Sewage sludge ZnCl₂-activated carbon intercalated MgFe–LDH nanocomposites: Insight of the sorption mechanism of improved removal of phenol from water

This work reports the synthesis of new layered double hydroxide (LDH) composites using sewage-based ZnCl2-activated carbon (AC) intercalated with MgFe (AC-MgFe-LDH) and an evaluation of their adsorptive performance for phenol removal from water. The effect of the AC loading on the final properties of synthesized composites was investigated via various characterization techniques. The results showed efficient decoration at 0.1–0.25 g AC loading within the layers of AC–MgFe composites LDH, which was reflected in the higher surface area (233.75 m²/g) and surface functionalities (OH, NO3, C-O-C, and MMO) yielding a significant improvement of the phenol removal efficiency. However, at higher contents, AC loading led to the breakage of the LDH structure and agglomeration, as indicated by the deterioration in the textural and structural properties. The isotherm and kinetic data were well fitted by the Langmuir and pseudo-second-order model, respectively, with a maximum obtained monolayer adsorption capacity of 138.69 mg/g. The thermodynamics results demonstrated that phenol adsorption is an endothermic process. The sorption mechanism of phenol molecules on the AC–MgFe composite was governed by chemical bonding with OH, C=O, and MMO groups and pore diffusion via π–π interactions. Superior phenol removal with excellent recyclability up to five cycles of the new AC– MgFe composite suggested its use as a potential adsorbent for effective phenol removal from water and wastewater streams.