Adsorption of Pb (II) ions on variable charge oxidic calcined substrates with chemically modified surface.

Background: The paper describes lead ion adsorption on variable charge oxidic calcined substrates with chemically modified surfaces. Amphoteric oxides of iron, aluminum, titanium, and manganese, change their surface electric charge after acid or alkaline treatment, letting cationic or anionic adsorption reactions from aqueous solutions. This property allows using them as adsorbing substrate for heavy metals retention in water treatment systems. Methods: Substrate was prepared by extruding cylindrical strips from a saturate paste of the oxidic lithological material-OLM; dries it up and thermally treated by calcination. The study was performed by triplicated trial, on batch mode, using 2 grams samples of treated with NaOH 0.1N and non-treated substrate. Lead analysis was performed by AAS-GF. Freundlich and Langmuir models were used to fit results. Comparing differential behavior between treated and non-treated substrates showed the variable charge nature of the OLM. Results: Results show L-type isotherms for the adsorption of Pb(II) ions on the activated substrate, suggesting good affinity between Pb(II) ions and OLM's surface. Average value of adsorption capacity ( K) for activated substrate (1791.73±13.06), is around four times greater than the non-activated substrate (491.54±31.97), during the adsorption reaction, 0.35 and 0.26 mmolH + of proton are produced on the activated and non-activated substrate respectively using a 1 mM Pb(II) solution and 72.2 and 15.6 mmolH + using a 10 mM Pb(II) solution. This acidification agrees with the theoretic model of transitional metals chemisorption on amphoteric oxides, present in lithological material used for the preparation of adsorbent substrates, confirming the information given by the L-type isotherms. Conclusions: Results suggest that these variable charge oxidic adsorbent substrate show great potential as an alternative technique for water treatment at small and medium scale using granular filtration system. The easiness and low price make them suitable to apply in rural media where no treating water systems is available.

Field study of parasitic contamination of fruits, vegetables and leafy greens in the Ecuadorian Andes.

Background: Raw vegetables have been considered vehicles of enteroparasites. South American countries are among the most important exporters of fresh vegetables, including Ecuador, which has a tropical climate and soils rich in organic matter that allow it to harvest throughout the year for sale to different countries. The aim of the study was to assess the occurrence of the parasitic contamination of fruits, vegetables and leafy greens grown in an agricultural area of the Ecuadorian Andes. Methods: A cross-sectional field study was conducted with snowball sampling on 1,416 samples (516 fruits, 488 vegetables, and 412 leafy greens). Each sample were washed with water, and the resulting solution after removing the vegetables, was subjected to 24-hour sedimentation. The concentrated sediment underwent microscopic analysis. Results: The overall positivity for parasitic contamination was 63.4%, with leafy greens having the highest contamination rate (76.9%) (P<0.0001), surpassing vegetables (67.8%) and fruits (48.4%). Cabbage (100%), onions (84%), and strawberries (60.2%) emerged as the most contaminated within their respective groups. Protozoa were more prevalent (49.6%) than helminths (15.5%) (P<0.0001). Blastocystis sp. (33.5%) ranked highest, followed by Eimeria spp. (26.3%), Entamoeba spp. (10.3%), Giardia spp. (8.3%), Balantidium spp. (6.9%), Cryptosporidium spp. (6.6%), Cyclospora spp. (4.4%), Cystoisospora spp. (0.5%), Strongylida (15.5%), and Ascaris spp. (0.4%). Conclusions: The study reveals that vegetables and fruits for human consumption from this area of the Ecuadorian Andes are highly contaminated with various parasites, constituting a possible source of infection for humans and animals in this area, or in non-endemic areas where these products are marketed. The finding emphasizes the need for strict hygienic measures in agricultural crops, which will be properly achieved through the treatment of soil, manure and water used for cultivation.