sustainability
Article Research on Recycling Various Wastes in Papermaking as Eco-Friendly Slurry
Teng Yi *, Shuenn-Ren Liou and Wen-Yih Kuo
Department of Architecture, National Cheng Kung University, 701 No. 1, East District, Tainan 701401, Taiwan * Correspondence: n78083503@gs.ncku.edu.tw; Tel.: +886-(06)-275-7575 (ext. 54122)
Abstract: Waste recycling has always been a priority in the paper industry. In this study, the potential of translating various wastes in papermaking into building materials was separately evaluated. For the first time, the improvement of flexibility and sample texture after translating wastes into cementitious materials was analyzed. The results showed that 20% of the waste in alkali-activated slag slurry is the best proportion for papermaking. In addition, paper sludge and wood chips significantly improved the slurry flexibility while lime mud and bottom ash did not have this effect. Considering the effect of adding wood chips on the optimization of the sample texture, the most appropriate proportion of the paper sludge was 5% when the wood chips in the mixture were 15%. The most suitable alkali equivalent was 6%, with a silicate modulus of 0.9. According to the experimental results, wastes in papermaking had great potential for exploitation and application as circular materials.
Keywords: alkali-activated binder; wastes in papermaking; blast furnace slag; compressive strength; flexibility; texture
Citation: Yi, T.; Liou, S.-R.; Kuo, W.-Y. Research on Recycling Various Wastes in Papermaking as Eco-Friendly Slurry. Sustainability 2022 , 14 , 13536. https://doi.org/ 10.3390/su142013536
1. Introduction In 2021, the global output of paper products was 90.2 million tons, which continues to grow due to the COVID-19 pandemic [1]. In addition, approximately 3 billion USD is spent each year on waste disposal from the paper industry and related expenses. For a medium- sized mill, the cost is close to 7 million USD [2]. The waste in papermaking includes many solid wastes such as chips from wood processing, lime muds from kraft pumping, bottom ash in the recovery boiler, and paper sludges from on-site sewage treatment [3,4]. Several programs have been developed to manage these wastes. For example, biomass materials such as wood chips and water treatment sludge could be partially added as fuel to fuel boilers of paper mills [5]. However, this process created additional air and water pollution while supplying electricity to the paper manufacturing process [6]. Some other solid wastes, such as lime sludge, were difficult to reuse as fuel. These materials were usually landfilled with the ashes from incineration [7], causing occupancy of the waste plant and posing the risk of soil and water contamination [8]. Therefore, it is necessary to select suitable resource-based methods to reprocess these wastes without increasing or shifting the environmental burden. By investigating the main components of waste in papermaking [9], the conversion of waste into building materials could be a suitable solution [10]. Among the solid wastes, lime mud replaced the raw materials of ordinary Portland cement by calcination, with a maximum replacement ratio of 20% [11,12]. The paper sludge thermally activated at 600–750 ◦ C replaced 10% of cement as the cementitious binder [13]. In addition, 15% of wood chip ash from paper mills could be used as a raw material for the cementitious binder [14]. Although these methods helped convert waste into building materials, they still caused some energy consumption and environmental impact [15]. In addition, some studies investigated the use of bottom ashes as aggregates [16].
Academic Editors: Rui Zhao, Tianxue Yang and Sebastiano Patti
Received: 19 September 2022 Accepted: 17 October 2022 Published: 19 October 2022
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Sustainability 2022 , 14 , 13536. https://doi.org/10.3390/su142013536
https://www.mdpi.com/journal/sustainability
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