Open Access

ARTICLE

Phosphoric Acid Pretreatment and Saccharification of Paper Sludge as a Renewable Material for Cellulosic Fibers

Samar El-Mekkawi¹, Wafaa Abou-Elseoud², Shaimaa Fadel², Enas Hassan², Mohammad Hassan^2,*

1 Chemical Engineering and Pilot Plant Department, National Research Centre, Dokki, Giza, 12622, Egypt
2 Cellulose and Paper Department, National Research Centre, Dokki, Giza, 12622, Egypt

* Corresponding Author: Mohammad Hassan. Email:

Journal of Renewable Materials 2024, 12(9), 1573-1591. https://doi.org/10.32604/jrm.2024.053589

Received 05 May 2024; Accepted 31 July 2024; Issue published 25 September 2024

Abstract

Recycling of paper sludge waste is crucial for establishing a sustainable green industry. This waste contains valuable sugars that can be converted into important chemicals such as ethanol, poly hydroxybutyrate, and lactic acid. However, the main challenge in obtaining sugars in high yield from paper sludge is the high crystallinity of cellulose, which hinders hydrolysis. To address this, pretreatment using phosphoric acid was optimized using response surface methodology to facilitate cellulose hydrolysis with minimal energy and chemicals. The created prediction model using the response surface method considered factors such as acid concentration (ranging from 60% to 85%), consistency (ranging from 4% to 10%), temperature (ranging from 25°C to 80°C), and time (ranging from 0.5 to 4 h). The results revealed that the model’s significant factors affecting the yield were acid concentration, reaction time, temperature, and the product of acid concentration and temperature, while the model’s significant factors affecting the crystallinity were the consistency, the temperature, and their product. The results showed that the optimum conditions for pretreatment were using an acid concentration of 64%, temperature of 25°C, consistency of 10%, and time of 30 min. The hydrolysis of the conditionally pretreated paper sludge resulted in a weight loss of 42%, compared to only 18% weight loss in non-pretreated paper sludge. Furthermore, the optimized conditions led to low levels of furfurals and acetic acid, which are undesirable by-products that can interfere with sugar fermentation. The total sugar obtained under the optimized conditions was 0.43 g glucose/g sample (10.46 g/L), while the contents of methyl furfural, furfural, and acetic acid were 21.65, 235.7, and 4.57 mg/L, respectively. This study demonstrates the potential of phosphoric acid for pretreatment and hydrolysis of paper sludge, enabling efficient saccharification and the production of sugars with minimal undesired by-products.

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