Abstract: Converting silicon- and aluminum-rich industrial solid waste into functional adsorbent materials is an effective approach to achieving efficient treatment of heavy metal-contaminated wastewater. In this study, coal gasification slag (CGS) was used as the raw material, and a CGS-derived zeolite material (CGS-Z) was successfully prepared via an alkali fusion–hydrothermal method, aiming to achieve synergy between the resource utilization of solid waste and the efficient treatment of heavy metal-contaminated wastewater. Systematic characterization using XRD, FT-IR, SEM-EDS, XPS, BET, and zeta potential analysis revealed that the resulting material possesses a stable silicon-aluminum framework; a well-developed pore structure, and a high specific surface area (86.35 m2/g); the surface is rich in hydroxyl groups and framework oxygen, providing abundant adsorption sites; the zero-potential point (pHpzc) is 3.58, and the surface charge is tunable with pH changes. Adsorption experiments indicate that CGS-Z exhibits excellent removal capabilities for Pb2?, Cd2?, and Cu2?. The adsorption of Pb2? and Cd2? follows the Langmuir model, with maximum adsorption capacities of 384.98 and 110.51 mg/g, respectively, while the adsorption of Cu2? follows the Freundlich model, with a maximum adsorption capacity of 182.57 mg/g. In a multi-metal system, the adsorption priority order is Pb2? > Cu2? > Cd2?. The kinetic results conform to the pseudo-second-order model, indicating that chemical adsorption is dominant. Mechanism analysis indicates that the removal of heavy metals by CGS-Z primarily results from the synergistic effects of ion exchange, surface complexation, electrostatic attraction, and physical adsorption: exchangeable cations in the aluminosilicate framework participate in ion exchange, surface hydroxyl groups form coordination bonds with metal ions, surface charges of the material generate electrostatic interactions that vary with pH, and the porous structure facilitates mass transfer and diffusion. This study successfully achieved the effective conversion of coal gasification slag into high-value-added adsorbent materials. The prepared materials are simple to synthesize and cost-effective, demonstrating excellent application potential in the treatment of multi-metal wastewater. This work provides a theoretical basis and technical support for the resource utilization of industrial solid waste and the remediation of heavy metal pollution.