*Important notice: This news reports on an unedited version of an accepted paper and is awaiting final editing. Therefore, the paper should not be regarded as conclusive or treated as established information.
A bamboo-derived adsorption-controlled solar evaporator (ASE) has been developed to treat contaminated water by reconstructing a single biomass feedstock at two length scales. Researchers published their findings in the journal npj Clean Water.
Study: Multiscale bamboo reconstruction enables adsorption-coupled solar evaporation for contaminated water treatment. Image Credit: George Trumpeter/Shutterstock.com
The system uses specially reconstructed bamboo fibers to capture pollutants in wastewater while harnessing solar energy to produce purified water. Laboratory tests demonstrated high dye-removal efficiency and strong resistance to salt accumulation.
Why Does Solar Water Purification Struggle With Pollutant Buildup?
Solar-driven interfacial evaporation represents an alternative to traditional water treatment technologies for decentralized use. At the water–air interface, this approach converts solar energy into localized heat to promote water vaporization while minimizing needless heating of the entire liquid.
Solar evaporators primarily rely on differences in volatility between nonvolatile solutes and water, with water leaving as vapor while contaminants such as metal ions, salts, and dyes remain in the evaporator.
Retained solutes can be carried to the evaporation zone by constant capillary transport, where a gradual increase in their local concentrations as water evaporates can promote surface fouling, deterioration of interfacial transport, and salt crystallization.
Mobile organic contaminants are not directly immobilized by the current salt-management approaches. This limitation can be addressed by combining interfacial evaporation and adsorption.
Bamboo and MOFs Combine Pollutant Capture With Solar Heating
Contaminants can be immobilized by porous adsorbents through aromatic interactions, hydrogen bonding, pore confinement, and electrostatic interactions.
In this context, metal–organic frameworks (MOFs) like zeolitic imidazolate framework-67 (ZIF-67) are suitable owing to their tunable adsorption
sites and highly accessible surface areas. Specifically, the cobalt-containing component can potentially introduce antibacterial functionality.
This MOF can be integrated with polydopamine (PDA), a protective photothermal coating. PDA combines versatile coating chemistry and broadband photothermal absorption with nitrogen- and oxygen-containing functional groups, enabling the incorporation of surface functionalization and light harvesting in the same layer.
Natural biomass offers a renewable structural framework for combining water transport, thermal regulation, and adsorption. Bamboo has long fibers and a short harvesting cycle compared to typical hardwood sources.
While native bamboo can be used as a solar evaporator through surface carbonization, its hierarchical heterogeneous structure offers limited flexibility to independently regulate the photothermal interface and the underlying thermal-management and water-transport layers.
Two-Layer Bamboo Design Combines Adsorption and Solar Evaporation
In this work, researchers proposed a bamboo-derived ASE created by multiscale reconstruction of bamboo, using an innovative scale-differentiated bilayer design. This design coupled active adsorption of interfacial dyes with phase-change separation.
ZIF-67 and PDA were used to functionalize bamboo microfibers (BMFs), thereby creating an adsorption-active photothermal layer. Similarly, a porous aerogel support/bamboo nanofiber aerogel (BNA) was formed via directional assembly of bamboo nanofibers (BNFs) to enable capillary water transport.
The PDA/ZIF-67-functionalized BMF layer provided pollutant immobilization and photothermal conversion, while thermal management and continuous water supply were enabled by a directionally aligned BNA.
Researchers used this design to assess whether active interfacial adsorption can complement traditional phase-change rejection in solar water treatment.
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Reconstructed Bamboo Fibers Form a Porous Water Treatment System
Researchers prepared ZIF-67-modified bamboo microfibers (Z-BMF) by in situ growth. Initially, they immersed BMF in a methanolic cobalt(II) nitrate solution to adsorb Co2+ on the fiber surfaces and then added 2-methylimidazole in methanol. Following this, ultrasonication was carried out to promote ZIF-67 growth and nucleation.
Subsequently, dopamine hydrochloride and Z-BMF were dispersed in Tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl) buffer and stirred. On the ZIF-67 surface, dopamine formed a PDA coating after undergoing oxidative self-polymerization. Finally, PDA/ZIF-67-functionalized bamboo microfibers (PZ-BMF) were obtained.
Researchers prepared BNF by mechanical fibrillation assisted by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidation. They prepared the ASE through layered assembly.
BNF suspension and Al3+ solution were mixed and mechanically stirred to obtain a hydrogel precursor. Then, researchers placed the PZ-BMF functional layer on top of the precursor and transferred the assembly to a polytetrafluoroethylene mold.
In liquid nitrogen, directional freezing was performed to generate aligned pores. Subsequently, ASE was obtained by freeze-drying the frozen sample under vacuum.
The Solar Evaporator Removes Up to 99.5% of Tested Dyes
Researchers successfully developed a bamboo-derived ASE. An estimated equivalent evaporation enthalpy of 1838.60 J g-1 was obtained through isothermal gravimetric measurements, and cobalt release was reduced by 99.1% due to PDA encapsulation.
The ASE attained an evaporation rate of 3.5 kg m-2 h-1 and remained stable during the test in 20 wt% sodium chloride under one-sun irradiation.
Removal efficiencies reached 98.75% and 99.50% for methylene blue and rhodamine B, respectively, while metal-ion concentrations in condensates were reduced by over 99.5%. Heterogeneous multisite adsorption was supported by surface analyses.
P-BMF-BNA displayed antibacterial efficiencies of 8.57% against Escherichia coli (E. coli) and 0% against Staphylococcus aureus (S. aureus), indicating that PDA alone provides little antibacterial activity. ZIF-67-containing Z-BMF-BNA enhanced these values to 99.96% and 99.83%, respectively.
The fabricated ASE retained antibacterial efficiencies of 99.99% against S. aureus and 99.89% against E. coli. Thus, ZIF-67 was the primary source of antibacterial activity and provided an additional means of reducing microbial fouling risk.
The findings demonstrate that the proposed bamboo-derived aerogel-based solar evaporator could effectively function as a renewable material platform that combines pollutant immobilization with solar-driven water purification.
Journal Reference
Gao, Q., et al. (2026). Multiscale bamboo reconstruction enables adsorption-coupled solar evaporation for contaminated water treatment. npj Clean Water. DOI: 10.1038/s41545-026-00644-w, https://www.nature.com/articles/s41545-026-00644-w.
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