The contamination of water resources by heavy metals, particularly cadmium, represents a severe environmental crisis due to its high toxicity and biopersistence. This research evaluates the performance of an eco-friendly biochar adsorbent for optimal cadmium ion removal from aqueous solutions. The structural and morphological characteristics of the biochar surface were investigated using Brunauer-Emmett-Teller (BET) analysis, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FT-IR), and X-ray Diffraction (XRD). Batch adsorption experiments were conducted at cadmium concentrations ranging from 50 to 200 mg/L with varying adsorbent doses (0.01 to 0.5 g). Residual cadmium concentrations were determined using Atomic Absorption Spectroscopy (AAS). The biochar adsorbent demonstrated excellent performance at both investigated doses, achieving removal efficiencies exceeding 98%. Adsorption isotherm and kinetic studies revealed that the experimental data best fit the Langmuir isotherm and pseudo-second-order kinetic models, indicating that cadmium adsorption occurs as a monolayer on a homogeneous surface through chemisorption via interaction with surface functional groups. Thermodynamic analysis at 298 K yielded negative standard Gibbs free energy values (ΔG° = −30 to −30.46 kJ/mol), demonstrating the spontaneous nature and high feasibility of the cadmium adsorption process. Given its superior efficiency and economic viability, biochar is proposed as an effective option for treating heavy metal-contaminated wastewater.