Aloe Vera as a Natural Coagulant for Nitrate Removal from Textile Wastewater

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Access to clean water remains a critical global challenge, particularly in regions where industrial activities like textile manufacturing contribute to water pollution.

A 2025 study published in Results in Chemistry offers a groundbreaking solution: using Aloe vera, a common succulent plant, as a natural coagulant to remove nitrate pollutants from textile wastewater.

By optimizing key treatment parameters, the researchers achieved 97% nitrate removal efficiency, surpassing conventional methods.

The Problem with Nitrates and Traditional Coagulants

Textile wastewater is notoriously difficult to treat due to its high concentration of nitrates, dyes, and organic compounds. Nitrates, in particular, pose severe health and environmental risks.

For instance, nitrate levels above 3.48 mg/L (the WHO safety limit) can cause methemoglobinemia in infants and contribute to algal blooms that suffocate aquatic life.

The wastewater tested in this study had an initial nitrate concentration of 1.26 mg/L, along with turbidity (17.1 NTU) and acidic pH (4.4), all of which exceed safe thresholds. Traditional coagulants like alum are widely used but come with drawbacks.

For every kilogram of pollutants removed, alum generates 2.5–3.0 kg of toxic sludge, which is expensive to dispose of and harmful to ecosystems.

Moreover, alum residues have been linked to neurological disorders like Alzheimer’s disease. These challenges have driven scientists to explore eco-friendly alternatives, and Aloe vera has emerged as a promising candidate due to its natural abundance and non-toxic properties.

Aloe Vera’s Secret: Proteins and Functional Groups

Aloe vera’s effectiveness as a coagulant lies in its biochemical composition. The plant contains cationic proteins (positively charged molecules) and functional groups like hydroxyl (-OH) and carboxyl (-COOH), which bind to negatively charged pollutants in wastewater.

During the study, Aloe vera powder was prepared by drying and grinding the plant’s leaves.

Proximate analysis revealed that the powder contained 32.11% protein before use and 28.65% protein after treatment. This reduction confirmed that proteins played a key role in adsorbing nitrates.

Advanced imaging techniques provided further insights. Scanning Electron Microscopy (SEM) showed that raw Aloe vera has a porous, irregular surface, ideal for trapping contaminants.

After treatment, the SEM images revealed dense clusters of nitrate particles stuck to the plant material.

Fourier-transform infrared spectroscopy (FTIR) identified functional groups responsible for coagulation, including peaks at 3005–3761 cm⁻¹ (indicating hydroxyl groups) and 2376 cm⁻¹ (linked to methyl groups).

These findings underscore Aloe vera’s natural ability to act as a molecular “glue” for pollutants.

Optimizing the Process with Advanced Statistics

To maximize nitrate removal, the researchers used Response Surface Methodology (RSM), a statistical tool that analyzes how multiple variables interact.

Four factors were tested: agitation time (20–40 minutes), settling time (60–120 minutes), Aloe vera dosage (0.5–1.5 g/L), and agitation speed (150–250 rpm).

Over 30 experimental runs, the team discovered that shorter agitation periods, lower doses of Aloe vera, and gentle mixing yielded the best results. The optimal conditions were determined to be:

20 minutes of agitation, 120 minutes of settling, 0.5 g/L of Aloe vera, 150 rpm agitation speed. Under these settings, 97% of nitrates were removed from the wastewater.

Statistical validation using ANOVA confirmed the model’s reliability, with an R² value of 0.9252 (indicating that 92.5% of the variability in results was explained by the model) and a p-value <0.0001 (proving statistical significance).

Why Lower Dosages and Gentle Mixing Work Best

A surprising finding was that smaller amounts of Aloe vera (0.5 g/L) outperformed higher doses. Excess coagulant caused “over-coagulation,” where particles repelled each other instead of clumping together, reducing efficiency to 87% at 1.5 g/L.

Similarly, gentle agitation (150 rpm) allowed flocs to grow without breaking apart, whereas faster speeds (250 rpm) created turbulence that disrupted aggregation, lowering efficiency to 80%.

Settling time also played a critical role. Allowing flocs to settle for 120 minutes ensured complete precipitation, while shorter durations (60 minutes) left particles suspended, cutting efficiency to 84%.

These insights highlight the importance of balancing variables to achieve optimal results.

Aloe Vera vs. Other Coagulants: A Clear Winner

When compared to alternatives, Aloe vera stood out for its efficiency and sustainability. For example:

Papaya seeds achieve 96.19% turbidity removal but require higher doses. Moringa oleifera and okra mixtures remove 87.2% of turbidity but struggle with nitrates. Alum achieves 90–95% nitrate removal but generates toxic sludge.

Aloe vera not only matched alum’s performance (97% nitrate removal) but also eliminated the need for hazardous chemicals. Additionally, the “press cake” (used Aloe vera residue) retained 28.65% protein content, suggesting it could be reused or composted, further reducing waste.

Economic and Environmental Benefits

Switching to Aloe vera offers significant cost savings. Cultivating the plant costs 0.50–1.00 per kilogram, compared to 2.50–3.00 per kilogram for alum.

Factories could also cut sludge disposal costs, as Aloe vera residues are biodegradable. Environmentally, this method aligns with global sustainability goals by preventing toxic byproducts and reducing reliance on synthetic chemicals.

Challenges and the Path Forward

Despite its promise, scaling up Aloe vera-based treatment requires addressing practical challenges. For instance, large-scale cultivation is needed to meet industrial demand, and variations in plant composition due to soil or climate must be standardized.

The researchers recommend pilot trials in textile factories to test real-world feasibility and explore hybrid systems combining Aloe vera with other natural coagulants like Moringa seeds for enhanced performance.

Conclusion: A Greener Future for Water Treatment

This study demonstrates that Aloe vera is far more than a household remedy—it is a powerful tool for sustainable water treatment.

By leveraging its natural proteins and optimizing treatment conditions, industries can achieve high pollutant removal without harming the environment.

As the world grapples with water scarcity and pollution, solutions like this remind us that nature often holds the key to solving human-made problems. With further research and investment, Aloe vera could revolutionize wastewater management, ensuring cleaner water for generations to come.