Enhancing the anti-biofouling property of solar evaporator through the synergistic antibacterial effect of lignin and nano silver

Solar desalination is an effective solution to address the global water scarcity issue. However, biofouling poses a significant challenge for solar evaporators due to the presence of bacteria in seawater. In this study, an anti-biofouling evaporator was constructed using the synergistic antibacterial effect of lignin and silver nanoparticles (AgNPs). The AgNPs were easily synthesized using lignin as reductant under mild reaction conditions. Subsequently, the Lignin-AgNPs solution was integrated into polyacrylamide hydrogel (PAAm) without any purification steps, resulting in the formation of Lignin/AgNPs-PAAm (LAg-PAAm). Under the combined action of AgNPs and the hydroquinone groups present in oxidized lignin, LAg-PAAm achieved over 99 % disinfection efficiency within 1 h, effectively preventing biofilm formation in pore channels of solar evaporators. The anti-biofouling solar evaporator demonstrated an evaporation rate of 1.85 kg m-2 h-1 under 1 sun irradiation, and maintained stable performance for >30 days due to its high efficient bactericidal effect. Furthermore, it also exhibited exceptional salt-rejection capability attributed to its superior hydrophilicity.

Superhydrophobic sand evaporator with core-shell structure for long-term salt-resistant solar desalination

Solar-driven water evaporation, as an environmentally benign pathway, provides an opportunity for alleviating global clean water scarcity. However, the rapidly generated interfacial steam and localized heating could cause increased salt concentration and accumulation, deteriorating the evaporation performance and long-term stability. Herein, a novel superhydrophobic sand solar (FPPSD) evaporator with a core-shell structure was proposed through interface functionalization for continuous photothermal desalination. The collective behavior essence of the sand aggregate gave itself micron-scale self-organized pores and configurable shapes, generating desirable capillary force and supplying effective water-pumping channels. More importantly, combining the dopamine, polypyrrole (PPy), and 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTS) through π-π conjugation and multiple hydrogen bonding effects gave the FPPSD evaporator with stable superhydrophobic property and highly efficient photothermal conversion capability. Therefore, the FPPSD evaporator showed a continuous and stable photothermal performance even after 96 h continuous evaporation under 3-sun irradiation for 10 wt% saline solution, among the best values in the reported works of literature, demonstrating its excellent salt-resistance stability. Furthermore, this novel FPPSD evaporator displayed outstanding environmental stability that kept its initial water transport capacity even after being treated under harsh conditions for 30 days. With excellent salt-resistance ability and stable environmental stability, the FPPSD evaporator will provide an attractive platform for sustainable solar-driven water management.

A solar evaporator fabricated from corncob waste for the desalination of seawater and removal of oil/herbicides from contaminated water

Corncob (CC) based solar evaporators were employed to desalinize seawater brought from the Vallarta coast in Mexico. The pure CC produced an evaporation-rate and evaporation-efficiency of 0.63 kg m-2 h-1 and 38.4%, respectively, under natural solar light. Later, the CC was coated with carbonized CC (CCCE evaporator) or was coated with graphene (CCGE evaporator). Those evaporators were used for the desalination of seawater and obtained higher evaporation rates of 1.59-1.67 kg m-2 h-1, and higher evaporation efficiencies of 92-94% (under natural solar light). The desalination experiments were repeated under artificial solar light and the evaporation-rates/evaporation-efficiencies slightly decreased to 1.43-1.52 kg m-2 h-1/88-92%. The surface analysis of the evaporators by FTIR, XPS and Raman revealed that the CCGE evaporator had on its surface a lower content of defects and a higher amount of OH groups than the CCCE evaporator. Therefore, the CCGE evaporator had higher evaporation-rates/evaporation-efficiencies in comparison with the CCCE evaporator. Furthermore, we purified water contaminated with three different herbicides (fomesafen, 2-6 dichlorobenzamide and 4-chlorophenol at 30 ppm) by evaporation and using natural solar light. Interestingly, the CCCE and CCGE evaporators also removed the herbicides by physical adsorption with efficiencies of 12-22.5%. Moreover, the CCGE evaporator removed vegetable oil from contaminated water by adsorption and its maximum adsorption capacity was 1.72 g/g. Overall, our results demonstrated that the corncob-based evaporators studied here are a low-cost alternative to obtain clean water under natural solar light and this one was more effective for the desalination of seawater than the artificial sunlight (Xe lamp).

Development of evaporation technique for concentrating lead acid wastewater from the battery recycling plant, by nanocomposite ceramic substrates and solar/wind energy

Wastewater from car battery recycling plants contains lead ions. This acidic wastewater was treated by the solar steam generation method. In this research, a light porous ceramic substrate (PCS) was made based on clay, human hair, and nano-hydroxyapatite. The physical and chemical characteristics of this PCS were identified by SEM, XRD, FTIR, BET, and TGA. The high porosity in PCSs was created due to the removal of human hair in the calcination process inside the furnace. Microchannels with capillarity and hydrophilicity of nano-hydroxyapatite quickly pump water molecules to the surface of PCSs. The wastewater treatment process was carried out on two laboratory and semi-industrial scales. The temperature of the surface of the PCSs reached 70 °C in less than 60 min with the radiant heat transfer mechanism, and the water molecules were evaporated with an evaporation rate and thermal conversion efficiency were 9.22 Kgm^-2h^-2 and 90%, respectively. The wind blew the vapor away from the system and the rate of evaporation increased. PCSs had the ability to regenerate after several consecutive cycles.

The emerging development of solar evaporators in materials and structures

To tackle the increasingly severe freshwater resource scarcity problem, desalination using solar evaporators is potentially an effective approach. This article reviews the research progress of solar evaporators in recent years, including materials, structures, and performance evaluations. In terms of material research, this article introduces the mechanism of photothermal conversion of metallic, semiconductor, polymeric, and carbon-based materials and their applications in the research of solar evaporators. The structure design of solar evaporators that can improve the photothermal conversion efficiency and water transport efficiency are summarized in detail. Regarding the evaluation of the evaporator performance, common evaluation methods for steam efficiency and environmental benefits of solar evaporators were introduced. Finally, this article analyzes the current problems of evaporators and proposes a prospect for the development of new types of high-efficiency evaporators.

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.