Adsorption Behavior During Decolorization of Crude Glycerin Solution

Abstract

Crude glycerin, a by-product of the transesterification of oleochemicals, undergoes several processes to recover glycerine, which is commercially used in many daily personal care products. Crude glycerin is typically brown due to the solution's presence of lignin, tannin, and organic matter. This study uses sewage sludge as an adsorbent to decolorize crude glycerin through an adsorption process. Initially, the crude glycerin and the prepared adsorbent will be characterized using Fourier Transform Infrared Spectroscopy (FTIR) for functional groups, color concentration with UV-visible spectroscopy (UV-Vis), and particle size distribution using a Particle Size Analyzer (PSA). The adsorption behavior was elucidated at different agitation speeds (62.5 rpm, 125 rpm, and 250 rpm), adsorbent dosages (10 g/L, 20 g/L, and 30 g/L), and particle sizes of the adsorbent (100 microns, 200 microns, and 300 microns). The color intensity before and after adsorption was analyzed using UV-Vis spectroscopy, and the absorbance was used to determine the percentage of color removal. The findings showed that the optimum color removal from crude glycerin was achieved at 125 rpm agitation speed, 30 g/L adsorbent dosage, and 100 microns of adsorbent particle size, with 33.4%, 40.8%, and 40.2% of removal, respectively. At a 125 rpm agitation speed, the Langmuir isotherm fit the experimental data with K_L­­​ and q_max values of 0.0028 L/mg and 8.25 mg/g, respectively. The Freundlich isotherm could describe the adsorption process at 30 g/L adsorbent dosage with K_F and 1/n values of 0.142 mg/g and 0.135, respectively. Additionally, the experimental findings using 100 microns of adsorbent fit well with the Langmuir isotherm, with K_L​ and q_max​ values of 0.057 L/mg and 0.246 mg/g, respectively.