A Utilization of Choline Chloride-Based Deep Eutectic Solvent Integrated with Alkaline Earth Metal Hexahydrate in the Pretreatment of Oil Palm Fronds

Abstract

Over the past decade, deep eutectic solvents (DESs) have been touted as promising reagents in biomass valorization. This study focused on the novel utilization of type II choline chloride (ChCl)-based DESs by integrating group II metal chloride hexahydrate, namely, calcium chloride hexahydrate (CaCl2·6H2O) and magnesium chloride hexahydrate (MgCl2·6H2O) as the hydrogen bond donors for the pretreatment of oil palm fronds (OPF). Under atmospheric conditions, pretreatment with ChCl:CaCl2·6H2O (125 °C and 4.5 h) resulted in dual biomass valorization effects with a delignification of 46.51%, followed by xylose recovery and xylan removal at 54.12% and 78.67%, respectively. Such performance of ChCl:CaCl2·6H2O as a pretreatment solvent expedited the enzymatic glucose (59.31%) and total reducing sugar (63.89%) conversion in the OPF at a subsequent stage. Thus, the characterizations of pretreated OPF samples endorsed the application of type II ChCl-based DESs, particularly, ChCl:CaCl2·6H2O as a propitious approach for ligno-hemicellulose removal in pretreatment.

Breaking new grounds: metal salts based-deep eutectic solvents and their applications- a comprehensive review

“…New and his colleagues 14 utilized alkaline earth metal-based DESs for the pretreatment of oil palm fronds (OPF) and valorization. ChCl was chosen as HBA and CaCl 2 ·6H 2 O/MgCl 2 ·6H 2 O as HBD.…”

“…However, SrCl 2 •6H 2 O shows a similar structure to MgCl 2 •6H 2 O and CaCl 2 •6H 2 O but is incapable of forming a DES once combined with ChCl, where the mixture of both solid chemicals was not fully dissolved. 14 To date, no biodegradability and toxicity studies have been established with MSDESs, therefore, more research needs to be done. The advantages and disadvantages of MSDESs are presented in Table 1.…”

“…New and his colleagues 14 utilized alkaline earth metalbased DESs for the pretreatment of oil palm fronds (OPF) and valorization. ChCl was chosen as HBA and CaCl 88 For the pretreatment of delignification and sugar recovery, two essential variables, i.e., pretreatment temperature and pretreatment duration, play an important role.…”

“…Many metal salts are hazardous and cannot be used while some of them cannot form MSDESs. 14 There are some limits to MSDESs and MDESs as compared to traditional DESs. Despite the same methods for the synthesis of eutectic mixtures, the preparation of DESs is much easier and shorter than that of MSDESs and MDESs.…”