Mesocosm experimental study on sustainable riparian restoration using sediment-modified planting eco-concrete.

The continued deterioration of riparian ecosystems is a worldwide concern, which can lead to soil erosion, plant degradation, biodiversity loss, and water quality decline. Here, taking into account waste resource utilization and eco-environmental friendliness, the sediment-modified planting eco-concrete with both H. verticillata and T. orientalis (SEC-H&T) was prepared and explored for the first time to achieve sustainable riparian restoration. Concrete mechanical characterizations showed that the compressive strength and porosity of SEC with 30% sediment content could reach up to 15.8 MPa and 21.25%, respectively. The mechanical properties and the sediment utilization levels of SEC were appropriately balanced, and potentially toxic element leaching results verified the environmental safety of eco-concrete modified with dredged sediments. Plant physiological parameters of both aquatic plants (biomass, chlorophyll, protein and starch) were observed to reach the normal levels in SEC during the 30-day culture period, and T. orientalis seemed better adapted to SEC environment than H. verticillate. Importantly, compared to SEC-H and SEC-T, SEC-H&T could effectively reduce the concentrations of COD, TN and TP by 58.59%, 74.00% and 79.98% in water, respectively. Notably, water purification mechanisms by SEC-H&T were further elucidated from the perspective of microbial community responses. Shannon index of bacterial diversity and proliferation of specific populations dominating nutrient transformation (such as Bacillus and Nitrospira) was increased under the synergy of SEC and aquatic plants. Correspondingly, functional genes involved in nitrogen and phosphorus transformation (such as nosZ and phoU) were also enriched. Our study can not only showcase an effective and flexible approach to recycle dredged sediments into eco-concrete with low environment impacts, but also provide a promising alternative for sustainable riparian restoration.

A novel TiO2-x/TiN@ACB composite for synchronous photocatalytic Cr(VI) reduction and water photothermal evaporation under visible/infrared light illumination.

Relatively large band-gap, fast charge carriers recombination, and mono-functionality of photocatalytic materials are still representing stumbling hurdles against their optimal usage for water cleaning. Herein, a novel black titanium oxide/plasmonic titanium nitride@activated coconut biochar (TiO2-x/TiN@ACB) composite was designed to have both photocatalytic and photothermal functions. Intermediate states of black TiO2-x, plasmonic effect of TiN, and high electrons (e-) capacity of biochar enhanced band-gap narrowing, light absorbance extension, and charge carriers separation respectively. Black TiO2-x and plasmonic TiN sensitization via visible/infrared (Vis/IR) portion of photonic spectrum in addition to the confirmed close contact of composite constituents explained the demonstrated major role of e- in photocatalytic mechanism through efficient excitation and facile transfer. Thanks to black photocatalytic semiconductor and carbonic materials for their ultimate photons harnessing and efficient photothermal conversion where the composite exhibited a remarkable photothermal water evaporation upon Vis/IR illumination as well. TiO2-x/TiN@ACB composite revealed 92.8 and 89.7% photocatalytic reduction of hexavalent chromium (Cr(VI)) and water evaporation efficiencies up to 92.9 and 51.1% upon IR and Vis light illumination respectively. This study proposes a new approach for efficient water cleaning by coupling of oxygen deficient and plasmonic semiconductors supported on naturally derived carbonic material as a broad spectrum harvester and bi-functional photocatalytic and photothermal material.

Promoted microbial denitrification and carbon dioxide fixation via photogenerated electrons stored in novel core/shell memory photocatalysts in darkness.

Excess nitrogen in water and greenhouse gases, especially atmospheric carbon dioxide (CO2) from the rapid development of modern society have become an acute threat to the environment. Herein, novel core/shell structured g-C3N4@WO3 memory photocatalyst was fabricated by coating g-C3N4 on the surface of WO3 nanoparticles and applied in the simultaneous coupling of memory photocatalysts and microbial communities (SCMPMC) for the synergistic removal of microbial nitrate and CO2 fixation in darkness. The results showed that ∼98.6% of nitrate was removed and ∼17.7% of CO2 was fixed in darkness by microorganisms in the presence of g-C3N4@WO3 memory photocatalyst within 48 h. Besides, the investigation of the mechanism evidenced that g-C3N4@WO3 memory photocatalyst can promote electron transfer in the SCMPMC system. Moreover, key enzyme activities (i.e., NAR, NIR, CAT, and ETSA) were accelerated, indicating that the activities of enzymes within microorganisms could be remarkably enhanced by the continuous release of stored electrons by the g-C3N4@WO3 memory photocatalyst in the dark. Furthermore, microbial community analysis revealed that the g-C3N4@WO3 memory photocatalyst increased the relative abundance of denitrifiers (i.e., Acidobacterota, Actinobacteria, Chloroflexi, and Proteobacteria) and CO2-assimilating microorganisms (i.e., Pseudomonas), in the treated communities compared with the original community in river sediment, demonstrating the positive effects of g-C3N4@WO3 memory photocatalyst on river sediment microbial communities. The results in this study could shed new light on the establishment of promising synergistic microbial nitrate removal and CO2 fixation methods and mechanisms in darkness.