Wastewater Purification Research Articles

Highly efficient removal of uranium (VI) from aqueous solutions by APTES/ATP

Uranium-containing wastewater poses a significant threat to both the ecological environment and human health. Adsorption is a crucial method for purifying uranium wastewater. Using 3-Aminopropyltriethoxysilane (APTES) to modify attapulgite (ATP), we successfully prepared a cost-effective and high-performance adsorbent material, APTES-modified attapulgite (APTES/ATP). This material was utilized for the purification of uranium-containing wastewater. Characterization techniques were employed to study the structure and surface properties of the material. The adsorption performance of the material was investigated using single-factor experiments. The adsorption isotherms, kinetics, and thermodynamics were also studied and discussed. The results indicated that APTES/ATP exhibited an adsorption capacity of 382.13 mg·g−1 for uranium at room temperature. The adsorption process followed the Langmuir adsorption model and pseudo-second-order kinetics, indicating that the adsorption of uranium by the material was a monolayer chemisorption. Adsorption thermodynamics revealed that the process was endothermic and spontaneous. The adsorption mechanism primarily involved electrostatic attraction and interactions between −NH2, Si-O, and −OH groups with uranium. In summary, the prepared APTES/ATP demonstrated excellent adsorption capacity for uranium and shows promise for the purification of uranium-containing wastewater.

Biocompatible Ionic Liquids Functionalized Activated Carbon of Local Agri-Waste for Wastewater Purification and Cytotoxic Evaluation of Purified Water

Biocompatible Ionic Liquids Functionalized Activated Carbon of Local Agri-Waste for Wastewater Purification and Cytotoxic Evaluation of Purified Water

Graphene oxide-polydopamine loaded uniform fibrous membranes via robust multi-channel microfluidic-electrospinning method

The rapid development of modern industries has caused serious water pollution such as dyes wastewater, which brings environmental problems and threatens human health. Thus, methods allowing efficient dyes removal from wastewater are substantially desirable. In this work, we fabricated graphene oxide-polydopamine (GO-PDA) by microfluidics, which enables rapid synthesis of products with excellent uniformity due to the precise control of reaction conditions. In addition, the GO-PDA/ thermoplastic polyurethane (GO-PDA/TPU) composite fibrous membrane was prepared in a high-efficiency manner by microfluidic electrospinning with a four-channel chip. Interestingly, GO-PDA not only improves the mechanical strength and hydrophilicity of the composite fibrous membrane, but also endows the membrane with efficient dye adsorption and separation capacity both for single and mixed dyes. It has been proved that the GO-PDA/TPU composite fibrous membrane exhibits selectivity towards cationic dyes, where the removal efficiency is up to 99 wt%. Moreover, the fibrous membrane could be utilized in a continuous and cyclic manner, which still maintains a high adsorption rate (>95 wt%) after 5 recycling, illustrating outstanding durability and reusability. This work proposes an efficient GO-PDA/TPU composite fibrous membrane towards selective adsorption of cationic dyes, which is of great significance in wastewater purification.

Exploring performance and mechanism of modified metal-organic frameworks in calcium alginate/polyvinyl alcohol double-network hydrogels for effective dye wastewater treatment

To address the growing problem of dye wastewater pollution, a novel MOFs adsorbent calcium alginate/polyvinyl alcohol@UiO-66 was developed using environmentally friendly polymers, sodium alginate and polyvinyl alcohol creating gel spheres with a double-network structure through cross-linking. UiO-66 metal-organic frameworks are then grown onto the gel spheres, resulting in the final CA/PVA@UiO-66 adsorbent. This adsorbent boasts a high surface area (17.4 m2/g) and a mesoporous-nested microporous structure. It effectively removes MB from water, the actual maximum adsorption capacity was measured at 275.8 mg/g, which surpasses most existing adsorbents. Remarkably, the adsorbent retains 93.9 % of its initial capacity even after 10 reuse cycles. The adsorption process adhered to the Redlich-Peterson model and the PFO model. The N2-Sorption isotherm, actual Methylene blue (MB) adsorption experiments, and model analysis further suggest that the adsorption process is a complex heterogeneous diffusion process involving simultaneous chemical and physical adsorption. Additionally, the adsorption process is endothermic, indicating that it can occur spontaneously at 298 K. Increasing the temperature promotes the forward progress of the adsorption reaction, thereby enhancing the adsorption capacity. The gel adsorbent exhibited excellent dye wastewater purification capabilities, coupled with commendable reusability.

