Waste-to-Wealth Strategy: Ti<sub>3</sub>AlC<sub>2</sub>-Max-Supported WS<sub>2</sub>/Halloysite Nanocomposite for the Removal of Nickel Metal Ions from Wastewater with Machine Learning Simulation and Subsequent Application in Supercapacitors
Fouzia Mashkoor, Sayed Mohammed Adnan, Mohd Shoeb, Changyoon Jeong
Abstract
We proposed an innovative approach employing the “waste-to-wealth” concept, transforming expended adsorbent into electrode materials for energy storage with a focus on sustainability. Ti 3 AlC 2 MAX phase-decorated WS 2 and halloysite (Mx-WS 2 -Hal NCs) were synthesized hydrothermally for the efficient removal of nickel metal ions from wastewater. Subsequently, the spent adsorbent, enriched with Ni 2+ (Mx-WS 2 -Hal@Ni-adsorbed), was repurposed for supercapacitor applications, thus minimizing the environmental impact. The batch adsorption results revealed that WS 2 -Hal and 1, 3, and 5% Mx functionalized WS 2 -Hal NCs show removal efficiencies of 79.82, 86.146, 95.59, and 93.66%, respectively, for Ni 2+ . Furthermore, machine learning models were employed to predict the removal efficiency of Ni 2+ onto the Mx-WS 2 -Hal NCs. The column research showed that the removal efficiency of Ni 2+ was higher at low inlet solution concentration, low flow rate, or high column depth. The column experimental data presented the better fitting of Thomas and Yoon-Nelson model for the Ni 2+ adsorption onto the Mx-WS 2 -Hal NCs. After adsorption, the expended Ni adsorbed Mx-WS 2 -Hal adsorbent was employed for energy storage to minimize the risk of causing additional pollution. The fabricated Mx-WS 2 -Hal@Ni-adsorbed NCs based symmetric supercapacitor device displayed 59.47 W h/kg of energy density at 0.583 kW/kg of power density. Moreover, it maintained a capacitance retention of 90% even after undergoing 10,000 cycles, highlighting the long-term sustainability and reliability of the proposed approach.