Effect of biochar-derived DOM on the interaction between Cu(II) and biochar prepared at different pyrolysis temperatures

The structure and composition of biochar-derived dissolved organic matter (DOM) at different pyrolysis temperatures differed significantly, affecting the environmental geochemical behavior of heavy metals (HMs). Herein, the binding properties of Cu(II) onto walnut-shell DOM were investigated using spectroscopic methods. The results showed that the DOM at low pyrolysis temperatures (300 degrees C and 500 degrees C) showed higher Cu(II) affinity than that at high pyrolysis temperature (700 degrees C). There was a preferential Cu(II) binding with fulvic-like substances (360 nm) at 300 degrees C, and with protein-like materials (275 nm) at 500 degrees C and 700 degrees C. The C- O group of alcohols, ethers, and esters showed preferential binding with Cu(II) at 300 degrees C and 700 degrees C pyrolysis temperatures. However, preferential bonding of Cu(II) to the C-O stretching vibration and O-H bending vibration of carboxyl was exhibited at 500 degrees C pyrolysis temperature. Pyrolysis temperature played a crucial role in the release of biochar-derived DOM and in the migration and bioavailability of HMs. Meanwhile, the adsorption effect of Cu(II) increased by 11.2% for biochar at 300 degrees C, and decreased by 15.0% and 61.1% for biochar at 500 degrees C and 700 degrees C, respectively, after the removal of DOM, suggesting that the presence of DOM influenced the adsorption behavior of biochar towards Cu(II).

Automated summary

The structure and composition of biochar-derived dissolved organic matter varied significantly at different pyrolysis temperatures, impacting the binding properties of Cu(II) onto walnut-shell DOM. The preferential Cu(II) binding with fulvic-like and protein-like substances at different temperatures were observed, suggesting that pyrolysis temperature plays a crucial role in heavy metal behavior. The presence of DOM influenced the adsorption behavior of biochar towards Cu(II).