Investigation on the coordination conduct within the heavy metal oxyanions and non-metal functionalities during the environmental remediation processes

The highly efficient elimination of highly reactive heavy metal oxyanions remains a critical task from the chemical perspective owing to their very strong oxidative property. In our project, we have synthesized nitrogen (N) and sulfur (S) functionalized covalent organic framework (COF) composites (COF-N and COF-N-S) as model composites, then applied to remove vanadium(V), chromium(VI), and selenium(IV) oxyanions heavy metals in a single-metal system or multi-metal system in the range of working pHs (pH 2-6).
Firstly, we have targeted the coordination conduct and kinetic modes for the reduction of V(V) by nitrogen and sulfur functionalities in working pHs are comprehensively investigated for the first time. The kinetics follow 3 steps; (1) diffusion of V(V) species, (2) reduction of V(V) to V(IV), and (3) adsorption of existing V species. The diffusion of V(V) is controlled by the protonated =NH2+, −SH2+, −C=SH+ functional groups and oxo-vanadate speciation. The reduction of V(V) to V(IV) was efficient by −SH than =NH, −NH−, because of the higher oxidation potential of sulfur and which acted as the sole electron donor in the process. The coordination of V(V)/V(IV) species interacted with oxygen, nitrogen and sulfur atoms via parallel orientation and leads to multi-docking or single-ionic interactions, revealing the previously unrecognized track. The system tested in the real water matrix for practical applicability. From this, the data outlined for 2 papers; (1) published in Journal of Hazardous Materials 448 (2023) 130810 (IF 14.224), (2) Writing a manuscript for the differences in the vanadium(V) removal performances for water samples of tap and lake with the same pH.
Secondly, we have focused on chromium(VI) removal. This finding is separated into 2 parts; (1) “The journey in the comprehensive investigation on diverse chromate elimination mechanisms during the environmental remediation: Critical review” submitted to Water Research, (2) Writing a manuscript for the chromate reduction coupled adsorption mechanism study by nitrogen and sulfur functionalities.
Thirdly, multi-metal removal systems’ results clearly showed the simultaneous removal of multi-metals by COF composites. The research will continue in the near future.
This study proposes a novel tactic to design an efficient wastewater treatment system by considering its water parameters.

In this project, we have targeted to investigate the coordination conduct within the heavy metal oxyanions and non-metal functionalities during the environmental remediation processes. To achieve this.
(1)We have designed, synthesized and characterized nitrogen (N) and sulfur (S) functionalized covalent organic framework (COF) composites (COF-N and COF-N-S).
(2)The synthesized COF composites were applied to remove V(V), Cr(VI) and Se(IV) oxyanionic heavy metals in a single-metal system or multi-metal system in the range of working pHs (pH 2-6).
(3)Metal removal capacities were compared and picked the highly attractive oxyanions for further studies.
(4)The redox behavior, coordination conducts and kinetic insights between the oxyanions and non-metal functionalities were comprehensively elucidated in the range of pH 2-6.
(5)The explained systems were further tested in real water matrixes to elucidate the applicability of the proposed system.
(6)Finally, the influencing factors of the real water matrixes were identified for the co-treatment.
Other than this research topic, our group carried out work for phosphate removal by lanthanum-layered rare earth hydroxides and published it in Science of the Total Environment 830 (2022) 154786 (IF-10.754) under this project number.

Together with, the following outcomes/ achievements obtained from this project.
1.“Study on the coordination conduct and kinetic insights within the oxo-vanadate and organic reductive nitrogen and sulfur functionalities during the reduction coupled adsorption processes: Implications in practical applications”. The paper was published in Journal of Hazardous Materials 448 (2023) 130810 (IF 14.224).
2.“Phosphate sequestration by lanthanum-layered rare earth hydroxides through multiple mechanisms while avoiding the attenuation effect from sediment particles in lake water.” The paper was published in Science of the Total Environment 830 (2022) 154786 (IF-10.754).
3. "Review on technologies for the development of effective and practical chromate removal from wastewaters" The paper was published in Journal of Environmental Chemical Engineering, 11 (2023) 110735 (IF 7.968).
4. "Simultaneous elimination of vanadium(V) and sulfamethoxazole from livestock wastewater with nitrogen-impregnated biochar" The paper was published in Journal of Environmental Chemical Engineering 11 (2023) 111105 (IF 7.968).
5. "Elimination of hazardous Se(IV) through adsorption‑coupled reduction by iron nanoparticles embedded on mesopores of chitin obtained from waste shrimp shells" The paper published in Environmental Science and Pollution Research, 30 (2023) 119961–119973 (IF 5.8)
6. "Nitrogen-rich carbon composite fabricated from waste shrimp shells for highly efficient oxo-vanadate adsorption-coupled reduction" The paper published in Chemosphere 340 (2023) 139915 (I.F. 8.943).