Integration of Membrane Distillation with solar photo-Fenton for purification of water contaminated with Bacillus sp. and Clostridium sp. spores

An overview of wastewater treatment using combined heterogeneous photocatalysis and membrane distillation

The need for efficient remediation solutions to wastewater has risen due to the concerning prevalence of toxic organic pollutants. It is possible for the linked photocatalysis-membrane separation system to concurrently achieve the photoreaction of pollutants and their removal from wastewater in order to accomplish the goal of completely purifying the wastewater. This investigation's objective is to provide analytical overview of the photocatalytic and membrane coupling process, photocatalytic membrane reactors, and the potential applications of these technologies in the treatment of wastewater for the persistent organic matter removal. In the review, an examination of photocatalytic and membrane processes to remove organic compounds from wastewater is presented. Based on the literature analysis, it was observed that the application of photocatalytic membrane reactors is significantly influenced by a wide variety of factors. Some of these factors include pollutant concentration, dissolved oxygen, aeration, pH, and hydraulic retention time. Light intensity is another factor that has a significant influence. It was also revealed how distillation membranes work when integrated with photocatalytic process. This brief overview will help researchers understand how successful coupled photocatalytic and membrane distillation are in the treatment of wastewater containing organic pollutants.

A review of the potential of conventional and advanced membrane technology in the removal of pathogens from wastewater

Consumption of pathogenic contaminated water has claimed the lives of many people. Hence, this scenario has emphasized the urgent need for research methods to avoid, treat and eliminate harmful pathogens in wastewater. Therefore, effective water treatment has become a matter of utmost importance. Membrane technology offers purer, cleaner, and pathogen-free water through the water separation method via a permeable membrane. Advanced membrane technology such as nanocomposite membrane, membrane distillation, membrane bioreactor, and photocatalytic membrane reactor can offer synergistic effects in removing pathogen through the integration of additional functionality and filtration in a single chamber. This paper also comprehensively discussed the application, challenges, and future perspective of the advanced membrane technology as a promising alternative in battling pathogenic microbial contaminants, which will also be beneficial and valuable in managing pandemics in the future as well as protecting human health and the environment. In addition, the potential of membrane technology in battling the ongoing global pandemic of coronavirus disease 2019 (COVID-19) was also discussed briefly.

Evaluation of Fenton and modified Fenton oxidation coupled with membrane distillation for produced water treatment: Benefits, challenges, and effluent toxicity

Membrane distillation is a promising technology to desalinate hypersaline produced waters. However, the organic content can foul and wet the membrane, while some fractions may pass into the distillate and impair its quality. In this study, the applicability of the traditional Fenton process was investigated and preliminarily optimized as a pre-treatment of a synthetic hypersaline produced water for the following step of membrane distillation. The Fenton process was also compared to a modified Fenton system, whereby safe iron ligands, i.e., ethylenediamine-N,N'-disuccinate and citrate, were used to overcome practical limitations of the traditional reaction. The oxidation pre-treatments achieved up to 55% removal of the dissolved organic carbon and almost complete degradation of the low molecular weight toxic organic contaminants. The pre-treatment steps did not improve the productivity of the membrane distillation process, but they allowed for obtaining a final effluent with significantly higher quality in terms of organic content and reduced Vibrio fischeri inhibition, with half maximal effective concentration (EC₅₀) values up to 25 times those measured for the raw produced water. The addition of iron ligands during the oxidation step simplified the process, but resulted in an effluent of slightly lower quality in terms of toxicity compared to the use of traditional Fenton.

