Fouling of WO 3 nanoparticle-incorporated PSf membranes in ultrafiltration of landfill leachate and dairy a combined wastewaters: An investigation using model

Modification of reinforced hollow fiber membranes with WO3 nanosheets for treatment of textile wastewater by membrane bioreactor

In this study, performance of braid reinforced hollow fiber membrane containing polyvinylidene fluoride (PVDF) embedded with tungsten trioxide (WO₃) nanosheets in a membrane bioreactor (MBR) was examined for textile wastewater treatment. The WO₃ nanosheets was synthesized and blended at different concentrations (0.1-0.02 wt%) in casting solutions of the membranes. The WO₃ nanosheets characterized using various tests such as XRD, FTIR, SEM, EDS, dot-mapping, and TEM. Furthermore, the effects of the increased WO₃ nanosheets into the PVDF matrix on the membrane morphology, hydrophilicity, permeability, antifouling, and COD and color removal efficiency was investigated. The addition of 0.1 wt% of the nanosheets reduces the water contact angle from 69.3° to 62.5° while increasing overall porosity from 37.5 to 43.2%. COD and color removal for PVDF/0.10 wt% WO₃ membrane was between 86-89% and 72-76%, respectively. While the TMP of modified WO₃ membranes did not significantly increase due to antimicrobial properties of the WO₃ nanosheets, the TMP of the pure PVDF membrane increase, indicating considerable cake layer fouling. The results of this study showed that modification of PVDF braid reinforced hollow fiber membrane using WO₃ nanosheets is promising membrane for MBR systems.

High-performance photocatalytic membranes for water purification in relation to environmental and operational parameters

Growing technologies, increasing population and environmental pollution lead to severe contamination of water and require advanced water treatment technologies. These aspects lead to the need to purify water with advanced smart materials. This paper reviews the recent advances (during the last 5 years) in photocatalytic composite membranes used for water treatment. For this purpose, the authors have reviewed the main materials used in the development of (photocatalytic membranes) PMs, environmental and operational factors affecting the performance of photocatalytic membranes, and the latest developments and applications of PMs in water purifications. The composite photocatalytic membranes show good performance in the removal and degradation of pollutants from water.

Leaching of CuO Nanoparticles from PES Ultrafiltration Membranes

Recent studies have incorporated nanoparticles such as CuO, ZnO, and TiO₂ to improve membrane physical and filtration properties. However, one of the major concerns about membrane modification with nanoparticles is the possible leaching of the nanoparticles leading to further contamination of source waters. Therefore, this study investigated the effects of prolonged exposure of polyethersulfone (PES) membranes incorporated with CuO nanoparticles, to different cleaning solutions. The cleaned membranes were extensively characterized for both material properties and separation performance, which enabled a closer look at particle leaching effect through a prolonged exposure. After 840 h of exposure, the presence of CuO in the cleaning solutions was confirmed using dynamic light scattering (DLS), energy-dispersive X-ray spectroscopy (EDS), and inductively coupled plasma mass spectroscopy (ICP-MS) techniques. Nanoparticle leaching resulted in changes in membrane hydrophobicity, surface roughness, pure water permeability, and salt rejection properties. Through comparison with the bare PES membranes, it was shown that cleaning solutions also degraded the membrane polymer. However, the marked effect was less pronounced compared to combined leaching of nanoparticles and degradation of the polymer noted with PES membranes incorporated with CuO nanoparticles. Therefore, when membranes incorporated with nanoparticles are used, a polishing step may be required to remove potentially leached nanoparticles. Leached nanoparticles may result in secondary pollution and pose a health risk concern to nontarget organisms. This work provides insights into the stability of nanocomposite membranes, and the achieved results can be extrapolated to other nanoparticles such as TiO₂ and ZnO because they possess similar physicochemical behavior.

Sequential coagulation and Fe0-O3/H2O2 process for removing recalcitrant organics from semi-aerobic aged refuse biofilter leachate: Treatment efficiency and degradation mechanism

Landfill leachate effluent obtained after semi-aerobic aged refuse biofilter (SAARB) treatment still contains various recalcitrant organics. In this study, a sequential coagulation and Fe⁰-O₃/H₂O₂ process was developed for treating SAARB leachate. The effects in terms of degradation of recalcitrant organics and the related mechanisms due to the coagulation and Fe⁰-O₃/H₂O₂ processes were systematically explored and discussed. The results indicated that polymerized ferric sulfate was the most efficient coagulant for treating SAARB leachate where the chemical oxygen demand (COD), UV₂₅₄, and CN removal efficiencies were 59.60%, 63.22%, and 70.32%, respectively. In the Fe⁰-O₃/H₂O₂ process under the optimized conditions comprising Fe⁰ dose = 0.6 g/L, O₃ dose = 26.80 mg/min, H₂O₂ dose = 1.0 mL/L, and reaction time = 20 min, the COD, UV₂₅₄, and CN removal efficiencies with the coagulated supernatant were 43.39%, 59.47%, and 93.20%, respectively, and the biodegradability (biochemical oxygen demand/COD) improved greatly from 0.06 to 0.34. Analysis of UV-Vis and 3D-EEM spectra indicated that coagulation-resistant substances in the SAARB leachate could be effectively degraded and destroyed by the Fe⁰-O₃/H₂O₂ process. In the O₃/H₂O₂ environment, Fe⁰ generated Fe²⁺ and iron oxides (Fe₂O₃, Fe₃O₄, and FeOOH) with homogeneous and heterogeneous catalytic roles against O₃/H₂O₂ to produce reactive oxygen species. Furthermore, Fe(OH)₂ and Fe(OH)₃ colloids contributed to the removal of organics to some extent via adsorption and precipitation effects. In conclusion, the proposed sequential coagulation and Fe⁰-O₃/H₂O₂ process is an efficient method for treating recalcitrant organics in SAARB leachates.

Photocatalytic Membranes in Photocatalytic Membrane Reactors

The present work gives a critical overview of the recent progresses and new perspectives in the field of photocatalytic membranes (PMs) in photocatalytic membrane reactors (PMRs), thus highlighting the main advantages and the still existing limitations for large scale applications in the perspective of a sustainable growth. The classification of the PMRs is mainly based on the location of the photocatalyst with respect to the membranes and distinguished in: (i) PMRs with photocatalyst solubilized or suspended in solution and (ii) PMRs with photocatalyst immobilized in/on a membrane (i.e., a PM). The main factors affecting the two types of PMRs are deeply discussed. A multidisciplinary approach for the progress of research in PMs and PMRs is presented starting from selected case studies. A special attention is dedicated to PMRs employing dispersed TiO2 confined in the reactor by a membrane for wastewater treatment. Moreover, the design and development of efficient photocatalytic membranes by the heterogenization of polyoxometalates in/on polymeric membranes is discussed for applications in environmental friendly advanced oxidation processes and fine chemical synthesis.