In this study, synthesis and characterization of chitosan/maghemite (Cs/Fe₂O₃) composites thin film has been described. Its properties were characterized using Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and ultraviolet-visible spectroscopy (UV-Vis). FTIR confirmed the existence of Fe–O bond, C–N bond, C–C bond, C–O bond, O=C=O bond and O–H bond in Cs/Fe₂O₃ thin film. The surface morphology of the thin film indicated the relatively smooth and homogenous thin film, and also confirmed the interaction of Fe₂O₃ with the chitosan. Next, the UV-Vis result showed high absorbance value with an optical band gap of 4.013 eV. The incorporation of this Cs/Fe₂O₃ thin film with an optical-based method, i.e., surface plasmon resonance spectroscopy showed positive response where mercury ion (Hg²⁺) can be detected down to 0.01 ppm (49.9 nM). These results validate the potential of Cs/Fe₂O₃ thin film for optical sensing applications in Hg²⁺ detection.

The purposes of this study were to investigate the effects of operating parameters, such as electrode material, current density, percentage of hydrogen peroxide and amount of polialuminum chloride (PAC) on chemical oxygen demand (COD) removal of palm oil mill effluent (POME). The current density was varied between 30–80 mA cm−2, PAC (1–3 g L−1) as coagulant-aid and 1 and 2% of hydrogen peroxide as an oxidizing agent. As for the performance of electrode type, iron was more effective than aluminum. It appeared that the removal of COD increased with the increased of current density. When PAC and H2O2 increased, the percent of COD removal was increasing as well. The overall results demonstrate that electrocoagulation is very efficient and able to achieve more than 70% COD removal in 180 min at current density 30–80 mA cm−2 reliant upon the concentration of H2O2 and PAC