Browsing by Author "Exposto, Bruno Marques"
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- Estrogen removal through adsorption using carbon materials prepared from biomass wastePublication . Exposto, Bruno Marques; Queiroz, A.M.; Ribeiro, António E.; Brito, PauloEndocrine disruptors are class of micropollutants that can influence and deregulate the endocrine system in humans and animals. Endocrine disruptors can consist of natural estrogenic hormones, such as E1 and E2, and synthetic estrogenic hormones, such as EE2, that are not easily removed by conventional treatment processes in water and sewage treatment plants, becoming dangerous emerging pollutants. This work addresses the removal of such compounds from aqueous matrices through adsorption processes onto activated carbon produced from biomass waste. The materials selected were almond shell in natura (ASiN) and cork in natura (CiN). These were activated through carbonization at 550ºC for 1 h, obtaining carbonized almond shell (CAS) and carbonized cork (CC). These materials were characterized by carbonization yield, moisture and ash content, PZC value, quantification of acidic and basic sites and FTIR analysis. For the adsorption assays, the impact of conditions such as adsorbent type, temperature and medium pH was assessed in relation to removal performance. Kinetic and isotherm assays were also performed in batch mode, together with the assessment of the thermodynamic data. The results show that equilibrium time was 16 h for ASiN, 4 h for CAS, 6 h for CiN and 24 h for CC. The adsorption process was regulated through the Elovich model for all adsorbents except for CiN, where the best model was PSO. Moreover, cork-based adsorbents presented higher adsorption capacities and activation through carbonization did not contribute to an increase in estrogen removal. Therefore, CiN was selected as the best material for estrogen removal to the posterior assays. A temperature increase did not affect CiN’s adsorption capacity, and Ea was determined to be 136.15, 80.84 and 146.81 kJ/mol for E2, EE2 and E1, respectively. Moreover, pH change only negatively affects adsorption when in extreme basic media. CiN’s adsorption process has been characterized by the Sheindorf-Rebuhn-Sheintuch multicomponent isotherm for all estrogens, with maximum adsorption capacities of 3.75, 7.23 and 3.82 mg/g achieved for estrogens E2, EE2 and E1, respectively, at 25ºC. Average removal percentage increased with the adsorbent’s dosage until it reached a maximum of 66.1% at 1 g/L. Both the adsorption capacity and removal percentage decreased with the increase in temperature. Thermodynamic data was determined and negative values for ΔGº and ΔHº and positive values for ΔSº were obtained, meaning that adsorption was characterized as spontaneous, exothermic and entropically favourable. It was verified that estrogen adsorption occurred through a combination of chemisorption and physisorption phenomena. Chemisorption occurred mainly through pEDA interactions and hydrogen bridges between estrogen and CiN’s functional groups and aromatic rings, while physisorption occurred mainly through pore filling. pEDA bonding assisted by hydrophobic interactions could be an explanation for the higher adsorption rates verified for EE2 in CiN.