Adsorption of Colour Pigments from Palm Kernel Oil onto Biopolymer Prepared from Periwinkle Shell Waste

Abstract

The study was carried out to investigate the bleaching efficiency of chitosan for pigments removal from palm kernel oil (PKO). Chitosan was synthesized from periwinkle shell waste by chemical technique involving demineralization, deproteinization and deacetylation. The bleaching was carried out (batch process) at various adsorbent dosages (1.0-3.0 g). The bleaching adsorbents (Periwinkle Shell Powder, PSP and chitosan periwinkle shell powder, CPSP) were characterized using X-ray fluorescence (XRF) for their elemental composition, scanning electron microscopy (SEM) for surface morphology and Fourier Transform Infrared (FTIR) was used to observe the presence of functional groups in the samples. The results obtained revealed alteration in the concentration (wt. %) and distribution of different compositional elements. The broad peak at 3272.6 cm-1 and the absence of bands 1744.4, 1628.8, 1461.1 cm-1 in PSP revealed forming and breaking of bonds in PSP and CPSP. The bleaching process was tested with four different adsorption isotherms (Langmuir, Freundlich, Temkin and Dubinin – Radushkevich (D-R). The PSP has the higher percentage bleaching efficiency (66.56) while CPSP has 47.05 using 1.0 g each of the biopolymer however 1/n Freundlich isotherm constants which is an indication of adsorption intensity was higher in CPSP (3.4) compare with PSP (2.68). The adsorption process followed D-R in both CPSP and PSP (R2; 0.827 and 0.988 respectively) the mean free energies (EkJ/mol) of both CPSP and PSP (-35.71 and -12.90 respectively) were less than 8 kJ/mol suggesting physical adsorption.