Enhanced adsorption of ranitidine onto activated carbon‑modified zeolite composite and investigation of the removal mechanism.

Ranitidine is an H2-receptor antagonist that inhibits histamine activity, thereby decreasing gastric acid secretion. The presence of ranitidine in water resources poses environmental risks, potentially leading to disrupting aquatic ecosystems, and affecting human health through contaminated drinking water sources. Therefore, its removal from aquatic environments is essential. The maximum removal rate of 99.8% was achieved under best operating condition of a solution pH of 8.5, ranitidine concentration of 20 mg L⁻¹, activated carbon (AC) /modified zeolite (AC/MZ) composite mass of 250 mg L⁻¹, and a contact time of 35 min, closely aligning with the predicted removal rate of 100% from the model. The proposed model accuracy evaluated by analysis of variance. Kinetic model studies indicate that the adsorption of ranitidine onto the AC/MZ composite follows a second-order model, with a R2 of 0.9998, suggesting a chemisorption mechanism. Equilibrium studies demonstrate a strong alignment with the Langmuir isotherm, exhibiting a correlation coefficient of 0.9993, which suggests monolayer and homogeneous adsorption characteristics. The maximum adsorption capacity (qₘ) and RL values were calculated as 463.0 mg g⁻¹ and 0.0162, respectively.