Preparation of a biochar-lignosulfonate composite material and its adsorption performance for Cu²

Biochar was prepared using peanut shells as raw materials, and then composite amino-functionalized lignosulfonate was used to prepare a biochar/lignosulfonate adsorbent (BC-CLS). The morphology and structure of BC-CLS were characterized using FT-IR, SEM, zeta potential, and XPS. The adsorption performance of BC-CLS was evaluated by batch adsorption experiments and dynamic adsorption experiments (adsorption column flow adsorption). The results showed that BC-CLS adsorbent exhibited significant adsorption performance for Cu²⁺, including a short equilibrium time (50 min), fast adsorption rate (11 mg g^-1 min^-1), and high static saturation adsorption capacity (354 mg g^-1). Dynamic adsorption experiments indicated that the maximum adsorption capacity of BC-CLS adsorbent was approximately 280 mg g^-1, with a removal rate of over 99% after five cycles, meeting the wastewater discharge standard (less than 1 mg L^-1). The results demonstrated that the adsorption capacity of BC-CLS adsorbent for Cu²⁺ was controlled by multiple adsorption mechanisms, including electrostatic attraction, precipitation, and metal ion complexation. Additionally, under pH = 5 conditions, using a 40 mg per L Cu²⁺ solution, the adsorption performance of BC-CLS adsorbent remained above 60% after five adsorption-desorption experiments, indicating good cycling stability of BC-CLS adsorbent.