Synthesis And Efficiency Evaluation of Chitosan-Alginate Hydrogel Polyelectrolyte Complex Filter for Treatment of Oil Spillage

Crude oil spills pose considerable environmental concerns thereby demanding the development of effective, sustainable, and eco-friendly remediation solutions. In this study, we synthesized and evaluated the efficiency of a biodegradable polymer filter using sodium alginate and chitosan for the treatment of oil spillage. The sodium alginate-chitosan hydrogel polyelectrolyte complex (SACHPC) filter was synthesized via dipping method using a layer-by-layer self-assembly technique integrated with cotton wool as the filter medium. The efficiency of the filter was evaluated based on flow rate of recovered oil and reusability of the filter. Simulated oil spillage of 0.5 M was subjected to filtration using the SACHPC filter. The flow rate was determined based on the time taken for 1 L of oil to pass through the filter. The SACHPC filter exhibited underwater superoleophobic behaviour with exceptional filtration efficiency (> 98.3%) in acidic, neutral and alkaline conditions (pH 3, 7 and 11). The flow rate of the filter was 120 mL/min, while the third-use filter exhibited a decrease flow rate of 50 ml/min. Moreover, the filter achieved an impressive crude oil recovery rate of 85%. X-ray diffraction analysis confirmed crude oil adsorption in the presence of an amorphous phase while scanning electron microscopy analysis revealed the structural morphology of the SACPHC filter. Overall, the SACHPC filter maintained high filtration efficiency thereby offering a sustainable strategy for oily wastewater purification and oil spill clean-up.

Hierarchical TiO2-coated metal-organic framework-derived carbon material for efficient co-generation of drinkable water and electricity

Co-generation of drinkable water and electricity through interface solar steam generation process is gradually becoming the preferred strategy to solve the current energy shortage and freshwater resources crisis. Inspired by the biological channel structures, flexible carbonized TiO2@Co-MOF nickel foam (CTCNF) based photothermal material with hierarchical nano-arrays structure is successfully fabricated on nickel foam surfaces by atomic layer deposition combined with an ingenious carbonization scheme, which endows CTCNF with combined excellent abilities including seawater desalination, evaporation-induced electricity generation, and wastewater purification, that is a three-in-one photothermal configuration. With the synergistic photothermal effect and hierarchical structure, CTCNF achieves a solar absorption efficiency of 93.65 %. Moreover, benefiting from its abundant oxygen- and nitrogen- containing functional groups, CTCNF not only possesses excellent hydrophilicity and salt resistance, but also reduces the water evaporation enthalpy (from 2453.3 J g−1 to 1378.6 J g−1). Importantly, combined with ingenious design of the evaporation device, CTCNF not only capture energy from environment during the evaporation process, with an evaporation rate of 3.60 kg m−2 h−1 and an evaporation efficiency of 109.9 % under 1 sun, but also obtains an open-circuit voltage (Voc) of 151.15 mV. This enriches the design ideas of high-performance photothermal materials for efficient co-generation of drinkable water and electricity.

Cr3+doped α-Fe2O3 nanoparticles for photodegradation of organic pollutants with their disinfection efficacy

