Efficient and selective adsorption of Ni(II) and Mo(VI) utilizing novel materials derived from in situ aminated Co/Zn-ZIF-Modified biochar

Efficient Ni(II), Mo(VI) adsorbent BECZN: biomass char with in situ aminated Co/Zn-ZIF. [Display omitted] •A novel aminated Co/Zn-ZIF composite biochar (BECZN) was prepared.•In situ amination favors the adsorption of Ni(II)/Mo(VI) by BECZN porous structure.•The maximum adsorption capacities of Ni(II) and Mo(VI) reach 151.84 and 842.54 mg/g.•After 5 adsorption cycles, the adsorption capacity of BECZN remains above 75%.•Density functional theory reveals the selective adsorption mechanism of BECZN. The imperative need for efficient and selective adsorption of Ni(II) and Mo(VI) is crucial for resource utilization and environmental protection. However, this process faces a challenge due to the scarcity of adsorbents that can adeptly adsorb both metal ions simultaneously. To address this, this study introduces a novel composite adsorbent material, denoted as BECZN, achieved through composite cross-linking of waste orange peel biochar with in situ aminated cobalt/zinc-zeolitic imidazolate frameworks (Co/Zn-ZIF-NH2). The incorporation of Co/Zn-ZIF-NH2 enhances the availability of active groups within BECZN. The aerogel structure of BECZN prevents ZIF material collapse and agglomeration, thereby improving active site exposure. BECZN exhibits notable adsorption capacities, reaching 151.84 mg/g for Ni(II) at pH = 7 and 842.54 mg/g for Mo(VI) at pH = 3. Further investigations indicated that the adsorption of Ni(II) and Mo(VI) obeys the Langmuir isotherm model, while exhibiting pseudo-second-order kinetics and intraparticle diffusion characteristics. Notably, BECZN selectively adsorbs Ni(II) and Mo(VI) efficiently under acidic and neutral conditions, respectively. It can maintain high capacity under the interference of various cations and anions. Meanwhile, this excellent selective adsorption of Ni(II) and Mo(VI) by Co/Zn-ZIF-NH2 is revealed at the atomic level using density functional theory (DFT) calculations. This study offers a theoretical basis and experimental reference for the design and synthesis of ZIF and biomass-based composite adsorbents.