Author: Reynaldo M. Rosa Neto

Dedication: “To all those who try to take away dreams: as long as there is life, there will be willpower; and as long as there is willpower, a dream will never die.”

Introduction

This is the initial study on water treatment with phenolic compounds from red Aroeira (Schinus terebinthifolius) for expansion, including detailed analyses, quantitative calculations, and recommendations for future cultivation. The sample, collected in Campos dos Goytacazes, RJ, exhibits high acidity (pH 2.7) and significant metal concentrations, making it limited for safe use without treatment. This is a primary or original study addressing issues such as ionic balance, treatment efficacy, and method sustainability, comparing it with alternative treatments like limestone and aluminum sulfate combined with lime, and including a comparison with other studies on natural coagulants, although there are no specific studies on Schinus terebinthifolius extract in water treatment.

Methodology

Extraction of Phenolic Compounds

The extraction was performed using 100 g of red Aroeira bark in 4 L of water, subjected to pressurized hot water extraction, an efficient method for extracting bioactive compounds (Pressurized Hot Water Extraction of Bioactives). After extraction, 10 mL of the extract were added to 1 L of the sample, along with 1 g of sodium bicarbonate (NaHCO₃) as an alkalizing agent.

Chemical Calculations

• Tannin Concentration: Assuming 15% w/w tannins in the bark (Phytochemical Analysis of Schinus terebinthifolius Bark), 100 g of bark contains 15 g of tannins in 4 L, or 3.75 g/L. When adding 10 mL to 1 L, the final concentration is approximately 37.5 mg/L, comparable to iron (13.52 mg/L) and manganese (14.62 mg/L) concentrations.
• Neutralization with NaHCO₃: 1 g/L of NaHCO₃ equates to approximately 0.012 M. With an initial [H⁺] of 0.002 M (pH 2.7), the excess NaHCO₃ (0.01 M) should raise the pH, but the high acidity and presence of sulfate may limit this effect.

Sample Context and Data

The INT 1 sample, collected from a ceramic waste lagoon in the Mineiros region, Campos dos Goytacazes, RJ, presents the following initial chemical characteristics:

• pH: 2.7 (extremely acidic)
• Electrical Conductivity (EC): 7.561 dS/m, corrected to 7.561 mS/cm (7,561 μS/cm)
• Chemical Composition (in mg/L):
  • Sodium (Na): 21.35
  • Calcium (Ca): 21.63
  • Magnesium (Mg): 25.20
  • Sulfate (SO₄²⁻): 1,980.00
  • Iron (Fe): 13.52
  • Manganese (Mn): 14.62
  • Chloride (Cl⁻): 878.75
  • Total Solids: 4,128.00
  • SAR: 4.41
  • Carbonates (CO₃) and Bicarbonates (HCO₃): 0.00 (absence of alkalinity)

Results

Initial Reaction

Upon adding the extract and bicarbonate, the water instantly changed from translucent to black.

After 24 Hours

The formation of a precipitate (sludge) was observed, indicating coagulation and metal removal.

Post-Treatment Analytical Data

• pH: 6.9
• EC: 7.21 dS/m
• Calcium (Ca): 108.93 mg/L
• Magnesium (Mg): 261.08 mg/L
• Sulfate (SO₄²⁻): 1,240.00 mg/L
• Iron (Fe): 0.05 mg/L
• Manganese (Mn): 8.37 mg/L
• Chloride (Cl⁻): 420.00 mg/L
• Bicarbonate (HCO₃): 137.25 mg/L
• SAR: Approximately 20 (calculated based on Na, Ca, and Mg)

Percentage Reduction

• Iron (Fe): (13.52 – 0.05) / 13.52 × 100 = 99.63%
• Manganese (Mn): (14.62 – 8.37) / 14.62 × 100 = 42.75%
• Sulfate (SO₄²⁻): (1,980.00 – 1,240.00) / 1,980.00 × 100 = 37.37%
• Chloride (Cl⁻): (878.75 – 420.00) / 878.75 × 100 = 52.21%

Discussion

Immediate Color Change

The black coloration suggests a rapid reaction between the tannins in the extract and iron, forming dark complexes (Analysis of Iron Complexes of Tannic Acid). With 13.52 mg/L of iron, these insoluble complexes are likely responsible. Bicarbonate was added to raise the pH, but the initial acidity (pH 2.7) and sulfate may have limited initial efficacy.

Precipitation After 24 Hours

The sludge formation may be attributed to the oxidation of ferrous iron (Fe²⁺) to ferric iron (Fe³⁺), forming Fe(OH)₃, which precipitates (Redox Transformations of Iron at Extremely Low pH). Bicarbonate may have gradually neutralized the acidity, facilitating the precipitation of heavy metals like iron and manganese. Phenolic compounds may have catalyzed or stabilized this process.

Efficacy of Phenolic Compounds

Tannins demonstrated potential as natural coagulants, removing iron and possibly other metals through complex formation and precipitation. Compared to synthetic coagulants like aluminum sulfate (Al₂(SO₄)₃) or ferric chloride (FeCl₃), phenolics offer a sustainable alternative, especially using commercial waste (Residues from the Brazilian Pepper Tree Processing Industry).

Sludge Toxicity

The formed sludge contains iron, manganese, and possibly other metals. Toxicity depends on concentration and bioavailability, but phenolics may reduce solubility, potentially making it less toxic than synthetic coagulant residues. Tests like the TCLP Test for Sludge Toxicity are needed.

