ENVIRONMENTALLY FRIENDLY METHODS FOR PULP BLEACHING Inese Sable Latvian State Institute of Wood Chemistry 7th International Symposium „Chosen Processes at the Wood Processing“ Slovakia 2007

Cl 2 Cl 2 NaOCl NaOCl Ca(OCl) 2 Ca(OCl) 2 ClO 2 ClO 2 NaClO 2 NaClO 2 Cl 2 O Cl 2 O Na 2 S 2 O 4 Na 2 S 2 O 4 ZnS 2 O 4 ZnS 2 O 4 NaHSO 3 NaHSO 3 H 2 O 2 H 2 O 2 Na 2 O 2 Na 2 O 2 O 2 O 2 O 3 O 3 SO 2 SO 2 CH 3 COOH CH 3 COOH CaS 2 O 4 CaS 2 O 4 Al2(S 2 O 4 ) 3 Al2(S 2 O 4 ) 3 KMnO 4 KMnO 4 Today:

Chlorine and its compounds - harmful for the environment

Na 2 S 2 O 4 Na 2 S 2 O 4 ZnS 2 O 4 ZnS 2 O 4 NaHSO 3 NaHSO 3 H 2 O 2 H 2 O 2 Na 2 O 2 Na 2 O 2 O 2 O 2 O 3 O 3 SO 2 SO 2 CH 3 COOH CH 3 COOH CaS 2 O 4 CaS 2 O 4 Al 2 (S 2 O 4 ) 3 Al 2 (S 2 O 4 ) 3 KMnO 4 KMnO 4 Future:

New method: ( based on method of determination of cellulose ) Pulp bleaching by ammonium persulphate 1. First stage - oxidation: Treatment with (NH 4 ) 2 S 2 O 8 in acidic medium (using H 2 SO 4, HNO 3, HCl, CH 3 COOH) in 80 o C 4 hours Treatment with (NH 4 ) 2 S 2 O 8 in acidic medium (using H 2 SO 4, HNO 3, HCl, CH 3 COOH) in 80 o C 4 hours 2. Second stage - reduction: Treatment with NaBH 4, Na 2 S 2 O 4, Na 2 SO 3, NaH 2 PO 2 for alkaline medium (2% NaOH) in 80 o C 40 minutes Treatment with NaBH 4, Na 2 S 2 O 4, Na 2 SO 3, NaH 2 PO 2 for alkaline medium (2% NaOH) in 80 o C 40 minutes

(NH 4 ) 2 S 2 O 8 in acid medium gives: O 2 O 3 H 2 O 2 H 2 SO 5 H 2 S 2 O 8 H 2 S 2 O 8

Mechanisms of lignin destructurization by Caro’s acid

Soda pulp samples Spruce (Picea abies ) 13,5 % Aspen tree (Populus tremula ) 3,8 % Grey alder (Alnus incana ) 2,2 %

Rapid- Kothen Sheet Former

Test methods Brightness - TAPPI Test Method T 452 om- 02 with Carl Zeiss Elrepho No.19986; Brightness - TAPPI Test Method T 452 om- 02 with Carl Zeiss Elrepho No.19986; Mechanical properties - LVS EN ISO :2001 and EN ISO :2005 with a vertical Frank Prufgerate Tensile Tester Mechanical properties - LVS EN ISO :2001 and EN ISO :2005 with a vertical Frank Prufgerate Tensile Tester

Vertical Frank Prufgerate Tensile Tester

Conclusions Methods for pulp bleaching with ammonium persulphate in an acidic medium have been developed Methods for pulp bleaching with ammonium persulphate in an acidic medium have been developed The highest quality indices for the pulp are reached in the case of realising the bleaching in the sulphuric acid medium; in the nitric acid medium, the mechanical indices of the handsheets are somewhat inferior; the reaction practically does not occur in nitric acid and acetic acid. The highest quality indices for the pulp are reached in the case of realising the bleaching in the sulphuric acid medium; in the nitric acid medium, the mechanical indices of the handsheets are somewhat inferior; the reaction practically does not occur in nitric acid and acetic acid.

Applying the offered method, it is recommended to obtain paper fibres with the average brightness and average mechanical strength Applying the offered method, it is recommended to obtain paper fibres with the average brightness and average mechanical strength Using Na 2 S 2 O 4, Na 2 SO 3 and NaH 2 PO 2 as reduction agents, the obtained handsheets show lower quality indices. Using Na 2 S 2 O 4, Na 2 SO 3 and NaH 2 PO 2 as reduction agents, the obtained handsheets show lower quality indices.

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