Abstract:Nickel (Ni), a heavy metal, poses a significant threat to both the ecological environment and human health. Traditional treatment technologies are limited by high costs and the potential for secondary pollution, which severely restricts their widespread application. Biochar, recognized as a green adsorbent material, has attracted considerable attention in recent years. Its adsorption performance can be effectively enhanced through modification, offering a promising alternative for heavy metal remediation. Against this backdrop, this study used distiller's grains as the biomass feedstock. By combining pyrolysis temperature regulation with the addition of specific substances, Mg/Al layered double hydroxide modified biochar (E-Mg/Al-LDH BC) was successfully synthesized. A systematic study was conducted on its performance and underlying mechanism in adsorbing Ni(Ⅱ) ions, focusing on factors such as pH, initial concentration, and biochar dosage. The study found that the adsorption efficiency of E-Mg/Al-LDH BC for Ni(Ⅱ) was influenced by multiple factors. The optimal adsorption occurred at pH 6, with a capacity of 78.10 mg/g and a removal rate of 97.62%. Lower pH values resulted in reduced efficiency, reflecting competition between H+ and Ni(Ⅱ) ions in solution. When the biochar dosage was 1.25 g/L, it maintained excellent adsorption performance for Ni(Ⅱ) solutions with initial concentrations ranging from 25 to 150 mg/L. Adsorption isotherm and kinetic analyses indicated that the Langmuir model fit the experimental data better than the Freundlich isotherm model, suggesting a monolayer adsorption mechanism. The strong fit with the pseudo-second-order kinetic model further indicated that chemical adsorption was the dominant process. FTIR analysis showed that after E-Mg/Al-LDH BC adsorbed Ni(Ⅱ), —OH groups may participate in surface precipitation or complexation. Enhanced C—O and O—H signals, along with weakened C=O peaks, suggested surface complexation and possible π-Ni(Ⅱ) interactions. SEM-EDS mapping analysis revealed a high surface accumulation of Ni, with elements such as Al, P, O, and Mg potentially playing roles in its removal. In summary, the adsorption of Ni(Ⅱ) by E-Mg/Al-LDH BC is primarily driven by complexation, with ion exchange and π-Ni(Ⅱ) interactions contributing to the overall efficiency. This study elucidates the adsorption characteristics and mechanisms of E-Mg/Al-LDH BC for Ni(Ⅱ) and offers theoretical and technical support for the application of this modified biochar in heavy metal remediation. The findings provide innovative insights for practical environmental remediation and lay the groundwork for developing green and efficient treatment technologies. Close-