Abstract
Cupuaçu husk (CH) is the waste of a common fruit from a native species of the Brazilian Legal Amazon. The current study investigated the influence of ultrasound (US) combined with aqueous, acid, alkaline, and ionic liquid (IL) pretreatments on the chemical and physical aspects of CH and the yield of chemical platforms production, 5-hydroxymethylfurfural (HMF) and furfural (FF), using IL. Scanning electron microscopy, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy were used to feature the raw and pretreated biomass. The highest levels of glucose (9.90 g L-1) were observed in the liquid fraction resulting from the acid + US pretreatment followed by acid hydrolysis. The IL + US pretreatment recorded the best performance in removing lignin. Based on XRD analyses, ultrasound increased crystallinity of all pretreated samples as a result of the removal of cellulose’s amorphous fraction. However, it promoted accessibility to adopted reagents by increasing biomass exposure due to cavitation. The best yields of HMF and FF were recorded from hydrolysis of the solid fraction resulting from the acid + US (12.94%) and alkaline + US (48.84%) pretreatment, respectively. These results indicate satisfactory performance of ultrasound assisted pretreatments to the simplified and economic conversion of biomass into value-added products.
Highlights
Cupuaçu (Theobroma grandiflorum) is a fruit native to the Brazilian Amazon, predominant produced in Brazilian Legal Amazon.[1,2] Its commercialization increases every year in the national and international markets through the sale of its pulp.[3]
In view of the research importance related to the effects and applicability of new pretreatment technologies for fruit waste materials in biorefineries and in high value added chemicals production, the present study aims to investigate the process of cupuaçu husk pretreatment by using ultrasound with different solvents followed by dilute acid hydrolysis
The X-ray diffraction (XRD) analysis has shown an increased in crystallinity in all ultrasound pretreatments, possibly in consequence of amorphous cellulose remotion associated with the ultrasonic energy
Summary
Cupuaçu (Theobroma grandiflorum) is a fruit native to the Brazilian Amazon, predominant produced in Brazilian Legal Amazon.[1,2] Its commercialization increases every year in the national and international markets through the sale of its pulp.[3]. Klason (KL) and acid soluble lignin (ASL) contents were obtained based on the NREL/TP-510-42618 protocol.[26] After acid hydrolysis, the remaining solids were filtrated and heated until 105 °C in stove (SolidSteel SSD 110 L, Piracicaba, Brazil) to determine the acid insoluble residue (AIR). They were taken to muffle furnace at 575 °C to determine the acid insoluble ash (AIA). Where, 96 is the molecular weight of FF, 162 is the molecular weight of the basic unit of hemicellulose FFc is the concentration of FF (mg L-1) and hemicellulosec is the concentration of cellulose in the sample (mg)
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