Pristine and Cr-doped α-Fe2O3 nanoparticles were synthesized using a low-cost and simple one-step hydrothermal method without any precipitating agent. Cr-doped α-Fe2O3 was found to be a promising candidate for recyclable photocatalytic application for Tetracycline (TC) and Congo-red (CR) degradation under normal sunlight irradiation along with excellent antibacterial properties. Addition of Cr shows a significantly improved degradation efficiency from 20% to 91% in just 25 min for CR, while the degradation rate reached to 81% for TC, which was also monitored in real-time using internet of things (IoT). Also, a high degree of mineralization was achieved (∼87.9%), which was confirmed using total organic carbon (TOC) content. In parallel, the biochemical oxygen demand/chemical oxygen demand (BOD5/COD) ratio confirmed the fast degradation efficiency using a small amount of catalytic dosage (∼ 0.40 g/L). Also, degradation of multiple dyes provides a promising avenue for addressing complex waste water treatment challenges. Moreover, Cr-doped α-Fe2O3 displays excellent antibacterial activity towards E.coli and E.Faecium. Major factors involved in sunlight driven photocatalytic activity for example absorbance range, porosity, separation between e--h+, and charge transfer property were surprisingly improved by Cr doping and henceforth increased photocatalytic activity and antibacterial properties. This work highlights the potential utilization of Cr-doped α-Fe2O3 for the purification and disinfection of industrial waste water.

Purification of textile wastewater by collective degradation using nanorods of cesium titanium bromide (CsTiBr3) perovskite

The present work recommends a sustainable environmentally safe method for the removal of textile dyes in an economically viable way.The wastewater expelled from the textile dying units contains a mixture of dyes. Here we address the challenge of using a single catalyst for the collective photocatalytic degradation of mixture of six dyes and two samples of textile effluents collected from a local dying unit under direct sunlight. The lead-free perovskite of CsTiBr3 nanorods prepared via the solvothermal process is effective in the collective photocatalytic degradation of dye mixture containing toxic dyes like congo red, crystal violet, malachite green, methylene blue, rhodamine, and methyl orange. The six-dye mixture turned colorless within three hours of direct sunlight exposure. The collective photocatalytic degradation ability of CsTiBr3 perovskite nanorods is successfully exploited for the degradation of the textile effluents. The chemical oxygen demand (COD) analysis guarantees the degradation of dye into non-toxic components. The recycling of wastewater is made possible by the removal of CsTiBr3 catalysts through adsorption using biochar derived from invasive plants. The biochars are extracted from invasive plants such as Acrostichum Aureum, Alternanthera bettzickiana, cyclosorus interrupts, and Quisqualis indica in which Acrostichum Aureum showed maximum adsorption. The scavenger studies using isopropyl alcohol (IPA), ethylene diamine tetra acetic acid (EDTA), and silver nitrate (AgNO3) suggest that holes control the photocatalysis mechanism.

Comparative study of silica-based porous materials in the purification of radioactive wastewater

A significant challenge in the treatment of low-level radioactive wastewater is the effective purification of low-concentration radionuclides. Silica-based adsorbents are advantageous for the deep-purification of low-concentration metal ions. This study investigates three primary types of silica-based adsorbents: functionalized mesoporous silica, various modified zeolites, and mesoporous calcium silicate hydrate (C-S-H). These adsorbents were synthesized and their deep-purification effects on heavy metals and radionuclides were compared. The results indicated that mesoporous silica showed relatively poor adsorption for most metal ions. Zeolites outperformed mesoporous silica, with Zn framework-modified zeolites showing enhanced adsorption for several metal ions. Notably, C-S-H displayed superior adsorption performance, achieving high adsorption capacities for various metal ions and radionuclides. Specifically, at a dose of 0.5 g/L, the adsorption efficiency of C-S-H for numerous radionuclides in nuclear power plant wastewater exceeded 92–99 %, highlighting its potential for practical applications. An in-depth analysis of the physical and chemical structure and the adsorption mechanisms of C-S-H revealed its large mesoporous structure and electrostatic attraction to cations across a wide pH range. Multivalent cations were removed through exchange with Ca2+ in C-S-H, whereas monovalent cations were removed through exchange with Na+ in C-S-H. The cyclic structure of silica-oxygen tetrahedra in C-S-H, which promotes large pore formation and provides abundant ion exchange sites, underpins its excellent adsorption properties. This study offers valuable insights for the selection and application of silica-based materials in radioactive wastewater treatment.

