Search

Electron beam irradiation (EBI) is an alternative treatment for intrinsic viscosity (IV) control in cellulose pulps, but has never been integrated in full bleaching sequences for comparison to conventional methods. Both eucalyptus kraft (EK) paper pulp and beech sulfite (BS) dissolving pulp were subjected to totally chlorine free (TCF) bleaching sequences comprising either EBI, ozone, or both for IV control. Additionally, effects of EBI on hexenuronic acid (HexA) and xylan were investigated. IV was adjusted to 450–500 mL g−1 and properties including carbonyl content, kappa, brightness, alkali-resistance and sugar composition were compared. Pulps produced with EBI had a higher alkali-resistance, uniformity and less cellulose oxidation. However, the degree of bleaching (DoB) was low without the use of ozone. HexA content in a birch pulp was halved by EBI. Isolated xylans were more resistant to irradiation than cellulose with little decrease of molar masses and moderate oxidation.

The re-oxidation capacity of partially reduced heptamolybdo-pentavanado-phosphate polyanion (HPA� 5red or heteropoly blue) by ozone in water and aqueous acetone solution has been examined under conditions simulating pulp bleaching process. Two oxidation stages/phases were revealed indicating the presence of two reactive states (forms) of catalyst in ozonation solution. The bulk of HPA� 5red (ca. 90%) was completely recovered within a few first minutes of ozonation ([HPA]red = 0.5 mM; 0.39 mmol O3/min), whereas residual catalyst portion reacted very slowly (two orders lower rate) with ozone. Addition of organic solvent was shown to have a favorable effect on HPA� 5red re-oxidation by ozone (k of 0.29 min � 1 vs. 0.43 min � 1 for ozonation, respectively, in water and 10% v/v acetone solution; pH 2), being evidently the principal reason for high efficiency of solvent-assisted HPA/O3 pulp bleaching approach. The pH of reaction media (medium acidity) was found to have a notable effect on HPA� 5red ozonation. 2010 Elsevier Ltd. All rights reserved.

Wood pulping and paper production generate a considerable amount of wastewater, containing many pollutants among them resin and fatty acids. Resin acids contribute substantially to effluent toxicity and were identified to be detrimental to microorganisms of activated sludge and in particular to bacteria in anaerobic wastewater treatment system and other forms of aquatic life. The objective of the present study was to check the applicability of the ozone and advanced oxidation processes (AOPs) to eliminate resin acids from aqueous solutions and to determine the ozone dose required. Furthermore, an investigation of the influence of the oxidation methods on subsequent biological destruction of the byproducts was performed. Aqueous solution of the resin acids: abietic, dehydroabietic and isopimaric acids with different initial composition were subjected to ozonation or AOP processes at different ozone doses. After ozonation or advanced oxidation pretreatment the model solutions were biodegraded in aerated vessels containing activated sludge. During ozonation of the resin acids aqueous solutions the resin acids were almost eliminated, however the reduction of chemical oxygen demand (COD) was rather low. The ozone dose required to obtain reduction of resin acids >90% was in the range of 0.1–0.7 mgO 3 /mgCOD, depending on the composition and concentration of model solutions. The toxicity of ozonated resin acids solutions decreased with increasing applied ozone dose up to about 0.3–0.5 mgO 3 /mgCOD, thereafter increased. Ozonation and other AOP processes did not increase the rate of biodegradation of resin acids model solutions in aerated activated sludge systems compared to not pretreated solutions.

Different advanced oxidation processes (AOPs) have been applied to remove the organic carbon content of a paper mill effluent originating from the Kraft pulp bleaching process. The considered AOPs were: TiO2-mediated heterogeneous photocatalysis, TiO2-mediated heterogeneous photocatalysis assisted with H2O2, TiO2-mediated heterogeneous photocatalysis coupled with Fenton, photo-Fenton, ozonation and ozonation with UV-A light irradiation. The application of the selected AOPs all resulted in a considerable decrease in dissolved organic carbon (DOC) content with variable treatment efficiencies depending upon the nature/type of the applied AOP. A Life Cycle Assessment (LCA) study was used as a tool to compare the different AOPs in terms of their environmental impact. Heterogeneous photocatalysis coupled with the Fenton’s reagent proved to have the lowest environmental impact accompanied with a moderate-to-high DOC removal rate. On the other hand, heterogeneous photocatalysis appeared to be the worst AOP both in terms of DOC abatement rate and environmental impact. For the studied AOPs, LCA has indicated that the environmental impact was attributable to the high electrical energy (power) consumption necessary to run a UV-A lamp or to produce ozone.

