Introduction
Optical Brightening Agent is a relatively new term for people, but when we hear Brighteners, the immediate response is: Stilbene or Benzimidazolone?
Long story short, these are chemical solutions formulated using the abovementioned organic compounds and some other groups (Coumarins, Triazoles, Pyrazolines). The name comes from their primary utility, i.e. absorbing UV light and emitting visible blue light, counteracting yellow tinge and brightening the optical appearance of surfaces.
They enhance aesthetics, improve material longevity and give better light reflectivity, instantly becoming the favourite finishing touch of the public & manufacturers alike.
How They Work
Actually, brighteners are brilliant absorbers and emitters of the photon particles of light. Scientists have successfully incorporated fluorescence chemistry to formulate these optical finishing agents (know more about finishing agents).
As one of the large-scale chemical manufacturers in India, we can vouch for these organic wonders – they never fail to amaze us during lab research. They create the perfect optical phenomenon with their ability to absorb the invisible ultra-violet spectrum of light and emit blue/bluish-white rays in the visible spectrum.
OBAs eliminate the yellow pigment of the surface and, in a way, maintain the brightness of textiles, upholstery and papers. Textile and paper manufacturers use these materials and laundry detergents to enhance their products’ functionality and visual appeal.
Types of Optical Brighteners
The chemical industry is always polarised over the premium optical brightener uses and which class of OBAs to choose for the best results. So here we are, giving a clear idea of the types of fluorescent whitening agents; let’s see if the following table does justice to all the types of brightening chemicals that exist.
| OBA Groups | Textile Industry | Plastic Industry | Detergent Industry | Paper Industry | Paint Industry |
| Stilbenes | ✔ | ✔ | ✔ | ✔ | |
| Coumarins | ✔ | ✔ | |||
| Triazoles | ✔ | ✔ | ✔ | ||
| Pyrazolines | ✔ | ✔ | |||
| Benzimidazolones | ✔ | ✔ |
A common misconception occurs when people mistake bleaches with brighteners. Agreed, both impart a similar whitening finish upon acting on fabrics, but from the textile industry’s POV, these two chemicals are fundamentally and functionally poles apart. Hopefully, this comparative study helps segregate the two categories of textile chemicals, focusing on their similarities and dissimilarities.
| Parameters | Bleaches | Optical Brighteners |
| Functional Group | The functional group is either Hypochlorite or Peroxide. | The functional group is always the Sulphonic. |
| Mechanism | Bleaches always work on the principle of rapid oxidation. | Brighteners absorb UV light and then emit bluish white visible light rays. |
| Purpose | Generally used to remove tough stains or to wash out ink spillage during fabric dyeing. | Generally used to enhance appearance of surfaces like textiles, upholsteries, papers, & also giving a brighter finish to paints & detergents. |
| Dermatological POV | Laundry and surface bleach are dermatologically unsafe and always come with health hazard warning. | These brighteners can be strong or mild, depending upon their formulation/concentration, but never exhibit corrosive effect on skin. |
Environmental Impact
One of the potential and persistent challenges faced with these brightening chemicals is their inability to readily and organically decompose into nature. An alarming aspect of these chemicals is an issue that scientists and eco-activists are constantly working on. Studies have shown that OBAs can enter aquatic ecosystems through wastewater discharge, where they may not fully degrade and can be detected in surface waters.
“Most OBAs are not readily biodegradable, so chemicals remain in wastewater for long periods of time, negatively affecting water quality and animal and plant life. It is assumed that the substances accumulate in sediment or sludge, leading to high concentrations.” – says Dr Ruma Chakrabarti, Business Head India, Centexbel in her article THE CHEMISTRY OF OPTICAL BRIGTENING AGENT AND ITS ENVIRONMENTAL IMPACT
The concentration of certain fluorescent whitening agents in wastewater influents can be 10 µg/l, 20 times lower than the predicted no-effect concentration (PNEC). Hence, we are re-evaluating the OBA formula and implementing stricter regulations on their release into the environment.
Eco-Friendly Alternatives to Conventional Brighteners
Growing environmental hazards and stricter regulations to align industrial practices with the international Sustainable Development Goals have inspired chemical manufacturers to develop innovative, greener solutions that eliminate the non-bio aspects of these chemicals, turning them into much safer solutions. Take a look below at the list of optical brighteners made to diminish the harmful eco-impact of the traditional OBAs.
Tinopal CBS-X – A stilbene-based brightener with lower environmental impact. Used nowadays in laundry detergents for the safer and cost-effective formula.
Leucophor AP – A formaldehyde-free brightener, known for its mild nature and excellent finish. Trusted by the paper & textile manufacturers for efficient biodegradability.
Blankophor BBH – A trusted name in sustainable textile processing. Delivers superior finish in amphoteric or acidic conditions, with low aquatic toxicity index.
Uvitex OB – The latest innovation in the OBA industry, popular for its high photo-stability and minimum chemical runoff in coatings & plastic manufacturing.
FAQs
- Q. Are optical brighteners harmful to human health?
- A. Most conventional OBAs, such as stilbene and benzoxazole-based compounds, are considered low in acute toxicity. However, prolonged exposure may cause mild allergic reactions or skin sensitivity in some individuals.
- Q. Do brighteners contribute to environmental pollution?
- A. Brighteners can contribute to environmental pollution, primarily through wastewater discharge after coming in contact with sunlight. EPA and EU REACH have imposed limits on specific OBAs to mitigate their environmental impact.
- Q. Can brighteners be completely removed from water sources?
- A. Traditional wastewater treatment methods, such as filtration and sedimentation, are often ineffective. However, advanced treatment technologies like activated carbon adsorption, ozonation, and advanced oxidation processes (AOPs) using UV/H₂O₂ or Fenton reactions have shown promising results in degrading OBAs and their by-products.
- Q. Are there natural alternatives to synthetic brighteners?
- A. Bio-based whitening agents derived from renewable sources, such as lignin derivatives, flavonoids, and certain enzymes, offer sustainable solutions. Laccase enzymes, derived from fungi, can break down dulling impurities in textiles, offering a whitening effect without synthetic chemicals.
- Q. Why do some detergents claim to be “brightener-free”?
- A. Detergents labelled “brightener-free” cater to consumers looking for gentler, eco-friendly, and hypoallergenic cleaning solutions. Brightener-free detergents are favoured for washing baby clothes, military uniforms, and hunting gear, where fluorescence could be undesirable.