Study on the Co-pyrolysis Behavior of Copper Slag and Pine Sawdust and the Adsorption of Chromium

The co-pyrolysis behavior of pine sawdust (PS) biochar doped with copper slag (CS) and the adsorption performance of the prepared CS catalyzed composite adsorbent is studied. Thermogravimetric, SEM, and BET are used to analyze the co-pyrolysis characteristics and the adsorption performance of PS and its mixed samples with different ratios of PS and CS. The co-pyrolysis of CS and PS effectively improves the pyrolysis characteristics. Compared with PS pyrolysis alone, with little change in activation energy, the reaction order changed from 1.5 to 0.5. When the mixing ratio PS:CS = 3:1, the pyrolysis release characteristics were the highest; the most favorable for the pyrolysis reaction. The H₃PO₄, KOH, and ZnCl₂ used to modify PS biochar improved its adsorption capacity. The results show that the modified PS biochar has a larger specific surface area and provides more adsorption sites, effectively improving the adsorption effect. The adsorption capacity of the PS biochar is inversely proportional to the concentration of the Cr(VI) solution. Under the conditions of modified PS at 1:1 based on H₃PO₄, KOH, and ZnCl₂, the concentration of the Cr(VI) solution is 20 mg, and the adsorption effect is best in an acidic environment with pH = 1. The high value-added utilization of metallurgical solid waste and agricultural waste was realized, namely the governance concept of “treating danger with waste.”