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Arundo donax L. reed: new perspectives for pulping and bleaching--organosolv delignification.

Application: Comparative experiments on organosolv delignification of Arundo donax are necessary to select more promising pulping processes with possible use for additional optimization of pulping conditions.

Comparative study on applicability to Arundo donax 1 reed of a few modern organic-solvent based technologies showed a great potential of organosolv pulping to produce high quality nonwood fibers. Pulps with high yield and low content of residual lignin, comparable with kraft pulps from hardwoods (Eucalyptus globulus L.) were produced by alkali-sulfite-anthraquinone-methanol (ASAM), alkali-methanol-anthraquinone (ORGANO-CELL), ethanol-soda, and peroxyacids organosolv processes. All organosolv methods were applied to Arundo donax without optimization using conditions reported for pulping of similar crops or hardwood such as ORGANOCELL. The results received should therefore be preliminary and might improve by by further adaptation of process-specific cooking conditions to Arundo donax.

Results and discussion

Table 1 shows the results of pulp properties of Arundo donax for the different organosolv processes and for the reference kraft pulping.

The main benefit of ASAM pulping independent of the kind of raw material used is a high yield. The results of Arundo donax supported this tendency. The yield total and screened--and the viscosity of ASAM pulps are superior to kraft. This demonstrates resistance of the carbohydrate complex to degradation. Other workers showed that xylan and cellulose are stable under these organosolv conditions and exhibit some tendency to degradation only in the final cooking phase. The low alkalinity and the presence of anthraquinone and methanol had a beneficial effect on carbohydrate dissolution through suppressing of a peeling reaction and alkaline hydrolysis. This provides high yield and high viscosity of pulps.

The mechanical properties of ASAM pulp are comparable with kraft, and the bursting strength is higher. The remarkable feature of ASAM pulp from Arundo donax is a substantially higher brightness compared with the kraft pulp from Arundo donax or to industrial kraft pulps from E. globulus.

Conclusions

The organosolv delignification of Arundo donax L. reed showed the potential applicability of modern unconventional pulping technologies for this crop with production of high quality nonwood fibers. Bleachable grade pulps with high yield and low content of residual lignin comparable with kraft pulps from hardwoods (E. globulus L.) were produced by a few acid- and alkali-based organosolv processes (ASAM, ORGANOCELL, Ethanol-Soda and Peroxyacids). The papermaking properties of unbeaten organosolv pulps were higher than for kraft pulp from Arundo donax. Some properties such as tear strength were superior to kraft pulp from E. globulus. This offers promise to produce paper with competitive properties.

The main disadvantage of organosolv pulps and kraft pulp from Arundo donax is the fast response on beating combined with significant drainage problems compared with wood pulps.
1. Physical properties of unbeaten Arundo donax pulps produced by
conventional kraft and organosolv methods

 DRAINAGE BURST TENSILE
 RESISTANCE, INDEX, INDEX,
PULP [degrees]SR kPa*[m.sup.2]/g N*m/g

Kraft (reference) 10 0.5 17.4
ASAM 11 0.9 14.1
Ethanol-soda 11 1.7 27.9
ORGANOCELL 11 1.0 16.9
Peroxyacids 16 0.6 14.2
Kraft from E. globulus L. -- 2.0 46.9

 TEAR
 INDEX, BULK, BRIGHTNESS,
PULP mN*[m.sup.2]/g [cm.sup.3]/g % ISO

Kraft (reference) 10.5 2.1 22.8
ASAM 10.5 2.0 37.1
Ethanol-soda 11.4 1.8 36.5
ORGANOCELL 9.2 1.8 26.5
Peroxyacids 7.1 1.9 24.9
Kraft from E. globulus L. 6.0 1.6 --


Both authors are at Centro de Estudos Florestais, Universidade Tecnica de Lisboa, Instituto Superior de Agronomia, Tapada da Ajuda, 1349-017 Lisboa Codex, Portugal. Address correspondence to Shatalov by email at anatoly@isa.utl.pt.
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Title Annotation:Nonwood fiber: summary of peer-reviewed paper *
Author:Pereira, Helena
Publication:Solutions - for People, Processes and Paper
Date:Nov 1, 2001
Words:606
Previous Article:APMP pulps from nonwood fiber part 2: Jute.
Next Article:Brightness reversion of mechanical pulps XIV: application of FWAs for high-brightness, high-yield pulps.


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