Efficient iron removal from petroleum refinery wastewater using RCC-natural clay ceramic adsorbents: An isotherm and kinetic study

Abstract

The treatment of petroleum refinery wastewater (PRW) continues to pose a serious environmental issue, particularly due to its high content of heavy metals, especially iron (Fe). This study investigates the adsorption performance and kinetics of iron removal from synthetic petroleum refinery wastewater using ceramic adsorbents formulated from a mixture of clay and RCC spent catalysts. The adsorbent is prepared from a mixture of clay and RCC spent catalysts (ratio 1:1) and evaluated through both batch adsorption systems. Adsorption efficiency was tested at different adsorbent dosages (2.5, 5.0, and 7.5 g), contact times (5-60 minutes), and initial iron concentrations (20-100 mg/L). This study successfully demonstrated the high efficiency of ceramic-based adsorbents in removing iron ions from petroleum refinery wastewater. The maximum removal efficiency of 99.94% was achieved under batch conditions using 2.5 g of adsorbent at an initial iron concentration of 40 mg/L with a contact time of 60 minutes. Adsorption equilibrium and kinetic analyses confirmed that the process well described the Langmuir isotherm and pseudo-second order kinetic models, suggesting monolayer chemisorption on a homogeneous surface with strong interactions between iron ions and the reactive surface site on the adsorbent. The strong linear correlation coefficients (R2 > 0.98 and R2 > 0.99, respectively) confirmed the reliability of these models in describing the adsorption mechanism. The use of RCC spent catalyst as a low-cost, thermally stable, and sustainable adsorbent material contributes to both wastewater remediation and industrial waste valorization.