Long-lived superhydrophobic micro/nano-locked fiber membranes for long-lasting oil-water separation effectiveness

Superhydrophobic/superoleophilic oil-water separation membranes have great potential for treating industrial, domestic, and marine oily wastewater. However, the robustness of these membranes remains a challenge that restricts their ability to maintain long-lasting oil-water separation effectiveness. Inspired by the adhesion mechanisms of snail and tree frog, exploiting the synergistic effects of interfacial hydrogen bonding and mechanical interlocking, we herein achieved strong adhesion between hydrophobicized in-situ nanoparticles and textile fibers to fabricate a long-lived superhydrophobic micro/nano-locked fiber membrane (LSMFM). LSMFM maintains excellent superhydrophobicity even when exposed to mechanical and chemical damage, such as continuous sandpaper abrasion, tape-peeling, weight impact, water jet, and acid/alkali/salt erosion. Additionally, LSMFM efficiently separates various light/heavy oil-water mixtures, achieving a remarkable separation flux of >10,000 L·m−2·h−1 and an efficiency >98 %, even after 200 cycles with n-hexane. Importantly, such membranes still maintain a high separation flux >19,000 L·m−2·h−1 and efficiency >97 % after sequentially being subjected to acids, alkalis, freezing, and high temperatures, and even the adsorption bag formed by wrapping LSMFM with superhydrophilic wood pulp cotton can adsorb oil at fixed-point and continuously recover pure oil from oily wastewater. This study paves a new way for the sustainable purification of oily wastewater in extreme environments.

Electronic structure regulation of Cu-based Ruddlesden-Popper perovskites by cobalt doping for enhanced degradation of oilfield fracturing wastewater in electrocatalytic peroxymonosulfate system

Purification of oilfield fracturing wastewater is the most challenging type of oilfield wastewater treatment. In this work, a heterogeneous electrocatalytic peroxymonosulfate (PMS) system was established to treat oilfield wastewater using Co-doping induced Cu-based Ruddlesden-Popper (RP) perovskites as catalysts. Characterization results illustrated that the obtained catalysts were generated the heterojunction of LaCoO3/La2CuO4 and the Co would transfer electrons to Cu, resulting in a higher chemical oxygen demand (COD) degradation efficiency (> 80 %) of oilfield fracturing wastewater under the neutral environment. Singlet oxygen (1O2) played the main function for COD removal with analysis results of reactive oxygen species (ROS). Experimental results and theoretical calculations indicated that the reduction effect of carbon felt (GF) cathode and the redox cycle of Cu(I)/Cu(II) and Co(II)/Co(III) accelerated the activation of PMS. Moreover, the lattice oxygen participated in the generation of ROS. Significantly, the LaCoO3/La2CuO4 heterojunction displayed a higher total density of states (TDOS) value near the Fermi level, implying their favorable electron transfer for PMS activation. This study opens new avenue for resolving the challenge of oilfield fracturing wastewater pollution.

Tree-like 3D GNP-rPN composite structure for solar-thermal evaporation and photocatalytic degradation of antibiotic wastewater

To realize high-yield and long-term purification of wastewater containing antibiotic ciprofloxacin hydrochloride (CIP) and seawater, a tree-like 3D GNP-rPN solar-driven water evaporation and photocatalysis evaporator is developed by preparing and assembling GO/NPDI/PVA (GNP) hydrogel (canopy) and rGO/PU/NPDI (rPN) foam (trunk). The “tree-like” evaporation and photocatalysis evaporator design in this work has the following three characteristics: First of all, graphene oxide (GO) and reduced graphene oxide (rGO) sheets broaden the light absorption range of the photocatalyst perylene imide nanowires (NPDI), which facilitates absorption of more sunlight; secondly, GO and rGO adsorb pollutants in water and provide them to NPDI for catalytic degradation under sunlight irradiation because of their huge specific surface area; thirdly, the excellent photothermal conversion ability of GO and rGO converts solar energy into heat energy, thus facilitating the catalytic degradation of CIP by NPDI. Thanks to the reduced enthalpy of water evaporation by GNP hydrogel, the sufficient top-down water supply, the superior photocatalytic performance of NPDI nanowires, and the efficient solar light absorption and solar-thermal energy conversion of the GO sheets and NPDI nanowires, the resultant GNP-rPN evaporation and photocatalysis system achieves an average water evaporation rate of 2.84 kg m−2 h−1 and a CIP degradation efficiency of 74.04 % within 1 h under 1-sun irradiation. The GNP-rPN system exhibits an optimal degradation efficiency of 74.04 % for a CIP solution with an initial concentration of 10 mg/L within 1 h of irradiation, reaching a degradation efficiency of 96.37 % after 4 h, demonstrating its effectiveness in purifying antibiotic-laden wastewater.

