In this work, we synthesized iron-oxide nanoparticles (NPsFeO) via a green synthesis method, using Moringa oleifera leaf extract, and evaluated its fluoride ion adsorption potential, comparing its efficiency with a commercially available adsorbent (activated carbon of bone [BGAC]). The adsorbent materials were characterized using X-ray diffraction, transmission, and scanning electronic microscopy, X-ray dispersive energy spectrometry, and N2 adsorption/desorption. The results showed that the maximum adsorption occurred in pH 7 for NPsFeO and pH 5 for the BGAC. Adsorption kinetic tests showed that the equilibrium was reached in 40 min for the NPsFeO, and 90 min for BGAC, with adsorption potential of 1.40 and 1.20 mg g, respectively. The model that best described the kinetic data was pseudo-first-order for NPsFeO and pseudo-second-order for BGAC. The Langmuir isotherm had a better fit for both adsorbents. The thermodynamic parameters indicated spontaneous and endothermic adsorption at 30°C, 40°C, and 50°C for BGAC, and at 30°C for NPsFeO. The regeneration process showed that it is possible to reuse NPsFeO three times in the fluoride ion adsorption process. As a result of its adsorption capabilities and the shortest contact time to achieve equilibrium, the NPsFeO is a highly promising material for fluoride ion removal.

Resumo -O processo de tratamento para produção de água potável gera resíduos em algumas etapas do processo de tratamento principalmente no decantador (lodo). Este lodo é formado durante o processo de coagulação/floculação, com o auxílio de coagulantes químicos (PAC-Policloreto de Alumínio) ou naturais (Moringa oleifera) que vêm sendo investigados intensamente. Pela ABNT NBR 10.004 este lodo é classificado como "resíduo sólido", portanto deve ser tratado e disposto conforme exigência dos órgãos reguladores. O objetivo deste trabalho foi classificar o lodo formado, no processo de coagulação/floculação, utilizando PAC e Moringa como coagulantes de acordo com o conjunto de normas ABNT NBR 10.004 ("Resíduos sólidos -Classificação"), ABNT NBR 10.005 (Procedimentos para obtenção de extrato lixiviado de resíduos sólidos") e ABNT NBR 10.006 ("Procedimentos para obtenção de extrato solubilizado de resíduos sólidos") segundo a análise de metais dos extratos lixiviado e solubilizado dos lodos. Os ensaios de lixiviação e solubilização dos lodos indicam que os lodos de PAC e Moringa são classificados como resíduos CLASSE II A, Não perigoso -Não inerte. Mesmo com o uso de um coagulante natural, o lodo pode possuir uma alta concentração de metais pesados em sua composição, pois estes possivelmente são oriundos da água bruta utilizada no tratamento. Portanto os lodos devem ser dispostos de modo adequado, de forma a não causar danos ao meio ambiente e aos seres humanos. Palavras-chave:Lodo, coagulante natural, classificação, resíduos sólidos.Abstract -The drinking-water treatment plants, generally, generates waste in some stages of the treatment, mainly in the settling vessel (sludge). This sludge is formed during the coagulation/flocculation stage, with aid of chemical coagulants (PAC -Poly Aluminium Chloride) or natural (Moringa oleifera) that currently are being intensively researched. According to ABNT NBR 10004 this sludge is classified as "solid waste" and therefore must be previously classified in order to be disposed of adequately. The classification of the sludge formed in coagulation/flocculation process, using PAC and Moringa as coagulant, is investigated. This was done according to the set of regulations ABNT NBR 10004 ("Solid Waste -Classification"), ABNT NBR 10005 ("Procedures for obtaining leached extract of solid waste") and ABNT NBR 10006 (2004) ("Procedures for obtaining soluble extract of solid waste") based on metals analysis of sludge leached and solubilized extract. The sludge leaching and solubilization tests indicate that PAC and Moringa sludge are classified as Class II A, non-hazardous and non-inert waste. Even with the use of a natural coagulant, the sludge can have a high concentration of heavy metals in its composition, as these are, probably, from raw water used in the treatment. Therefore, the sludge must be disposed adequately, as not to cause damage to the environment and humans.

The consumption of water that has a high level of fluoride can result in dental or skeletal fluorosis, which causes changes in the teeth and bones. Thus, this study aimed to verify the efficiency of the reduction of fluoride in groundwater using coagulation with extracts of Moringa oleifera Lam seeds (MO) combined with microfiltration. Coagulation/flocculation tests were carried out in Jar test with different concentrations of the coagulant and subsequent treatment of water by microfiltration membranes. The concentration of fluoride in water was adjusted to 5 mgF‐/L and pH set to 7.0. The test used 1.5 g/L of the coagulant MO, for a 3 mgF‐/L initial concentration of fluoride and pH 3.0 proved effective for the removal of fluoride, colour, and turbidity of water with residual amounts of 1.07 mgF‐/L, 19 mgPt‐Co/L, and 3 NTU, respectively. The best results were obtained using 5 g/L of the coagulant MO and 2 bar pressure in the microfiltration step. Under these conditions, the final water quality complies with the recommendations of the Brazilian legislation, with residual fluoride at 1.2 mgF‐/L, 1.56 NTU turbidity and 8.56 mgPt‐Co/L colour. These results indicate the potential of the proposed treatment and that this represents an alternative for reducing excessive fluoride from water by combining the use of a natural and biodegradable coagulant with microfiltration processes, which contributes to the final quality of water.

No abstract

<p align="justify">Este trabalho teve como objetivo o estudo de filtros de carvão ativado impregnado com zinco para remoção do protozoário parasita Giardia. Para a impregnação dos íons metálicos na superfície do carvão ativado foi utilizado o método de impregnação por excesso de solvente, para a caracterização textural do material produzido foram analisados os parâmetros: área superficial específica BET, área de microporos (método t), volume e diâmetro de microporos (método HK). A caracterização estrutural foi feita através de medidas de Difração de Raios-X (DRX). Os filtros de carvão ativado impregnado com zinco foram testados com água sintética (água deionizada contaminadas com cistos de Giardia, em uma concentração na ordem de 105 cistos/L). Os resultados desse trabalho mostraram que filtros de carvão ativado impregnados com zinco atingiram uma remoção de aproximadamente 100%, trazendo resultados promissores na remoção do protozoário parasita Giardia.</p><p align="justify">Abstract</p><p align="justify">This work aimed to study the activated carbon filters impregnated with zinc for removal of protozoan parasite Giardia. For impregnation of the metal ions on the surface of activated charcoal was used the method of impregnation by excess of solvent, for textural characterization of the materials produced were analyzed parameters: BET specific surface area, area of micropores (method t), diameter and volume micropores (HK method). Structural characterization was made through measurements of X-ray diffraction (XRD). The activated carbon filters impregnated with zinc were tested with synthetic water (water contaminated with Giardia cysts, with a concentration on the order of 105 cysts / L). The results of this study showed that activated carbon filters impregnated with zinc reached a removal of approximately 100%, bringing promising results in the removal of the protozoan parasite Giardia.</p>