Worldwide Research Trends on Solar-Driven Water Disinfection

“Ensure access to water for all”, states Goal 6 of the UN’s Sustainable Development Goals. This worldwide challenge requires identifying the best water disinfection method for each scenario. Traditional methods have limitations, which include low effectiveness towards certain pathogens and the formation of disinfection byproducts. Solar-driven methods, such as solar water disinfection (SODIS) or solar photocatalysis, are novel, effective, and financially and environmentally sustainable alternatives. We have conducted a critical study of publications in the field of water disinfection using solar energy and, hereby, present the first bibliometric analysis of scientific literature from Elsevier’s Scopus database within the last 20 years. Results show that in this area of growing interest USA, Spain, and China are the most productive countries in terms of publishing, yet Europe hosts the most highly recognized research groups, i.e., Spain, Switzerland, Ireland, and UK. We have also reviewed the journals in which researchers mostly publish and, using a systematic approach to determine the actual research trends and gaps, we have analyzed the capacity of these publications to answer key research questions, pinpointing six clusters of keywords in relation to the main research challenges, open areas, and new applications that lie ahead. Most publications focused on SODIS and photocatalytic nanomaterials, while a limited number focused on ensuring adequate water disinfection levels, testing regulated microbial indicators and emerging pathogens, and real-world applications, which include complex matrices, large scale processes, and exhaustive cost evaluation.

High-efficiency solar evaporator prepared by one-step carbon nanotubes loading on cotton fabric toward water purification

Solar-driven photothermal conversion devices are proved to promising in fresh water generation, but often hindered due to complex manufacturing processes, low efficiency and poor reusability. Herein, we proposed a one-step carboxylated multi-walled carbon nanotube (MWCNTs-COOH) loading on the cotton fabric (CF), and assembled a jellyfish-shaped solar evaporator in which the evaporation layer acted as the body and cotton yarns (CYs) as the tentacles used for water transportation. The jellyfish-shaped solar evaporator has the advantages of separating the evaporation layer from bulk water, thereby effectively prevents heat dissipation and improves evaporation efficiency. The assembled evaporator exhibited an evaporation rate of 1.18kgm^-2h^-1 and a high energy conversion efficiency of 86.01% under 1.0 sun illumination (1.0kWm^-2). This simple preparation, high efficiency and excellent reusability jellyfish-shaped solar evaporator is expected to be used efficiently under natural light conditions, and has great application prospects for remote areas that lack fresh water supplies.

A novel composite hydrogel for solar evaporation enhancement at air-water interface

This paper reports a facile approach to synthesize a novel composite hydrogel with graphene oxide (GO), silica aerogel (SA), acrylamide (AM), and poly(vinyl alcohol) (PVA) through physical and chemical cross-linking method. The composite hydrogel (GO/SA PAM-PVA hydrogel) exhibits excellent solar evaporation property, good water transmission capacity, and floatability. The GO nanosheets dispersed homogeneously in the hydrogel could provide prominent photothermal conversion efficiency to heat water for evaporation. Excellent hydrophilicity of hydrogel promotes the water molecules transport from the bottom to the top of the hydrogel, which can increase evaporation efficiency. The SA in the hydrogel makes the GO/SA PAM-PVA hydrogel floatable, which is crucial for improving evaporation efficiency because evaporation occurs primarily at several molecular layers on the surface of the water. Furthermore, the self-cleaning ability derived from SA of the GO/SA PAM-PVA hydrogel surface provides a convenient recycling and reusing process for practical applications. The evaporation mass of seawater achieved by the GO/SA PAM-PVA hydrogel is 6 times higher than that of traditional process at an optical density of 2 kW m^-2 for 30 min. Meanwhile, the evaporation efficiency of GO/SA PAM-PVA hydrogel remains good during reuse.

Heterogeneous photo-Fenton process using iron-modified regional clays as catalysts: photonic and quantum efficiencies

A regional raw clay was used as the starting material to prepare iron-pillared clays with different iron contents. The catalytic activity of these materials was tested in the heterogeneous photo-Fenton process, applied to the degradation of 2-chlorophenol chosen as the model pollutant. Different catalyst loads between 0.2 and 1.0 g L^-1 and pH values between 3.0 and 7.0 were studied. The local volumetric rate of photon absorption (LVRPA) in the reactor was evaluated solving the radiative transfer equation applying the discrete ordinate method and using the optical properties of the catalyst suspensions. The photonic and quantum efficiencies of the 2-chlorophenol degradation depend on both the catalyst load and the iron content of the catalyst. The higher values for these parameters, 0.080 mol Einstein^-1 and 0.152 mol Einstein^-1, respectively, were obtained with 1.0 g L^-1 of the catalyst with the higher iron content (17.6%). For the mineralization process, photonic and quantum efficiencies depend mainly on the catalyst load. Therefore, it was possible to employ a natural and cheap resource from the region to obtain pillared clay-based catalysts to degrade organic pollutants in water.