Enhanced piezo-photocatalytic activity of ZnS/Fe2O3: Benefit from type I junction and weak water flow-induced piezoelectric polarization

Photocatalysis is considered to be a sustainable and less polluting environmental purification technology, however, the limited photogenerated charge separation efficiency and light absorption hinder its large-scale application. Encouragingly, piezocatalysis is proposed as an emerging and appealing strategy to drive the migration and separation of photoinduced carriers. Nevertheless, the source of piezocatalysis is usually derived from high energy-consuming ultrasonic vibration. Herein, we realize superior piezo-photocatalytic chlortetracycline hydrochloride degradation performance stimulated by low-frequency water flow-driven piezoelectric polarization of I-type ZnS/Fe2O3 junction. The integration of Fe2O3 is beneficial to extend the light absorption from ultraviolet region to visible range and boost the charge separation efficiency of ZnS/Fe2O3. Meanwhile, the piezoelectric polarization triggered by weak water flow further promotes the directional separation of photogenerated carriers. With all these merits, the optimized ZnS/Fe2O3 shows a piezo-photocatalytic chlortetracycline hydrochloride (CTC) degradation rate of 73.2 % within 20 min, which is 2.8 and 2.1 times that of Fe2O3 and ZnS, respectively, and 17.4-fold and 1.1-fold that of single stirring and light, respectively. This work provides a feasible guidance for designing efficient piezo-photocatalysts for in-situ purification of wastewater in natural environmental with effective visible light responsiveness and sensitivity to weak mechanical stress.

Phytopurifying activity of Salvia officinalis L. from Tunisia

The sage (Salvia officinalis L.) is an annual and biennial plant of Mediterranean origin from the Lamiaceae family. It's a valuable medicinal plant, which is widely used in traditional medicine in world and in Tunisia; this species is very rich in active biological compounds.The objective of this study was to determine the phyto-purifying activity of sage essential, fixed oil and ethanolic extracts in an extensive wastewater purification system of Tunisian national sanitation office. We have measured the physico-chemical parameters of wastewater treated with sage oils and extracts. Then, we have carried out a bacteriological analysis of this wastewater.Our results showed that pH values measured following treatment with sage essential oil gave a pH close to neutral. Therefore, this water can be used for irrigation. In addition, the sage leaves and stems have a considerable effect on the salinity and caused a very remarkable increase in electrical conductivity of the wastewater, the measure of elimination rate demonstrated the effectiveness of sage extracts in eliminating all the microorganisms existing in wastewater.In fact, sage essential oil has the greatest effectiveness in reducing the chemical oxygen demand of the wastewater and we have noticed that a decrease in chemical oxygen demand of microorganisms existing in the wastewater was necessarily accompanied by a decrease in biological oxygen demand. Therefore, sage leaves and stems were more effective in reducing suspended matter existing in wastewater.

Tubular nanofiber membranes combined with Z-scheme CuS@Co3S4 heterojunction catalyst for high-efficient removal of polyvinyl alcohol from waste water with high COD

