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Pharmaceutical contaminants are frequently encountered at trace concentrations in various environmental ecosystems. This study introduces a significant approach to water treatment and environmental remediation by combining liquid membrane and ozonation. Initially, diclofenac is transported across the supported liquid membrane using a neutral organic extractant Cyanex 923. The highest removal efficiency was achieved with a 40 % concentration of Cyanex923 dissolved in kerosene, resulting in a permeability of 10.2 cm/h. Additionally, diclofenac is extracted from different environmental matrices such as tap water and real effluent of wastewater, and the effect of ions species was studied. The post-ozonation in the stripping phase resulted in removal of pharmaceuticals and 72 % reduction of total organic carbon at pH = 10 and 45.3 g/Nm3 initial ozone concentration. The study also investigates the identification and tracking of the most prevalent by-product of diclofenac over time.

Pharmaceutical compounds present in water pose significant challenges, particularly due to their low concentrations in water streams. Hollow fiber liquid membranes provide a flexible and easily manageable solution, enabling the concentration of specific contaminants. This concentration step significantly improves their effective removal from water systems. The study focused on using hollow fiber liquid membrane technology to effectively remove diclofenac (DCF) and ibuprofen (IBU), two pharmaceutical compounds. A concentration of 40% Cyanex 923 (Cy923) dissolved in kerosene was selected as the preferred extractant due to its stability and quick extraction properties. The stability of the system was tested with a pseudo-emulsion, enabling repeated use of the system. Additionally, an analytical model was developed to calculate the membrane's permeability. In order to enhance the degradation and mineralization of the pharmaceutical compounds and their byproducts, ozonation was integrated with the hollow fiber liquid membrane system in a single system. Measurement of total organic carbon (TOC) revealed a significant reduction of 72% for diclofenac and 57% for ibuprofen with an initial ozone concentration of 10 mg/L and operating under the optimal conditions of hollow fiber liquid membrane.

Ceramic-supported graphene oxide membrane bioreactors have already shown their potential for the anaerobic decolorization of wastewater containing azo dyes. The primary goal of this investigation was to develop a mathematical model that would be able to describe the steady-state behavior of this biodegradation process. The developed model was calibrated and validated using independent experimental data sets with various dye structure, feed concentration, hydraulic retention time (HRT), and support materials on which the biofilm was grown. The calibrated and validated model was used to analyze the intrinsic mechanism of the process and the main finding was that hydrolysis is the rate limiting step. Hydrolysis rate constant is decreased with increasing the complexity of the dye structure. Support materials with high electron transfer capacity increased the biofilm activity, therefore, increased the hydrolysis rate constant. Acetate concentration, used as an external carbon source, improved the dye removal efficiency. However, acetate to dye ratio did not have a direct relation to dye removal efficiency. Higher hydraulic retention time (HRT) increased the contact time between dye molecules and biofilm and enhanced the dye removal efficiency, too. However, it is essential to impose the right balance between HRT and external carbon sources to make the process feasible.

This research investigates a highly efficient compact tubular ceramic-supported carbon-based membrane reactor integrated with anaerobic biodegradation to decolorize the azo dyes. Two carbon-based membranes, produced using Matrimid 5218 polyimide and graphene oxide solutions, are evaluated for the comparative color removal of three structurally different azo dyes, Acid Orange 7 (AO7), Reactive Black 5 (RB5), and Direct Blue 71 (DB71). Based on FESEM microscopic images, the average pore size of the tubular ceramic-supported carbonized membrane (TCSCM) was approximately 25 nm, while for the tubular ceramic-supported graphene oxide membrane (TCSGOM), it was 12 nm. Additionally, TCSCM had a thinner layer at only 1.10 µm, while TCSGOM was slightly thicker at 2.11 µm. These features influenced the permeate flux of the membrane, in which the TCSGOM exhibited lower permeate flux (18.2 L·m−2·h−1) than the TCSCM (45.6 L·m−2·h−1). However, the anaerobic decolorization results indicated that the TCSGOM bioreactor (B-TCSGOM) was more efficient and effective at removing color from all dye solutions than the TCSCM bioreactor (B-TCSCM) over a wide range of feed concentrations. In both reactors, the highest decolorization was achieved at low feed concentration (50 mg·L−1), and removal was 94 % for AO7, 90 % for RB5, and 88 % for DB71 in B-TCSGOM, whereas 88 %, 85 %, and 69 %, respectively, in B-TCSCM. These suggest that the robust conductive nanoporous surface of B-TCSGOM makes it more effective at removing different azo dye solutions from wastewater.

