RESUMO
Studies indicate that approximately two-thirds of the rivers of the world are contaminated by pharmaceutical compounds, especially antibiotics and hormones. Data reported by the World Health Organization (WHO, 2015) revealed an increase of 65% in antibiotic consumption between 2000 and 2015, with a worldwide increase of 200% expected up to 2030. Environmental contamination by antibiotics and their metabolites can cause the alteration of bacterial genes, leading to the generation of superbacteria. In this work, adsorption was explored as a strategy to mitigate antibiotic contamination, proposing the use of the Al-MCM-41 mesoporous material as an efficient and high-capacity adsorbent. Evaluation of the influence of the synthesis parameters enabled understanding of the main variables affecting the adsorption capacity of Al-MCM-41 for the removal of a typical antibiotic, amoxicillin (AMX). It was found that the adsorbent composition and specific surface area were the main factors that should be optimized in order to obtain the highest AMX removal capacity. Using statistical tools, the best Si/Al ratio in Al-MCM-41 was found to be 10.5, providing an excellent AMX uptake of 132.2 mg per gram of adsorbent. The Si/Al ratio was the most significant factor affecting the adsorption. The cation-π interactions increased with an increase of the Al content, while the interactions involving silanols (Yoshida H-bonding and dipole-dipole hydrogen bridges) decreased.
RESUMO
Anodic oxidation of recalcitrant organic compounds is still challenging concerning to the anode material and mass transport limitations imposed by the low concentration. In this work, we studied the degradation of a real wastewater containing glyphosate using an electrode of PbO2 electrodeposited on a three-dimensional matrix of reticulated vitreous carbon (RVC). The high mass transfer rate provided by the RVC/PbO2 anode is demonstrated. A Box-Behnken factorial design was used for a systematic analysis of the effects of current density, flow rate and temperature on the degradation and mineralisation kinetics, current efficiency and specific energy consumption. The optimised degradation performance was achieved applying 30â mAâ cm-2, 3000â mLâ min-1 and 50°C. As the flow rate increases from 150 to 1500â mLâ min-1, the current efficiency increases from 18% to 65% and the energy consumption dropped from 72 to 33â kWhâ kg-1 due to the mass transfer enhancement promoted by the porous matrix. The efficacy of the electrochemical process for the treatment of real effluents using the three-dimensional PbO2 has been demonstrated.