OPTIMIZATION OF ACTIVATION CONDITIONS OF LOCALLY AVAILABLE CLAYS FOR COTTONSEED OIL BLEACHING: CHARACTERIZATION AND PERFORMANCE EVALUATION

Abstract

ABSTRACTCottonseed oil is consumed either in raw state or after refining, which enables it to acquire the characteristics such as neutral taste and odor, limpidity, light color, oxidation stability to oxidation, and for it to be used for frying. Refining comprises several strategies including bleaching, which involves the fixation of beta‐carotene, the pigment that is responsible for the red color of cottonseed oils, on a solid support generally known as bleaching earth. In this work, possible application of locally available clay (Ordu, Turkey) as bleaching earth was investigated for cottonseed oil refining. Raw clay was activated via various treatment methods including acid activation, cation treatment and thermal treatment. Structural changes caused by acid activation were characterized using Fourier transform infrared spectroscopy, differential thermal analysis, N2 adsorption (BET surface area), X‐ray fluorescence and scanning electron microscopy. Bleaching capacities of the treated clays were also determined spectrophotometrically. Bleaching efficiency was increased from 3 (raw clay) to 23% by H2SO4 activation and to 34% by Al3+ and heat treatment. However, commercial clay's efficiency was 32%. Tetrahedral destruction with proton attack was higher in HCl solution than H2SO4 solution, resulting in collapse in micropores. Bleaching efficiency increment using H2SO4 was higher than that of HCl.PRACTICAL APPLICATIONSIt is important to reduce color in oils of low quality by cheap and appropriate adsorbent instead of expensive commercial earths. Activationconditions differ from one clay to another. In this study, several activation methods were applied and possible mechanisms relating to bleaching efficiency improvement were also investigated.