Uniform flexible carbon nitride coatings have been synthesized by means of annealing of films, fabricated from soluble triazine-based polymeric precursors. The coatings exhibit fascinating electrochemical stability and drastically increase the capacitance of coated carbon cloth electrodes. Following the analogue with turbostratic carbons, typically produced by means of polymeric precursors pyrolysis, we demonstrate that annealing of dried nitrogen-rich polymeric films results in coatings, composed by nearly equal atomic quantities of carbon and nitrogen, according to elemental analysis, and exhibiting noticeable mechanical robustness. X-ray difffraction patterns and infrared spectra of the materials allow to characterize them as partially amorphous carbon nitride with presumably heptazinic structure. Annealed films exhibit extrinsic semiconducting behavior with optical bandgaps in the range from 1.71 to 1.99 eV and fairly good conductivity. The outstanding long-term electrochemical stability of annealed films makes them competitive with pyrolytic carbon, while much lower annealing temperatures allow preparation of nanocomposites with various particles. The precursor polymers were obtained by self-condensation of 2-amino-4,6-dichloro-1,3,5-triazine and condensation of cyanuric chloride with 5-aminotetrazole and 3-amino-1,2,4-triazole-5-carboxylic acid, respectively, in N,N-dimethylacetamide. The polymers contain mainly C–N skeletal bonds and can therefore be viewed as “extension” of typical carbon nitride precursors, like melamine or dicyandiamide, to polymeric structure.

In the following study, the extraction of three pharmaceutical compounds: Diclofenac (DCF), ibuprofen (IBP), and carbamazepine (CBZ) by liquid-liquid extraction and their transport by supported liquid membrane (SLM) using different commercial extractants (Cyanex 923 (Cy923), trioctylamine (TOA), tributylphosphate (TBP), and Versatic Acid 10 (neodecanoic acid)) were evaluated. Cy923 was demonstrated to be an efficient extractant for diclofenac and ibuprofen removal through a facilitated transport mechanism from the aqueous feed phase to the aqueous stripping phase using hydroxide ions as stripping agent. Around 80 % of these pharmaceuticals were extracted in 4 h with 10 % of Cy923 and without extreme alteration in the pH. As for carbamazepine, the stripping conditions were achieved with 10 % of Versatic Acid 10. Variation of concentration of different extractants indicates that a higher transport of diclofenac can be obtained by using 40 % of Cy923. In addition, two commercial polymeric supports (PTFE and PVDF) were compared for the selected operational conditions. Finally, the lifetime of the membrane was extended by soaking the polymeric material in the organic solution under vacuum for 24 h and compared with the membrane prepared with an ultrasound-assisted method. Supported liquid membranes present many advantages and can easily be manipulated and integrated for the treatment of persistent pharmaceutical contaminants from water.

A continuous compact membrane bioreactor consisted of ceramic-supported graphene oxide membrane (CSGoM) was implemented for the first time for anaerobic biodecolorization of monoazo Acid Orange 7 (AO7), diazo Reactive Black 5 (RB5), and triazo Direct Blue 71 (DB71) solutions, showing excellent decolorization potential. The membrane was prepared by vacuum filtration of various graphene oxide solutions using a UF ceramic flat element. The decolorization efficiency of the CSGoM bioreactor, made from 1 mg·mL?1 of GO solution (B-CSGoM-1), was investigated for several structurally distinct azo dyes, initial feed concentrations, and permeate fluxes. Maximum color removal was achieved under low feed concentration (50 mg·L?1) and permeate flux (0.05 L·m?2·h?1), reaching 99% for AO7, 96% RB5, and 92% for DB71. At this low permeate flux, the biodecolorization was stable for all azo dye solutions irrespective of the feed concentration. In a subsequent experiment under higher feed concentration and permeate flux (100 mg·L?1 and 0.10 L·m?2·h?1), the decolorization slightly fell to 93%, 85%, and 81% for monoazo, diazo, and triazo solutions, respectively. The existence of anaerobic bacteria (Geobacter and Pseudomonas guangdongensis) in the B-CSGoM-1 biofilm confirms that they could perform efficient biodegradation of azo dye molecules in association with the graphene oxide membrane. © 2021 The Authors

Carbon-based membranes integrated with anaerobic biodegradation are presented as a unique wastewater treatment approach to deal with dye effluents. This study explores the scope of ceramic-supported carbon membrane bioreactors (B-CSCM) and ceramic-supported graphene oxide membrane bioreactors (B-CSGOM) to decolorize azo dye mixtures (ADM) and other dyes. The mixture was prepared using an equimolar composition of monoazo Acid Orange 7, diazo Reactive Black 5, and triazo Direct Blue 71 dye aqueous solution. Afterwards, as in the ADM experiment, both compact units were investigated for their ability in the biodecolorization of Methylene Blue (MB) and Rhodamine B (RhB) dye solutions, which do not belong to the azo family. The obtained outcomes revealed that the conductive surface of the graphene oxide (GO) membrane resulted in a more efficient and higher color removal of all dye solutions than B-CSCM under a wide feed concentration and permeate flux ranges. The maximum color removal at low feed concentration (50 mg·L−1) and permeate flux (0.05 L·m−2·h−1) was 96% for ADM, 98% for MB and 94% for RhB, whereas it was 89%, 94% and 66%, respectively, for B-CSCM. This suggests that the robust, cost-effective, efficient nanostructures of B-CSGOM can successfully remove diverse azo dye solutions from wastewater better than the B-CSCM does.