Observed Ionic Imbalance

There was an ionic imbalance, with positive charge (listed cations, including estimated H⁺) lower than negative charge (anions like Cl⁻ and SO₄²⁻), suggesting unlisted cations such as potassium or ammonium. The EC, initially reported as 7.561 dS/m, was adjusted to 7.561 mS/cm, but the imbalance persists.

Comparison with Other Studies

Although there are no specific studies on the use of Schinus terebinthifolius as a coagulant in water treatment, the literature on natural coagulants provides useful insights. A relevant study is “Study of the effect of Eucalyptus globulus lignin and Schinus terebinthifolius tannin extract on water in oil emulsions of heavy oil” (ScienceDirect), which investigates the use of Schinus terebinthifolius tannins as an emulsifier in water-in-oil emulsions. While not directly applicable to water treatment, it suggests that tannins have particle stabilization properties similar to the coagulation mechanism.

General reviews on natural coagulants, such as “Application of Natural Coagulants in Water Treatment: A Sustainable Alternative to Chemicals” (MDPI), highlight that tannin-rich natural coagulants are effective in removing turbidity, heavy metals, and other contaminants. These studies emphasize sustainability but note limitations, such as the need for dosage optimization and variation in efficacy depending on the source and extraction method.

Conclusions and Recommendations

The treatment combining Schinus terebinthifolius extract and sodium bicarbonate proved highly effective in removing iron (99.63%) and moderately effective in reducing manganese (42.75%). Although specific studies on this extract as a coagulant in water treatment are scarce, its tannin content supports its coagulant properties. However, the addition of sodium bicarbonate introduces sodium into the water, which may be undesirable for certain applications.

To enhance efficacy without increasing sodium levels, alternative alkalizing agents such as calcium hydroxide (Ca(OH)₂) or magnesium hydroxide (Mg(OH)₂) could be explored. Future research should focus on optimizing treatment processes, adjusting extract dosages, and testing combinations with other natural or synthetic coagulants to maximize contaminant removal and minimize side effects.

Antimicrobial Properties and Reduction of Chlorine Use

The Schinus terebinthifolius extract exhibits significant antimicrobial properties, with activity against bacteria (Escherichia coli, Salmonella enteritidis), fungi (Candida albicans), and viruses (Mayaro virus, MAYV), as documented in Antimicrobial Lectin from Schinus terebinthifolius Leaf (PubMed). This suggests potential for reducing reliance on chlorine in water disinfection, avoiding harmful byproducts like Trihalomethanes, per WHO Guidelines for Drinking Water Quality. Studies like Safe Water and Technology Initiative for Water Disinfection: Application of Natural Plant-Derived Materials (ScienceDirect) indicate that natural extracts can achieve up to 96% disinfection, though large-scale implementation requires further validation.

Methodology and Sources

Data were compiled from peer-reviewed studies on platforms like PubMed, ScienceDirect, and SciELO, covering in vitro, in vivo, and clinical applications of S. terebinthifolius extract. These include minimum inhibitory concentration (MIC) assays to quantify antimicrobial efficacy.

Antibacterial Properties

The extract shows broad-spectrum antibacterial activity against gram-positive and gram-negative pathogens. Key findings are summarized below:

Antifungal Properties

The extract’s antifungal activity was tested against various pathogens:

Antiviral Properties

Although less explored, antiviral activity has been documented:

Chemical Composition and Mechanisms

Antimicrobial effects stem from compounds like tannins, terpenoids, and essential oils (e.g., α-pinene, β-pinene, limonene), as described in SciELO (bNdsZSp6jMDqM6qVXxCHGgL). Tannins complex metals and exhibit antioxidant properties, while terpenoids disrupt microbial membranes, offering a chlorine-free disinfection mechanism.

Potential to Reduce Chlorine Use

Chlorine, while effective, produces carcinogenic byproducts like trihalomethanes (WHO Guidelines for Drinking Water Quality). The S. terebinthifolius extract, with its broad antimicrobial activity, presents a natural alternative. Studies like ScienceDirect (S146685641630114X) demonstrate microbial reduction in controlled settings (e.g., cheese), suggesting water treatment applications. Its efficacy against pathogens like E. coli and Listeria supports its use as a chlorine substitute, especially in chemically sensitive systems.

Key Citations

• Antimicrobial Lectin from Schinus terebinthifolius Leaf
• Schinus terebinthifolius: Phenolic Constituents and In Vitro Antioxidant, Antiproliferative and In Vivo Anti-inflammatory Activities
• Schinus terebinthifolius Raddi: Chemical Composition, Biological Properties and Toxicity
• Antibacterial Activity of Extracted Bioactive Molecules of Schinus terebinthifolius Ripened Fruits Against Some Pathogenic Bacteria
• Schinus terebinthifolius Raddi (Brazilian Pepper) Leaves Extract: In Vitro and In Vivo Evidence of Anti-inflammatory and Antioxidant Properties
• Antimicrobial and Antioxidant Activity of Essential Oil from Pink Pepper Tree In Vitro and In Cheese
• Schinus terebinthifolius (Brazilian Peppertree) Extract Used as Antifungal to Control Candida spp. in Planktonic Cultures and Biofilms
• Chemical Composition and Anti-Mayaro Virus Activity of Schinus terebinthifolius Fruits
• In Vitro Activity of Schinus terebinthifolius Extract and Fractions Against Sporothrix