Effect of terminal temperature on the morphology and heavy metal concentrations of typical rural domestic biochar and its potential use in ammonia nitrogen adsorption

Abstract

In this study, straw, kitchen waste and pine needles were used as raw materials to prepare biochar at terminal temperatures of 300, 500 and 700 °C (SB, KB and PB), respectively. The morphology and concentrations of heavy metals extracted from biochar at different synthetic temperatures were analyzed by BCR (European Community Bureau of Reference) method. The effects of temperature and pH on the adsorption of ammonia nitrogen (NH4-N) in landfill leachate with SB, KB and PB were studied. The results show that the yield of PB300 was the highest (86.47%). Further analysis presents that SB, KB and PB contain basic functional groups (pH > 8.50) and the heavy metal content of SB, KB and PB is low (<2.564 mg∙kg−1). Moreover, it is found that terminal temperature is negatively correlated with heavy metal concentration. The F3 and F4 are the primary states of zinc (Zn), lead (Pb) and barium (Ba) of SB, KB and PB, indicating relatively high biological stability of the products. The potential ecological risk (RI) values of SB, KB and PB was lower than 1, illustrating SB, KB and PB are non-hazardous waste (<1 mg∙L−1). When pH was alkaline (pH = 9), SB500 had the best ability for NH4-N adsorption in landfill leachate (19.14 mg∙g−1). Further improvement of adsorption performance with SB500 can be achieved at temperature of 35 °C (21.88 mg∙g−1). Overall, SB, KB and PB can be used as environmentally friendly remediation materials.