Adsorbent selection for pesticides removal from drinking water.

Pesticides present in water resources can cause adverse health effects even in low concentrations, due to their bio-accumulative character. Therefore, the challenge for drinking water production increases, due to the limitations of conventional water treatment technologies in the removal of small molecular weight dissolved compounds. This work aimed to provide technical and scientific support for the selection of pulverized activated carbon - PACs, granular activated carbon - GACs, and carbon nanotubes - CNT concerning atrazine - ATZ, simazine - SMZ, and diuron - DIU adsorption for application in water treatment plants, considering two forms of application commercial product - CP and analytical standard - SD. These forms of application were tested aiming to verify the influence of the purity of the products used in experiments on the adsorption efficiency. It was possible to verify the adsorption efficiencies were not guided only by the characteristics of the adsorptive materials used, and that the selection should not be carried out only based on the, specific superficial area - BET size and distribution of specific pore volume. The isotherms demonstrated that the parameter Kf associated with the results of the selection experiment can be considered an alternative technical tool of simple application and sufficient for this purpose. Also, the capacity of activated carbons - ACs and nanomaterials - NMs were affected by the application of the compounds, highlighting the importance of using commercial product - CP in scientific research and technical investigations.Hightlights The pesticides efficiency removal was affected due to the forms of application, SD and CP;The parameters IN and MBI were not decisive in the selection of the activated carbon;The main adsorption mechanism in all the materials was chemical;GAC was the most efficient adsorbent in the removal of the pesticides;An adequate adsorbent selection is crucial for satisfactory removal of pesticides in water.

Caracterização e avaliação de fatores que determinam a remoção de microcistina-LR em carvão ativado granular produzido a partir de diferentes matérias-primas / Characterization and evaluation of factors influencing microcystin-LR removal by granular activated carbon produced from different raw materials

RESUMO As microcistinas (MC), que estão entre as cianotoxinas mais encontradas em florações de cianobactérias, não são eficientemente removidas pelas tecnologias do ciclo completo de tratamento de água. Como barreira adicional para sua remoção, destaca-se o processo de adsorção com carvão ativado granular (CAG). Esta pesquisa comparou a eficiência de remoção de MC-LR por sete CAG produzidos a partir de diferentes matérias-primas, analisando as propriedades das amostras: umidade, teor de cinzas, pH e características texturais. Inicialmente, os resultados indicaram que as propriedades dos CAG foram influenciadas pelo material de origem, assim como pelo método de produção. Nos ensaios de adsorção, o modelo de Langmuir indicou que, em quatro horas, com dosagem de 100 mg.L-1, o CAG de linhito (CGLIN) apresentou a maior capacidade de remoção (97,2%) de MC-LR (Co: 115,1 µg.L-1), com qe,máx de 10,6 mg.g-1. O volume de mesoporos influenciou significativamente a capacidade adsortiva de MC dos carvões avaliados (r=0,98, Pearson). Esses resultados podem oferecer subsídios para a aplicação do processo de adsorção de MC-LR em estações de tratamento de água (ETA) para a minimização de intoxicações por água contaminada.

ABSTRACT Microcystins (MC), which are among the cyanotoxins more commonly found in cyanobacterial blooms, are not efficiently removed by full-cycle water treatment technologies. As an additional barrier, there is the adsorption process with granular activated carbon (GAC). This research compared the efficiency of MC-LR removal by seven GACs produced from different raw materials, analyzing these samples' properties: moisture, ash content, pH and textural characteristics. Initially, the results indicated that the GAC properties were influenced by the source material, as well as by the production method. In the adsorption assays, the Langmuir model indicated that in 4h, with 100 mg.L-1 dosage, the granular activated carbon of lignite (CGLIN) had the highest MC-LR (Co: 115.1 µg.L-1) removal capacity (97.2%), with qe,max of 10.6 mg.g-1. The volume of mesopores significantly influenced the adsorption capacity of microcystin by the evaluated GACs (r=0.98, Pearson). These results can support the application of the MC-LR adsorption process in water treatment plants to minimize intoxication with contaminated water.