What FFA level can WCO have before bleaching becomes ineffective?

Bleach Master can handle WCO with FFA up to 10–15% without significant reduction in bleaching performance, since FFA does not directly compete with colour pigments for adsorption sites. However, very high FFA content (>15%) can require higher dosage because FFA degradation products (dimers, trimers) have some affinity for clay sites. For WCO above 15% FFA, pre-neutralisation or direct use of alkali catalyst in transesterification (two-step acid-alkali process) is often more economical than clay treatment alone.

Can Bleach Master handle both food-grade and industrial oil applications?

Yes. Bleach Master is used for both edible oil refining (food-grade applications) and industrial oil treatments (engine oil re-refining, paraffin wax, transformer oil). The same product specification works effectively across both application categories. However, filter equipment and handling systems should be dedicated to either food or industrial use to prevent cross-contamination where food safety requirements apply.

Waste Oil Regeneration Using Activated Bleaching Earth

India generates tens of millions of litres of waste cooking oil annually from restaurants, hotels, food processing plants, and institutional kitchens. Separately, millions of litres of used lubricating oil are collected from automotive service centres and industrial facilities. Both categories of waste oil represent significant resource recovery opportunities — and activated bleaching earth plays a central role in their purification. This article covers the application of Bleach Master in waste cooking oil (WCO) treatment for biodiesel production and in used engine oil regeneration for industrial reuse.

Waste Cooking Oil: Composition and Challenges

Waste cooking oil from deep-frying operations has undergone extensive thermal oxidative degradation. Its characteristic composition includes:

Very high free fatty acid content: Hydrolysis during frying at 160–190°C generates 2–8% FFA in typical WCO vs 0.05–0.1% in freshly refined cooking oil.
High colour: Maillard reaction products, caramelised sugars, and polymerised pigments from the food give WCO a dark brown to black colour. Lovibond readings of 50–100R or beyond are common.
High peroxide and oxidation products: Peroxide values of 50–200 meq/kg and high p-anisidine values indicate extensive oxidative degradation.
Polymers: High-temperature oxidative polymerisation creates high-molecular-weight polymers that increase oil viscosity and create deposit problems in downstream equipment.
Food particles and moisture: Suspended food particles and absorbed moisture from the frying medium.

WCO Bleaching for Biodiesel Feedstock Preparation

The rapidly growing biodiesel sector in India uses WCO as one of its most cost-competitive feedstocks. Before transesterification (the reaction that converts oil to biodiesel), WCO typically requires:

Settling and filtration: Remove food particles and gross contamination by gravity settling and coarse filtration
Degumming: Remove phospholipids and mucilages that would poison the transesterification catalyst
Bleaching: Remove colour, oxidation products, trace metals, and remaining polar compounds
Drying: Remove moisture before transesterification (water poisons alkali catalysts)
Transesterification: React with methanol and catalyst to produce biodiesel (FAME)

Bleach Master at 2.5–4.0% dosage is effective for WCO bleaching in biodiesel feedstock preparation. The higher dosage requirement compared to fresh edible oil reflects the much greater impurity load in WCO. Key targets for bleached WCO entering transesterification: colour below 30R, phosphorus below 20 ppm, iron below 1 ppm.

WCO Bleaching Process Conditions

WCO bleaching requires more aggressive conditions than fresh edible oil:

Temperature: 110–120°C. The higher impurity loading requires slightly higher temperature for adequate adsorption kinetics.
Vacuum: Essential for WCO due to its high moisture content and high oxidation state. Target 50–100 mbar absolute.
Contact time: 30–45 minutes, longer than for fresh oil, to allow adsorption of the high polymer content.
Pre-treatment: Adding 500–1000 ppm phosphoric or citric acid to WCO before bleaching improves phospholipid removal and helps condition the clay surface for better adsorption of polar degradation products.
Two-stage bleaching: For very dark WCO (above 80R), a two-stage approach can be more economical: first stage at 2% Bleach Master removes the bulk of colour, second stage at 1% achieves the final target, with both stages using fresh earth rather than one heavy dose.

Used Engine Oil Regeneration with Bleaching Earth

Used engine oil (also called used lubricating oil or ULO) accumulates carbon deposits, oxidised oil components, metallic wear particles, water, and fuel dilution during service. Regeneration to produce re-refined base oil typically involves:

Dehydration at 100–150°C to remove water and light fuel fractions
Vacuum distillation to remove remaining light ends and separate base oil fractions from sludge and asphalt
Clay treatment (bleaching with activated earth) to remove colour bodies, residual oxidised oil, and polar degradation products
Hydrotreatment (in some plants) or filtration to produce finished base oil

Bleach Master at 3–6% dosage is used in clay treatment of vacuum-distilled used engine oil. The high dosage reflects the intense colour (often black to dark brown) and heavy loading of polar degradation products. Process conditions: 100–120°C, 30–45 minutes contact time, atmospheric pressure (unlike edible oil, engine oil oxidation during processing is less critical).

Paraffin Wax Bleaching

Paraffin wax from petroleum refining contains colour-contributing hydrocarbons and trace aromatics that give it a yellow to brown appearance. Bleach Master is effective for paraffin wax bleaching at 1–3% dosage, 80–100°C. The lower temperature (vs edible oil) reflects the fact that paraffin wax is already a refined product with much lower impurity loading than crude oil. Target: wax colour below 10 ASTM, oil content specification compliance.

Transformer and Mineral Oil Purification

Aged transformer oil and mineral oil accumulates colour bodies, oxidised oil components, and polar contaminants that reduce dielectric strength and increase conductivity. Bleach Master can be used for re-refining of these oils, though care must be taken with dosage — excessively acidic bleaching earth can saponify additives or cause pH-sensitive problems. For transformer oil applications, ensure that the bleached oil's final colour meets applicable IEC or IS standards before returning to service. Typical dosage: 1–2% Bleach Master at 80–90°C for 20 minutes.

Frequently Asked Questions

Can activated bleaching earth remove polycyclic aromatic hydrocarbons (PAH) from waste oil?

Activated bleaching earth has limited effectiveness for PAH removal because PAHs are large, non-polar molecules with low affinity for the polar surface of acid-activated clay. Vacuum distillation (which separates PAHs in the heavy fraction) and hydrotreatment are more effective for PAH removal in re-refining applications. Bleaching earth is most effective for polar and basic contaminants rather than non-polar hydrocarbons.

Is bleaching earth from WCO treatment considered hazardous waste?

Spent bleaching earth from WCO treatment for biodiesel production is generally not classified as hazardous waste under standard Indian solid waste management rules, since the oil is food-grade origin. However, spent earth from used engine oil treatment may contain trace metals (zinc, lead, copper from lubricant additives) at levels that could require characterisation before disposal. Consult your local SPCB guidelines for specific requirements.