Efficient removal of organic load from dairy wastewater using activated carbon derived from olive mill solid waste

Abstract

ABSTRACT This study investigates the preparation of a sustainable activated carbon derived from olive mill solid waste (AC-OMS) and its application for reducing chemical oxygen demand (COD) from dairy wastewater (DWW). The precursor was activated with potassium hydroxide (KOH) and characterized by FTIR, SEM, XRD, and pHPZC analysis. Batch adsorption experiments were conducted to assess the removal of COD from DWW, examining factors such as pH, contact time, adsorbent dose, initial COD concentration, and temperature. The results demonstrated that AC-OMS exhibits a high affinity for COD, achieving equilibrium within 180 min with a maximum capacity of 4,500 mg/g. Adsorption performance was influenced by acidic pH conditions favored electrostatic interactions with anionic organics, while higher doses of AC-OMS increased COD reduction up to the optimal level. Kinetic modeling indicated that the pseudo-second-order model best described the process, suggesting site-controlled chemisorption coupled with intraparticle diffusion. Isotherm analysis revealed a transition from Langmuir-type monolayer adsorption at low temperature to the Freundlich and Temkin models at higher temperatures, highlighting the coexistence of homogeneous and heterogeneous sorption mechanisms. Thermodynamic parameters revealed the exothermic and spontaneous nature of the process, while regeneration tests showed that AC-OMS retained over 68% efficiency after five cycles.