Paper BI+AS-TuA8
Fishing Manganese out from Cellulose: Impact of Coupling Desferrioxamine B to Stainless Steel Beads on the Circular Economy of Paper and Pulp Industry

Tuesday, October 22, 2019, 4:40 pm, Room A120-121

Important as an essential trace element with abundant applications, manganese (Mn) is rising attention due to its aesthetic, operational and health problems at higher concentration in the paper and water industry. When oxygen-containing paper bleaching chemicals (O₂, O₃, H₂O₂ or peracids) are used, the presence of heavy metals like Mn causes problems in the pulp processing, increasing the consumption of the bleaching chemicals and deteriorating pulp quality, including pulp darkening. An effective way to remove Mn from pulp is employing chelators, although its effectiveness is influenced by the overall water chemistry and concomitant contaminants. Successful chelation of Mn usually occurs at pH<8, otherwise highly oxidized species would form, precipitating insoluble Mn(III/IV) oxide minerals, and binding strongly to the pulp. Though the environmentally critical EDTA is used in the paper industry to chelate heavy metals, friendlier and greener alternatives are sought, like desferrioxamine B (DFOB) or E (DFOE), which are linear trihydroxamic acid siderophores produced by bacteria to acquire primarily Fe(III), but also Mn(II/III). Advantages of employing siderophores are its commercial availability, high solubility and stability over a wide pH range. The coupling of DFOB to ~3-4 mm stainless steel beads as solid support was performed. The beads were incubated overnight with several cellulose suspensions to allow formation of the Mn-DFOB complex (log K ~29.9). Control assays were performed using EDTA. After treatment, cellulose suspensions originally containing ~30‑40 mg Mn/kg, were submitted for Mn(II), Mn(III) analysis, employing the TCPP [Tetrakis(4-carboxyphenyl)porphyrin] method. Total Mn content was also determined by Inductively Coupled Plasma (ICP). Preliminary results show an approximate 80% reduction of Mn content from the cellulose suspension, though experimentation is still carried on; DFOE is planned to be also analyzed. Mn was recovered by decoupling from DFOB by metal exchange and the beads were reused for further activation with DFOB. This removal alternative resulted in a feasible, easy, greener and economical procedure, leading for improvement in the paper industry. Still, the most expedient option comprising circular economy statements based on sustainable management parameters (cost-effectiveness, performance, simplicity) must be deeper explored. Clearly, further research regarding Mn(II/III) formation and removal will help the water and paper industry, by developing better methods to diminish Mn oxide deposits in pipe networks and optimizing the paper bleaching process, ultimately reducing significant operational costs.