The ozonation of resin and fatty acids (RFAs) found in pulp mill effluents was investigated using rapid-scan stopped-flow spectrophotometry. RFAs oxidation (i.e., degradation) efficiency increased with increasing the amount of used ozone and temperature. The degradation process with respect to the acid was found to follow first-order kinetics. The ozonation of RFAs was modeled as an overall second-order reaction for both reactants. The apparent overall second-order rate constants were calculated based on the pseudo first-order rate constants obtained from the kinetic data fitting for the acid degradation. The apparent overall second-order rate constant was affected by pH and temperature. At 20 degrees C and when pH increased from 8 to 11, the apparent overall second-order rate constant increased almost by a factor of 5 (from 3.9 x10(3) to 1.8 x10(4)M(-1)s(-1)) for 9 mgL(-1) resin acid and a factor of 4 (from 9.6 x10(3) to 3.9 x10(4)M(-1)s(-1)) for 8 mgL(-1) fatty acid. At pH 8 and as temperature increased from 10 to 20 degrees C, the apparent overall second-order rate constant increased almost by a factor of 5 (from 8.2 x10(2) to 3.9 x10(3)M(-1)s(-1)) for 9 mgL(-1) resin acid and a factor of 3 (from 3.5 x10(3) to 9.6 x10(3)M(-1)s(-1)) for 8 mgL(-1) fatty acid. Microtox bioassay tests were completed to evaluate the toxicity of RFAs samples before and after ozonation. For the resin acid, there was an increase in toxicity as a result of ozonation. Meanwhile, toxicity of fatty acid samples decreased as a result of ozonation.

Studies were conducted on the response of 2,4,6-trichlorophenol ( 1 ), 2,3,4,5-tetrachloro-phenol ( 2 ) and 4,5-dichloroguaiacol ( 3 ) toward advanced oxidation processes, such as UV-, O 2 /UV-, H 2 O 2 /UV-, O 3 /UV- and O 3 –H 2 O 2 /UV-photolyses with irradiation of 254 nm photons. The compounds 1–3 are among the chlorophenols found in the Kraft-pulp bleach plant E-1 effluents. The studies were extended to treatment of these compounds with ozonation and O 3 –H 2 O 2 oxidation systems in alkaline aqueous solution. Except for the O 2 /UV-photolysis of 1 and H 2 O 2 /UV-photolysis of 2 , the dechlorination of 1–3 by O 2 /UV- and H 2 O 2 /UV-potolyses were less effective than the corresponding N 2 /UV-potolysis of 1–3 . Guaiacol-type chlorophenols were more readily able to undergo dechlorination than non-guaiacol type chlorophenols by N 2 /UV-, O 2 /UV- and H 2 O 2 /UV-potolyses. In addition, the efficiency for the dechlorination of 1–3 by N 2 /UV-, O 2 /UV- and H 2 O 2 /UV-potolyses appeared to be dependent upon the inductive and resonance effects of substituents as well as number and position of chlorine substituent in the aromatic ring of the compounds. The dechlorination of 2 by treatment with O 3 alone is slightly more effective than the corresponding the O 3 /UV-photlysis, whereas the dechlorination of 2 by treatment with the combination of O 3 and H 2 O 2 was slightly less effective than the corresponding O 3 –H 2 O 2 /UV-photolysis. In contrast, the dechlorination of 3 on treatment with O 3 alone was slightly less effective than the corresponding the O 3 /UV-photolysis, whereas the dechlorination of 3 on treatment with the combination of O 3 and H 2 O 2 was slightly more effective than the corresponding the O 3 –H 2 O 2 /UV-photolysis. In the dechlorination of 2 and 3 , chemical species derived from ozone and hydrogen peroxide in alkaline solution were dominant reactions in the O 3 /UV- and O 3 –H 2 O 2 /UV-photolysis systems as in the O 3 and O 3 –H 2 O 2 oxidation systems. Possible dechlorination mechanisms involved were discussed on the basis of kinetic data.

Pulp and paper mills generate varieties of pollutants depending upon the type of the pulping process. This paper is the state of the art review of treatability of the pulp and paper mill wastewater and performance of available treatment processes. A comparison of all treatment processes is presented. Combinations of anaerobic and aerobic treatment processes are found to be efficient in the removal of soluble biodegradable organic pollutants. Color can be removed effectively by fungal treatment, coagulation, chemical oxidation, and ozonation. Chlorinated phenolic compounds and adsorable organic halides (AOX) can be efficiently reduced by adsorption, ozonation and membrane filtration techniques.

Studies were conducted on the composition of chloro-organics in kraft-pulp bleach plant E-1 effluents and their response toward advanced oxidation processes, such as UV-, O(2)/UV-, O(3)/UV- and O(3)-H(2)O(2)/UV-photolysis processes with irradiation of 254 nm photons. The studies were extended to ozonation and O(3)-H(2)O(2) oxidation systems in alkaline aqueous solution. The effects of process variables included initial pH, addition of oxidant to the UV-photolysis system on the decolorization and dechlorination of the chloro-organics the E-1 bleaching effluents were also studied. The decolorization and dechlorination rate constants are increased in the presence of molecular oxygen in the UV-photolysis systems, but are decreased on addition of hydrogen peroxide. The dechlorination rate constants are increased appreciably on oxidation with ozone alone and a combination of ozone and hydrogen peroxide as compared to those of the corresponding UV-photolysis systems under aerial atmosphere.