Catalase for Pulp and Paper — H2O2 Removal in ECF and TCF Bleaching Sequences
Decompose residual hydrogen peroxide after peroxide bleaching stages in ECF and TCF pulp sequences, protecting downstream chemical stages and reducing effluent oxidant load.
Modern pulp bleaching sequences — both elemental chlorine-free (ECF) and totally chlorine-free (TCF) — routinely include hydrogen peroxide bleaching stages (P stages) to achieve target brightness. In ECF sequences, peroxide is used in combination or alternation with chlorine dioxide. In TCF sequences, peroxide is the primary bleaching agent, often supported by ozone or peracetic acid. In both cases, residual H2O2 carried from one stage to the next creates downstream problems: in ECF lines, peroxide can oxidize chlorine dioxide prematurely, reducing bleaching efficiency and increasing chemical cost; in TCF lines, peroxide carryover into ozone stages (Z stages) reacts uncontrollably with ozone and reduces ozone bleaching efficacy. At the mill effluent level, residual peroxide increases chemical oxygen demand (COD) and can inhibit biological wastewater treatment if carried through to the effluent. Catalase enzyme for pulp and paper bleaching solves this by providing a targeted, fast, and residue-free decomposition of H2O2 between bleaching stages. Applied during the pulp washing step between the P stage and the subsequent stage, catalase enzyme at pH 6.0–8.0 and 25–50°C decomposes residual peroxide without chemical carryover. The enzyme is inactivated in subsequent alkaline extraction stages, leaving no active enzyme in the pulp. For mill process engineers, the benefit is chemical efficiency — more predictable ClO2 consumption in ECF lines, better ozone yield in TCF lines, and lower peroxide in mill effluent. Technical buyers in pulp and paper typically specify catalase enzyme activity grade, form (powder or liquid), and dosing format to match their washing line design and throughput.
H2O2 removal between P and D stages in ECF bleaching
In ECF bleaching sequences with P stages before ClO2 (D) stages, residual H2O2 reacts with ClO2 and consumes it non-selectively, increasing chemical use and reducing brightness gain per ClO2 unit. Catalase enzyme added to the P stage washing filtrate or applied in the washing stage at 200–400 U/kg dry pulp at pH 6.5–8.0 and 40–50°C decomposes residual H2O2 within 15–30 minutes, protecting ClO2 from premature oxidation and improving bleach sequence economics.
TCF sequence peroxide removal before ozone stages
In TCF bleaching, peroxide carryover into the ozone stage (Z) causes uncontrolled ozone decomposition reactions that reduce ozone selectivity and increase ozone dose requirements. Catalase enzyme treatment of the P-stage pulp during washing, at 200–500 U/kg dry pulp, pH 7.0–8.0, and 40–50°C, minimizes carryover H2O2 before the Z stage, improving ozone bleaching efficiency and reducing ozone consumption per brightness point.
Peroxide reduction in mill effluent before biological treatment
Residual H2O2 in bleach plant effluent inhibits nitrifying bacteria and can stress activated sludge in biological treatment systems. Catalase enzyme added to the effluent stream or applied in an effluent neutralization tank at pH 6.5–8.0 and 20–40°C decomposes peroxide before discharge to the biological treatment basin, reducing effluent COD contribution from peroxide and protecting biological treatment performance.
Bleached kraft and mechanical pulp washing peroxide control
In bleached kraft and high-yield mechanical pulp operations, wash water recycling can accumulate residual peroxide in recirculated streams, creating variable and elevated H2O2 levels in wash filtrates. Catalase enzyme treatment of recycled filtrates before recirculation — at pH 6.5–8.0 and 30–50°C — removes accumulated peroxide, stabilizing filtrate chemistry and preventing H2O2 buildup in the closed-cycle water system.
| Parameter | Value |
| Activity range | 50,000 – 200,000 U/g |
| Optimal pH | 6.0 – 8.0 |
| Optimal temperature | 20°C – 50°C |
| Form | Dark brown powder or liquid |
| Shelf life | 12 months (sealed, cool, dry place) |
| Packaging | 25 kg drums / 25 kg jerricans |
Frequently Asked Questions
How is catalase enzyme applied in a pulp bleaching sequence?
Catalase enzyme is typically added during the washing step following the hydrogen peroxide bleaching stage, either as a dosing solution to the wash water or as a direct addition to the pulp slurry in the wash press or diffusion washer. The enzyme contact time during washing — usually 15–30 minutes at 40–50°C and pH 6.5–8.0 — is sufficient for near-complete decomposition of residual H2O2. Dosage is set based on the residual H2O2 level in the P-stage filtrate, typically 200–500 U enzyme activity per kg oven-dry pulp. After the washing stage, the enzyme is largely removed with the filtrate and inactivated in subsequent alkaline extraction stages.
What is the economic benefit of using catalase in ECF bleaching?
The primary economic benefit in ECF bleaching is protection of chlorine dioxide. Residual H2O2 from P stages that reaches the ClO2 stage reacts with ClO2 unselectively, meaning each unit of ClO2 that reacts with H2O2 is consumed without delivering brightness. Removing H2O2 before the D stage with catalase enzyme allows ClO2 to act on lignin chromophores more selectively, improving brightness per kg of ClO2 applied and reducing overall bleach chemical cost. The secondary benefit is reduced COD in effluent, which reduces treatment costs.
Does catalase enzyme leave any residue in the pulp or paper product?
No meaningful catalase enzyme residue remains in bleached pulp or finished paper. Catalase is a protein enzyme that is inactivated by the alkaline conditions of extraction stages (E, EO, EP) that typically follow P stages in bleaching sequences. In TCF sequences, subsequent high-temperature processing further denatures any residual enzyme. The decomposition products of H2O2 — water and oxygen — leave no chemical residue in the fiber. Catalase enzyme treatment in pulp bleaching is considered a processing aid with no carry-through to finished paper products.
What activity grade of catalase enzyme is appropriate for pulp and paper use?
For pulp and paper bleaching applications, catalase enzyme grades of 50,000–100,000 U/g are typically sufficient when applied at 200–500 U per kg of oven-dry pulp. Higher activity grades (100,000–200,000 U/g) reduce the mass of enzyme product added per tonne of pulp, which can be an advantage in continuous dosing systems where minimizing liquid addition to the pulp is important. The selection between grades should be based on the residual H2O2 level to be treated, available contact time, and the dosing system format — powder dissolved in dilution water or liquid concentrate metered directly.
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