AOX degradation of the pulp and paper industry bleaching wastewater using nZVI in two different agitation processes

The pulp and paper industry has been researching different treatments for the degradation of adsorbable organohalogens (AOX). In this work, two agitation processes (mechanical and ultrasound) were analyzed in the AOX degradation of the bleaching wastewater using nano zero valent iron (nZVI). The work used different variables for the AOX removal process, such as pH, time, nZVI, and hydrogen peroxide (H2O2) concentration. Results show an increase in AOX degradation when a higher nZVI concentration is used. The optimal combination of variables for the treatment with mechanical agitation was found in the ratio 2:5 (nZVI : H2O2), degrading 85% of AOX in 60 min, with acid pH. Ultrasound treatment consisted of half process time and less degradation than mechanical agitation treatment. The 2:5 ratio in ultrasound agitation degraded 55% of AOX within 30 min at the end of the process. Both methods of the homogenization process of zero valent iron nanoparticles in the bleaching wastewater of the paper and cellulose industry are efficient. However, the mechanical stirring process has a more significant potential for AOX degradation. The variables (pH, concentration of nZVI and H2O2 and duration of the process) used in the bleaching wastewater treatment process must be considered for future implementation in the pulp and paper industry. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The pulp and paper industry has investigated different agitation processes for the degradation of AOX in bleaching wastewater, finding that mechanical stirring is more effective than ultrasound, especially at a 2:5 ratio degrading 85% of AOX. Ultrasound treatment has a shorter processing time but results in less degradation. These findings provide valuable insights for future implementation of AOX degradation processes in the pulp and paper industry.