Elimination characteristics of sulfonated cobalt phthalocyanine catalyst (Europhtal) from wastewater in natural gas refineries by adsorption using modified natural zeolite

Abstract

The present research introduces adsorption of sulfonated cobalt phthalocyanine catalyst (Europhtal) from the real wastewater that is produced in the mercaptan removal unit (Merox) of the third refinery, South Pars Gas Complex (SPGC), Assaluyeh, Iran. Therefore, novel low-cost natural zeolite modified with polyaluminium chloride (PAC) was investigated as an adsorbent for the treatment of Europhtal wastewater. Central composite design (CCD), as a set of response surface methodology (RSM), was applied to acquire optimum operational conditions such as contact time, pH, adsorbent dosage, and Europhtal concentration. Results showed that the removal percentage of Europhtal in the real wastewater was 93.4% at best operating condition consisting of a pH of 6.7, sonication time of 8 min, 0.035 g of adsorbent. The obtained results were evaluated by adsorption isotherms and kinetic parameters. It was found that the equilibrium data matched the Freundlich model acceptably, with the maximum experimental adsorption capacity of this model was 687.51 mg g-1 at 301.15 K. From the kinetic data, it was revealed that the adsorption process followed the pseudo-second-order kinetic model. Furthermore, the obtained thermodynamic parameters such as ∆H°, ∆S°, and ∆G° imply the endothermic essence of adsorption proceeding spontaneously.