discharged directly to the rivers.


Despite great efforts the chemical recovery technology of these spent liquors is still to be developed. A better knowledge of their chemical composition and their soluble materials characteristics is necessary. In previous works, we used a design of experimental approach (Central Composite Design: 29 cooks including 5 central points) to optimize operating conditions.


The objectives were to optimize physical properties of NSSC pulps, using low chemical charges to reduce inorganic solids in spent liquors (1), and to obtain spent liquors containing the lowest ratio of inorganic/organic solids (2). Hybrid poplar (Populus deltoïdes) was used as raw material. The present work is concerned with the quantitation and qualification of organic components in spent liquors.


Hemicelluloses and lignosulfonates molecular weights are estimated with the objective of evaluate if a molecular separation of this species is possible using ultrafiltration. The following part of this project will show how the lignin contained in the liquor can be grafted using synthetic cationic monomers and eventually be used as a flocculating agent in the effluent system. This work is presented as an extended abstract.


Complete results can be found in references (3, 4, and 5). Materials and methods Hybrid poplar ( Populus deltoides ) from the delta of Paraná River in Argentina was used as raw material. The most important cooking parameters studied were: cooking time at maximum temperature, maximum temperature, sodium sulfite and calcium carbonate charges.


Process conditions were: - Time at maximal temperature: 10 to 30 minutes. - Temperature: 154 to 186ºC. - % SO3 = : 4 to 12% o.d..


- % CO3 = : 0 to 3% o.d. The whole pulping procedure was described in a previous work (1). The volume of all spent liquors were determined.


The spent liquors were stored in glass containers over chloroform and under toluene. In the organic fraction of the spent liquors the following measurements were included: lignosulfonates and hemicelluloses concentrations, molecular weights and MW distributions, acetic and formic acids concentration and sugar contents. In the spent liquors samples the following determinations were made: lignosulfonates and hemicelluloses concentrations, acetic and formic acids concentrations and sugar contents.


The spent liquors were analyzed by two different techniques: - Hydrolyzed by the Klason lignin technique (6, 7): Figure 1. - Separated in 3 fraction by solvent extraction (8): Figure 2. All the analytical methods used in this work are based in HPLC (liquid chromatography) or HPSEC (size exclusion liquid chromatography) techniques.


Fractions designed as A to E were analyzed by the corresponding methods. Figure 1: Scheme of analysis after hydrolysis ANALYSIS OF SPENT LIQUORS XILANES CONTENT FOR HEMICELLULOSES ESTIMATION ACETIC-FORMIC ACID CONTENT D - E FILTRATE HPLC (AMINEX-HPX87H, BIO-RAD) SPENT LIQUORS SOLIDS KLASON LIGNIN TAPPI T222 Figure 2: Scheme of analysis of organic components by separation using acetone Results The results of some qualitative and quantitative determination of organic components in NSSC spent liquors are presented in Figures 3 and 4. Figure 3: Organic solids composition ANALYSIS OF NSSC SPENT LIQUORS HPLC (AMINEX-HPX87H, BIO-RAD) ACETIC AND FORMIC ACIDS CONTENT A + PO3H3 DISTILLATION TAPPI T629 CONDUCTIMETRIC TITRATION SULFONIC ACIDS CONTENT G CARBOXILIC ACID CONTENT H GFC OF LIGNOSULFONATES WITH 2 COLUMNS ASAHIPAK GS520 + GS-320 ELUANT: NaNO3 0.1n/MeOH 80:20 - PSSNa STANDARDS MOLECULAR WEIGHT DISTRIBUTION AQUOUS SOLUTION: LIGNOSULFONATES ION EXCHANGE COLUMN (AMBERLITE IR 120) LIGNOSULFONATES CONTENT B ACETONE SOLUTION DESTILATION HPLC (AMINEX-HPX87H, BIO-RAD) SUGARS CONTENT F FRACTION 2 LIQUID ACETONE WATER 80:20 AGITATION 20 MIN SEPARATION GFC OF HEMICELLULOSES WITH 1 COLUMN WATERS ULTRAHYDROGEL LINEAR ELUANT: NaNO3 0.1n/MeOH 80:20 - PEG STANDARDS MOLECULAR WEIGHT DISTRIBUTION ETHANOL SOLUTION VACUUM EVAPORATION LS FROM ETHANOL WASHING OF HEMICELLULOSES FRACTION 1 SOLID WASHING WITH ETHANOL:WATER 3:1 SOLID WEIGHTED AS HEMICELLULOSES C ACETONE/WATER PROPORTIONAL TO S.I./S.T.


CENTRIFUGATION 10 MIN 3900 RPM SPENT LIQUORS (23% TOTAL SOLIDS) Figure 5: Molecular weight distribution: hemicelluloses and lignosulfonates comparison Cooking conditions: run 25: Time: 20 min, Temperature: 170ºC, NaSO 3 : 8.00%, NaCO 3 : 1.55% Conclusions Several methods were tried to obtain information on the substances present in NSSC spent liquors. The material balances using different techniques of products determination have shown similar results. The percentage of different organic materials present (based on organic solids) in all spent liquors was: - lignosulfonates: 59 - 69 %.


- hemicelluloses: 2 - 24 %. - simple sugars: no detected. - acetic acid: 12 - 29 %.


- formic acid: 1.6 - 2.4 %. Both, hemicelluloses and lignosulfonates show two peaks in GFC chromatograms. While LS present average Mw of about 1030 and 235, hemicelluloses average Mw vary between 8000 and 19600 for the first peak, and 1000 for the second one.


References 1. Area M.C., Felissia, F.E., Venica A., and Valade J.L. cNSSC Process Optimization.I.


Pulps Quality d, TAPPI Pulping Conf., (Montreal), pp 671-681, Oct. (1998). 2.


Area, M.C., Felissia, F.E., Venica, A. and Valade, J.L., cNSSC Process Optimization: II. Spent Liquors d, TAPPI Pulping Conf.


(Montreal), pp 683-690, Oct. (1998). 3.


Area, M.C., Felissia, F.E., Nuñez, C.E., Venica, A. and Valade, J.L., Symposium: « Structure and Properties of Lignocellulosic Materials », cUpgrading Spent Liquors from NSSC Process d, Fifth Chemical Congress of North America, Cancun, Nov. 11-15, 1997.


4. Area, M.C., Felissia, F.E., Nuñez, C.E., Venica, A., Valade, J.L., cUpgrading Spent Liquors from NSSC Process. I: Identification and Quantification of Organic Components d, accepted for publication in Cellulose Chemistry and Technology, 1998.


5. Area, M.C., Felissia, F.E., Venica, A., Valade, J.L., cUpgrading Spent Liquors from NSSC Process. II: Lignosulfonates and Hemicelluloses Molecular Weights Distributions d, accepted for publication in Cellulose Chemistry and Technology, 1998.


6. Lea D.C., An Orienting Study of the Effect of the Neutral Sulphite Semichemical Cook on the Hemicelluloses of Aspenwood. Tappi 37 (9): 393-399 (1954).


7. Quick, R.H., A Study of the Hemicellulose Removed During a Neutral Sulphite Semichemical Cook of Aspenwood, Tappi 39 (6): 357-366 (1956). 8.


Yokoyama, Sh., Ikari, Y., Separation of Organic Components of NSSC Spent Liquors by Acetone and their Characteristics, J. Natl. Chem.


Lab. Ind. (Japan), 77 (2): 101-109 (1982).

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