Tandem anaerobic-aerobic degradation of ranitidine, diclofenac, and simvastatin in domestic sewage
SCIENCE OF THE TOTAL ENVIRONMENT
Authors: da Silva, Thiago H. G.; Furtado, Rafaely X. de S.; Zaiat, Marcelo; Azevedo, Eduardo B.
Abstract
There is a consensus among scientists that domestic sewage treatment plants are the main sources of drugs entry into the aquatic environment. Therefore, this work studies the biodegradation of the drugs ranitidine (RNT), diclofenac (DCF), and simvastatin (SVT) (50 mu g L-1, each), in real domestic sewage, using a continuous anaerobic-aerobic reactor with immobilized biomass and an anaerobic batch reactor. The continuous anaerobic-aerobic reactor was operated for 6 months with hydraulic retention time (HRT) of 8 h. The initial degradation rates and the maximum oxidation capacities (MOC) of the system were estimated, achieving 90, 72, and 62% removals and 100, 93, and 72% of MOC for RNT, DCF and SVT, respectively, as well as 71% removal of soluble chemical oxygen demand (COD). RNT was degraded throughout the reactor, while DCF was degraded mainly in the two anaerobic chambers and SVT in the first anaerobic chamber. Anaerobic batches were used for the identification of biodegradation by-products (2,6-dichloro-N-(2-methylphenyl) aniline and simvastatin acid), the evaluation of the specific methanogenic activity (SMA) inhibition, and the estimation of acute and chronic ecotoxicities using the ECOSAR 1.11 software. The present study showed that, even at environmental concentrations, RNT, DCF, and SVT were capable of inhibiting the SMA. Lipophilicities dictated the behavior of those three drugs. The greater their lipophilicities, the greater the SMA inhibition and their ecotoxicity. (C) 2020 Elsevier B.V. All rights reserved.
Surface defective g-C3N4-xClx with unique spongy structure by polarization effect for enhanced photocatalytic removal of organic pollutants
JOURNAL OF HAZARDOUS MATERIALS
Authors: Bai, Xiaojuan; Wang, Xuyu; Lu, Xiongwei; Liang, Yunjie; Li, Junqi; Wu, Liyuan; Li, Haiyan; Hao, Qiang; Ni, Bing-Jie; Wang, Chongchen
Abstract
Natural sponge is an ancient marine organism with a single lamellar structure, on which there are abundant porous channels to compose full-fledged spatial veins. Illumined by the natural spongy system, herein, the Cl doped surface defective graphite carbon nitride (g-C3N4-xClx) was constructed through microwave etching. In this process, microwave with HCl was employed to produce surface defects and peel bulk g-C3N4 to form natural spongy structured g-C3N4-xClx with three-dimensional networks. The spongy structure of the photocatalyst could provide abundant and unobstructed pathways for the transfer and separation of electron-hole pairs, and it was beneficial for photocatalytic reaction. The spongy defective g-C3N4-xClx achieved excellent degradation of diclofenac sodium (100%), bisphenol A (88.2%), phenol (85.7%) and methylene blue (97%) solution under simulated solar irradiation, respectively. The chlorine atoms were introduced into the g-C3N4 skeleton in mi-crowave field with HCl, forming C-Cl bonds and surface polarization field, which could significantly accelerate the separation of photogenerated electrons and holes. As an efficient and universal approach, microwave etching can be generally used to create surface defects for most photocatalysts, which may have potential applications in environmental purification, energy conversion and photodynamic therapy.