Adsorption of Aqueous Nickel Ion by Biomass Carboxymethyl Cellulose-Doped Boron Nitride Composites and Its Subsequent Energy Storage

As a typical heavy metal pollutant discharged from industrial activities, nickel ions are highly bioaccumulative and carcinogenic, and low concentrations (>0.5 mg/L) can disrupt the balance of aquatic ecosystems and pose a threat to human health. In this study, a bifunctional adsorbent based on a carboxymethyl cellulose/boron nitride hydrogel was prepared for the treatment of nickel-containing wastewater with a high adsorption capacity of Ni²⁺ (800 mg/L, 344 mg/g), and after adsorption, the waste gel was converted into nickel-doped porous carbon material through carbonization and used as a bilayer capacitor electrode to achieve a specific capacitance of 40.6 F/g at a current density of 1 A/g. The capacity retention rate was >98% after 150 cycles. This strategy simultaneously solves the problems of nickel-containing wastewater purification (the adsorption method is applicable to medium- and high-concentration heavy-metal wastewater) and environmental pollution caused by waste adsorbents, and provides a new paradigm of the "adsorption-resourcing" closed-loop treatment of heavy-metal pollutants.