Facile one-pot synthesis of polyethyleneimine functionalized α-FeOOH nanoraft consisted of single-layer parallel-aligned ultrathin nanowires for efficient removal of Cr (VI): Synergy of reduction and adsorption

Chromium removal via coprecipitation with carbonates and iron oxyhydroxides minerals: The effect of organic complexing agents

With the recent review of the European Environmental Regulations for Water Quality, which plan to reduce contaminant concentration limits in drinking and surface waters by 2036, an increasing demand for wastewater depollution arises. Metastable amorphous nanoprecursors of iron oxyhydroxides (IOH) and calcium carbonates (CC) interact with various pollutants in natural systems via processes such as coprecipitation and adsorption. In this research, ferrihydrite (FHY) and calcium carbonates were testes for Cr (VI) retention to cover acidic to neutral environments and neutral to basic media, respectively. An original and novel approach is proposed for investigating Cr uptake capacity and mechanisms as well as minerals transformation in the presence of Cr (VI) and two biodegradable organic compounds (EDTA - ethylenediaminotetraacetic acid and EDDS - ethylenediamine-N,N'-disuccinic acid). Geochemical modelling of Cr coprecipitated species was also considered. TCLP (toxicity characteristic leaching procedure) experiments revealed that Cr remains fixed in FHY structure under near neutral conditions. One year old ferrite's stability in the presence of Cr and organic compounds was examined and showed that the addition of organics and Cr slowed FHY transformation into crystalline polymorphs. Cr (VI) sequestration by ferrites also occurred as reduced Cr (III) - its less toxic specie. Quantitatively, higher amount of Cr (VI) was removed by coprecipitation (up to 97.65 mg/g) then adsorption (ca. 33.76 mg/g). These findings provide insight into the uptake processes that influence Cr (bio)availability and mobility, that affect the elemental cycle, including transition across the trophic chain as well as at contaminated environments (i.e., mining sites and acid mine drainage) were ferrihydrite form naturally.

Tailoring phases of ferrihydrite/α-Fe2O3@C nanocomposites using syringyl and guaiacyl-rich biomass-derived carbon nanodots for electrochemical application

Biomass-derived carbon nanodots (CNDs) hold promise as effective reducing agents for metal oxide nanoparticles yet understanding the intricate interplay with CND structure remains challenging. This study explores the impact of lignin types, specifically syringyl (S), and guaiacyl (G) units in CNDs on metal oxide phases and their electrochemical activity toward dopamine oxidation. We design phases of ferrihydrite/α-Fe2O3@C nanocomposites, using hazelnut carbon nanodots (HS-CNDs (S-rich)) and beetroot carbon nanodots (BS-CNDs (G-rich)) via a one-pot hydrothermal technique. Our findings show S units in HS-CNDs promote α-FeOOH/α-Fe2O3@CHS, while G units in BS-CNDs favor α (β)-FeOOH/α-Fe2O3@CBS. In contrast to α(β)-FeOOH/α-Fe2O3@CBS, α-FeOOH/α-Fe2O3@CHS exhibits superior electrochemical performance in dopamine oxidation due to its larger electrochemical active surface area, higher absorbance capacity, and shortened electron transfer length. Moreover, α-FeOOH/α-Fe2O3@CHS nanocomposites demonstrate remarkable dopamine selectivity, achieving rapid detection response in 10 s with a low LOD of 4 nM within a broad linear range (0.05-0.3 μM), demonstrating impressive reproducibility (97.5 %), stability (96.4 %), and works in real-time human urine detection with a recovery rate of ranging from 94.57 % and 102.2 %. Therefore, the utilization of biomass-derived CNDs, particularly S and G units-rich CNDs, in tailoring the phases of ferrihydrite/α-Fe2O3@C nanocomposites for electrochemical dopamine detection is promising.

One-pot synthesis of novel mesoporous FeOOH modified NaZrH(PO4)2·H2O for the enhanced removal of Co(II) from aqueous solution

One-pot synthesis of a novel mesoporous hydroxyl oxidize iron functional Na-zirconium phosphate (FeOOH-NaZrH(PO4)2·H2O) composites was firstly characterized and investigated its Co(II) adsorption from aqueous solution. Compared to NaZrH(PO4)2·H2O (65.7 mg⋅g-1), the maximum Co(II) adsorption capacity of FeOOH-NaZrH(PO4)2·H2O was improved to be 95.1 mg⋅g-1. BET verified the mesoporous structures of FeOOH-NaZrH(PO4)2·H2O with a larger pore volume than NaZrH(PO4)2·H2O. High pH values, initial Co(II) concentration, and temperature benefited the Co(II) adsorption. Kinetics, isotherms, and thermodynamics indicated an endothermic, spontaneous chemisorption process. FeOOH-NaZrH(PO4)2·H2O has a better Co(II) adsorption selectivity than that of NaZrH(PO4)2·H2O. In particular, FeOOH-NaZrH(PO4)2·H2O exhibited an outstanding reusability after ten cycles of tests. The main possible mechanism for adsorbents uptake Co(II) involved in ion exchange, electrostatic interaction, and -OH, Zr-O bond coordination based on FTIR and XPS analysis. This work presents a feasible strategy to prepare novel modified zirconium phosphate composites for extracting Co(II) from solutions and providing a new insight into the understanding of Co(II) adsorption in the real nuclear Co(II)-containing wastewater.