Effect of water of crystallization on the dissolution efficiency of molten zinc chloride hydrate salts during the pre‐treatment of corncob biomass

Abstract

BACKGROUND: Agro-wastes albeit abundant and cheap, require pre-treatment steps tailored to overcome the characteristic recalcitrance of lignocellulosic biomass. In this study, zinc chloride hydrate salts were studied for their biomass deconstruction potential. The role of salts' hydration and to what degree it affects the dissolution efficiency was evaluated. Milled corn cobs from local farmlands were dissolved in the following solvent systems; ZnCl 2 .3H 2 O, ZnCl 2 .4H 2 O, ZnCl 2 .5H 2 O and ZnCl 2 .7H 2 O at 70 ∘ C for 60 mins at a biomass to solvent ratio of 1:12. RESULTS: The difference between the least and most hydrated solvent systems in terms of total released sugars as a percentageof recoverable sugar is 70.1%. The ZnCl 2 .4H 2 O solvent system extracted up to 49.1% of glucose and 95% of xylose. There were significant differences in the crystallinity indices and surface morphologies between the untreated and treated biomass. CONCLUSION: The findings as documented contribute to current insights on the mechanisms of disintegration of lignocellulosic biomass in molten hydrate salts. The extraction of sugar components of biomass by ZnCl 2 .4H 2 O solvation was about 43% glucan and 99% xylan.

Biocompositional and thermodecompositional analysis of South African agro‐waste corncob and husk towards production of biocommodities

“…It is important to note that the higher the hydroxyl group functionality of the structural components of biomass, the higher the potential of pre‐treatment especially with the use of mild ionic solvents that dissolve lignocellulosic biomass by attacking the –OH groups on the glycosidic linkages of sugar polymers . As such, the variants of corn waste samples investigated from this indication are more than likely to be susceptible to non‐derivatising solvents such as molten hydrate salt . The degree of crystallinity of the sugar polymers in the raw biomass samples was related to total crystallinity index, and lateral order index that measures the overall degree of order, while the hydrogen bond intensity is related to the crystal system and the degree of intermolecular regularity.…”

“…[40] As such, the variants of corn waste samples investigated from this indication are more than likely to be susceptible to non-derivatising solvents such as molten hydrate salt. [41] The degree of crystallinity of the sugar polymers in the raw biomass samples was related to total crystallinity index, and lateral order index that measures the overall degree of order, while the hydrogen bond intensity is related to the crystal system and the degree of intermolecular regularity. As shown in Table 4, the respective ratios of the different biomass samples were found to be analogous.…”

The role of the molecular formula of ZnCl2·nH2O on its catalyst activity: a systematic study of zinc chloride hydrates in the catalytic valorisation of cellulosic biomass

“…Within these exemplary findings, including our recent work in which some changes in response to the molecular formula of ZnCl2•nH2O were noted, 13 the exact role of the molecular formula of the ZnCl2•nH2O system is unclear, on the outcomes and the catalyst activity. For example, a study on the low temperature (70 °C) pretreatment of corncob 14 for n = 3, 4, 5, 6, 7 in ZnCl2•nH2O revealed an ability of the lower hydrates (n = 3, 4) to dissolve and convert small amounts of the biomass but with no rationalisation of the differences in underpinning features of these systems. An improved fundamental understanding would therefore be an enabler for the selective transformation of varied cellulosic substrates in this IL.…”

High enhancement of the hydrolysis rate of cellulose after pretreatment with inorganic salt hydrates

“…The salt hydrate intercalates between the cellulose fibers, breaking hydrogen bonds and allowing the dissolution of cellulose. [32][33][34][35] The structure of salt hydrates is governed by coordination complexation between Cl − or Br − and water around Zn 2+ or Li + . The proposed structure of inorganic zinc hydrate is {[Zn (H 2 O) 6 ][ZnX 4 ]•2H 2 O} (where X = Cl or Br).…”