Due to the relentless exploitation of non-renewable resources, humanity is faced with a resource depletion crisis in the coming decades and serious environmental issues. Achieving efficient removal and upcycling of pollutants (ERUP) may become a potential strategy to address these issues. Wastewater, characterized by its large production volume and fluidity, can easily cause widespread environmental pollution through natural water networks. Due to solubility constraints, pollutants in wastewater typically exhibit low concentrations and complex compositions, thereby impeding effective recovery. Therefore, achieving ERUP in wastewater is both highly significant and extremely challenging. Unlike conventional wastewater treatment strategies that are focused on removing pollutants, ERUP strategies can not only realize the efficient removal of pollutants from water but also convert pollutants into valuable and functional products. Herein, we enumerated the latest research progress on ERUP in wastewater and highlighted studies that demonstrate the simultaneous achievement of pollutant removal and the direct conversion of these contaminants into high-efficiency catalysts, hydrogen energy, electrical energy, and other high-value chemicals. Finally, we identified the problems and challenges in the development of ERUP in wastewater and outlined potential research directions for future studies.

A novel carboxylated lactose/sodium lignosulfonate/polyacrylic acid hydrogel composites with self-reduction capacity was successfully synthesized by self-assembly method. The hydrogel with well-developed porous structure provided abundant anchoring points and reduction capacity for transforming Ag⁺ into silver nanoparticles. Silver nanoparticles dispersed among the network of hydrogel and the composites exhibited catalytic capacity. The catalytic performance was evaluated via degradation of p-nitrophenol, rhodamine B, methyl orange and methylene blue, which were catalyzed with corresponding reaction rate constants of 0.04338, 0.07499, 0.04891, and 0.00628 s^–1, respectively. In addition, the catalyst exhibited stable performance under fixed-bed condition and the corresponding conversion rate still maintained more than 80% after 540 min. Moreover, the catalytic performance still maintained effective in tap water and simulated seawater. The catalytic efficiency still remained 99.7% with no significant decrease after 8 cycles.

The efficient fractionation and recovery of monosaccharides (xylose and glucose) from lignocellulosic biomass facilitates subsequent sugar-based derivative production. This study introduces a one-pot γ-valerolactone/CuCl₂ biphasic pretreatment system (100-mmol·L^–1 CuCl₂, 180 °C, 60 min) capable of achieving removal rates of 92.25% and 90.64% for xylan and lignin, respectively, while retaining 83.88% of cellulose. Compared to other metal chlorides (NaCl, LiCl, FeCl₃, and AlCl₃), the γ-valerolactone/CuCl₂ system recovered 121.2 mg·(g eucalyptus)^–1 of xylose and 55.96 mg·(g eucalyptus)^–1 of glucose during the pretreatment stage and 339.2 mg·(g eucalyptus)^–1 of glucose during the enzymatic hydrolysis stage (90.78% of glucose yield), achieving a total monosaccharide recovery of 86.31%. In addition, the recovery of γ-valerolactone was 79.33%, exhibiting minimal changes relative to the pretreatment performance. The method proposed in this study allows a high total monosaccharides recovery and a circular economy-oriented pretreatment approach, offering a viable pathway for biorefinery.

Owing to its uncomplicated synthetic methodology and exorbitant market demand, malachite green is widely used in numerous industries, particularly as a fungicide in aquaculture. Considering its intrinsic toxicity and potential long-term health impacts, deployable and cost-effective strategies must be developed for eliminating water-soluble malachite green. In this study, chemically activated phosphogypsum, a byproduct of fertilizer production, was used to remove malachite green from an aqueous system. Due to its low cost and abundance, the use of phosphogypsum as a sorbent material may significantly reduce the cost of adsorption-based processes. Moreover, its structural durability allows efficient recycling without significant deformation during reactivation. However, untreated phosphogypsum exhibits minimal efficiency in adsorbing synthetic dyes due to its unfavorable surface chemistry. Our investigation revealed that Zn activation induced a noticeable increase in pore volume from 0.03 to 0.06 cm³·g^–1. A 60 mg·L^–1 sorbent dose, pH 7, 150 r·min^–1, and operational temperature of 30 °C produced 99% quantitative sorption efficiency. Response surface methodology and artificial neural network were used to optimize process parameters by validating experimental values. No detectable toxicity was observed in Escherichia coli when exposed to the treated water.

Herein, we introduced a nitrogen-alkali lignin-doped phenolic resin (N@AL_nPR) to produce palladium nanoparticles through an in situ reduction of palladium in an aqueous phase, without the need for additional reagents or a reducing atmosphere. The phenolic resin nanospheres and the resulting palladium nanoparticles were extensively characterized. Alkali lignin created a highly conducive environment for nitrogen incorporation, dispersion, reduction, and stabilization of palladium, leading to a distinct catalytic performance of palladium nanoparticles in vanillin hydrodeoxygenation. Under specific conditions of 1 mmol of vanillin, 40 mg of catalyst, 1 MPa H₂, 90 °C, and 3 h, the optimized Pd/N@AL₃₀PR catalyst exhibited a nearly complete conversion of vanillin, 98.9% selectivity toward p-creosol, and good stability for multiple reuses. Consequently, an environmentally friendly lignin-based catalyst was developed and used for the efficient hydrodeoxygenation conversion of lignin-based platform compounds.

Triboelectric nanogenerators (TENGs) are among the most promising available energy harvesting methods. Cellulose-based TENGs are flexible, renewable, and degradable. However, the flammability of cellulose prevents it from being used in open-flame environments. In this study, the lattice of cellulose was adjusted by the hydroxyl ionization of cellulose molecules, and Na⁺ was introduced to enhance the flame retardancy of cellulose nanofibers (CNFs). The experimental results showed that the amount of hydrogen bonding between cellulose molecules increased with the introduction of Na⁺ and that the limiting oxygen index reached 36.4%. The lattice spacing of cellulose increased from 0.276 to 0.286 nm, and the change in lattice structure exposed more hydroxyl groups, which changed the polarity of cellulose. The surface potential of the fibers increased from 239 to 323 mV, the maximum open-circuit voltage was 25 V·cm^–2, the short-circuit current was 2.10 μA, and the output power density was 4.56 μW·cm^–2. Compared with those of CNFs, the output voltage, current, and transferred charge increased by 96.8%, 517%, and 23%, respectively, and showed good stability and reliability during cyclic exposure. This study provides a valuable strategy for improving the performance of cellulose-based TENGs.

Engineered photosynthetic bacterium Rhodopseudomonas palustris is excellent at one-step CO₂ biomethanation and can use near-infrared light sources, overcoming the limitations of conventional photosynthetic systems. The current study constructed a biohybrid system that deposited CdS nanoparticles on R. palustris. This biohybrid system broadens the capture of sustainable solar energy, achieving a 155 nmol·mL^–1 biological CH₄ production under full visible light irradiation, 13.4-fold of that by the pure R. palustris. The transcriptome profiles revealed that gene expression related to photosynthetic electron transfer chain, nitrogenase, nanofilaments, and redox stress defense was activated. Accordingly, we attributed the much-enhanced CO₂ biomethanation in the biohybrid system to the remarkable increase in the intracellular reducing power and the stronger rigidity of the cells assisted by photoexcited electrons from CdS nanoparticles. Our discovery offers insight and a promising strategy for improving the current CO₂–CH₄ biomanufacturing system.