Polyvinyl alcohol (PVA), a typical water-soluble polymer with huge global production, is becoming one of the most ubiquitous pollutants and indeed the villain of the piece contributing high chemical oxygen demand (COD) in wastewater. Membrane technology is an effective method for wastewater purification, in particular, with the combination of peroxymonosulfate (PMS)-assisted advanced oxidation or photocatalytic process, is capable of maintaining high water flux and anti-fouling. Herein, a ZIF-67 derived Z-scheme CuS@Co3S4 heterojunction catalyst immobilized by poly (m-phenylene isophthalamide) (PMIA) tubular nanofiber membrane (CuS@Co3S4/PMIA-TNM) is designed using a polyester braided tube as interior reinforcement. The resultant membrane features with outstanding superhydrophilicity and commendable porosity (82.1%), leading to a significantly enhanced permeability (water flux > 82.3L·m-2·h-1). Meanwhile, the membrane shows promising PVA removal efficiency (> 99.9%) with a high COD removal efficiency (~ 83.4%) and enhanced antifouling capacity (flux recovery ratio > 99.7%) with the assistance of PMS driven by an ultra low-power LED lamp. The universal applicability and environmental adaptability are also verified in various reaction conditions. In terms of ecotoxicological impacts of the PVA wastewater before and after treatment on aquatic organisms, Zebrafish embryonic development dynamically demonstrated that the treated PVA waste water by the developed hybrid membrane is healthy for fish to grow. Our study definitely opens up a new avenue to develop high-performance catalytic membranes for PVA-based wastewater treatment.

Innovative Use of Eco-Enzymes for Domestic Wastewater Purification

The rapid pace of urbanization and the resultant increase in waste generation have significantly escalated the challenges associated with managing organic waste. In line with contemporary sustainable practices, it is imperative to recycle and repurpose waste effectively. This study investigates the use of eco-enzyme, an environmentally friendly product derived from fruit and vegetable scraps, along with natural sweeteners, in the treatment of domestic wastewater. The study assessed the impact of eco-enzyme concentrations at 15% and 20% over a five-day period. Results demonstrated that treated wastewater met irrigation standards after the treatment period. Parameters such as acidity, dissolved solids, biochemical oxygen demand, chemical oxygen demand, and microbial counts were analyzed. The 15% eco-enzyme solution reduced biochemical oxygen demand by 90.54% and chemical oxygen demand by 83.33%, while the 20% solution achieved reductions of 94.20% and 86.34%, respectively. Dissolved solids levels were reduced to 412 ppm and 422 ppm for the 15% and 20% solutions, respectively, and microbial counts decreased significantly. However, the study is limited by the short duration of the treatment period and the scope of the parameters analyzed, which may not fully capture the long-term effectiveness and broader environmental impacts of eco-enzyme use. This research underscores the potential of eco-enzyme technology in enhancing wastewater treatment processes, promoting environmental sustainability, and alleviating the burden on waste management systems. The eco-enzyme production process is straightforward and accessible, involving the fermentation of kitchen waste, and can be readily adopted in both urban and rural settings. Further research is recommended to optimize the fermentation process, reduce digestion time, and explore the broader applications of eco-enzymes in fields such as agriculture and domestic cleaning.

Construction of LED-light-driven Z-scheme WO3/Bi12O15Cl6 heterojunction for photocatalytic degradation and antimicrobial

In order to alleviate the problem of water pollution, a novel Z-scheme WO3/Bi12O15Cl6 heterojunction was successfully designed to remove organic pollutants and bacteria from water bodies. Various characterization proved that WO3/Bi12O15Cl6 composites were successfully prepared. Photocurrent and electrochemical impedance (EIS) results verified the formation of heterojunctions could facilitate charge separation and migration. Under LED irradiation, the best sample 5 % WO3/Bi12O15Cl6 was able to remove 76.0 % tetracycline (TC) in 120 min and 98.9 % rhodamine B (RhB) in 90 min and kill Escherichia coli (E. coli) in 50 min. A possible mechanism of photocatalysis was proposed through active species removal experiments and the corresponding characterization. This research offers a new path to construct effective Z-scheme heterojunctions, which is a promising option for wastewater purification.

Study of Low Temperature-Treated Aldolized Cellulose Nanocrystals for Enhancing Dye Separation and Self-Healing Properties of Graphene Oxide Membranes.

