Efficient Solar Water Purification Research Articles

Robust and Elastic Thermoresponsive Hydrogels with High Swelling Properties for Efficient Solar Water Purification

Robust and Elastic Thermoresponsive Hydrogels with High Swelling Properties for Efficient Solar Water Purification

Cellulose-based bi-layer hydrogel evaporator with a low evaporation enthalpy for efficient solar desalination

Interfacial evaporation through hydrogel-based evaporators is emerging as a sustainable and cost-effective strategy for drinkable water production. Herein, a specially designed bi-layer hydrogel evaporator was fabricated and used for efficient solar water desalination. With cotton linter as cellulose precursor, it was dispersed in a highly concentrated ZnCl2 (65 %) solution, and cross-linked by epichlorohydrin to prepare cellulose composite hydrogel. After removing inorganic salts by salt-leaching, polyaniline (PANi) with broadband and wide-range light absorption was then integrated into the top surface of hydrogel through in situ polymerization to construct a bi-layer evaporator. As a solar evaporator, the water could be evaporated with a low-energy demand, and the heat from the sunlight could be confined at the interface to achieve efficient water evaporation. Therefore, the hydrogel evaporator demonstrates an optimal water evaporation rate of 3.02 kg m−2 h−1 and photothermal conversion efficiency of 89.09 % under 1 sun (1 kW m−2) irradiation. This work provides new possibilities for efficient solar water purification systems with assured water quality.

Copper sulfide integrated functional cellulose hydrogel for efficient solar water purification

Hydrogels are emerging materials for solar steam generation to alleviate water scarcity. Herein, a semiconductor of copper sulfide (CuS) was integrated into cellulose hydrogel to fabricate a solar steam evaporator. Sustainable and low-cost cotton linter (cellulose) was regenerated by NaOH/urea solvent. Epichlorohydrin was added as a cross-linking agent to enhance the mechanical robustness of the composite hydrogel, and CuS crystals were tightly attached to cellulose fibers and uniformly distributed in the hydrogel matrix. Under simulated solar light, a heating zone was established at the top surface of the composite hydrogel, and CuS can efficiently absorb and convert light into heat. The hydrophilic cellulose network affords an adequate water supply and a low water vaporization enthalpy. By tuning the CuS loadings, the optimized evaporation rate and solar-to-vapor efficiency could reach 2.2 kg/m2/h and 87 %, respectively, under 1 sun irradiation. The evaporation rate remained above 2.1 kg/m2/h after 48 h of irradiation. Moreover, the hydrogels (with a CuS loading of 30 wt%) showed a efficiently photocatalytic degradation of 95 % for methylene blue and 92 % for Rhodamine B. Such functional hydrogel evaporator holds great potential for practical water treatment and solar-driven applications.

Molecular architecting of photothermal hydrogels reinforced by polar-porous C2NxO1-x for efficient solar water purification

Solar-powered interfacial evaporation provides a sustainable and effective means of harvesting green energy to relieve the global water scarcity issues. While hydrogel evaporators are effective for purifying the contaminated or saline water, the use of hydrophobic carbon-based light-absorbers that compromises the hydratability and local heat exchange poses an impediment to the evaporation rates. Herein, we propose a concept of using heteroatoms-rich and porous C2NxO1-x as the light absorber for molecular design of hydrogel-based evaporators for solar-powered water purification. The synergy of abundant polar groups within C2NxO1-x and hydratable skeleton (chitosan and polyvinyl alcohol) enables the decline of water evaporation enthalpy and thus facilitates vapor generation. The hydrophilic C2NxO1-x that penetrates hydrogel network enlarges the pore aperture with improved pore interconnectivity, which allows for rapid water transport and sufficient water supply. Importantly, the converted energy was localized to sufficiently power the evaporation of water molecules present in polar pores of C2NxO1-x due to adequate heat exchange. The resultant photothermal hydrogel attains a high evaporation rate of ca. 2.9 kg m−2 h−1 with an ultrahigh ion removal efficiency (99.9 %) in both simulated seawater and complex ionic contaminants under one sun irradiation. This study offers a useful guideline of utilizing hydrophilic porous light-absorber to develop high-performance hydrogel for efficient solar-powered water purification.

Surface Microlenses for Much More Efficient Photodegradation in Water Treatment

The global need for clean water requires sustainable technology for purifying contaminated water. Highly efficient solar-driven photodegradation is a sustainable strategy for wastewater treatment. In this work, we demonstrate that the photodegradation efficiency of micropollutants in water can be improved by ~2-24 times by leveraging polymeric microlenses (MLs). These microlenses (MLs) are fabricated from the in-situ polymerization of surface nanodroplets. We found that photodegradation efficiency ({\eta}) in water correlates approximately linearly with the sum of the intensity from all focal points of MLs, although no difference in the photodegradation pathway is detected from the chemical analysis of the byproducts. With the same overall power over a given surface area, {\eta} is doubled by using ordered arrays, compared to heterogeneous MLs on an unpatterned substrate. Higher {\eta} from ML arrays may be attributed to a coupled effect from the focal points on the same plane that creates high local concentrations of active species to further speed up the rate of photodegradation. As a proof-of-concept for ML-enhanced water treatment, MLs were formed on the inner wall of glass bottles that were used as containers for water to be treated. Three representative micropollutants (norfloxacin, sulfadiazine, and sulfamethoxazole) in the bottles functionalized by MLs were photodegraded by 30% to 170% faster than in normal bottles. Our findings suggest that the ML-enhanced photodegradation may lead to a highly efficient solar water purification approach without a large solar collector size. Such an approach may be particularly suitable for portable transparent bottles in remote regions.

