This study investigated the adsorptive removal of selected heavy metals from pharmaceutical wastewater using a zinc oxide/geopolymer (zno/geopolymer) nanocomposite as an efficient adsorbent. The nanocomposite was synthesized and applied for the removal of cd, pb, and fe ions under varying experimental conditions, including contact time, temperature, and adsorbent dosage. The results showed that heavy metal removal efficiency increased with increasing contact time and adsorbent dosage due to the availability of more active adsorption sites. The diffraction peaks observed at 2θ values around 31.7°, 34.4°, 36.2°, 47.5°, 56.6°, 62.8°, 66.3°, 68.0°, 72.5°, and 76.9° correspond to the characteristic crystalline planes of the hexagonal wurtzite zno structure, indicating high crystallinity of the zno phase. The most intense peak at approximately 36.2° is assigned to the (101) plane, suggesting that zno nanoparticles are the dominant crystalline component. The geopolymer shows a broad o–h stretching band around ~3400 cm⁻¹ and an h–o–h bending band near ~1630 cm⁻¹, indicating adsorbed moisture and hydroxyl groups. Its main structural band appears between 1000–1100 cm⁻¹, corresponding to asymmetric si–o–t (t = si or al) stretching, along with symmetric stretching (800–700 cm⁻¹) and si–o–si bending (600–450 cm⁻¹). The zno nanoparticles display a characteristic zn–o stretching vibration around ~430–450 cm⁻¹. Isotherm studies revealed that the adsorption process fitted well with the langmuir and freundlich models, suggesting both monolayer and heterogeneous surface adsorption mechanisms. Kinetic investigations indicated that the adsorption followed pseudo-second-order kinetics, implying that chemisorption was the dominant mechanism controlling the adsorption process. The zno/geopolymer nanocomposite exhibited high adsorption capacity, stability, and reusability due to its porous structure and large surface area. The findings demonstrate that zno/geopolymer nanocomposites are promising, cost-effective, and environmentally sustainable materials for the treatment of pharmaceutical wastewater contaminated with toxic heavy metals.