Sequential delignification of watermelon rind using ultrasonication and deep eutectic solvent (DES) pretreatment methods was demonstrated in this study. The effects of pretreatment factors on ...delignification were investigated using parametric screening and subsequent optimization of significant factors. Plackett–Burman Design was used for the screening of pretreatment variables, while optimization was performed adopting Central Composite Rotatable Design. For the range of variables considered in the study, the screening experiments revealed that the effects of ultrasonication power, ultrasonication frequency, ultrasonication time, DES reaction temperature and DES reaction time on delignification were significant, while the effects of ultrasonication solid-liquid ratio, ultrasonication temperature, hydrogen bond acceptor/hydrogen bond donor molar ratio, and DES solid-to-liquid ratio were not significant. The significant factors were further investigated and maximum lignin removal of 43.56 % was achieved at ultrasonication power 180 W, ultrasonication frequency 60 kHz, ultrasonication time 40 min, reaction temperature 120°C and reaction time 180 min. Synergistic effect between the two pretreatment methods was observed and it correlated positively with the severity of the ultrasound pretreatment. The SEM and FTIR analyses further established the effectiveness of the sequential combinative pretreatment methods on watermelon rind delignification.
•Novel two-pot approach ultrasound-assisted DES pretreatment was demonstrated.•Effect of pretreatment factors on watermelon rind delignification was investigated.•Synergistic effect between ultrasonication and DES pretreatments was observed.•Synergistic effect correlated positively with severity of ultrasound pretreatment.•SEM and FTIR established the effectiveness of the combinative pretreatment methods.
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•Lignocellulosic and macroalgae biomasses have been targeted for biochar production.•Co-pyrolysis improves the performance of biomass pyrolysis and biochar properties.•Biochar ...properties are influenced by biomass type & pyrolysis operating conditions.•Co-pyrolysis aids development of multiple biochar properties for various uses.•Morphological & surface compositional changes in biochar require characterization.
Biochar properties are significantly influenced and controlled by biomass feedstock type and pyrolysis operating conditions, and the development of multiple biochar properties for various applications has necessitated the need for blending different feedstocks together. Co-pyrolysis as a potential technology has been proposed to improve the overall performance of biomass pyrolysis and has proved effective in improving biochar properties. Consequently, the combination of lignocellulosic and macroalgae biomasses has been targeted for biochar production and improvement of biochar properties through co-pyrolysis. This paper therefore presents a critical review of biochar production from co-pyrolysis of lignocellulosic and macroalgae biomass (CLMB). It discusses the biomass feedstock selection, characterization, pre-processing and suitability for thermal processing; and analyzes biochar production, characterization and reactor technologies for CLMB. Furthermore, the potential and economic viability of biochar production system from CLMB are highlighted; and finally, the current state and future directions of biochar production from CLMB are extensively discussed.
