Engineering and Applied Science Research (Jan 2022)
Insight into molecular weight cut off characteristics and reduction of melanoidin using microporous and mesoporous adsorbent
Abstract
A detailed breakdown of synthetic melanoidin at the fractionations of molecular cut off points of 10kDa, 5kDa and 1kDa using sterlitech ultrafiltration membranes had been conducted by applying DOC, pH, UV-vis254, SSAC346, FTIR and EEMs as a surrogate parameter to examine the structural fractioned melanoidin and favored specific pore size of the adsorption process. At room temperature, pH did not have any specific changes subsequent to fractionation. DOC, UV254 and SSAC436 were significantly increased for a higher MWCO fraction in the order 5-10kDa, 1-5kDa and <1kDa, respectively. Multifunctional groups of fractioned melanoidin at different fractionation groups were found to react easily with the hydroxyl functional group present in the carbon material surface, likely contributing to the adsorption. Using EEMs (excitation-emission 3-dimensional matrices), the spectra showed that at the different fractionations of melanoidin, peaks of fulvic acid-like materials and humic acid-like organic materials corresponding to the Ex/Em regions of 237-260/400-500 nm and 300-370/400-500 nm, belonged to tryptophan and protein-like compounds. The sorption behaviors were all well-fitted to Langmuir isotherm with physisorption of maximum melanoidin adsorbed about 17.88 mg melanoidin g-1 (<1kDa) and about 23.71 mg melanoidin g-1 (5-10kDa) for micropore and mesoporous adsorbent respectively. The above confirmed that the MWCO affected the adsorption process mechanism due to a mass balance transfer between solution bulk density concentration and porous structure. These results may be able to provide clues to evaluate the role of the elimination of recalcitrant melanoidin in wastewater and other specific purposes using suitable adsorbent material for particular molecular weight cut off points.
