and 7.12, and no acid or alkaline pollution was generated. Co-pyrolysed biochar can effectively reduce the leaching toxicity and bioavailability of lead in soil. For soil with a lead pollution concentration of less than 1600 mg/kg, adding 12 to 16 g/kg of co-pyrolysed biochar produced at 600 °C can achieve a satisfactory repair effect.