Multifunctional Au/Ti3C2 Photothermal Membrane with Antibacterial Ability for Stable and Efficient Solar Water Purification under the Full Spectrum

Multifunctional Au/Ti₃C₂ Photothermal Membrane with Antibacterial Ability for Stable and Efficient Solar Water Purification under the Full Spectrum

Multifunctional oligomer sponge for efficient solar water purification and oil cleanup

A DPP-2T embedded sponge (DES) is explored as a solar evaporator to achieve a high evaporation rate of 2.60 kg m−2 h−1 under 1 sun illumination and has good oil absorption capacity.

Sandwich hydrogel with confined plasmonic Cu/carbon cells for efficient solar water purification

A sandwich hydrogel evaporator is obtained by confining plasmonic Cu/carbon cell solar absorbers in the evaporation surface of a PVA hydrogel to achieve high-efficiency solar water purification.

Hydrogels as an Emerging Material Platform for Solar Water Purification.

Growing concern over water scarcity leads to increased research interest in advanced water purification technologies. Solar water purification, which uses solar energy to separate water and impurities through vaporization, enables the utilization of sustainable energy and potential freshwater resources to alleviate water scarcity. However, the essential process of solar water evaporationto remove impurities is energy intensive. Insufficient solar absorption and thermal loss limited the vapor generation rate and, thus, lowered the purified water yield. Diffuse natural sunlight cannot satisfy the intrinsic energy demand for rapid water vaporization. Therefore, developing new material platforms that can simultaneously provide high solar absorption, effective energy utilization, and low energy demand for water vaporization to achieve highly efficient solar water purification under natural sunlight is anticipated. In this Account, we review our recent progress on hydrogel-based evaporators for solar water purification in terms of material selection, molecular engineering, and structural design. First, we introduce the unique water state in hydrogels consisting of free, intermediate, and bound water, of which intermediate water has a reduced energy demand for water evaporation. Then, we describe the design principles of hydrogel-based solar evaporators, where the polymeric networks are tailored to regulate the water state. The water state in hydrogels defines the vaporization behavior of water. Thus, the polymer networks of hydrogels can be architected to tune the water state and, hence, to further reduce the evaporation enthalpy of water. Armed with fundamental gelation chemistry, we discuss synthetic strategies of hydrogels for efficient vapor generation. By incorporating solar absorbers with hydrophilic polymer networks, solar energy is harvested and converted to heat energy, which can be in situ utilized to power the vaporization of contained water in the molecular meshes, and the solar absorbers having strong interaction with hydrogels guide the formation of microstructure to reduce the energy loss and ensure adequate water transport of evaporative water. Regulating the vaporizing fronts, engineering the surfaceof hydrogels has been focused to favor the evaporationof waterto further enhance the solar-to-vapor efficiency. By using hydrophilic polymers as building blocks, the hydrogel-based solar evaporators have also been endowed with multiple functionalities, such as antifouling, permselectivity, and thermal responsiveness, to improve water collection andpurification abilities. Taking advantages of these merits, hydrogels have emerged as apromising materials platform to enable efficient solar water purification under natural sunlight. This Account serves to promote future efforts toward practical purification systems using hydrogel-based solar evaporators to mitigate water scarcity by improving their performance, scalability, stability, and sustainability.

Self-floating Bi2S3/poly (vinylidene fluoride) composites on polyurethane sponges for efficient solar water purification

Solar water purification (SWP) has been considered as one of the most sustainable techniques to address clean water shortage problem. Although significant strategies have been proposed to explore portable SWP device, many challenges, such as complicated fabrication, high costs and poor practicability, still remain to be solved. Here, a facilely and integrally designed Bi2S3/poly (vinylidene fluoride) (BP) composites based on polyurethane (PU) Sponges (PBP composites) is reported. The PBP composites consist of integrated structures, in which multiple internal reflections guarantee sufficient harvest of incident light and tip thermal effects of chrysanthemum-like Bi2S3 ensure efficient solar thermal conversion, and porous BP endows it with adequate water supply, thus exhibiting a high water evaporation rate of 1.66 kg m−2 h−1 and a solar thermal efficiency of 92.9% under one sun irradiation. This bionic optical design and heat management design may provide a new inspiration to utilize solar energy in water purification and other related applications.