Abstract
Biochar from sewage sludge is a low-cost sorbent that may be used for several environmental functions. This study evaluates the induced effects of pyrolysis temperature on the physicochemical characteristics of sewage sludge (SS) biochar produced at 350 (SSB350), 450 (SSB450) and 600 (SSB600), based on the metal enrichment index, metal mobility index (MMI), and potential ecological risk index (PERI) of Cd, Cu, Pb, and Zn. Increased pyrolysis temperature reduced the biochar concentration of elements that are lost as volatile compounds (C, N, H, O, and S), while the concentration of stable aromatic carbon, ash, alkalinity, some macro (Ca, Mg, P2O5, and K2O) and micronutrients (Cu and Zn), and toxic elements such as Pb and Cd increased. Increasing the pyrolysis temperature is also important in the transformation of metals from toxic and available forms into more stable potentially available and non-available forms. Based on the individual potential ecological risk index, Cd in the SS and SSB450 were in the moderate and considerable contamination ranges, respectively. For all pyrolysis temperature biochar Cd was the highest metal contributor to the PERI. Despite this, the potential ecological risk index of the SS and SSBs was graded as low.
Highlights
Biochar from sewage sludge is a low-cost sorbent that may be used for several environmental functions
When compared to biochar produced from other feedstocks, sewage biochar is characterized by low C, N, and H values, especially C 38,39
The pyrolysis temperature affects the ultimate and proximate composition, the stability, aromaticity, and polarity of the biochar produced at different temperature
Summary
Biochar from sewage sludge is a low-cost sorbent that may be used for several environmental functions. The diversity of physicochemical characteristics of biochar has allowed the tailoring of the material for use as an agricultural amendment[6], for sequestration of carbon, and as a sorbent for potentially hazardous organic and inorganic compounds in aquatic environment, soil, and sediments[7]. It has applications in mitigation of climate change[8], energy production[3,9] industry, and e ngineering[10]. The resultant biochar is a pathogen-free material with great potential for immobilizing inorganic c ontaminants[13], and PTEs are transformed into less toxic forms[14]
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