solution finder

solution finder

H2O2

Author/Compiled by
Félicien Mazille (Aquasis, cewas - international centre for water management services)
Dorothee Spuhler (seecon international gmbh)
Executive Summary

Hydrogen peroxide (H2O2), a colourless water-like liquid, is one of the most versatile, reliable and environmentally friendly oxidising agents. The relative safety and simplicity of its uses has led to the development of a number of applications in water treatment such as odour removal, disinfection or metal removal. Hydrogen peroxide is also used in advanced oxidation processes (AOP) and can be combined with catalysts or other oxidisers to produce reactive oxygen species (ROS) able to attack a wide range of organic compounds and microorganisms. The production of hydrogen peroxide is usually performed at industrial scale but can also be done directly in drinking water (or pre-treated wastewater) by electrolysis.

Advantages
Destroys toxic organic compounds without pollution transfer to another phase
Does not produce harmful residues
Can be combined with catalysts and other oxidisers
Efficient in treating almost all organic pollutants and in removing some toxic metals
Works for water disinfection (destruction of microorganisms)
Disadvantages
Relatively high operation costs due to input of H2O2
Engineers, additional power and/or chemicals are required for the design of “catalysed” H2O2 treatment systems
In Out

Freshwater, Drinking Water, Non-biodegradable Wastewater, Treated Water

Drinking Water, Treated Water

Introduction

Computer model of a molecule of hydrogen peroxide:hydrogen (red) and oxygen (gold) SOURCE: Science Photo Library

Computer model of a molecule of hydrogen peroxide: hydrogen (red) and oxygen (gold). Source: SCIENCE PHOTO LIBRARY

Hydrogen peroxide (H2O2) is a powerful oxidiser that decomposes into an environmental compatible product (water and oxygen). H2O2 is formed under the action of sunlight in natural surface waters due to the presence of natural organic constituents (COOPER & ZIKA 1983). This mechanism contributes to water purification within the environment.

H2O2 is widely used as a bleaching agent for paper and textiles as well as in industrial applications to manufacture or process products. H2O2 can be used for water treatment alone or combined with UV light, a catalyst and/or other oxidants like ozone (see also ozonation). The hydrogen peroxide-based processes are versatile and can treat organics, microbial contamination as well as some inorganic compounds.

H2O2-based treatments can be used both for drinking water purification (e.g. to remove bacteria, odour, micropollutants, etc.), and for municipal or industrial wastewater treatment (effluent disinfection, organics degradation, see also advanced oxidation).

Hydrogen Peroxide Process

The active part of hydrogen peroxide is the peroxide group, which is an oxidant similar to ozone (see ozonation) or chlorine (see chlorination). When dissolved in water, H2O2 spontaneously breaks down into water and oxygen. This decomposition leads to the formation of reactive oxygen species (ROS), which can oxidise certain organics and metal ions and can also kill pathogens (NEDERHOFF 2000). Optimisation of conditions using H2O2 to destroy these pollutants can involve control of pH, temperature and reaction time. No additional additives are required.

“Catalysed” Hydrogen Peroxide

H2O2 can be used in combination with catalysts: UV light and/or other oxidants. The UV light allows the production of an oxidising agent (ROS) called hydroxyl radical (.OH). .OH is one of the strongest oxidants known, much more efficient than hydrogen peroxide alone (AMIN et al. 2008) and is therefore much more efficient in killing microorganisms and degrading organics in water.

H2O2 + UV light --> 2 .OH

Another way of generating hydroxyl radical from H2O2 is the use of a catalyst. The use of iron ions as a catalyst is a common approach and is referred to as Fenton process (STASINAKIS 2008).

Fe2+ + H2O2 --> Fe3+ + OH- + .OH

This reaction is enhanced by the use of solar light (photo-Fenton).

The addition of both hydrogen peroxide and ozone (peroxone) to wastewater accelerates the decomposition of ozone and enhances the production of hydroxyl radical (AL-KDASI 2004).

Hydrogen Peroxide Generation

The classical manufacturing process involves the catalytic reaction of Hydrogen (H2) with atmospheric oxygen (O2) to give H2O2. Anthraquinone (Q) is used as a hydrogen carrier. Palladium catalyses the reaction between H2 and Q to create H2Q in solution. Then the solution is oxidised by blowing air producing H2O2 (H2Q + O2 --> H2O+ Q) (DEED 1998). Hydrogen peroxide can also be produced directly in wastewater by water electrolysis using electrodes. The required oxygen can be supplied by transfer from the atmosphere (DROGUI et al. 2001).

Costs

Costs depend on the specifics of the requirement (e.g. H2O2 strength and grade, volume per year, packaging and delivery volumes, and location/proximity to production plant, etc.). For large amounts of technical grade 30% H2O2, the price is roughly a few dollars per kg.

At a Glance

Working Principle

H2O2 s breaks down (spontaneously or with a catalyst) into water producing reactive species that react with microorganisms and pollutants

Capacity/Adequacy

Relatively high-tech equipment required for “catalysed” H2O2 treatments

Performance

High efficiency

Costs

Relatively high operation costs for “catalysed” H2O2 treatments

Self-help Compatibility

Engineers are required for the design

O&M

Continuous input of H2O2 required

Reliability

Reliable if the treatment is designed according to each application

Main strength

Very versatile and environmentally compatible oxidising agent

Main weakness

Continuous input of H2O2 required

Applicability

The strong oxidising power of H2O2 makes it suitable for the destruction of a variety of pollutants such as bacteria, toxic organic compounds and some metals. The process has many applications in drinking water production: taste and odour control, hydrogen sulphide removal, metal removal, ozone enhancement and disinfection. H2O2has also been used for many years to degrade organics in industrial or municipal wastewater. It can also be used for the disinfection of wastewater treatment plants.

When H2O2 is combined with UV light, catalyst or other oxidants, the resulting treatment is more efficient in destroying organics present in high strength wastewaters.

When H2O2 is used on its own, the operational costs are limited to input of H2O2. In case of “catalysed” H2O2 treatments, the design is more complex and additional power and/or chemicals input is required.

Library references
Further Readings
Case Studies
Training Material

Chemical Summary on Hydrogen Peroxide

This document provides information on chemical properties, environmental fate, and human health effects of hydrogen peroxide.

OAK RIDGE NATIONAL LABORATORY (1995): URL [Accessed: 10.10.2011]

Alternative Versions to

No Structure Described.