Neutralac®: A Liquid Lime for the Removal of Heavy Metals, Fluorides, Phosphates and Sulphates in Effluent plants
The decontamination of Industrial wastewater effluent faces increasing pressure to meet stringent environmental discharge standards and simplifying chemical treatment systems. Neutralac® SLS45, a milk of Lime developed by Lhoist, has emerged as one of the most effective Liquid lime technologies for wastewater effluent treatment plants which need PH correction, and heavy metal contaminant precipitation. Neutralac® SLS45 is a high-reactivity suspension of calcium hydroxide, for industrial effluent treatment and sludge processing. neutralisation of acidic streams while delivering calcium ions that facilitate the precipitation of fluoride, phosphate, sulphate, and heavy metals.
We examine the chemistry and applications of Neutralac® SLS45, with particular emphasis on fluoride, phosphate, and sulphate removal. The article also explains the removal of heavy metals, Zinc, Copper, Nickel, Chromium, Cadmium, & Lead which represents a major benefit.
We also include a table of comparison of Neutralac® SLS45 with two alternative treatment options; powdered hydrated lime and liquid caustic soda.
1. Introduction
Water treatment has evolved significantly over the past three decades. Traditional approaches relied heavily on powdered hydrated lime, caustic soda, sulphuric acid, and ferric salts. Although these chemicals remain effective, many users have experienced challenges associated with dust generation, handling risks, inconsistent dosing, and rising costs.
Neutralac® SLS45 is a highly reactive “Milk of Lime,” slurry containing approximately 45% solids, formulated for easy pumping, storage, and dosing with fast reaction kinetics.
Neutralac® SLS45 is used to:
- Neutralise acidic wastewater
- Control pH
- Remove heavy metals
- Precipitate fluorides
- Remove phosphates
- Reduce sulphate concentrations
Neutralac provides both hydroxide ions (OH⁻) and calcium ions (Ca²⁺), simultaneously creating a highly efficient chemical environment for contaminant removal.
2. What is Neutralac® SLS45?
Neutralac® SLS45 is a specialised milk of lime containing finely dispersed Calcium hydroxide:
Chemical Formula
𝐶𝑎(𝑂𝐻)2
Typical Characteristics
| Property | Typical Value |
|---|---|
| Active Material | Calcium Hydroxide |
| Solids Content | Approximately 45% |
| pH | Approximately 12.3 |
| Density | Approximately 1.4 kg/L |
| Reactivity | 90% conversion in under 5 seconds |
| Physical Form | Pumpable liquid suspension |
3. How Neutralac® SLS45 Works
Neutralac® SLS45 has two mechanisms of Action :
Neutralisation
When calcium hydroxide dissolves:
𝐶𝑎(𝑂𝐻)2→𝐶𝑎2++2𝑂𝐻−
The hydroxide ions react with acids present in wastewater:
𝐻++𝑂𝐻−→𝐻2𝑂
This raises pH rapidly and stabilises acidic effluent streams.
Chemical Precipitation
The liberated calcium ions react with dissolved contaminants to form insoluble compounds.
This twin approach explains why Neutralac® often replaces combinations of caustic soda and calcium chloride used in traditional treatment systems.
4. Fluoride Removal Chemistry
Why Fluoride is a Problem
Fluoride is commonly found in waste streams from:
- Semiconductor manufacturing
- Glass production
- Electronics industries
- Fertiliser production
- Pharmaceutical manufacturing
- Metal finishing operations
Even small fluoride concentrations can exceed a plants discharge limit.
Precipitation Reaction
Calcium ions supplied by Neutralac® react with dissolved fluoride:
𝐶𝑎2++2𝐹−→𝐶𝑎𝐹2
Calcium fluoride is highly insoluble.
The resulting solid particles can be separated by:
- Sedimentation
- Clarification
- Lamella separators
- Filter presses
Neutralac® SLS45 is particularly effective for fluoride removal because the reagent simultaneously provides the calcium and alkalinity required for optimised fluoride precipitation.
5. Phosphate Removal Chemistry
Environmental Importance
Phosphate discharge contributes to:
- Eutrophication
- Algae blooms
- Oxygen depletion
- Regulatory non-compliance
Industries that generate phosphate-rich wastewater include:
- Dairy processing
- Food manufacturing
- Agriculture
- Fertiliser production
- Pharmaceutical plant
Chemical Reaction
The calcium ions form insoluble calcium phosphate compounds:
3𝐶𝑎2++2𝑃𝑂43−→𝐶𝑎3(𝑃𝑂4)2
The precipitate settles readily and can be removed using standard solids separation processes.
Phosphate precipitation is one of the most common treatment functions for Neutralac® SLS45 for industrial effluent treatment plants.
