Low concentrations of fluoride (F⁻) in drinking water are beneficial for oral health, but the natural occurrence of high F⁻ content has been reported in various groundwater sources, posing a continuous ingestion threat to humans. The utilization of biochar (BC) produced from residual biomass has emerged as a technically, economically, and environmentally sustainable alternative for fluoride removal through adsorption. Therefore, this study aimed to investigate the physicochemical characteristics of BC derived from coffee grounds and the influence of various factors on the adsorption process of F⁻ in aqueous media, including pH, adsorbent dosage, contact time, temperature, and initial F⁻ concentration. The BC exhibited a surface area of 12.94 m²·g⁻¹ and a pore volume of 0.0349 cm³·g⁻¹. The adsorption process was strongly pH dependent, demonstrating a significant decline in performance as pH increased from 2.0 onwards. The majority of F⁻ removal occurred within the first 5 min, reaching adsorption equilibrium after 1 h of testing, regardless of the initial F⁻ concentration employed. The data fitting to the Webber–Morris model indicated a two-step adsorption process on BC, with the first step being external surface sorption and the second step being intra-articular diffusion. The process was determined to be endergonic, and the data satisfactorily matched both the Freundlich and Langmuir models, with a q_m of 0.53 mg·L⁻¹ (T = 55 °C), indicating the predominance of physisorption. The findings suggest the potential of coffee grounds for BC production; nevertheless, surface structure modifications are necessary to enhance F⁻ affinity and subsequently improve adsorption capacity.

Purpose: The purpose of this study was to apply electrocoagulation with aluminum electrodes to evaluate the removal efficiency of microplastic in the form of Glitter. Method: This study consisted of an experimental system, composed of a benchtop scale reactor, with aluminum electrodes inside, connected to a direct current source, responsible for performing the water electrolysis process, forming microbubbles and the chemical coagulation process, contributing to the formation of microplastic aggregates Results and conclusion: The results showed high efficiency of microplastic removal in the form of glitter that increased proportionally with the increase in conductivity and current intensity. The maximum efficiency achieved was equal to 90.3%. Implications of the research: As demonstrated by the results of the experimental assays, the electrocoagulation technique proved to be very efficient to make the removal of microplastic in the form of glitter. Originality/value: It has been shown that it is possible to remove microplastic in an efficient way, without the need for the introduction of an external coagulant because it was generated within the system itself.

The adsorption of atrazine (ATZ) onto pristine and aged polyethylene microplastics (MPs) was investigated in distilled water (DW) and hydroponic nutrient-enriched water (EW) to evaluate its phytotoxic effects on Lactuca sativa germination. Aged microplastics (AMPs) exhibited higher ATZ adsorption in both conditions: 0.646 mg/g (14.49%) in DW and 0.742 mg/g (15.87%) in EW, compared to 0.405 mg/g (9.08%) and 0.504 mg/g (10.78%) for pristine microplastics (PMPs), respectively. This increase was attributed to photodegradation-induced surface modifications on MP, including increased roughness and the formation of oxygenated functional groups. The phytotoxicity assays showed that ATZ adsorbed onto AMPs inhibited seed germination more severely, with a maximum inhibition of 34% at 2 mg/L, evidencing that microplastic aging enhances ATZ adsorption and increases toxicity risks in aquatic environments, particularly under eutrophic conditions. The combined presence of MP and ATZ resulted in greater toxicity, attributed to a synergistic effect, as observed in dry and wet mass inhibition. These findings indicate that pollutant interactions amplify negative impacts on plant development. Furthermore, ATZ primarily affects root growth through direct physical contact with MP rather than via desorption into water.

Microplastics are emerging pollutants, formed through weathering, with sizes equal to or smaller than 5 mm. They can reach surface and groundwater sources, as well as oceans and seas through natural pathways or from the discharge of liquid effluents, causing immeasurable effects on human beings....