Water Treatment by Adsorption on Sage-Based Adsorbents: Removal of Pollutants and Phytotoxicity

Water pollution is a critical global issue that endangers ecosystems and human health. The development of eco-friendly and sustainable adsorbent materials is essential for removing various contaminants, including synthetic dyes, nitrates, phosphates, and pathogenic microorganisms from water sources. In this study, we explored the adsorption efficiency and phytotoxicity of three bioadsorbents derived from Salvia officinalis (sage): (1) untreated sage powder (S), (2) sage-derived biochar produced by pyrolysis at 300 °C (C), and (3) activated charcoal (AC) prepared by chemical activation with phosphoric acid followed by pyrolysis at 450 °C. The materials were tested for their capacity to remove methylene blue dye, nitrates, phosphates, and bacterial contaminants (Escherichia coli, total coliforms, and Streptococcus D) under controlled laboratory conditions. Results showed that activated charcoal (AC) had the highest removal efficiency for phosphates (0.122 mg/g, 49%) and nitrates (1.72 mg/g), along with the most significant reduction in bacterial concentrations. Interestingly, the untreated sage powder (S) displayed the greatest capacity for methylene blue adsorption (4.34 mg/g), suggesting its potential for dye-contaminated water treatment. Phytotoxicity assays using Eruca vesicaria (arugula) indicated that AC exhibited low toxicity in aqueous conditions, and both S and AC supported plant growth in solid (soil-like) media. These findings suggest that sage-derived bioadsorbents, particularly activated charcoal, offer a promising, low-cost, and sustainable solution for integrated water treatment. Their dual capacity to remove chemical and biological pollutants while maintaining low phytotoxicity makes them attractive candidates for eco-friendly environmental remediation strategies.