Graphene oxide (GO) membranes with a 2D layered structure and nanoscale channels have great application prospects for dye wastewater purification. In this paper, ethylenediamine (EDA) was grafted onto the surface of GO nanosheets at 70 °C and aldolized cellulose nanocrystals (ICNC) were introduced to form EDA-ICNC hydrogel structures between the GO nanosheets by Schiff base reaction. The interlayer structure of the membrane was determined by adjusting the amount of ICNC added and the degree of aldolization, and the EGOICNC-24 membrane with the best performance was prepared. The water flux is not only 12 times higher than that of GO membrane but also has a good separation ability for dye molecules with a molecular weight around 300. Following the EDA-ICNC-24 hydrogel cross-linking process, the tensile strength of the EGOICNC-24 membrane exhibited a 173% increase relative to that of the GO membrane. Additionally, the dye rejection rate reached 97.16% after 130 h of dye separation. When the surface of the membrane was damaged, it was self-healed by regulating the repair temperature and adding a very small amount of ICNC to undergo a dynamic Schiff base reaction and a synergistic effect of hydrogen bonding.

Exceeding the theoretical limit of interfacial evaporation efficiency by using the carbon-based aerogel evaporator with cold evaporation surface

Solar-driven interfacial evaporation technology has shown significant potential in the field of water treatment. Heat loss is still inevitable during the SIE process, since the temperature at the evaporation interface surpasses both the ambient temperature and the temperature of the water below. In this study, we presented a study on an aerogel composed of reduced graphene oxide (rGO), multi-walled carbon nanotubes (MWCNTs) and polypyrrole (PPy). The self-aggregation effect of rGO was mitigated through π-π interactions with MWCNTs and PPy, resulting in the formation of a three-dimensional porous structure. This provided the aerogel with a large specific surface area for pollutant adsorption and ample pore volume for photo-induced degradation and photothermal water purification. Using infrared thermography, thermocouples and numerical simulation, it was demonstrated that introducing a cold evaporation surface resulted in thermal flow reversal. This process allowed the evaporator to extract energy from bulk water, thereby enhancing solar evaporation. Due to this gain, under one sun illumination, the aerogel reached an evaporation rate as high as 3.31 kg·m−2·h−1 and achieved an evaporation efficiency of 135.6 %. Simultaneously, the aerogel exhibited a photocatalytic efficiency of over 90 % for various organic pollutants (methylene blue trihydrate, trypan blue and tetracycline hydrochloride). Moreover, it also demonstrated excellent purification ability for combined wastewater, including high-salinity water, seawater and lubricant/water emulsions. Therefore, high-performance interfacial evaporators hold great promise for achieving sustainable wastewater purification and serve as a valuable reference for the development of new solar energy conversion systems.

Simulated sunlight-driven photocatalytic activation of peroxydisulfate by core–shell Ag@SiO2/TiO2 nanocomposite for efficient methyl orange degradation

Herein, core–shell Ag@SiO2/TiO2 nanocomposites were synthesized and applied to activate peroxydisulfate (PDS) for wastewater purification. The Ag core and Ag-doped TiO2 shell were obtained by stober method and calcination method. The dispersion degree and size of Ag in TiO2 would influence the oxygen vacancy. Ag enhanced the visible absorption of TiO2 and activated PDS. Improved degradation performance was attributed to enhanced PDS activation by photogenerated e−, which separated h+and thus promoted methyl orange(MO) degradation. Reactive oxidative species were verified under dark and light conditions via quenching experiments and electron paramagnetic resonance tests, demonstrating SO4•–, h+, O2•–, and1O2were formed in light,whereasSO4•–, •OH, O2•–, and 1O2were responsible for MO degradation under dark conditions. The Ag@SiO2/TiO2/PDS/light system showed selectivity for removal of cationic dyes (e.g., methylene blue and malachite green) through adsorption and photocatalysis, whereas anionic dyes (e.g., MO) were degraded by photocatalysis alone. Besides, we found excess adsorption of micropollutant onto catalyst may be adverse to the activation of PDS. Therefore, the adsorption of oxidant (such as PDS) onto the catalyst surface would be beneficial for catalytic activation and micropollutant degradation, especially onto active sites. This work aims to provide a new avenue for core-shell structure catalyst synthesis in wastewater purification.