6. Sulphate Reduction and Control
Sources of Sulphate
Sulphate contamination may arise from:
- Mining
- Chemical manufacture
- Pulp and paper mills
- Metal processing
- Fertiliser plants
High sulphate concentrations can:
- Increase scaling
- Affect biological treatment
- Damage infrastructure
- Cause discharge compliance issues
Sulphate Precipitation
When calcium is introduced:
𝐶𝑎2++𝑆𝑂42−→𝐶𝑎𝑆𝑂4
This forms calcium sulphate (gypsum).
While gypsum possesses some solubility, substantial sulphate reduction can be achieved when treatment systems are optimised. Neutralac improves sulphate removal from industrial effluent treatment systems.
7. Heavy Metal Removal
Although the focus of this article is fluoride, phosphate, and sulphate removal, the simultaneous removal of heavy metals represents a major benefit.
Typical heavy metals treated include:
- Zinc
- Copper
- Nickel
- Chromium
- Cadmium
- Lead
These contaminants precipitate as hydroxides at elevated pH:
𝑀𝑒2++2𝑂𝐻−→𝑀𝑒(𝑂𝐻)2
The calcium hydroxide supplied by Neutralac® creates optimum precipitation conditions for many industrial metals.
8. Application in Agricultural Industries
Fertiliser Production
Fertiliser manufacturing often produces acidic waste streams containing:
- Phosphates
- Fluorides
- Sulphates
Neutralac® SLS45 provides:
- pH correction
- Fluoride precipitation
- Phosphate removal
- Reduced operating cost
The calcium supplied is already compatible with agricultural nutrient systems, simplifying sludge management.
Biological and Anaerobic Digestion
Agricultural waste treatment facilities use lime products for:
- Odour control
- Digester optimisation
- Pathogen reduction
Higher operating pH improves digestion performance while reducing odour generation in biological sludge systems.
Irrigation Water Treatment
In some agricultural regions groundwater and recycled water contain elevated fluoride or phosphate levels.
Neutralac® SLS45 can be integrated into:
- Clarification systems
- Dissolved air flotation units
- Settlement lagoons
The result is better water quality for irrigation and reduced risk of soil contamination.
9. Comparison with Competitive Technologies
Neutralac® SLS45 vs Powdered Lime vs Caustic Soda
| Parameter | Neutralac® SLS45 | Powdered Hydrated Lime | Liquid Caustic Soda (NaOH) |
|---|---|---|---|
| Physical Form | Pumpable liquid slurry | Dry powder | Liquid |
| Active Component | Ca(OH)₂ | Ca(OH)₂ | NaOH |
| Neutralisation Capacity | Excellent | Excellent | Excellent |
| Fluoride Removal | Excellent | Excellent but slower handling | Poor without additional calcium |
| Phosphate Removal | Excellent | Excellent | Limited |
| Sulphate Precipitation | Excellent | Excellent | No calcium provided |
| Heavy Metal Removal | Excellent | Excellent | Good pH control only |
| Dust Generation | None | High | None |
| Safety | Moderate hazard | Dust inhalation risk | Highly corrosive |
| Storage Simplicity | High | Moderate | High |
| Equipment Wear | Low | Moderate | Moderate |
| Reaction Speed | Very fast | Moderate | Very fast |
| Chemical Handling | Easy | Labour intensive | Easy |
| Need for Calcium Source | No | No | Usually yes |
| Overall Wastewater Performance | Outstanding | Good | Limited for precipitation processes |
10. Environmental Impact
Environmental regulations worldwide continue to tighten.
Neutralac® SLS45 contributes to compliance by:
- Reducing fluoride concentrations
- Removing phosphorus compounds
- Lowering dissolved metals
- Stabilising pH
- Improving sludge treatment
The product is described by Lhoist as a safe and environmentally friendly neutralising reagent specifically designed for wastewater and sludge treatment.
11. Future Opportunities
Several trends favour increased adoption of Neutralac® technologies.
These include:
- Stricter phosphorus discharge limits
- Growth in semiconductor manufacturing
- Expansion of pharmaceutical production
- Increased water recycling
- Greater emphasis on industrial sustainability
The ability of a single reagent to neutralise wastewater while simultaneously removing fluoride, phosphate, sulphate and heavy metals provides significant process advantages.
In Conclusion
Neutralac® a high-reactivity liquid Calcium hydroxide suspension, combines the neutralisation capability of hydroxide ions with the heavy metal contaminant-removal power of calcium ions. This dual-action mechanism enables efficient precipitation of fluorides, phosphates, sulphates and heavy metals while maintaining stable process ph.
Compared with powdered lime, Neutralac® has much faster reaction rates. Compared with caustic soda, it has the critical calcium ion required for heavy metal precipitation reactions and this often eliminates the need for supplementary chemicals.
A single product that simplifies treatment systems while improving heavy metal contaminant removal will continue to gain in importance. Neutralac® will become the effluent industries most effective solution for pH control, fluoride removal, phosphate precipitation, sulphate reduction and heavy metal contamination management.
