In-situ growth of α-Ni(OH)2 from industrial waste residue for efficient wastewater purification

Wastewater containing various organic dyes and highly alkaline industrial waste residues such as red mud (RM) poses serious threats to human health and aquatic ecosystems. Although adsorbents are widely used to remove organic dyes, their performance is often limited by low adsorption efficiency and high production cost. Herein, we report a cost-effective and high-capacity adsorbent, denoted as RM/α-Ni(OH) 2 , synthesized by in-situ growth of α-Ni(OH) 2 nanosheets on the surface of RM via a one-step hydrothermal process. The resulting RM/α-Ni(OH) 2 exhibits a hierarchical porous structure, large specific surface area (96.71 m 2 g −1 ), and abundant surface functional groups, enabling an outstanding adsorption capacity of 686.3 mg g −1 for Congo Red (CR) within 180 min, 11 times higher than pristine RM (62.12 mg g −1 ) and 5.75 times greater than that of commercial Ni(OH) 2 . The excellent purification performance originates from a synergistic effect of pore filling, hydrogen bonding, and electrostatic interactions. This study not only achieves high-value utilization of industrial waste residue for dye wastewater purification but also provides an environmentally friendly and low-cost pathway consistent with the green concept of “using waste to treat waste”. • A “using waste to treat waste” strategy was developed. • In-situ grown α-Ni(OH) 2 nanosheets on red mud (RM) using its inherent alkalinity. • A high efficient RM/α-Ni(OH) 2 adsorbent has been successfully prepared. • Achieving a Congo red adsorption capacity of 686.3 mg g −1 within 180 min.