Optimization of biochar production based on environmental risk and remediation performance: Take kitchen waste for example

Two major obstacles that need to be addressed for environmental application of biochar include its environmental risk and remediation performance for target pollutants. In this study, kitchen waste was taken as an example to optimize the pyrolysis temperature for biochar production based on its heavy metal risk and Cd(II) remediation performance. The results showed that the pH and ash content of kitchen waste biochar (KWB) increased; however, the yield, H/C, and N/C decreased with increasing pyrolysis temperature. Total content of heavy metals in KWB got enriched after pyrolysis, while heavy metals' risk was reduced from moderate to low due to the transformation of directly toxic heavy metal fractions into potentially and/or non-toxic fractions. The equilibrium adsorption capacities of biochar for Cd(II) ranked as follows: 49.0 mg/g (600 degrees C), 46.5 mg/g (500 degrees C), 23.6 mg/g (400 degrees C), 18.2 mg/g (300 degrees C). KWB pyrolyzed at 500 degrees C was found to be the most suitable for green, efficient, and economic remediation of Cd(II) contaminated water. SEM-EDS and XPS characterization results indicated that KWB removed Cd(II) via precipitation, complexation with carboxyl/hydroxyl, ion exchange with metal cations, and coordination with pi-electrons. This study puts forward a new perspective for optimizing biochar production for environmental application.

Automated summary

This study optimized the production conditions of biochar using kitchen waste to reduce heavy metal risk and enhance remediation performance towards Cd(II) pollutants. The results showed that pyrolysis temperature significantly affected the properties of biochar, with KWB pyrolyzed at 500 degrees Celsius found to be the most suitable for Cd(II) contaminated water remediation.