Process Optimization for Aqueous Ethanosolv Pretreatment of Coffee Husk Biomass Using Response Surface Methodology

ABSTRACT

This study targeted to optimize process factors using response surface methodology and determining their effect on delignification and cellulose recovery. Optimization of pretreatment conditions with desirability value of 0.828 was done at temperature (A) 150°C, contact time (B) 2 h, and liquid-to-solid ratio (LSR) (C) 15 ml/g. The sample was soaked in an aqueous ethanol solution (48% ethanol). Chemical composition was determined to be 1.87 ± 0.20, 7.03 ± 0.99, 28.05 ± 0.27, 39.29 ± 3.39, and 23.77 ± 3.91 wt% for ash, extractives, lignin, hemicellulose, and cellulose, respectively. Experimental results were validated by comparing actual value with predicted value. The model was verified as the best for improving delignification and cellulose yield. Coefficient of determination (R²), analysis of variance (ANOVA), response plots, and optimization nodes were used to examine the experimental results. The quadratic equation was used to test the model, and ANOVA was used to evaluate the model’s statistical performance and correctness. Temperature, interaction term (BC), and quadratic terms (A², B², and C²) showed significance, while contact time, LSR, and interaction terms (AC and AB) indicated insignificance for cellulose recovery. Temperature, contact time, interaction term (AB), and quadratic terms (B² and C²) showed significance, but LSR, interaction terms (AC and BC), and quadratic term (A²) showed insignificance for delignification. Pretreatment efficacy for delignification (6.0%) and cellulose recovery (151.80%) were achieved at optimal conditions. The pretreatment method is able to produce cellulose-rich coffee husk residues.

摘要

本研究旨在使用响应面法优化工艺因素，并确定其对脱木素和纤维素回收的影响. 在温度（A）150°C、接触时间（B）2小时和液固比（C）15 ml/g下进行预处理条件的优化，期望值为0.828. 将样品浸泡在乙醇水溶液（48%乙醇）中. 灰分、提取物、木质素、半纤维素和纤维素的化学组成分别为1.87 ± 0.20、7.03 ± 0.99、28.05 ± 0.27、39.29 ± 3.39和23.77 ± 3.91 wt%. 通过将实际值与预测值进行比较，验证了实验结果. 经验证，该模型是提高脱木素和纤维素收率的最佳模型. 决定系数（R2）、方差分析（ANOVA）、响应图和优化节点用于检验实验结果. 二次方程用于检验模型，ANOVA用于评估模型的统计性能和正确性. 温度、相互作用项（BC）和二次项（A2、B2和C2）显示出显著性，而接触时间、液固比、相互作用项数（AC、AB）显示出对纤维素回收的不显著性. 温度、接触时间、相互作用项（AB）和二次项（B2和C2）对脱木素有显著影响，但液固比、相互作用项数（AC、BC）、二次项数（A2）对脱木质素无显著影响. 在最佳条件下，预处理的脱木素率（6.0%）和纤维素回收率（151.80%）达到了预期效果. 该预处理方法能够产生富含纤维素的咖啡外壳残留物.

KEYWORDS:

• Aqueous ethanosolv
• pretreatment
• response surface methodology
• delignification
• coffee husk
• central composite design

关键词:

• 含水乙醇溶剂
• 预处理
• 响应面方法
• 脱木素
• 咖啡外壳
• 中央组合设计

Highlights

• Aqueous ethanosolv pretreatment conditions have been optimized.

• Highest cellulose yield (151%) was obtained at optimal conditions.

• Delignification of coffee husk was achieved at optimal process conditions.

• The effect of temperature, contact time, and LSR was investigated

• The effectiveness of the aqueous ethanosolv pretreatment method was investigated

Acknowledgements

The authors would like to acknowledge the Bahir Dar University Institute of Technology for providing the necessary laboratory facilities and resources for this study.

Disclosure statement

No potential conflict of interest was reported by the authors.

Author’s contribution

All authors contributed equally to this manuscript.

Ethical approval

This research work does not contain any studies performed on animals/humans subjects by any of the authors.

Consent

This research work does not involve information about any individual, e.g., case studies, survey, interview, etc., and no consent was needed.

Additional information

Funding

No funding received for this study, but the Bahr Dar institute of Technology supports the required laboratory facilities and chemicals.