Competitive Adsorption of Cu(II), Ni(II), and Cd(II) Using Amine‐Functionalized Sugar Beet Pulp Biochar in Ternary Aqueous Systems

ABSTRACT A novel biochar derived from sugar beet pulp (O,N‐SBB) was created through an initial surface activation in an acidic medium, followed by the functionalization with 3‐aminopropyltrimethoxysilane. The adsorption of Cu(II), Ni(II), and Cd(II) was studied in ternary metal system. Optimal conditions included a pH of 8.14, an initial metal ion concentration of 77.23 mg L −1 , and a dosage of O,N‐SBB at 1.40 g L −1 . Kinetic studies indicated that the adsorption process is predominantly governed by chemisorption, as evidenced by the superior fit of the pseudo‐second‐order model to the experimental data. The calculated Δ H ° values, ranging from 48.91 to 54.42 kJ mol −1 , further supported the occurrence of chemisorption of metal cations on the adsorbent surfaces. In a ternary mixed system, the adsorption isotherm studies indicated that the Sips model provided the best fit for the experimental data, confirming the heterogeneous nature of the O,N‐SBB adsorbent, which exhibited notable maximum adsorption capacities of 158.31 mg g −1 for Cu(II), 373.42 mg g −1 for Ni(II), and 67.91 mg g −1 for Cd(II). The observed preference of O,N‐SBB for Ni over Cu and Cd can be attributed to the cation's characteristics in solution, particularly the charge‐to‐radius ratio of the hydrated ion, which affects the strength of interaction between the adsorbent and the ions.