Green Strategy Guided by Raman Spectroscopy for the Synthesis of Ammonium Carboxylated Nanocrystalline Cellulose and the Recovery of Byproducts
2013
Lam, Edmond | Leung, Alfred C. W. | Liu, Yali | Majid, Ehsan | Hrapovic, Sabahudin | Male, Keith B. | Luong, John H. T.
A one-pot green procedure for the treatment of cellulosic biomass with ammonium persulfate (APS) was developed for the synthesis of highly crystalline carboxylated nanocrystalline cellulose (NCC–COOH), an emerging nanomaterial with a plethora of diversified applications. Raman spectroscopy proved applicable for monitoring the fate of APS and its two byproducts during the production of NCC–COOH from microcrystalline cellulose (MCC). The two main byproducts were then identified and quantified as ammonium sulfate (AS) and H₂SO₄ with the latter accounted for 60% of the total sulfate ions in solution. On the basis of such findings, one-step neutralization of H₂SO₄ and NCC with NH₄OH immediately after reaction was implemented for the formation of additional AS, followed by its quantitative recovery by precipitation. This was a very effective and critical step in waste stream management and cost reduction for the large scale production of NCC. In addition, the process resulted in highly crystalline NCC with COO–NH₄⁺ groups, a nanomaterial with improved dispersion and thermal characteristics over NCC with COOH and COO–Na⁺ groups.
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