separations
Article Catalytic Ozonation for Pulp and Paper Mill Wastewater Treatment: COD Reduction and Organic Matter Degradation Mechanism Chenxu Zhou, Jiaming Zhang, Yuxuan Cai and Jianhua Xiong *
College of Resources, Environment and Materials, Guangxi University, Nanning 530004, China * Correspondence: xjh@gxu.edu.cn
Abstract: Rapid degradation of pulping and papermaking wastewater in a pulp and paper mill is crucial for recycling purposes yet challenging to achieve. The purpose of this research is to provide a technical guide for the ozone degradation treatment process of pulp and paper mill wastewater and to explore the reaction mechanism of dissolved and colloidal substances (DCSs). This study is vital for effectively treating pulp and paper mill wastewater through ozonation. In the catalytic ozonation process to treat pulp and paper mill wastewater, a polyurethane sponge loaded with titanium dioxide was used as a catalyst. The optimal process conditions were determined to be 8 min of treatment time, a 16 mg/L ozone concentration, pH 9, and a 7.5% catalyst filling ratio. The COD reduction under these conditions is approximately 52%. The catalytic ozonation system, according to the FI-IR and GC-MS analyses, could degrade the large-molecule volatile organic compounds in the raw wastewater into small-molecule substances. Furthermore, the relative content of common DCSs in paper wastewater, such as palmitic acid and stilbene, could be reduced. The catalytic ozonation system is more effective for treating refractory organic compounds and has a higher COD reduction than the ozonation system.
Keywords: ozonation; GC-MS analysis; FT-IR analysis; pulp and paper mill wastewater
Citation: Zhou, C.; Zhang, J.; Cai, Y.; Xiong, J. Catalytic Ozonation for Pulp and Paper Mill Wastewater Treatment: COD Reduction and Organic Matter Degradation Mechanism. Separations 2023 , 10 , 148. https://doi.org/10.3390/ separations10030148 Academic Editors: Amin Mojiri and HongboGu
1. Introduction The paper industry is an industrial sector with a high consumption of water resources. With the development of the pulp and paper industry in recent years, more and more pollutants are being produced and the types are complex. More than 250 organic pollutants have been detected in pulp and pulp and paper mill wastewater [1]. They come from the wood itself and with various paper-making additives. These pollutants are more diverse and include fatty acids, resin acids, alcohols, phenols, etc. They are also usually complicated to degrade. According to data from the Food and Agriculture Organization of the United Nations Statistics (FAOSTAT), global paper production in 2015 exceeded 390 million tons [2]. China’s total pulp consumption was 100.51 million tons, of which 63.02 million tons of waste pulp accounted for 63% in 2019. In 2017, imported wastepaper accounted for 36% of the raw material composition of waste paper in papermaking. The release of the discharge standard of water pollutants for the pulp and paper industry in 2008 (GB354-2008) also reflects the trend of increasingly strict requirements for pulp and paper mill wastewater in China. Therefore, more and more enterprises have the demand of a closed water cycle. DCSs generally refer to adhesives with a size of less than 5 μ m. The main sources of DCSs are adhesives and resin components (fatty acids and esters) in adhesives and printing inks [3]. Although the DCS content is not much, it is difficult to remove, and easy to gather again with the change of system environmental conditions [4], which greatly impacts the reuse of wastewater from the paper mill [5]. As a result, more and more recycled pulp and paper mill wastewater in China needs to be treated.
Received: 31 December 2022 Revised: 14 February 2023 Accepted: 17 February 2023 Published: 22 February 2023
Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).
Separations 2023 , 10 , 148. https://doi.org/10.3390/separations10030148
https://www.mdpi.com/journal/separations
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