This study assessed the effectiveness of a composite adsorbent, synthesized using modified Iranian clinoptilolite, potassium hydroxide, and biochar derived from rapeseed oilseed meal, for removing pharmaceutical contaminants (amoxicillin and metronidazole) and heavy metals (chromium(III), nickel(II), and lead(II)) from individual laboratory-prepared aqueous solutions. Its practical performance was separately evaluated using unspiked industrial wastewater from the Kermanshah oil refinery based on the removal of native Pb and Ni, COD, and BOD. The synthesized composite was characterized using FTIR, XRD, SEM, and BET techniques, revealing a semi-crystalline porous structure with a specific surface area of 156.29 m2/g, indicating a high potential for pollutant adsorption. The impact of operational parameters, including pH (2-11), temperature (15-55°C), time (0.5-20 min), adsorbent dosage (0.1-1 g/L), and initial pollutant concentration (5-300 mg/L), on pollutant removal efficiency was investigated and evaluated under various conditions. Nonlinear kinetic modeling showed that the Elovich model provided the best empirical fit for all investigated pollutants, as indicated by its higher R2 and lower RMSE, χ2, AIC, and AICc values compared with the PFO and PSO models. However, the superior Elovich fit does not conclusively establish a specific rate-controlling mechanism, particularly for heavy metals, because hydroxide precipitation may also have contributed to their measured removal under alkaline conditions. Similarly, because independent pharmaceutical-degradation controls were not conducted, the measured pharmaceutical concentration decreases cannot be attributed exclusively to adsorption. In the real refinery wastewater, the synthesized composite removed up to 99% of the measured Pb and Ni and over 90% of COD and BOD. Pharmaceutical removal was not evaluated in this real wastewater matrix. Although the adsorbent’s efficiency decreased by approximately 10% after five uses, it still maintained acceptable performance, indicating its preliminary potential for reuse under the specific tested hot-water washing conditions. These results suggest that the synthesized composite could be used as an effective treatment material for removing the investigated pharmaceuticals and metals from aqueous solutions and reducing metal and organic loads in refinery wastewater; however, its economic and environmental feasibility remains to be established through systematic cost and life-cycle assessments.
