Nanocellulose production from recycled paper mill sludge using ozonation pretreatment followed by recyclable maleic acid hydrolysis.

• Nanocellulose production from Recycled Paper Sludge (RPS). • Ozonation was applied to RPS as a pretreatment, followed by maleic acid hydrolysis. • Ozonation affected the RPS fibers, as analyzed by various methods. • NC production improved with higher ozone doses, up to 0.8% (w/w) maxima. • Maleic acid was recyclable, thus contributing to the "green-industry" concept. Nanocellulose (NC) have garnered much interest worldwide due to its physical and chemical properties. Nanocellulose is produced from biomass materials by bleaching pretreatment, followed by acid hydrolysis. This work demonstrated the production of NC from recycled paper sludge (RPS), a crystalline cellulose rich waste, by ozonation pretreatment, followed by maleic acid hydrolysis. Ozonation resulted in removal of lignin (as evident by TGA analysis), negative zeta potential of RPS and enhanced NC production, from 60 mg/L to over 80 mg/L after 60–120 min of ozone treatment. Maleic acid was successfully recovered, although longer ozonation times reduced the amount of acid available for recovery. These results demonstrate that ozonation can be used as an effective pretreatment for NC production. [ABSTRACT FROM AUTHOR]