Hydrothermal carbonization of acerola (Malphigia Emarginata. D.C.) waste pretreated with supercritical CO2 and zinc chlorine as an additive.

This study investigates the application of supercritical CO 2 (SC-CO 2) in acerola waste pretreatment for hydrothermal carbonization, examining the impact of ZnCl 2 as an additive. Quantified response variables included hydrochar yield, high heat value, energy yield and oxygenated functional groups. Four equations were proposed to correlate the independent variables-additive concentration (C), temperature (T) and residence time (t)-with each response. Subsequently, a multiple-response optimization study was conducted to determine the best conditions, considering all responses. Utilizing SC-CO 2 pretreatment and ZnCl 2 additive resulted in hydrochar with the highest values for all responses. The optimum conditions obtained were T = 161.4°C, t = 105.5 min, and C = 1.43%. The hydrochar obtained under optimal conditions demonstrated that the supercritical CO 2 pretreatment associated to the use of ZnCl 2 additive increased the process yield in 11.02% and the energy yield in 13.02%, confirming the potential application of the hydrochar as a solid fuel. [Display omitted] • The application Supercritical CO 2 pretreatment to hydrothermal carbonization was investigated. • The effect of using ZnCl2 solution in the process was analyzed. • Supercritical CO 2 enhance hydrochar and energy yield in, 9.58% and 10.58% respectively. • The supercritical CO 2 pretreatment with ZnCl 2 increased the hydrochar yield in 11.02%. • The combine treatment raised the energy yield in 13.02%. [ABSTRACT FROM AUTHOR]