In this study, we developed a glycerol-mediated safe and facile method to synthesize colored titania nanoparticles (NPs) via solution route. Our method is considerably effective and greener than other options currently available. Colored titania NPs were produced by hydrolyzing TiCl₄ precursor in aqueous solution containing different concentrations of glycerol (0.0, 1.163, 3.834, and 5.815 mol/L) and subsequent calcination at 300 °C for 1 h. Our results highlight firstly that glycerol-mediated synthesis is unlikely to affect the anatase crystalline structure of TiO₂, and secondly, that it would lead to coloration, band gap narrowing, and a remarkable bathochromic redshift of the optical response of titania. More importantly, the synthesized colored titania have Ti³⁺ ions, which, at least in terms of our samples, is the major factor responsible for its coloration. These Ti³⁺ species could induce mid gap states in the band gap, which significantly improve the visible light absorption capability and photocatalytic performance of the colored titania. The photocatalytic experiments showed that the colored TiO₂ NPs prepared in 1.163 mol/L aqueous glycerol solution displayed the best photocatalytic performance. Almost 48.17% of phenolic compounds and 62.18% of color were removed from treated palm oil mill effluent (POME) within 180 min of visible light irradiation.

The interfacial behavior of four sodium salt of alpha-sulphonated methyl ester derived from palm oil (C₁₂MES, methyl laurate sulphonate; C₁₄MES, methyl myristate sulphonate; C₁₆MES, methyl palmitate sulphonate; and C_16/18MES, mixtures of palmitate and methyl stearate sulphonate) was determined at the water–oil interface. Five linear hydrocarbon chained methyl esters from methyl laurate (C₁₂ME) to methyl stearate (C₁₆ME) were used as an oil phase. From the interfacial tension measurements the following values were calculated: critical micelle concentration (CMC), the interfacial tension at the CMC (γ _CMC), surface pressure at the CMC (π_CMC), area per molecule at the CMC (A _CMC), standard free energy of micellization , and standard free energy of adsorption . The C₁₂MES had the highest CMC values and C_16/18MES had the largest molecular area than the other MES surfactants. With the same oil phase, the γ _CMC was slightly lowered as the hydrophobicity of the methyl ester sulfonate was increased. was less negative for C₁₂MES and the value was slightly more negative for C_16/18MES. The effect of the oil phase was obvious, where by increasing the hydrocarbon chain length of the oil phase increases both the γ_CMC and cmc values while A _CMC was decreased. However the difference between π_CMC values of the four MES was small. As the length of the hydrocarbon chain of the oil phase was increased, and became less negative.