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- Coal fly ash waste, a low-cost adsorbent for the removal of Mordant Orange dye from aqueous mediaPublication . Rosa, Teresa; Martins, Angela; Santos, Maria Teresa; Trindade, Teodoro; Nunes, NelsonIn this study, a coal fly ash material generated in a Portuguese coal thermal powerplant was tested as a low-cost adsorbent to remove dye molecules. Pre-treatment of the coal fly ash samples was not performed in order to reduce end use cost. Physical and chemical characterization revealed their inert nature and low effects lixiviation in aqueous media. Preliminary adsorption studies include adsorbent quantity, and adsorption kinetics. The adsorption studies focused on Mordant Orange 1 (Mo1) dye, but two other molecules, Rhodamine B (RhB) and Methylene Blue (MeB) were also included for comparison reasons. The adsorption isotherms were tested with different models including Langmuir, Freundlich and modified Langmuir-Freundlich. The effect of temperature, pH and unburn carbon in the adsorption process were also studied. The results show that adsorption capacity of the coal fly ash occurs mainly due to electroestatic interactions between the adsorbent surface and the adsorbate, which depends on the pH of the aqueous media and the surface chemistry of the material, quantified by the point of zero charge, pHpzc. These joint effects are responsible for the higher retention of Mo1 that is about 16 times higher, when compared to the other two molecules tested.
- Sludge recovery from industrial wastewater treatmentPublication . Santos, Maria Teresa; Lopes, Pedro AndréIndustry is a fundamental sector that allows mass production to support a large population. As population grows, many industries produce large amounts of industrial effluents with different pollutants, that must be removed at the industrial wastewater treatment plants, with the consequent production of large amounts of sludge. The present study was conducted to identify and evaluate different sludge treatment/valorisation methodologies, being given priority to the valorisation in detriment of the elimination operations, like incineration or landfill. Therefore, sludges from the wastewater treatment plant of a resin industry, after dehydration operation by a press, were submitted to several valorisation methodologies, such as: application in anaerobic digestion aiming the production of biogas and allowing energy recovery, use in the preparation of adsorbents for the treatment of industrial wastewater, use as cement replacement in mortar production, and application of heterogeneous catalysts to produce biodiesel. The results revealed that all methodologies can be applied as sludge recovery. However, it is possible to conclude that the most promising industrial sludge treatment/recovery hypothesis is anaerobic co-digestion followed by the production of heterogeneous catalysts for biodiesel production.